l3backend (2jul19)

git-svn-id: svn://tug.org/texlive/trunk@51533 c570f23f-e606-0410-a88d-b1316a301751

7 files changed, 5384 insertions, 0 deletions

diff --git a/Master/texmf-dist/source/latex/l3backend/l3backend-basics.dtx b/Master/texmf-dist/source/latex/l3backend/l3backend-basics.dtx
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--- /dev/null
+++ b/Master/texmf-dist/source/latex/l3backend/l3backend-basics.dtx
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+% \iffalse meta-comment
+%
+%% File: l3backend-basics.dtx
+%
+% Copyright (C) 2019 The LaTeX3 Project
+%
+% It may be distributed and/or modified under the conditions of the
+% LaTeX Project Public License (LPPL), either version 1.3c of this
+% license or (at your option) any later version.  The latest version
+% of this license is in the file
+%
+%    https://www.latex-project.org/lppl.txt
+%
+% This file is part of the "l3backend bundle" (The Work in LPPL)
+% and all files in that bundle must be distributed together.
+%
+% -----------------------------------------------------------------------
+%
+% The development version of the bundle can be found at
+%
+%    https://github.com/latex3/latex3
+%
+% for those people who are interested.
+%
+%<*driver>
+\documentclass[full,kernel]{l3doc}
+\begin{document}
+  \DocInput{\jobname.dtx}
+\end{document}
+%</driver>
+% \fi
+%
+% \title{^^A
+%   The \textsf{l3backend-basics} package\\ Backend basics^^A
+% }
+%
+% \author{^^A
+%  The \LaTeX3 Project\thanks
+%    {^^A
+%      E-mail:
+%        \href{mailto:latex-team@latex-project.org}
+%          {latex-team@latex-project.org}^^A
+%    }^^A
+% }
+%
+% \date{Released 2019-07-01}
+%
+% \maketitle
+%
+% \begin{documentation}
+%
+% \end{documentation}
+%
+% \begin{implementation}
+%
+% \section{\pkg{l3backend-basics} Implementation}
+%
+%    \begin{macrocode}
+%<*initex|package>
+%    \end{macrocode}
+%
+% Whilst there is a reasonable amount of code overlap between backends,
+% it is much clearer to have the blocks more-or-less separated than run
+% in together and DocStripped out in parts. As such, most of the following
+% is set up on a per-backed basis, though there is some common code (again
+% given in blocks not interspersed with other material).
+%
+% All the file identifiers are up-front so that they come out in the right
+% place in the files.
+%    \begin{macrocode}
+%<*package>
+\ProvidesExplFile
+%<*dvipdfmx>
+  {l3backend-dvipdfmx.def}{2019-04-06}{}
+  {L3 Experimental backend support: dvipdfmx}
+%</dvipdfmx>
+%<*dvips>
+  {l3backend-dvips.def}{2019-04-06}{}
+  {L3 Experimental backend support: dvips}
+%</dvips>
+%<*dvisvgm>
+  {l3backend-dvisvgm.def}{2019-04-06}{}
+  {L3 Experimental backend support: dvisvgm}
+%</dvisvgm>
+%<*pdfmode>
+  {l3backend-pdfmode.def}{2019-04-06}{}
+  {L3 Experimental backend support: PDF mode}
+%</pdfmode>
+%<*xdvipdfmx>
+  {l3backend-xdvipdfmx.def}{2019-04-06}{}
+  {L3 Experimental backend support: xdvipdfmx}
+%</xdvipdfmx>
+%</package>
+%    \end{macrocode}
+%
+% The order of the backend code here is such that we get somewhat logical
+% outcomes in terms of code sharing whilst keeping things readable. (Trying to
+% mix all of the code by concept is almost unmanageable.) The key parts which
+% are shared are
+% \begin{itemize}
+%   \item Color support is either \texttt{dvips}-like or \texttt{pdfmode}-like.
+%   \item \texttt{pdfmode} and \texttt{(x)dvipdfmx} share drawing routines.
+%   \item \texttt{xdvipdfmx} is largely the same as \texttt{dvipdfmx} so
+%     takes most of the same code.
+% \end{itemize}
+%
+% \begin{macro}
+%   {
+%     \__kernel_backend_literal:e,
+%     \__kernel_backend_literal:n,
+%     \__kernel_backend_literal:x
+%   }
+%  The one shared function for all backends is access to the basic
+%  \tn{special} primitive: it has slightly odd expansion behaviour
+%  so a wrapper is provided.
+%    \begin{macrocode}
+\cs_new_eq:NN \__kernel_backend_literal:e \tex_special:D
+\cs_new_protected:Npn \__kernel_backend_literal:n #1
+  { \__kernel_backend_literal:e { \exp_not:n {#1} } }
+\cs_generate_variant:Nn \__kernel_backend_literal:n { x }
+%    \end{macrocode}
+% \end{macro}
+%
+% \subsection{\texttt{dvips} backend}
+%
+%    \begin{macrocode}
+%<*dvips>
+%    \end{macrocode}
+%
+% \begin{macro}
+%   {\__kernel_backend_literal_postscript:n, \__kernel_backend_literal_postscript:x}
+%   Literal PostScript can be included using a few low-level formats. Here,
+%   we use the form with no positioning: this is overall more convenient as
+%   a wrapper. Note that this does require that where position is important,
+%   an appropriate wrapper is included.
+%    \begin{macrocode}
+\cs_new_protected:Npn \__kernel_backend_literal_postscript:n #1
+  { \__kernel_backend_literal:n { ps:: #1 } }
+\cs_generate_variant:Nn \__kernel_backend_literal_postscript:n { x }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\__kernel_backend_postscript:n, \__kernel_backend_postscript:x}
+%   PostScript data that does have positioning, and also applying
+%   a shift to |SDict| (which is not done automatically by
+%   |ps:| or |ps::|, in contrast to |!| or |"|).
+%    \begin{macrocode}
+\cs_new_protected:Npn \__kernel_backend_postscript:n #1
+  { \__kernel_backend_literal:n { ps: SDict ~ begin ~ #1 ~ end } }
+\cs_generate_variant:Nn \__kernel_backend_postscript:n { x }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\__kernel_backend_postscript_header:n}
+%   PostScript for the header: a small saving but makes the code clearer.
+%   This is held until the start of shipout such that a document with no
+%   actual output does not write anything.
+%    \begin{macrocode}
+\cs_new_protected:Npx \__kernel_backend_postscript_header:n #1
+%<*initex>
+  { \__kernel_backend_literal:n { ! #1 } }
+%</initex>
+%<*package>
+  {
+    \cs_if_exist:NTF \AtBeginDvi
+      { \exp_not:N \AtBeginDvi }
+      { \use:n }
+        { \__kernel_backend_literal:n { ! #1 } }
+  }
+%</package>
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}
+%   {
+%     \__kernel_backend_align_begin:,
+%     \__kernel_backend_align_end:
+%   }
+%   In \texttt{dvips} there is no build-in saving of the current
+%   position, and so some additional PostScript is required to set up the
+%   transformation matrix and also to restore it afterwards. Notice the use
+%   of the stack to save the current position \enquote{up front} and to
+%   move back to it at the end of the process. Notice that the |[begin]|/^^A
+%   |[end]| pair here mean that we can use a run of PostScript statements
+%   in separate lines: not \emph{required} but does make the code and
+%   output more clear.
+%    \begin{macrocode}
+\cs_new_protected:Npn \__kernel_backend_align_begin:
+  {
+    \__kernel_backend_literal:n { ps::[begin] }
+    \__kernel_backend_literal_postscript:n { currentpoint }
+    \__kernel_backend_literal_postscript:n { currentpoint~translate }
+  }
+\cs_new_protected:Npn \__kernel_backend_align_end:
+  {
+    \__kernel_backend_literal_postscript:n { neg~exch~neg~exch~translate }
+    \__kernel_backend_literal:n { ps::[end] }
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\__kernel_backend_scope_begin:, \__kernel_backend_scope_end:}
+%   Saving/restoring scope for general operations needs to be done with
+%   \texttt{dvips} positioning (try without to see this!). Thus we need the
+%   |ps:| version of the special here. As only the graphics state is ever
+%   altered within this pairing, we use the lower-cost |g|-versions.
+%    \begin{macrocode}
+\cs_new_protected:Npn \__kernel_backend_scope_begin:
+  { \__kernel_backend_literal:n { ps:gsave } }
+\cs_new_protected:Npn \__kernel_backend_scope_end:
+  { \__kernel_backend_literal:n { ps:grestore } }
+%    \end{macrocode}
+% \end{macro}
+%
+%    \begin{macrocode}
+%</dvips>
+%    \end{macrocode}
+%
+% \subsection{\texttt{pdfmode} backend}
+%
+%    \begin{macrocode}
+%<*pdfmode>
+%    \end{macrocode}
+%
+% The direct PDF backend covers both \pdfTeX{} and \LuaTeX{}. The latter
+% renames and restructures the backend primitives but this can be handled
+% at one level of abstraction. As such, we avoid using two separate backends
+% for this material at the cost of some \texttt{x}-type definitions to get
+% everything expanded up-front.
+%
+% \begin{macro}{\__kernel_backend_literal_pdf:n, \__kernel_backend_literal_pdf:x}
+%   This is equivalent to \verb|\special{pdf:}| but the engine can
+%   track it. Without the \texttt{direct} keyword everything is kept in
+%   sync: the transformation matrix is set to the current point automatically.
+%   Note that this is still inside the text (\texttt{BT} \dots \texttt{ET}
+%   block).
+%    \begin{macrocode}
+\cs_new_protected:Npx \__kernel_backend_literal_pdf:n #1
+  {
+    \cs_if_exist:NTF \tex_pdfextension:D
+      { \tex_pdfextension:D literal }
+      { \tex_pdfliteral:D }
+        { \exp_not:N \exp_not:n {#1} }
+  }
+\cs_generate_variant:Nn \__kernel_backend_literal_pdf:n { x }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\__kernel_backend_literal_page:n}
+%  Page literals are pretty simple. To avoid an expansion, we write out
+%  by hand.
+%    \begin{macrocode}
+\cs_new_protected:Npx \__kernel_backend_literal_page:n #1
+  {
+    \cs_if_exist:NTF \tex_pdfextension:D
+      { \tex_pdfextension:D literal ~ }
+      { \tex_pdfliteral:D }
+        page
+        { \exp_not:N \exp_not:n {#1} }
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\__kernel_backend_scope_begin:, \__kernel_backend_scope_end:}
+%  Higher-level interfaces for saving and restoring the graphic state.
+%    \begin{macrocode}
+\cs_new_protected:Npx \__kernel_backend_scope_begin:
+  {
+    \cs_if_exist:NTF \tex_pdfextension:D
+      { \tex_pdfextension:D save \scan_stop: }
+      { \tex_pdfsave:D }
+  }
+\cs_new_protected:Npx \__kernel_backend_scope_end:
+  {
+    \cs_if_exist:NTF \tex_pdfextension:D
+      { \tex_pdfextension:D restore \scan_stop: }
+      { \tex_pdfrestore:D }
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\__kernel_backend_matrix:n, \__kernel_backend_matrix:x}
+%   Here the appropriate function is set up to insert an affine matrix
+%   into the PDF. With \pdfTeX{} and \LuaTeX{} in direct PDF output mode there
+%   is a primitive for this, which only needs the rotation/scaling/skew part.
+%    \begin{macrocode}
+\cs_new_protected:Npx \__kernel_backend_matrix:n #1
+  {
+    \cs_if_exist:NTF \tex_pdfextension:D
+      { \tex_pdfextension:D setmatrix }
+      { \tex_pdfsetmatrix:D }
+        { \exp_not:N \exp_not:n {#1} }
+  }
+\cs_generate_variant:Nn \__kernel_backend_matrix:n { x }
+%    \end{macrocode}
+% \end{macro}
+%
+%    \begin{macrocode}
+%</pdfmode>
+%    \end{macrocode}
+%
+% \subsection{\texttt{dvipdfmx} backend}
+%
+%    \begin{macrocode}
+%<*dvipdfmx|xdvipdfmx>
+%    \end{macrocode}
+%
+% The \texttt{dvipdfmx} shares code with the PDF mode one (using the common
+% section to this file) but also with \texttt{xdvipdfmx}. The latter is close
+% to identical to \texttt{dvipdfmx} and so all of the code here is extracted
+% for both backends, with some \texttt{clean up} for \texttt{xdvipdfmx} as
+% required.
+%
+% \begin{macro}{\__kernel_backend_literal_pdf:n, \__kernel_backend_literal_pdf:x}
+%   Equivalent to \texttt{pdf:content} but favored as the link to
+%   the \pdfTeX{} primitive approach is clearer.
+%    \begin{macrocode}
+\cs_new_protected:Npn \__kernel_backend_literal_pdf:n #1
+  { \__kernel_backend_literal:n { pdf:literal~ #1 } }
+\cs_generate_variant:Nn \__kernel_backend_literal_pdf:n { x }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\__kernel_backend_literal_page:n}
+%  Whilst the manual says this is like |literal direct| in \pdfTeX{},
+%  it closes the |BT| block!
+%    \begin{macrocode}
+\cs_new_protected:Npn \__kernel_backend_literal_page:n #1
+  { \__kernel_backend_literal:n { pdf:literal~direct~ #1 } }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\__kernel_backend_scope_begin:, \__kernel_backend_scope_end:}
+%   Scoping is done using the backend-specific specials.
+%    \begin{macrocode}
+\cs_new_protected:Npn \__kernel_backend_scope_begin:
+  { \__kernel_backend_literal:n { x:gsave } }
+\cs_new_protected:Npn \__kernel_backend_scope_end:
+  { \__kernel_backend_literal:n { x:grestore } }
+%    \end{macrocode}
+% \end{macro}
+%
+%    \begin{macrocode}
+%</dvipdfmx|xdvipdfmx>
+%    \end{macrocode}
+%
+% \subsection{\texttt{dvisvgm} backend}
+%
+%    \begin{macrocode}
+%<*dvisvgm>
+%    \end{macrocode}
+%
+% \begin{macro}{\__kernel_backend_literal_svg:n, \__kernel_backend_literal_svg:x}
+%   Unlike the other backends, the requirements for making SVG files mean
+%   that we can't conveniently transform all operations to the current point.
+%   That makes life a bit more tricky later as that needs to be accounted for.
+%   A new line is added after each call to help to keep the output readable
+%   for debugging.
+%    \begin{macrocode}
+\cs_new_protected:Npn \__kernel_backend_literal_svg:n #1
+  { \__kernel_backend_literal:n { dvisvgm:raw~ #1 { ?nl } } }
+\cs_generate_variant:Nn \__kernel_backend_literal_svg:n { x }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\__kernel_backend_scope_begin:, \__kernel_backend_scope_end:}
+%   A scope in SVG terms is slightly different to the other backends as
+%   operations have to be \enquote{tied} to these not simply inside them.
+%    \begin{macrocode}
+\cs_new_protected:Npn \__kernel_backend_scope_begin:
+  { \__kernel_backend_literal_svg:n { <g> } }
+\cs_new_protected:Npn \__kernel_backend_scope_end:
+  { \__kernel_backend_literal_svg:n { </g> } }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\__kernel_backend_scope_begin:n, \__kernel_backend_scope_begin:x}
+%   In SVG transformations, clips and so on are attached directly to scopes so
+%   we need a way or allowing for that. This is rather more useful than
+%   \cs{__kernel_backend_scope_begin:} as a result.
+%   No assumptions are made about the nature
+%   of the scoped operation(s).
+%    \begin{macrocode}
+\cs_new_protected:Npn \__kernel_backend_scope_begin:n #1
+  { \__kernel_backend_literal_svg:n { <g~ #1 > } }
+\cs_generate_variant:Nn \__kernel_backend_scope_begin:n { x }
+%    \end{macrocode}
+% \end{macro}
+%
+%    \begin{macrocode}
+%</dvisvgm>
+%    \end{macrocode}
+%
+%    \begin{macrocode}
+%</initex|package>
+%    \end{macrocode}
+%
+% \end{implementation}
+%
+% \PrintIndex
diff --git a/Master/texmf-dist/source/latex/l3backend/l3backend-box.dtx b/Master/texmf-dist/source/latex/l3backend/l3backend-box.dtx
new file mode 100644
index 00000000000..ef25fe95e1e
--- /dev/null
+++ b/Master/texmf-dist/source/latex/l3backend/l3backend-box.dtx
@@ -0,0 +1,473 @@
+% \iffalse meta-comment
+%
+%% File: l3backend-box.dtx
+%
+% Copyright (C) 2019 The LaTeX3 Project
+%
+% It may be distributed and/or modified under the conditions of the
+% LaTeX Project Public License (LPPL), either version 1.3c of this
+% license or (at your option) any later version.  The latest version
+% of this license is in the file
+%
+%    https://www.latex-project.org/lppl.txt
+%
+% This file is part of the "l3backend bundle" (The Work in LPPL)
+% and all files in that bundle must be distributed together.
+%
+% -----------------------------------------------------------------------
+%
+% The development version of the bundle can be found at
+%
+%    https://github.com/latex3/latex3
+%
+% for those people who are interested.
+%
+%<*driver>
+\documentclass[full,kernel]{l3doc}
+\begin{document}
+  \DocInput{\jobname.dtx}
+\end{document}
+%</driver>
+% \fi
+%
+% \title{^^A
+%   The \textsf{l3backend-box} package\\ Backend box support^^A
+% }
+%
+% \author{^^A
+%  The \LaTeX3 Project\thanks
+%    {^^A
+%      E-mail:
+%        \href{mailto:latex-team@latex-project.org}
+%          {latex-team@latex-project.org}^^A
+%    }^^A
+% }
+%
+% \date{Released 2019-07-01}
+%
+% \maketitle
+%
+% \begin{documentation}
+%
+% \end{documentation}
+%
+% \begin{implementation}
+%
+% \section{\pkg{l3backend-box} Implementation}
+%
+%    \begin{macrocode}
+%<*initex|package>
+%<@@=box>
+%    \end{macrocode}
+%
+% \subsection{\texttt{dvips} backend}
+%
+%    \begin{macrocode}
+%<*dvips>
+%    \end{macrocode}
+%
+% \begin{macro}{\@@_backend_clip:N}
+%   The \texttt{dvips} backend scales all absolute dimensions based on the
+%   output resolution selected and any \TeX{} magnification. Thus for any
+%   operation involving absolute lengths there is a correction to make. See
+%   \texttt{normalscale} from \texttt{special.pro} for the variables, noting
+%   that here everything is saved on the stack rather than as a separate
+%   variable. Once all of that is done, the actual clipping is trivial.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_clip:N #1
+  {
+    \__kernel_backend_scope_begin:
+    \__kernel_backend_align_begin:
+    \__kernel_backend_literal_postscript:n { matrix~currentmatrix }
+    \__kernel_backend_literal_postscript:n
+      { Resolution~72~div~VResolution~72~div~scale }
+    \__kernel_backend_literal_postscript:n { DVImag~dup~scale }
+    \__kernel_backend_literal_postscript:x
+      {
+        0 ~
+        \dim_to_decimal_in_bp:n { \box_dp:N #1 } ~
+        \dim_to_decimal_in_bp:n { \box_wd:N #1 } ~
+        \dim_to_decimal_in_bp:n { -\box_ht:N #1 - \box_dp:N #1 } ~
+        rectclip
+      }
+    \__kernel_backend_literal_postscript:n { setmatrix }
+    \__kernel_backend_align_end:
+    \hbox_overlap_right:n { \box_use:N #1 }
+    \__kernel_backend_scope_end:
+    \skip_horizontal:n { \box_wd:N #1 }
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_backend_rotate:Nn}
+% \begin{macro}{\@@_backend_rotate_aux:Nn}
+%   Rotating using \texttt{dvips} does not require that the box dimensions
+%   are altered and has a very convenient built-in operation. Zero rotation
+%   must be written as |0| not |-0| so there is a quick test.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_rotate:Nn #1#2
+  { \exp_args:NNf \@@_backend_rotate_aux:Nn #1 { \fp_eval:n {#2} } }
+\cs_new_protected:Npn \@@_backend_rotate_aux:Nn #1#2
+  {
+    \__kernel_backend_scope_begin:
+    \__kernel_backend_align_begin:
+    \__kernel_backend_literal_postscript:x
+      {
+        \fp_compare:nNnTF {#2} = \c_zero_fp
+          { 0 }
+          { \fp_eval:n { round ( -(#2) , 5 ) } } ~
+        rotate
+      }
+   \__kernel_backend_align_end:
+   \box_use:N #1
+   \__kernel_backend_scope_end:
+  }
+%    \end{macrocode}
+% \end{macro}
+% \end{macro}
+%
+% \begin{macro}{\@@_backend_scale:Nnn}
+%   The \texttt{dvips} backend once again has a dedicated operation we can
+%   use here.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_scale:Nnn #1#2#3
+  {
+    \__kernel_backend_scope_begin:
+    \__kernel_backend_align_begin:
+    \__kernel_backend_literal_postscript:x
+      {
+        \fp_eval:n { round ( #2 , 5 ) } ~
+        \fp_eval:n { round ( #3 , 5 ) } ~
+        scale
+      }
+    \__kernel_backend_align_end:
+    \hbox_overlap_right:n { \box_use:N #1 }
+    \__kernel_backend_scope_end:
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+%    \begin{macrocode}
+%</dvips>
+%    \end{macrocode}
+%
+% \subsection{\texttt{pdfmode} backend}
+%
+%    \begin{macrocode}
+%<*pdfmode>
+%    \end{macrocode}
+%
+% \begin{macro}{\@@_backend_clip:N}
+%   The general method is to save the current location, define a clipping path
+%   equivalent to the bounding box, then insert the content at the current
+%   position and in a zero width box. The \enquote{real} width is then made up
+%   using a horizontal skip before tidying up. There are other approaches that
+%   can be taken (for example using XForm objects), but the logic here shares
+%   as much code as possible and uses the same conversions (and so same
+%   rounding errors) in all cases.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_clip:N #1
+  {
+    \__kernel_backend_scope_begin:
+    \__kernel_backend_literal_pdf:x
+      {
+        0~
+        \dim_to_decimal_in_bp:n { -\box_dp:N #1 } ~
+        \dim_to_decimal_in_bp:n { \box_wd:N #1 } ~
+        \dim_to_decimal_in_bp:n { \box_ht:N #1 + \box_dp:N #1 } ~
+        re~W~n
+      }
+    \hbox_overlap_right:n { \box_use:N #1 }
+    \__kernel_backend_scope_end:
+    \skip_horizontal:n { \box_wd:N #1 }
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_backend_rotate:Nn}
+% \begin{macro}{\@@_backend_rotate_aux:Nn}
+% \begin{variable}{\l_@@_backend_cos_fp, \l_@@_backend_sin_fp}
+%   Rotations are set using an affine transformation matrix which therefore
+%   requires sine/cosine values not the angle itself. We store the rounded
+%   values to avoid rounding twice. There are also a couple of comparisons to
+%   ensure that |-0| is not written to the output, as this avoids any issues
+%   with problematic display programs.  Note that numbers are compared to~$0$
+%   after rounding.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_rotate:Nn #1#2
+  { \exp_args:NNf \@@_backend_rotate_aux:Nn #1 { \fp_eval:n {#2} } }
+\cs_new_protected:Npn \@@_backend_rotate_aux:Nn #1#2
+  {
+    \__kernel_backend_scope_begin:
+    \box_set_wd:Nn #1 { 0pt }
+    \fp_set:Nn \l_@@_backend_cos_fp { round ( cosd ( #2 ) , 5 ) }
+    \fp_compare:nNnT \l_@@_backend_cos_fp = \c_zero_fp
+      { \fp_zero:N \l_@@_backend_cos_fp }
+    \fp_set:Nn \l_@@_backend_sin_fp { round ( sind ( #2 ) , 5 ) }
+    \__kernel_backend_matrix:x
+      {
+        \fp_use:N \l_@@_backend_cos_fp \c_space_tl
+        \fp_compare:nNnTF \l_@@_backend_sin_fp = \c_zero_fp
+          { 0~0 }
+          {
+            \fp_use:N \l_@@_backend_sin_fp
+            \c_space_tl
+            \fp_eval:n { -\l_@@_backend_sin_fp }
+          }
+        \c_space_tl
+        \fp_use:N \l_@@_backend_cos_fp
+      }
+   \box_use:N #1
+   \__kernel_backend_scope_end:
+  }
+\fp_new:N \l_@@_backend_cos_fp
+\fp_new:N \l_@@_backend_sin_fp
+%    \end{macrocode}
+% \end{variable}
+% \end{macro}
+% \end{macro}
+%
+% \begin{macro}{\@@_backend_scale:Nnn}
+%   The same idea as for rotation but without the complexity of signs and
+%   cosines.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_scale:Nnn #1#2#3
+  {
+    \__kernel_backend_scope_begin:
+    \__kernel_backend_matrix:x
+      {
+        \fp_eval:n { round ( #2 , 5 ) } ~
+        0~0~
+        \fp_eval:n { round ( #3 , 5 ) }
+      }
+    \hbox_overlap_right:n { \box_use:N #1 }
+    \__kernel_backend_scope_end:
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+%    \begin{macrocode}
+%</pdfmode>
+%    \end{macrocode}
+%
+% \subsection{\texttt{dvipdfmx} backend}
+%
+%    \begin{macrocode}
+%<*dvipdfmx|xdvipdfmx>
+%    \end{macrocode}
+%
+% \begin{macro}{\@@_backend_clip:N}
+%   The code here is identical to that for \texttt{pdfmode}: unlike rotation and
+%   scaling, there is no higher-level support in the backend for clipping.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_clip:N #1
+  {
+    \__kernel_backend_scope_begin:
+    \__kernel_backend_literal_pdf:x
+      {
+        0~
+        \dim_to_decimal_in_bp:n { -\box_dp:N #1 } ~
+        \dim_to_decimal_in_bp:n { \box_wd:N #1 } ~
+        \dim_to_decimal_in_bp:n { \box_ht:N #1 + \box_dp:N #1 } ~
+        re~W~n
+      }
+    \hbox_overlap_right:n { \box_use:N #1 }
+    \__kernel_backend_scope_end:
+    \skip_horizontal:n { \box_wd:N #1 }
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_backend_rotate:Nn}
+% \begin{macro}{\@@_backend_rotate_aux:Nn}
+%   Rotating in \texttt{(x)}dvipdmfx can be implemented using either PDF or
+%   backend-specific code. The former approach however is not \enquote{aware}
+%   of the content of boxes: this means that any embedded links would not be
+%   adjusted by the rotation. As such, the backend-native approach is preferred:
+%   the code therefore is similar (though not identical) to the \texttt{dvips}
+%   version (notice the rotation angle here is positive). As for
+%   \texttt{dvips}, zero rotation is written as |0| not |-0|.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_rotate:Nn #1#2
+  { \exp_args:NNf \@@_backend_rotate_aux:Nn #1 { \fp_eval:n {#2} } }
+\cs_new_protected:Npn \@@_backend_rotate_aux:Nn #1#2
+  {
+    \__kernel_backend_scope_begin:
+    \__kernel_backend_literal:x
+      {
+        x:rotate~
+        \fp_compare:nNnTF {#2} = \c_zero_fp
+          { 0 }
+          { \fp_eval:n { round ( #2 , 5 ) } }
+      }
+    \box_use:N #1
+    \__kernel_backend_scope_end:
+  }
+%    \end{macrocode}
+% \end{macro}
+% \end{macro}
+%
+% \begin{macro}{\@@_backend_scale:Nnn}
+%   Much the same idea for scaling: use the higher-level backend operation to allow
+%   for box content.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_scale:Nnn #1#2#3
+  {
+    \__kernel_backend_scope_begin:
+    \__kernel_backend_literal:x
+      {
+        x:scale~
+        \fp_eval:n { round ( #2 , 5 ) } ~
+        \fp_eval:n { round ( #3 , 5 ) }
+      }
+    \hbox_overlap_right:n { \box_use:N #1 }
+    \__kernel_backend_scope_end:
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+%    \begin{macrocode}
+%</dvipdfmx|xdvipdfmx>
+%    \end{macrocode}
+%
+% \subsection{\texttt{dvisvgm} backend}
+%
+%    \begin{macrocode}
+%<*dvisvgm>
+%    \end{macrocode}
+%
+% \begin{macro}{\@@_backend_clip:N}
+% \begin{variable}{\g_@@_clip_path_int}
+%   Clipping in SVG is more involved than with other backends. The first issue
+%   is that the clipping path must be defined separately from where it is used,
+%   so we need to track how many paths have applied. The naming here uses
+%   \texttt{l3cp} as the namespace with a number following. Rather than use
+%   a rectangular operation, we define the path manually as this allows it to
+%   have a depth: easier than the alternative approach of shifting content
+%   up and down using scopes to allow for the depth of the \TeX{} box and
+%   keep the reference point the same!
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_clip:N #1
+  {
+    \int_gincr:N \g_@@_clip_path_int
+    \__kernel_backend_literal_svg:x
+      { < clipPath~id = " l3cp \int_use:N \g_@@_clip_path_int " > }
+    \__kernel_backend_literal_svg:x
+      {
+        <
+          path ~ d =
+            "
+              M ~ 0 ~
+                  \dim_to_decimal:n { -\box_dp:N #1 } ~
+              L ~ \dim_to_decimal:n { \box_wd:N #1 } ~
+                  \dim_to_decimal:n { -\box_dp:N #1 } ~
+              L ~ \dim_to_decimal:n { \box_wd:N #1 }  ~
+                  \dim_to_decimal:n { \box_ht:N #1 + \box_dp:N #1 } ~
+              L ~ 0 ~
+                  \dim_to_decimal:n { \box_ht:N #1 + \box_dp:N #1 } ~
+              Z
+            "
+        />
+      }
+    \__kernel_backend_literal_svg:n
+      { < /clipPath > }
+%    \end{macrocode}
+%   In general the SVG set up does not try to transform coordinates to the
+%   current point. For clipping we need to do that, so have a transformation
+%   here to get us to the right place, and a matching one just before the
+%   \TeX{} box is inserted to get things back on track. The clip path needs to
+%   come between those two such that if lines up with the current point, as
+%   does the \TeX{} box.
+%    \begin{macrocode}
+    \__kernel_backend_scope_begin:n
+      {
+        transform =
+          "
+            translate ( { ?x } , { ?y } ) ~
+            scale ( 1 , -1 )
+          "
+      }
+    \__kernel_backend_scope_begin:x
+      {
+        clip-path =
+          "url ( \c_hash_str l3cp \int_use:N \g_@@_clip_path_int ) "
+      }
+    \__kernel_backend_scope_begin:n
+      {
+        transform =
+          "
+            scale ( -1 , 1 ) ~
+            translate ( { ?x } , { ?y } ) ~
+            scale ( -1 , -1 )
+          "
+      }
+    \box_use:N #1
+    \__kernel_backend_scope_end:
+    \__kernel_backend_scope_end:
+    \__kernel_backend_scope_end:
+%    \skip_horizontal:n { \box_wd:N #1 }
+  }
+\int_new:N \g_@@_clip_path_int
+%    \end{macrocode}
+% \end{variable}
+% \end{macro}
+%
+% \begin{macro}{\@@_backend_rotate:Nn}
+%   Rotation has a dedicated operation which includes a centre-of-rotation
+%   optional pair. That can be picked up from the backend syntax, so there is
+%   no need to worry about the transformation matrix.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_rotate:Nn #1#2
+  {
+    \__kernel_backend_scope_begin:x
+      {
+        transform =
+          "
+            rotate
+            ( \fp_eval:n { round ( -(#2) , 5 ) } , ~ { ?x } , ~ { ?y } )
+          "
+      }
+    \box_use:N #1
+    \__kernel_backend_scope_end:
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_backend_scale:Nnn}
+%   In contrast to rotation, we have to account for the current position in this
+%   case. That is done using a couple of translations in addition to the scaling
+%   (which is therefore done backward with a flip).
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_scale:Nnn #1#2#3
+  {
+    \__kernel_backend_scope_begin:x
+      {
+        transform =
+          "
+            translate ( { ?x } , { ?y } ) ~
+            scale
+              (
+                \fp_eval:n { round ( -#2 , 5 ) } ,
+                \fp_eval:n { round ( -#3 , 5 ) }
+              ) ~
+            translate ( { ?x } , { ?y } ) ~
+            scale ( -1 )
+          "
+      }
+    \hbox_overlap_right:n { \box_use:N #1 }
+    \__kernel_backend_scope_end:
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+%    \begin{macrocode}
+%</dvisvgm>
+%    \end{macrocode}
+%
+%    \begin{macrocode}
+%</initex|package>
+%    \end{macrocode}
+%
+% \end{implementation}
+%
+% \PrintIndex
diff --git a/Master/texmf-dist/source/latex/l3backend/l3backend-color.dtx b/Master/texmf-dist/source/latex/l3backend/l3backend-color.dtx
new file mode 100644
index 00000000000..0e80de0117c
--- /dev/null
+++ b/Master/texmf-dist/source/latex/l3backend/l3backend-color.dtx
@@ -0,0 +1,307 @@
+% \iffalse meta-comment
+%
+%% File: l3backend-color.dtx
+%
+% Copyright (C) 2019 The LaTeX3 Project
+%
+% It may be distributed and/or modified under the conditions of the
+% LaTeX Project Public License (LPPL), either version 1.3c of this
+% license or (at your option) any later version.  The latest version
+% of this license is in the file
+%
+%    https://www.latex-project.org/lppl.txt
+%
+% This file is part of the "l3backend bundle" (The Work in LPPL)
+% and all files in that bundle must be distributed together.
+%
+% -----------------------------------------------------------------------
+%
+% The development version of the bundle can be found at
+%
+%    https://github.com/latex3/latex3
+%
+% for those people who are interested.
+%
+%<*driver>
+\documentclass[full,kernel]{l3doc}
+\begin{document}
+  \DocInput{\jobname.dtx}
+\end{document}
+%</driver>
+% \fi
+%
+% \title{^^A
+%   The \textsf{l3backend-color} package\\ Backend color support^^A
+% }
+%
+% \author{^^A
+%  The \LaTeX3 Project\thanks
+%    {^^A
+%      E-mail:
+%        \href{mailto:latex-team@latex-project.org}
+%          {latex-team@latex-project.org}^^A
+%    }^^A
+% }
+%
+% \date{Released 2019-07-01}
+%
+% \maketitle
+%
+% \begin{documentation}
+%
+% \end{documentation}
+%
+% \begin{implementation}
+%
+% \section{\pkg{l3backend-color} Implementation}
+%
+%    \begin{macrocode}
+%<*initex|package>
+%<@@=color>
+%    \end{macrocode}
+%
+% Color support is split into two parts: a \enquote{general} concept and
+% one directly linked to drawings (or rather the split between filling
+% and stroking). General color is relatively easy to handle: we have a color
+% stack available with all modern drivers, and can use that.
+% Whilst \texttt{(x)dvipdfmx} does have its own approach to color specials,
+% it is easier to use \texttt{dvips}-like ones for all cases except direct
+% PDF output.
+%
+% \subsection{\texttt{dvips}-style}
+%
+%    \begin{macrocode}
+%<*dvisvgm|dvipdfmx|dvips|xdvipdfmx>
+%    \end{macrocode}
+%
+% \begin{macro}{\@@_backend_pickup:N}
+% \begin{macro}{\@@_backend_pickup:w}
+%   Allow for \LaTeXe{} color. Here, the possible input values are limited:
+%   \texttt{dvips}-style colors can mainly be taken as-is with the exception
+%   spot ones (here we need a model and a tint).
+%    \begin{macrocode}
+%<*package>
+\cs_new_protected:Npn \@@_backend_pickup:N #1 { }
+\AtBeginDocument
+  {
+    \@ifpackageloaded { color }
+      {
+        \cs_set_protected:Npn \@@_backend_pickup:N #1
+          {
+            \exp_args:NV \tl_if_head_is_space:nTF \current@color
+              {
+                \tl_set:Nx #1
+                   {
+                     spot ~
+                     \exp_after:wN \use:n \current@color \c_space_tl 1
+                   }
+              }
+              {
+                \exp_last_unbraced:Nx \@@_backend_pickup:w
+                  { \current@color } \q_stop #1
+              }
+          }
+        \cs_new_protected:Npn \@@_backend_pickup:w #1 ~ #2 \q_stop #3
+          { \tl_set:Nn #3 { #1 ~ #2 } }
+      }
+      { }
+  }
+%</package>
+%    \end{macrocode}
+% \end{macro}
+% \end{macro}
+%
+% \begin{macro}{\@@_backend_cmyk:nnnn}
+% \begin{macro}{\@@_backend_gray:n}
+% \begin{macro}{\@@_backend_rgb:nnn}
+% \begin{macro}{\@@_backend_spot:nn}
+% \begin{macro}{\@@_backend_select:n, \@@_backend_select:x}
+% \begin{macro}{\@@_backend_reset:}
+% \begin{macro}{color.fc}
+%    Push the data to the stack. In the case of \texttt{dvips} also reset the
+%    drawing fill color in raw PostScript.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_cmyk:nnnn #1#2#3#4
+  {
+    \@@_backend_select:x
+      {
+        cmyk~
+        \fp_eval:n {#1} ~ \fp_eval:n {#2} ~
+        \fp_eval:n {#3} ~ \fp_eval:n {#4}
+      }
+  }
+\cs_new_protected:Npn \@@_backend_gray:n #1
+  { \@@_backend_select:x { gray~ \fp_eval:n {#1} } }
+\cs_new_protected:Npn \@@_backend_rgb:nnn #1#2#3
+  {
+    \@@_backend_select:x
+      { rgb~ \fp_eval:n {#1} ~ \fp_eval:n {#2} ~ \fp_eval:n {#3} }
+  }
+\cs_new_protected:Npn \@@_backend_spot:nn #1#2
+  { \@@_backend_select:n { #1 } }
+\cs_new_protected:Npn \@@_backend_select:n #1
+  {
+    \__kernel_backend_literal:n { color~push~ #1 }
+%<*dvips>
+    \__kernel_backend_postscript:n { /color.fc~{ }~def }
+%</dvips>
+    \group_insert_after:N \@@_backend_reset:
+  }
+\cs_generate_variant:Nn \@@_backend_select:n { x }
+\cs_new_protected:Npn \@@_backend_reset:
+  { \__kernel_backend_literal:n { color~pop } }
+%    \end{macrocode}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+%
+%    \begin{macrocode}
+%</dvisvgm|dvipdfmx|dvips|xdvipdfmx>
+%    \end{macrocode}
+%
+% \subsection{\texttt{pdfmode}}
+%
+%    \begin{macrocode}
+%<*pdfmode>
+%    \end{macrocode}
+%
+% \begin{macro}{\@@_backend_pickup:N}
+% \begin{macro}{\@@_backend_pickup:w}
+%   The current color in driver-dependent format: pick up the package-mode
+%   data if available. We end up converting back and forward in this route as
+%   we store our color data in \texttt{dvips} format.
+%   The \tn{current@color} needs to be \texttt{x}-expanded before
+%   \cs{@@_backend_pickup:w} breaks it apart, because for instance
+%   \pkg{xcolor} sets it to be instructions to generate a colour
+%    \begin{macrocode}
+%<*package>
+\cs_new_protected:Npn \@@_backend_pickup:N #1 { }
+\AtBeginDocument
+  {
+    \@ifpackageloaded { color }
+      {
+        \cs_set_protected:Npn \@@_backend_pickup:N #1
+          {
+            \exp_last_unbraced:Nx \@@_backend_pickup:w
+              { \current@color } ~ 0 ~ 0 ~ 0 \q_stop #1
+          }
+        \cs_new_protected:Npn \@@_backend_pickup:w
+          #1 ~ #2 ~ #3 ~ #4 ~ #5 ~ #6 \q_stop #7
+          {
+            \str_if_eq:nnTF {#2} { g }
+              { \tl_set:Nn #7 { gray ~ #1 } }
+              {
+                \str_if_eq:nnTF {#4} { rg }
+                  { \tl_set:Nn #7 { rgb ~ #1 ~ #2 ~ #3 } }
+                  {
+                     \str_if_eq:nnTF {#5} { k }
+                       { \tl_set:Nn #7 { cmyk ~ #1 ~ #2 ~ #3 ~ #4 } }
+                       {
+                         \str_if_eq:nnTF {#2} { cs }
+                           {
+                             \tl_set:Nx #7 { spot ~ \use_none:n #1 ~ #5 }
+                           }
+                           {
+                             \tl_set:Nn #7 { gray ~ 0 }
+                           }
+                       }
+                  }
+              }
+          }
+      }
+      { }
+  }
+%</package>
+%    \end{macrocode}
+% \end{macro}
+% \end{macro}
+%
+% \begin{variable}{\l__kernel_color_stack_int}
+%   \pdfTeX{} and \LuaTeX{} have multiple stacks available, and to track
+%   which one is in use a variable is required.
+%    \begin{macrocode}
+\int_new:N \l__kernel_color_stack_int
+%    \end{macrocode}
+% \end{variable}
+%
+% \begin{macro}{\@@_backend_cmyk:nnnn, \@@_backend_cmyk_aux:nnnn}
+% \begin{macro}{\@@_backend_gray:n, \@@_backend_gray_aux:n}
+% \begin{macro}{\@@_backend_rgb:nnn, \@@_backend_rgb_aux:nnn}
+% \begin{macro}{\@@_backend_spot:nn}
+% \begin{macro}{\@@_backend_select:n, \@@_backend_select:x}
+% \begin{macro}{\@@_backend_reset:}
+%   Simply dump the data, but allowing for \LuaTeX{}.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_cmyk:nnnn #1#2#3#4
+  {
+     \use:x
+       {
+         \@@_backend_cmyk_aux:nnnn
+           { \fp_eval:n {#1} }
+           { \fp_eval:n {#2} }
+           { \fp_eval:n {#3} }
+           { \fp_eval:n {#4} }
+       } 
+  }
+\cs_new_protected:Npn \@@_backend_cmyk_aux:nnnn #1#2#3#4
+  {
+    \@@_backend_select:n
+      { #1 ~ #2 ~ #3 ~ #4 ~ k ~ #1 ~ #2 ~ #3 ~ #4 ~ K }
+  }
+\cs_new_protected:Npn \@@_backend_gray:n #1
+  { \exp_args:Nx \@@_backend_gray_aux:n { \fp_eval:n {#1} } }
+\cs_new_protected:Npn \@@_backend_gray_aux:n #1
+  { \@@_backend_select:n { #1 ~ g ~ #1 ~ G } }
+\cs_new_protected:Npn \@@_backend_rgb:nnn #1#2#3
+  {
+     \use:x
+       {
+         \@@_backend_rgb_aux:nnn
+           { \fp_eval:n {#1} }
+           { \fp_eval:n {#2} }
+           { \fp_eval:n {#3} }
+       } 
+  }
+\cs_new_protected:Npn \@@_backend_rgb_aux:nnn #1#2#3
+  { \@@_backend_select:n { #1 ~ #2 ~ #3 ~ rg ~ #1 ~ #2 ~ #3 ~ RG } }
+\cs_new_protected:Npn \@@_backend_spot:nn #1#2
+  { \@@_backend_select:n { /#1 ~ cs ~ /#1 ~ CS ~ #2 ~ sc ~ #2 ~ SC } }
+\cs_new_protected:Npx \@@_backend_select:n #1
+  {
+    \cs_if_exist:NTF \tex_pdfextension:D
+      { \tex_pdfextension:D colorstack }
+      { \tex_pdfcolorstack:D }
+        \exp_not:N \l__kernel_color_stack_int push {#1}
+      \group_insert_after:N \exp_not:N \@@_backend_reset:
+  }
+\cs_generate_variant:Nn \@@_backend_select:n { x }
+\cs_new_protected:Npx \@@_backend_reset:
+  {
+    \cs_if_exist:NTF \tex_pdfextension:D
+      { \tex_pdfextension:D colorstack }
+      { \tex_pdfcolorstack:D }
+        \exp_not:N \l__kernel_color_stack_int pop \scan_stop:
+  }
+%    \end{macrocode}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+%
+%    \begin{macrocode}
+%</pdfmode>
+%    \end{macrocode}
+%
+%    \begin{macrocode}
+%</initex|package>
+%    \end{macrocode}
+%
+% \end{implementation}
+%
+% \PrintIndex
diff --git a/Master/texmf-dist/source/latex/l3backend/l3backend-draw.dtx b/Master/texmf-dist/source/latex/l3backend/l3backend-draw.dtx
new file mode 100644
index 00000000000..e451d30a3e6
--- /dev/null
+++ b/Master/texmf-dist/source/latex/l3backend/l3backend-draw.dtx
@@ -0,0 +1,1368 @@
+% \iffalse meta-comment
+%
+%% File: l3backend-draw.dtx
+%
+% Copyright (C) 2019 The LaTeX3 Project
+%
+% It may be distributed and/or modified under the conditions of the
+% LaTeX Project Public License (LPPL), either version 1.3c of this
+% license or (at your option) any later version.  The latest version
+% of this license is in the file
+%
+%    https://www.latex-project.org/lppl.txt
+%
+% This file is part of the "l3backend bundle" (The Work in LPPL)
+% and all files in that bundle must be distributed together.
+%
+% -----------------------------------------------------------------------
+%
+% The development version of the bundle can be found at
+%
+%    https://github.com/latex3/latex3
+%
+% for those people who are interested.
+%
+%<*driver>
+\documentclass[full,kernel]{l3doc}
+\begin{document}
+  \DocInput{\jobname.dtx}
+\end{document}
+%</driver>
+% \fi
+%
+% \title{^^A
+%   The \textsf{l3backend-draw} package\\ Backend drawing support^^A
+% }
+%
+% \author{^^A
+%  The \LaTeX3 Project\thanks
+%    {^^A
+%      E-mail:
+%        \href{mailto:latex-team@latex-project.org}
+%          {latex-team@latex-project.org}^^A
+%    }^^A
+% }
+%
+% \date{Released 2019-07-01}
+%
+% \maketitle
+%
+% \begin{documentation}
+%
+% \end{documentation}
+%
+% \begin{implementation}
+%
+% \section{\pkg{l3backend-draw} Implementation}
+%
+%    \begin{macrocode}
+%<*initex|package>
+%<@@=draw>
+%    \end{macrocode}
+%
+% \subsection{\texttt{dvips} backend}
+%
+%    \begin{macrocode}
+%<*dvips>
+%    \end{macrocode}
+%
+% \begin{macro}{\@@_backend_literal:n, \@@_backend_literal:x}
+%   The same as literal PostScript: same arguments about positioning apply
+%   her.
+%    \begin{macrocode}
+\cs_new_eq:NN \@@_backend_literal:n \__kernel_backend_literal_postscript:n
+\cs_generate_variant:Nn \@@_backend_literal:n { x }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_backend_begin:, \@@_backend_end:}
+% \begin{macro}{color.fc}
+%   The |ps::[begin]| special here deals with positioning but allows us to
+%   continue on to a matching |ps::[end]|: contrast with |ps:|, which positions
+%   but where we can't split material between separate calls. The
+%   |@beginspecial|/|@endspecial| pair are from |special.pro| and correct the
+%   scale and $y$-axis direction. The definition of |/color.fc| deals with fill
+%   color in paths. In contrast to \pkg{pgf}, we don't save the current point:
+%   discussion with Tom Rokici suggested a better way to handle the necessary
+%   translations (see \cs{@@_backend_box_use:Nnnnn}). (Note that
+%   |@beginspecial|/|@endspecial| forms a backend scope.) The  |[begin]|/^^A
+%   |[end]| lines are handled differently from the rest as they are
+%   conceptually different: not really drawing literals but instructions to
+%   \texttt{dvips} itself.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_begin:
+  {
+    \__kernel_backend_literal:n { ps::[begin] }
+    \@@_backend_literal:n { @beginspecial }
+    \@@_backend_literal:n { SDict ~ begin ~ /color.fc ~ { } ~ def ~ end }
+  }
+\cs_new_protected:Npn \@@_backend_end:
+  {
+    \@@_backend_literal:n { @endspecial }
+    \__kernel_backend_literal:n { ps::[end] }
+  }
+%    \end{macrocode}
+% \end{macro}
+% \end{macro}
+%
+% \begin{macro}{\@@_backend_scope_begin:, \@@_backend_scope_end:}
+%   Scope here may need to contain saved definitions, so the entire memory
+%   rather than just the graphic state has to be sent to the stack.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_scope_begin:
+  { \@@_backend_literal:n { save } }
+\cs_new_protected:Npn \@@_backend_scope_end:
+  { \@@_backend_literal:n { restore } }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_backend_moveto:nn, \@@_backend_lineto:nn}
+% \begin{macro}{\@@_backend_rectangle:nnnn}
+% \begin{macro}{\@@_backend_curveto:nnnnnn}
+%   Path creation operations mainly resolve directly to PostScript primitive
+%   steps, with only the need to convert to \texttt{bp}. Notice that
+%   \texttt{x}-type expansion is included here to ensure that any variable
+%   values are forced to literals before any possible caching. There is
+%   no native rectangular path command (without also clipping, filling or
+%   stroking), so that task is done using a small amount of PostScript.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_moveto:nn #1#2
+  {
+    \@@_backend_literal:x
+      {
+        \dim_to_decimal_in_bp:n {#1} ~ 
+        \dim_to_decimal_in_bp:n {#2} ~ moveto
+      }
+  }
+\cs_new_protected:Npn \@@_backend_lineto:nn #1#2
+  {
+    \@@_backend_literal:x
+      {
+        \dim_to_decimal_in_bp:n {#1} ~
+        \dim_to_decimal_in_bp:n {#2} ~ lineto
+      }
+  }
+\cs_new_protected:Npn \@@_backend_rectangle:nnnn #1#2#3#4
+  {
+     \@@_backend_literal:x
+       {
+         \dim_to_decimal_in_bp:n {#4} ~ \dim_to_decimal_in_bp:n {#3} ~
+         \dim_to_decimal_in_bp:n {#1} ~ \dim_to_decimal_in_bp:n {#2} ~
+         moveto~dup~0~rlineto~exch~0~exch~rlineto~neg~0~rlineto~closepath
+      }
+  }
+\cs_new_protected:Npn \@@_backend_curveto:nnnnnn #1#2#3#4#5#6
+  {
+    \@@_backend_literal:x
+      {
+        \dim_to_decimal_in_bp:n {#1} ~ \dim_to_decimal_in_bp:n {#2} ~
+        \dim_to_decimal_in_bp:n {#3} ~ \dim_to_decimal_in_bp:n {#4} ~
+        \dim_to_decimal_in_bp:n {#5} ~ \dim_to_decimal_in_bp:n {#6} ~
+        curveto
+      }
+ }
+%    \end{macrocode}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+%
+% \begin{macro}{\@@_backend_evenodd_rule:, \@@_backend_nonzero_rule:}
+% \begin{variable}{\g_@@_draw_eor_bool}
+%    The even-odd rule here can be implemented as a simply switch.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_evenodd_rule:
+  { \bool_gset_true:N \g_@@_draw_eor_bool }
+\cs_new_protected:Npn \@@_backend_nonzero_rule:
+  { \bool_gset_false:N \g_@@_draw_eor_bool }
+\bool_new:N \g_@@_draw_eor_bool
+%    \end{macrocode}
+% \end{variable}
+% \end{macro}
+%
+% \begin{macro}
+%   {
+%     \@@_backend_closepath:   ,
+%     \@@_backend_stroke:      ,
+%     \@@_backend_closestroke: ,
+%     \@@_backend_fill:        ,
+%     \@@_backend_fillstroke:  ,
+%     \@@_backend_clip:        ,
+%     \@@_backend_discardpath:
+%   }
+% \begin{variable}{\g_@@_draw_clip_bool}
+%   Unlike PDF, PostScript doesn't track separate colors for strokes and other
+%   elements. It is also desirable to have the |clip| keyword after a stroke or
+%   fill. To achieve those outcomes, there is some work to do. For color, the
+%   stoke color is simple but the fill one has to be inserted by hand. For
+%   clipping, the required ordering is achieved using a \TeX{} switch. All of
+%   the operations end with a new path instruction  as they do not terminate
+%   (again in contrast to PDF).
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_closepath:
+  { \@@_backend_literal:n { closepath } }
+\cs_new_protected:Npn \@@_backend_stroke:
+  {
+    \@@_backend_literal:n { stroke }
+    \bool_if:NT \g_@@_draw_clip_bool
+      {
+        \@@_backend_literal:x
+          {
+            \bool_if:NT \g_@@_draw_eor_bool { eo }
+            clip
+          }
+      }
+    \@@_backend_literal:n { newpath }
+    \bool_gset_false:N \g_@@_draw_clip_bool
+  }
+\cs_new_protected:Npn \@@_backend_closestroke:
+  {
+    \@@_backend_closepath:
+    \@@_backend_stroke:
+  }
+\cs_new_protected:Npn \@@_backend_fill:
+  {
+    \@@_backend_literal:n { gsave }
+    \@@_backend_literal:n { color.fc }
+    \@@_backend_literal:x
+      {
+        \bool_if:NT \g_@@_draw_eor_bool { eo }
+        fill
+      }
+    \@@_backend_literal:n { grestore }
+    \bool_if:NT \g_@@_draw_clip_bool
+      {
+        \@@_backend_literal:x
+          {
+            \bool_if:NT \g_@@_draw_eor_bool { eo }
+            clip
+          }
+      }
+    \@@_backend_literal:n { newpath }
+    \bool_gset_false:N \g_@@_draw_clip_bool
+  }
+\cs_new_protected:Npn \@@_backend_fillstroke:
+  {
+    \@@_backend_literal:n { gsave }
+    \@@_backend_literal:n { color.fc }
+    \@@_backend_literal:x
+      {
+        \bool_if:NT \g_@@_draw_eor_bool { eo }
+        fill
+      }
+    \@@_backend_literal:n { grestore }
+    \@@_backend_literal:n { stroke }
+    \bool_if:NT \g_@@_draw_clip_bool
+      {
+        \@@_backend_literal:x
+          {
+            \bool_if:NT \g_@@_draw_eor_bool { eo }
+            clip
+          }
+      }
+    \@@_backend_literal:n { newpath }
+    \bool_gset_false:N \g_@@_draw_clip_bool
+  }
+\cs_new_protected:Npn \@@_backend_clip:
+  { \bool_gset_true:N \g_@@_draw_clip_bool }
+\bool_new:N \g_@@_draw_clip_bool
+\cs_new_protected:Npn \@@_backend_discardpath:
+  {
+    \bool_if:NT \g_@@_draw_clip_bool
+      {
+        \@@_backend_literal:x
+          {
+            \bool_if:NT \g_@@_draw_eor_bool { eo }
+            clip
+          }
+      }
+    \@@_backend_literal:n { newpath }
+    \bool_gset_false:N \g_@@_draw_clip_bool
+  }
+%    \end{macrocode}
+% \end{variable}
+% \end{macro}
+%
+% \begin{macro}{\@@_backend_dash_pattern:nn}
+% \begin{macro}{\@@_backend_dash:n}
+% \begin{macro}{\@@_backend_linewidth:n}
+% \begin{macro}{\@@_backend_miterlimit:n}
+% \begin{macro}
+%   {
+%     \@@_backend_cap_butt:, \@@_backend_cap_round:, \@@_backend_cap_rectangle:,
+%     \@@_backend_join_miter:, \@@_backend_join_round:, \@@_backend_join_bevel:
+%   }
+%   Converting paths to output is again a case of mapping directly to
+%   PostScript operations.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_dash_pattern:nn #1#2
+  {
+    \@@_backend_literal:x
+      {
+        [ 
+          \exp_args:Nf \use:n
+            { \clist_map_function:nN {#1} \@@_backend_dash:n }
+        ] ~
+        \dim_to_decimal_in_bp:n {#2} ~ setdash
+      }
+  }
+\cs_new:Npn \@@_backend_dash:n #1
+  { ~ \dim_to_decimal_in_bp:n {#1} }
+\cs_new_protected:Npn \@@_backend_linewidth:n #1
+  {
+    \@@_backend_literal:x
+      { \dim_to_decimal_in_bp:n {#1} ~ setlinewidth }
+  }
+\cs_new_protected:Npn \@@_backend_miterlimit:n #1
+  { \@@_backend_literal:x { \fp_eval:n {#1} ~ setmiterlimit } }
+\cs_new_protected:Npn \@@_backend_cap_butt:
+  { \@@_backend_literal:n { 0 ~ setlinecap } }
+\cs_new_protected:Npn \@@_backend_cap_round:
+  { \@@_backend_literal:n { 1 ~ setlinecap } }
+\cs_new_protected:Npn \@@_backend_cap_rectangle:
+  { \@@_backend_literal:n { 2 ~ setlinecap } }
+\cs_new_protected:Npn \@@_backend_join_miter:
+  { \@@_backend_literal:n { 0 ~ setlinejoin } }
+\cs_new_protected:Npn \@@_backend_join_round:
+  { \@@_backend_literal:n { 1 ~ setlinejoin } }
+\cs_new_protected:Npn \@@_backend_join_bevel:
+  { \@@_backend_literal:n { 2 ~ setlinejoin } }
+%    \end{macrocode}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+%
+% \begin{macro}
+%   {
+%     \@@_backend_color_fill_cmyk:nnnn   ,
+%     \@@_backend_color_stroke_cmyk:nnnn
+%   }
+% \begin{macro}
+%   {
+%     \@@_backend_color_fill_gray:n   ,
+%     \@@_backend_color_stroke_gray:n
+%   }
+% \begin{macro}
+%   {
+%     \@@_backend_color_fill_rgb:nnn   ,
+%     \@@_backend_color_stroke_rgb:nnn
+%   }
+% \begin{macro}
+%   {
+%     \@@_backend_color_fill:n, \@@_backend_color_fill:x,
+%     \@@_backend_color_stroke:n, \@@_backend_color_stroke:x
+%   }
+%   For \texttt{dvips}, we can use the standard color stack to deal with
+%   stroke color, but for fills have to switch to raw PostScript. This is
+%   thus not handled by the stack, but the context is very restricted. See
+%   also how fills are implemented.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_color_fill_cmyk:nnnn #1#2#3#4
+  {
+    \@@_backend_color_fill:x
+      {
+        \fp_eval:n {#1} ~ \fp_eval:n {#2} ~
+        \fp_eval:n {#3} ~ \fp_eval:n {#4} ~
+        setcmykcolor
+      }
+  }
+\cs_new_protected:Npn \@@_backend_color_stroke_cmyk:nnnn #1#2#3#4
+  {
+    \@@_backend_color_stroke:x
+      {
+        cmyk ~
+        \fp_eval:n {#1} ~ \fp_eval:n {#2} ~
+        \fp_eval:n {#3} ~ \fp_eval:n {#4}
+      }
+  }
+\cs_new_protected:Npn \@@_backend_color_fill_gray:n #1
+  { \@@_backend_color_fill:x { \fp_eval:n {#1} ~ setgray } }
+\cs_new_protected:Npn \@@_backend_color_stroke_gray:n #1
+  { \@@_backend_color_stroke:x { gray ~ \fp_eval:n {#1} } }
+\cs_new_protected:Npn \@@_backend_color_fill_rgb:nnn #1#2#3
+  {
+    \@@_backend_color_fill:x
+      { \fp_eval:n {#1} ~ \fp_eval:n {#2} ~ \fp_eval:n {#3} ~ setrgbcolor }
+  }
+\cs_new_protected:Npn \@@_backend_color_stroke_rgb:nnn #1#2#3
+  {
+    \@@_backend_color_stroke:x
+      { rgb ~ \fp_eval:n {#1} ~ \fp_eval:n {#2} ~ \fp_eval:n {#3} }
+  }
+\cs_new_protected:Npn \@@_backend_color_fill:n #1
+  { 
+    \__kernel_backend_postscript:n
+      { SDict ~ begin ~ /color.fc ~ { #1 } ~ def ~ end }
+  }
+\cs_generate_variant:Nn \@@_backend_color_fill:n { x }
+\cs_new_protected:Npn \@@_backend_color_stroke:n #1
+  {
+    \__kernel_backend_literal:n { color~push~#1 } 
+    \group_insert_after:N \@@_color_reset:
+  }
+\cs_generate_variant:Nn \@@_backend_color_stroke:n { x }
+%    \end{macrocode}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+%
+% \begin{macro}{\@@_backend_cm:nnnn}
+%   In \texttt{dvips}, keeping the transformations in line with the engine
+%   is unfortunately not possible for scaling and rotations: even if we
+%   decompose the matrix into those operations, there is still no backend
+%   tracking (\emph{cf.}~\texttt{(x)dvipdfmx}). Thus we take the shortest
+%   path available and simply dump the matrix as given.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_cm:nnnn #1#2#3#4
+  {
+    \@@_backend_literal:n
+      {
+        [
+          \fp_eval:n {#1} ~ \fp_eval:n {#2} ~
+          \fp_eval:n {#3} ~ \fp_eval:n {#4} ~
+          0 ~ 0
+        ] ~
+        concat
+      }
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_backend_box_use:Nnnnn}
+%   Inside a picture |@beginspecial|/|@endspecial| are active, which is
+%   normally a good thing but means that the position and scaling would be off
+%   if the box was inserted directly. To deal with that, there are a number of
+%   possible approaches. The implementation here was suggested by Tom Rokici
+%   (author of \texttt{dvips}). We end the current special placement, then
+%   set the current point with a literal |[begin]|. As for general
+%   literals, we then use the stack to store the current point and move to
+%   it. To insert the required transformation, we have to flip the $y$-axis,
+%   once before and once after it. Then we get back to the \TeX{} reference
+%   point to insert our content. The clean up has to happen in the right
+%   places, hence the |[begin]|/|[end]| pair around |restore|. Finally,
+%   we can return to \enquote{normal} drawing mode. Notice that the set up
+%   here is very similar to that in \cs{@@_align_currentpoint_\ldots}, but
+%   the ordering of saving and restoring is different (intermixed).
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_box_use:Nnnnn #1#2#3#4#5
+  {
+    \@@_backend_literal:n { @endspecial }
+    \@@_backend_literal:n { [end] }
+    \@@_backend_literal:n { [begin] }
+    \@@_backend_literal:n { save }
+    \@@_backend_literal:n { currentpoint }
+    \@@_backend_literal:n { currentpoint~translate }
+    \@@_backend_cm:nnnn { 1 } { 0 } { 0 } { -1 }
+    \@@_backend_cm:nnnn {#2} {#3} {#4} {#5}
+    \@@_backend_cm:nnnn { 1 } { 0 } { 0 } { -1 }
+    \@@_backend_literal:n { neg~exch~neg~exch~translate }
+    \@@_backend_literal:n { [end] }
+    \hbox_overlap_right:n { \box_use:N #1 }
+    \@@_backend_literal:n { [begin] }
+    \@@_backend_literal:n { restore }
+    \@@_backend_literal:n { [end] }
+    \@@_backend_literal:n { [begin] }
+    \@@_backend_literal:n { @beginspecial }
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+%    \begin{macrocode}
+%</dvips>
+%    \end{macrocode}
+%
+% \subsection{\texttt{pdfmode} and \texttt{(x)dvipdfmx}}
+%
+% Both \texttt{pdfmode} and \texttt{(x)dvipdfmx} directly produce PDF output
+% and understand a shared set of specials for drawing commands.
+%
+%    \begin{macrocode}
+%<*dvipdfmx|pdfmode|xdvipdfmx>
+%    \end{macrocode}
+%
+% \subsubsection{Drawing}
+%
+% \begin{macro}{\@@_backend_literal:n, \@@_backend_literal:x}
+%   Pass data through using a dedicated interface.
+%    \begin{macrocode}
+\cs_new_eq:NN \@@_backend_literal:n \__kernel_backend_literal_pdf:n
+\cs_generate_variant:Nn \@@_backend_literal:n { x }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_backend_begin:, \@@_backend_end:}
+%   No special requirements here, so simply set up a drawing scope.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_begin:
+  { \@@_backend_scope_begin: }
+\cs_new_protected:Npn \@@_backend_end:
+  { \@@_backend_scope_end: }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_backend_scope_begin:, \@@_backend_scope_end:}
+%   Use the backend-level scope mechanisms.
+%    \begin{macrocode}
+\cs_new_eq:NN \@@_backend_scope_begin: \__kernel_backend_scope_begin:
+\cs_new_eq:NN \@@_backend_scope_end: \__kernel_backend_scope_end:
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_backend_moveto:nn, \@@_backend_lineto:nn}
+% \begin{macro}{\@@_backend_curveto:nnnnnn}
+% \begin{macro}{\@@_backend_rectangle:nnnn}
+%   Path creation operations all resolve directly to PDF primitive steps, with
+%   only the need to convert to \texttt{bp}.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_moveto:nn #1#2
+  {
+    \@@_backend_literal:x
+      { \dim_to_decimal_in_bp:n {#1} ~ \dim_to_decimal_in_bp:n {#2} ~ m }
+  }
+\cs_new_protected:Npn \@@_backend_lineto:nn #1#2
+  {
+    \@@_backend_literal:x
+      { \dim_to_decimal_in_bp:n {#1} ~ \dim_to_decimal_in_bp:n {#2} ~ l }
+  }
+\cs_new_protected:Npn \@@_backend_curveto:nnnnnn #1#2#3#4#5#6
+  {
+    \@@_backend_literal:x
+      {
+        \dim_to_decimal_in_bp:n {#1} ~ \dim_to_decimal_in_bp:n {#2} ~
+        \dim_to_decimal_in_bp:n {#3} ~ \dim_to_decimal_in_bp:n {#4} ~
+        \dim_to_decimal_in_bp:n {#5} ~ \dim_to_decimal_in_bp:n {#6} ~
+        c
+      }
+ }
+\cs_new_protected:Npn \@@_backend_rectangle:nnnn #1#2#3#4
+  {
+     \@@_backend_literal:x
+      {
+        \dim_to_decimal_in_bp:n {#1} ~ \dim_to_decimal_in_bp:n {#2} ~
+        \dim_to_decimal_in_bp:n {#3} ~ \dim_to_decimal_in_bp:n {#4} ~
+        re
+      }
+  }
+%    \end{macrocode}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+%
+% \begin{macro}{\@@_backend_evenodd_rule:, \@@_backend_nonzero_rule:}
+% \begin{variable}{\g_@@_draw_eor_bool}
+%    The even-odd rule here can be implemented as a simply switch.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_evenodd_rule:
+  { \bool_gset_true:N \g_@@_draw_eor_bool }
+\cs_new_protected:Npn \@@_backend_nonzero_rule:
+  { \bool_gset_false:N \g_@@_draw_eor_bool }
+\bool_new:N \g_@@_draw_eor_bool
+%    \end{macrocode}
+% \end{variable}
+% \end{macro}
+%
+% \begin{macro}
+%   {
+%     \@@_backend_closepath:   ,
+%     \@@_backend_stroke:      ,
+%     \@@_backend_closestroke: ,
+%     \@@_backend_fill:        ,
+%     \@@_backend_fillstroke:  ,
+%     \@@_backend_clip:        ,
+%     \@@_backend_discardpath:
+%   }
+%   Converting paths to output is again a case of mapping directly to
+%   PDF operations.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_closepath:
+  { \@@_backend_literal:n { h } }
+\cs_new_protected:Npn \@@_backend_stroke:
+  { \@@_backend_literal:n { S } }
+\cs_new_protected:Npn \@@_backend_closestroke:
+  { \@@_backend_literal:n { s } }
+\cs_new_protected:Npn \@@_backend_fill:
+  {
+    \@@_backend_literal:x
+      { f \bool_if:NT \g_@@_draw_eor_bool * }
+  }
+\cs_new_protected:Npn \@@_backend_fillstroke:
+  {
+    \@@_backend_literal:x
+      { B \bool_if:NT \g_@@_draw_eor_bool * }
+  }
+\cs_new_protected:Npn \@@_backend_clip:
+  {
+    \@@_backend_literal:x
+      { W \bool_if:NT \g_@@_draw_eor_bool * }
+  }
+\cs_new_protected:Npn \@@_backend_discardpath:
+  { \@@_backend_literal:n { n } }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_backend_dash_pattern:nn}
+% \begin{macro}{\@@_backend_dash:n}
+% \begin{macro}{\@@_backend_linewidth:n}
+% \begin{macro}{\@@_backend_miterlimit:n}
+% \begin{macro}
+%   {
+%     \@@_backend_cap_butt:, \@@_backend_cap_round:, \@@_backend_cap_rectangle:,
+%     \@@_backend_join_miter:, \@@_backend_join_round:, \@@_backend_join_bevel:
+%   }
+%   Converting paths to output is again a case of mapping directly to
+%   PDF operations.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_dash_pattern:nn #1#2
+  {
+    \@@_backend_literal:x
+      {
+        [
+          \exp_args:Nf \use:n
+            { \clist_map_function:nN {#1} \@@_backend_dash:n }
+        ] ~
+        \dim_to_decimal_in_bp:n {#2} ~ d
+      }
+  }
+\cs_new:Npn \@@_backend_dash:n #1
+  { ~ \dim_to_decimal_in_bp:n {#1} }
+\cs_new_protected:Npn \@@_backend_linewidth:n #1
+  {
+    \@@_backend_literal:x
+      { \dim_to_decimal_in_bp:n {#1} ~ w }
+  }
+\cs_new_protected:Npn \@@_backend_miterlimit:n #1
+  { \@@_backend_literal:x { \fp_eval:n {#1} ~ M } }
+\cs_new_protected:Npn \@@_backend_cap_butt:
+  { \@@_backend_literal:n { 0 ~ J } }
+\cs_new_protected:Npn \@@_backend_cap_round:
+  { \@@_backend_literal:n { 1 ~ J } }
+\cs_new_protected:Npn \@@_backend_cap_rectangle:
+  { \@@_backend_literal:n { 2 ~ J } }
+\cs_new_protected:Npn \@@_backend_join_miter:
+  { \@@_backend_literal:n { 0 ~ j } }
+\cs_new_protected:Npn \@@_backend_join_round:
+  { \@@_backend_literal:n { 1 ~ j } }
+\cs_new_protected:Npn \@@_backend_join_bevel:
+  { \@@_backend_literal:n { 2 ~ j } }
+%    \end{macrocode}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+%
+% \begin{macro}
+%   {
+%     \@@_backend_color_fill_cmyk:nnnn   ,
+%     \@@_backend_color_stroke_cmyk:nnnn
+%   }
+% \begin{macro}
+%   {
+%     \@@_backend_color_fill_gray:n   ,
+%     \@@_backend_color_stroke_gray:n
+%   }
+% \begin{macro}
+%   {
+%     \@@_backend_color_fill_rgb:nnn   ,
+%     \@@_backend_color_stroke_rgb:nnn
+%   }
+% \begin{macro}{\@@_backend_color_select:n, \@@_backend_color_select:x}
+% \begin{macro}{\@@_backend_color_reset:}
+%    Color has to be split between \texttt{(x)dvipdfmx} and the PDF engines
+%    as there is no color stack for fill/stroke separation in the former.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_color_fill_cmyk:nnnn #1#2#3#4
+  {
+    \@@_backend_color_select:x
+      {
+        \fp_eval:n {#1} ~ \fp_eval:n {#2} ~ 
+        \fp_eval:n {#3} ~ \fp_eval:n {#4} ~
+        k
+      }
+  }
+\cs_new_protected:Npn \@@_backend_color_stroke_cmyk:nnnn #1#2#3#4
+  {
+    \@@_backend_color_select:x
+      {
+        \fp_eval:n {#1} ~ \fp_eval:n {#2} ~ 
+        \fp_eval:n {#3} ~ \fp_eval:n {#4} ~
+        k
+      }
+  }
+\cs_new_protected:Npn \@@_backend_color_fill_gray:n #1
+  { \@@_backend_color_select:x { \fp_eval:n {#1} ~ g } }
+\cs_new_protected:Npn \@@_backend_color_stroke_gray:n #1
+  { \@@_backend_color_select:x { \fp_eval:n {#1} ~ G } }
+\cs_new_protected:Npn \@@_backend_color_fill_rgb:nnn #1#2#3
+  {
+    \@@_backend_color_select:x
+      { \fp_eval:n {#1} ~ \fp_eval:n {#2} ~ \fp_eval:n {#3} ~ rg }
+  }
+\cs_new_protected:Npn \@@_backend_color_stroke_rgb:nnn #1#2#3
+  {
+    \@@_backend_color_select:x
+      { \fp_eval:n {#1} ~ \fp_eval:n {#2} ~ \fp_eval:n {#3} ~ RG }
+  }
+%<*pdfmode>
+\cs_new_protected:Npx \@@_backend_color_select:n #1
+  {
+    \cs_if_exist:NTF \tex_pdfextension:D
+      { \tex_pdfextension:D colorstack }
+      { \tex_pdfcolorstack:D }
+        \exp_not:N \l__kernel_color_stack_int push {#1}
+      \group_insert_after:N \exp_not:N \@@_backend_color_reset:
+  }
+\cs_new_protected:Npx \@@_backend_color_reset:
+  {
+    \cs_if_exist:NTF \tex_pdfextension:D
+      { \tex_pdfextension:D colorstack }
+      { \tex_pdfcolorstack:D }
+        \exp_not:N \l__kernel_color_stack_int pop \scan_stop:
+  }
+%</pdfmode>
+%<*dvipdfmx|xdvipdfmx>
+\cs_new_eq:NN \@@_backend_color_select:n \__kernel_backend_literal_pdf:n
+%</dvipdfmx|xdvipdfmx>
+\cs_generate_variant:Nn \@@_backend_color_select:n { x }
+%    \end{macrocode}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+%
+% \begin{macro}{\@@_backend_cm:nnnn}
+% \begin{macro}{\@@_backend_cm_aux:nnnn}
+%   Another split here between \texttt{pdfmode} and \texttt{(x)dvipdfmx}.
+%   In the former, we have a direct method to maintain alignment: the backend
+%   can use a matrix itself. For \texttt{(x)dvipdfmx}, we can to decompose the
+%   matrix into rotations and a scaling, then use those operations as they
+%   are handled by the backend. (There is backend support for matrix operations in
+%   \texttt{(x)dvipdfmx}, but as a matched pair so not suitable for the
+%   \enquote{stand alone} transformation set up here.)
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_cm:nnnn #1#2#3#4
+  {
+%<*pdfmode>
+    \__kernel_backend_matrix:x
+      {
+        \fp_eval:n {#1} ~ \fp_eval:n {#2} ~
+        \fp_eval:n {#3} ~ \fp_eval:n {#4}
+      }
+%</pdfmode>
+%<*dvipdfmx|xdvipdfmx>
+    \@@_backend_cm_decompose:nnnnN {#1} {#2} {#3} {#4}
+      \@@_backend_cm_aux:nnnn
+%</dvipdfmx|xdvipdfmx>
+  }
+%<*dvipdfmx|xdvipdfmx>
+\cs_new_protected:Npn \@@_backend_cm_aux:nnnn #1#2#3#4
+  {
+    \__kernel_backend_literal:x
+      {
+        x:rotate~
+        \fp_compare:nNnTF {#1} = \c_zero_fp
+          { 0 }
+          { \fp_eval:n { round ( -#1 , 5 ) } }
+      }
+    \__kernel_backend_literal:x
+      {
+        x:scale~
+        \fp_eval:n { round ( #2 , 5 ) } ~
+        \fp_eval:n { round ( #3 , 5 ) }
+      }
+    \__kernel_backend_literal:x
+      {
+        x:rotate~
+        \fp_compare:nNnTF {#4} = \c_zero_fp
+          { 0 }
+          { \fp_eval:n { round ( -#4 , 5 ) } }
+      }
+  }
+%</dvipdfmx|xdvipdfmx>
+%    \end{macrocode}
+% \end{macro}
+% \end{macro}
+%
+% \begin{macro}{\@@_backend_cm_decompose:nnnnN}
+% \begin{macro}
+%   {
+%     \@@_backend_cm_decompose_auxi:nnnnN,
+%     \@@_backend_cm_decompose_auxii:nnnnN,
+%     \@@_backend_cm_decompose_auxiii:nnnnN,
+%   }
+%   Internally, transformations for drawing are tracked as a matrix. Not all
+%   engines provide a way of dealing with this: if we use a raw matrix, the
+%   engine looses track of positions (for example for hyperlinks), and this is
+%   not desirable. They do, however, allow us to track rotations and scalings.
+%   Luckily, we can decompose any (two-dimensional) matrix into two rotations
+%   and a single scaling:
+%   \[
+%     \begin{bmatrix}
+%         A & B \\ C & D
+%     \end{bmatrix}
+%     =
+%     \begin{bmatrix}
+%       \cos\beta & \sin\beta \\ -\sin\beta & \cos\beta
+%     \end{bmatrix}
+%     \begin{bmatrix}
+%       w_{1} & 0 \\ 0 & w_{2}
+%     \end{bmatrix}
+%     \begin{bmatrix}
+%       \cos\gamma & \sin\gamma \\ -\sin\gamma & \cos\gamma
+%     \end{bmatrix} 
+%   \]
+%   The parent matrix can be converted to
+%   \[
+%     \begin{bmatrix}
+%       A & B \\ C & D
+%     \end{bmatrix}
+%      =
+%     \begin{bmatrix}
+%       E & H \\-H & E
+%     \end{bmatrix}
+%     +
+%     \begin{bmatrix}
+%       F & G \\ G & -F
+%     \end{bmatrix}
+%   \]
+%   From these, we can find that
+%   \begin{align*}
+%     \frac{w_{1} + w_{2}}{2} &= \sqrt{E^{2} + H^{2}} \\
+%     \frac{w_{1} - w_{2}}{2} &= \sqrt{F^{2} + G^{2}} \\
+%     \gamma - \beta &= \tan^{-1}(G/F) \\
+%     \gamma + \beta &= \tan^{-1}(H/E)
+%   \end{align*}
+%   at which point we just have to do various pieces of re-arrangement to
+%   get all of the values. (See J.~Blinn, \emph{IEEE Comput.\ Graph.\ Appl.},
+%   1996, \textbf{16}, 82--88.) There is one wrinkle: the PostScript (and PDF)
+%   way of specifying a transformation matrix exchanges where one would
+%   normally expect $B$ and $C$ to be.
+%    \begin{macrocode}
+%<*dvipdfmx|xdvipdfmx>
+\cs_new_protected:Npn \@@_backend_cm_decompose:nnnnN #1#2#3#4#5
+  {
+    \use:x
+      {
+        \@@_backend_cm_decompose_auxi:nnnnN
+          { \fp_eval:n { (#1 + #4) / 2 } }
+          { \fp_eval:n { (#1 - #4) / 2 } }
+          { \fp_eval:n { (#3 + #2) / 2 } }
+          { \fp_eval:n { (#3 - #2) / 2 } }
+      }
+        #5
+  }
+\cs_new_protected:Npn \@@_backend_cm_decompose_auxi:nnnnN #1#2#3#4#5
+  {
+    \use:x
+      {
+        \@@_backend_cm_decompose_auxii:nnnnN
+          { \fp_eval:n { 2 * sqrt ( #1 * #1 + #4 * #4 ) } }
+          { \fp_eval:n { 2 * sqrt ( #2 * #2 + #3 * #3 ) } }
+          { \fp_eval:n { atand ( #3 , #2 ) } }
+          { \fp_eval:n { atand ( #4 , #1 ) } }
+      }
+         #5
+  }
+\cs_new_protected:Npn \@@_backend_cm_decompose_auxii:nnnnN #1#2#3#4#5
+  {
+    \use:x
+      {
+        \@@_backend_cm_decompose_auxiii:nnnnN
+          { \fp_eval:n { ( #4 - #3 ) / 2 } }
+          { \fp_eval:n { ( #1 + #2 ) / 2 } }
+          { \fp_eval:n { ( #1 - #2 ) / 2 } }
+          { \fp_eval:n { ( #4 + #3 ) / 2 } }
+      }
+        #5
+  }
+\cs_new_protected:Npn \@@_backend_cm_decompose_auxiii:nnnnN #1#2#3#4#5
+  {
+    \fp_compare:nNnTF { abs( #2 ) } > { abs ( #3 ) }
+      { #5 {#1} {#2} {#3} {#4} }
+      { #5 {#1} {#3} {#2} {#4} }
+  }
+%</dvipdfmx|xdvipdfmx>
+%    \end{macrocode}
+% \end{macro}
+% \end{macro}
+%
+% \begin{macro}{\@@_backend_box_use:Nnnnn}
+%   Inserting a \TeX{} box transformed to the requested position and using
+%   the current matrix is done using a mixture of \TeX{} and low-level
+%   manipulation. The offset can be handled by \TeX{}, so only any rotation/^^A
+%   skew/scaling component needs to be done using the matrix operation. As this
+%   operation can never be cached, the scope is set directly not using the
+%   \texttt{draw} version.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_box_use:Nnnnn #1#2#3#4#5
+  {
+    \__kernel_backend_scope_begin:
+%<*pdfmode>
+    \@@_backend_cm:nnnn {#2} {#3} {#4} {#5}
+%</pdfmode>
+%<*dvipdfmx|xdvipdfmx>
+    \__kernel_backend_literal:x
+      {
+        pdf:btrans~matrix~
+        \fp_eval:n {#2} ~ \fp_eval:n {#3} ~
+        \fp_eval:n {#4} ~ \fp_eval:n {#5} ~
+        0 ~ 0
+      }
+%</dvipdfmx|xdvipdfmx>
+    \hbox_overlap_right:n { \box_use:N #1 }
+%<*dvipdfmx|xdvipdfmx>
+    \__kernel_backend_literal:n { pdf:etrans }
+%</dvipdfmx|xdvipdfmx>
+    \__kernel_backend_scope_end:
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+%    \begin{macrocode}
+%</dvipdfmx|pdfmode|xdvipdfmx>
+%    \end{macrocode}
+%
+% \subsection{\texttt{dvisvgm} backend}
+%
+%    \begin{macrocode}
+%<*dvisvgm>
+%    \end{macrocode}
+%
+% \begin{macro}{\@@_backend_literal:n, \@@_backend_literal:x}
+%   The same as the more general literal call.
+%    \begin{macrocode}
+\cs_new_eq:NN \@@_backend_literal:n \__kernel_backend_literal_svg:n
+\cs_generate_variant:Nn \@@_backend_literal:n { x }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_backend_begin:, \@@_backend_end:}
+%   A drawing needs to be set up such that the co-ordinate system is
+%   translated. That is done inside a scope, which as described below
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_begin:
+  {
+    \@@_backend_scope_begin:
+    \@@_backend_scope:n { transform="translate({?x},{?y})~scale(1,-1)" }
+  }
+\cs_new_protected:Npn \@@_backend_end:
+  { \@@_backend_scope_end: }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_backend_scope_begin:, \@@_backend_scope_end:}
+% \begin{macro}{\@@_backend_scope:n, \@@_backend_scope:x}
+% \begin{variable}{\g_@@_draw_scope_int, \l_@@_draw_scope_int}
+%   Several settings that with other backends are \enquote{stand alone} have
+%   to be given as part of a scope in SVG. As a result, there is a need to
+%   provide a mechanism to automatically close these extra scopes. That is
+%   done using a dedicated function and a pair of tracking variables. Within
+%   each graphics scope we use a global variable to do the work, with a group
+%   used to save the value between scopes. The result is that no direct action
+%   is needed when creating a scope.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_scope_begin:
+  {
+    \int_set_eq:NN
+      \l_@@_draw_scope_int
+      \g_@@_draw_scope_int
+    \group_begin:
+      \int_gzero:N \g_@@_draw_scope_int
+  }
+\cs_new_protected:Npn \@@_backend_scope_end:
+  {
+      \prg_replicate:nn
+        { \g_@@_draw_scope_int }
+        { \@@_backend_literal:n { </g> } }
+    \group_end:
+    \int_gset_eq:NN
+      \g_@@_draw_scope_int
+      \l_@@_draw_scope_int
+  }
+\cs_new_protected:Npn \@@_backend_scope:n #1
+  {
+    \@@_backend_literal:n { <g~ #1 > }
+    \int_gincr:N \g_@@_draw_scope_int
+  }
+\cs_generate_variant:Nn \@@_backend_scope:n { x }
+\int_new:N \g_@@_draw_scope_int
+\int_new:N \l_@@_draw_scope_int
+%    \end{macrocode}
+% \end{variable}
+% \end{macro}
+% \end{macro}
+%
+% \begin{macro}{\@@_backend_moveto:nn, \@@_backend_lineto:nn}
+% \begin{macro}{\@@_backend_rectangle:nnnn}
+% \begin{macro}{\@@_backend_curveto:nnnnnn}
+% \begin{macro}{\@@_backend_add_to_path:n}
+% \begin{variable}{\g_@@_draw_path_tl}
+%   Once again, some work is needed to get path constructs correct. Rather
+%   then write the values as they are given, the entire path needs to be
+%   collected up before being output in one go. For that we use a dedicated
+%   storage routine, which adds spaces as required. Since paths should
+%   be fully expanded there is no need to worry about the internal
+%   \texttt{x}-type expansion.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_moveto:nn #1#2
+  {
+    \@@_backend_add_to_path:n
+      { M ~ \dim_to_decimal:n {#1} ~ \dim_to_decimal:n {#2} }
+  }
+\cs_new_protected:Npn \@@_backend_lineto:nn #1#2
+  {
+    \@@_backend_add_to_path:n
+      { L ~ \dim_to_decimal:n {#1} ~ \dim_to_decimal:n {#2} }
+  }
+\cs_new_protected:Npn \@@_backend_rectangle:nnnn #1#2#3#4
+  {
+    \@@_backend_add_to_path:n
+      {
+        M ~ \dim_to_decimal:n {#1} ~ \dim_to_decimal:n {#2}
+        h ~ \dim_to_decimal:n {#3} ~
+        v ~ \dim_to_decimal:n {#4} ~
+        h ~ \dim_to_decimal:n { -#3 } ~
+        Z
+      }
+  }
+\cs_new_protected:Npn \@@_backend_curveto:nnnnnn #1#2#3#4#5#6
+  {
+    \@@_backend_add_to_path:n
+      {
+        C ~
+        \dim_to_decimal:n {#1} ~ \dim_to_decimal:n {#2} ~
+        \dim_to_decimal:n {#3} ~ \dim_to_decimal:n {#4} ~
+        \dim_to_decimal:n {#5} ~ \dim_to_decimal:n {#6}
+      }
+  }
+\cs_new_protected:Npn \@@_backend_add_to_path:n #1
+  {
+    \tl_gset:Nx \g_@@_draw_path_tl
+      {
+        \g_@@_draw_path_tl
+        \tl_if_empty:NF \g_@@_draw_path_tl { \c_space_tl }
+        #1
+      }
+  }
+\tl_new:N \g_@@_draw_path_tl
+%    \end{macrocode}
+% \end{variable}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+%
+% \begin{macro}{\@@_backend_evenodd_rule:, \@@_backend_nonzero_rule:}
+%   The fill rules here have to be handled as scopes.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_evenodd_rule:
+  { \@@_backend_scope:n { fill-rule="evenodd" } }
+\cs_new_protected:Npn \@@_backend_nonzero_rule:
+  { \@@_backend_scope:n { fill-rule="nonzero" } }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_backend_path:n}
+% \begin{macro}
+%   {
+%     \@@_backend_closepath:   ,
+%     \@@_backend_stroke:      ,
+%     \@@_backend_closestroke: ,
+%     \@@_backend_fill:        ,
+%     \@@_backend_fillstroke:  ,
+%     \@@_backend_clip:        ,
+%     \@@_backend_discardpath:
+%   }
+% \begin{variable}{\g_@@_draw_clip_bool}
+% \begin{variable}{\g_@@_draw_path_int}
+%   Setting fill and stroke effects and doing clipping all has to be done using
+%   scopes. This means setting up the various requirements in a shared
+%   auxiliary which deals with the bits and pieces. Clipping paths are reused
+%   for path drawing: not essential but avoids constructing them twice.
+%   Discarding a path needs a separate function as it's not quite the same.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_closepath:
+  { \@@_backend_add_to_path:n { Z } }
+\cs_new_protected:Npn \@@_backend_path:n #1
+  {
+    \bool_if:NTF \g_@@_draw_clip_bool
+      {
+        \int_gincr:N \g_@@_clip_path_int
+        \@@_backend_literal:x
+          {
+            < clipPath~id = " l3cp \int_use:N \g_@@_clip_path_int " >
+              { ?nl }
+            <path~d=" \g_@@_draw_path_tl "/> { ?nl }
+            < /clipPath > { ? nl }
+            <
+              use~xlink:href =
+                "\c_hash_str l3path \int_use:N \g_@@_path_int " ~
+                #1
+            />
+          }
+        \@@_backend_scope:x
+          {
+            clip-path =
+              "url( \c_hash_str l3cp \int_use:N \g_@@_clip_path_int)"
+          }
+      }
+      {
+        \@@_backend_literal:x
+          { <path ~ d=" \g_@@_draw_path_tl " ~ #1 /> }
+      }
+    \tl_gclear:N \g_@@_draw_path_tl
+    \bool_gset_false:N \g_@@_draw_clip_bool
+  }
+\int_new:N \g_@@_path_int
+\cs_new_protected:Npn \@@_backend_stroke:
+  { \@@_backend_path:n { style="fill:none" } }
+\cs_new_protected:Npn \@@_backend_closestroke:
+  {
+    \@@_backend_closepath:
+    \@@_backend_stroke:
+  }
+\cs_new_protected:Npn \@@_backend_fill:
+  { \@@_backend_path:n { style="stroke:none" } }
+\cs_new_protected:Npn \@@_backend_fillstroke:
+  { \@@_backend_path:n { } }
+\cs_new_protected:Npn \@@_backend_clip:
+  { \bool_gset_true:N \g_@@_draw_clip_bool }
+\bool_new:N \g_@@_draw_clip_bool
+\cs_new_protected:Npn \@@_backend_discardpath:
+  {
+    \bool_if:NT \g_@@_draw_clip_bool
+      {
+        \int_gincr:N \g_@@_clip_path_int
+        \@@_backend_literal:x
+          {
+            < clipPath~id = " l3cp \int_use:N \g_@@_clip_path_int " >
+              { ?nl }
+            <path~d=" \g_@@_draw_path_tl "/> { ?nl }
+            < /clipPath >
+          }
+        \@@_backend_scope:x
+          {
+            clip-path =
+              "url( \c_hash_str l3cp \int_use:N \g_@@_clip_path_int)"
+          }
+      }
+    \tl_gclear:N \g_@@_draw_path_tl
+    \bool_gset_false:N \g_@@_draw_clip_bool
+  }
+%    \end{macrocode}
+% \end{variable}
+% \end{variable}
+% \end{macro}
+% \end{macro}
+%
+% \begin{macro}{\@@_backend_dash_pattern:nn}
+% \begin{macro}{\@@_backend_dash:n}
+% \begin{macro}{\@@_backend_dash_aux:nn}
+% \begin{macro}{\@@_backend_linewidth:n}
+% \begin{macro}{\@@_backend_miterlimit:n}
+% \begin{macro}
+%   {
+%     \@@_backend_cap_butt:, \@@_backend_cap_round:, \@@_backend_cap_rectangle:,
+%     \@@_backend_join_miter:, \@@_backend_join_round:, \@@_backend_join_bevel:
+%   }
+%   All of these ideas are properties of scopes in SVG. The only slight
+%   complexity is converting the dash array properly (doing any required
+%   maths).
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_dash_pattern:nn #1#2
+  {
+    \use:x
+      {
+        \@@_backend_dash_aux:nn
+          { \clist_map_function:nn {#1} \@@_backend_dash:n }
+          { \dim_to_decimal:n {#2} }
+      }
+  }
+\cs_new:Npn \@@_backend_dash:n #1
+  { , \dim_to_decimal_in_bp:n {#1} }
+\cs_new_protected:Npn \@@_backend_dash_aux:nn #1#2
+  {
+    \@@_backend_scope:x
+      {
+        stroke-dasharray =
+          "
+            \tl_if_empty:oTF { \use_none:n #1 }
+              { none }
+              { \use_none:n #1 }
+          " ~
+          stroke-offset=" #2 "
+      }
+  }
+\cs_new_protected:Npn \@@_backend_linewidth:n #1
+  { \@@_backend_scope:x { stroke-width=" \dim_to_decimal:n {#1} " } }
+\cs_new_protected:Npn \@@_backend_miterlimit:n #1
+  { \@@_backend_scope:x { stroke-miterlimit=" \fp_eval:n {#1} " } }
+\cs_new_protected:Npn \@@_backend_cap_butt:
+  { \@@_backend_scope:n { stroke-linecap="butt" } }
+\cs_new_protected:Npn \@@_backend_cap_round:
+  { \@@_backend_scope:n { stroke-linecap="round" } }
+\cs_new_protected:Npn \@@_backend_cap_rectangle:
+  { \@@_backend_scope:n { stroke-linecap="square" } }
+\cs_new_protected:Npn \@@_backend_join_miter:
+  { \@@_backend_scope:n { stroke-linejoin="miter" } }
+\cs_new_protected:Npn \@@_backend_join_round:
+  { \@@_backend_scope:n { stroke-linejoin="round" } }
+\cs_new_protected:Npn \@@_backend_join_bevel:
+  { \@@_backend_scope:n { stroke-linejoin="bevel" } }
+%    \end{macrocode}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+%
+% \begin{macro}
+%   {
+%     \@@_backend_color_fill_cmyk:nnnn   ,
+%     \@@_backend_color_stroke_cmyk:nnnn
+%   }
+% \begin{macro}
+%   {
+%     \@@_backend_color_fill_gray:n   ,
+%     \@@_backend_color_stroke_gray:n
+%   }
+% \begin{macro}
+%   {
+%     \@@_backend_color_fill_rgb:nnn   ,
+%     \@@_backend_color_stroke_rgb:nnn
+%   }
+% \begin{macro}{\@@_backend_color_fill:nnn}
+%  SVG fill color has to be covered outside of the stack, as for
+%  \texttt{dvips}. Here, we are only allowed RGB colors so there is some
+%  conversion to do.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_color_fill_cmyk:nnnn #1#2#3#4
+  {
+    \use:x
+      {
+        \@@_backend_color_fill:nnn
+          { \fp_eval:n { -100 * ( (#1) * ( 1 - (#4) ) - 1 ) } }
+          { \fp_eval:n { -100 * ( (#2) * ( 1 - (#4) ) + #4 - 1 ) } }
+          { \fp_eval:n { -100 * ( (#3) * ( 1 - (#4) ) + #4 - 1 ) } }
+      }
+  }
+\cs_new_protected:Npn \@@_backend_color_stroke_cmyk:nnnn #1#2#3#4
+  {
+    \@@_backend_select:x
+      {
+        cmyk~
+        \fp_eval:n {#1} ~ \fp_eval:n {#2} ~
+        \fp_eval:n {#3} ~ \fp_eval:n {#4}
+      }
+  }
+\cs_new_protected:Npn \@@_backend_color_fill_gray:n #1
+  {
+    \use:x
+      {
+        \@@_backend_color_gray_aux:n
+          { \fp_eval:n { 100 * (#1) } }
+      }
+  }
+\cs_new_protected:Npn \@@_backend_color_gray_aux:n #1
+  { \@@_backend_color_fill:nnn {#1} {#1} {#1} }
+\cs_new_protected:Npn \@@_backend_color_stroke_gray:n #1
+  { \@@_backend_select:x { gray~ \fp_eval:n {#1} } }
+\cs_new_protected:Npn \@@_backend_color_fill_rgb:nnn #1#2#3
+  {
+    \use:x
+      {
+        \@@_backend_color_fill:nnn
+          { \fp_eval:n { 100 * (#1) } }
+          { \fp_eval:n { 100 * (#2) } }
+          { \fp_eval:n { 100 * (#3) } }
+      }
+  }
+\cs_new_protected:Npn \@@_backend_color_fill:nnn #1#2#3
+  {
+    \@@_backend_scope:x
+      {
+        fill =
+         "
+           rgb
+             (
+               #1 \c_percent_str ,
+               #2 \c_percent_str ,
+               #3 \c_percent_str
+             )
+         "
+      }
+  }
+\cs_new_protected:Npn \@@_backend_color_stroke_rgb:nnn #1#2#3
+  {
+    \@@_backend_select:x
+      { rgb~ \fp_eval:n {#1} ~ \fp_eval:n {#2} ~ \fp_eval:n {#3} }
+  }
+%    \end{macrocode}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+%
+% \begin{macro}{\@@_backend_cm:nnnn}
+%   The four arguments here are floats (the affine matrix), the last
+%   two are a displacement vector. 
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_cm:nnnn #1#2#3#4
+  {
+    \@@_backend_scope:n
+      {
+       transform =
+         "
+           matrix
+             (
+               \fp_eval:n {#1} , \fp_eval:n {#2} ,
+               \fp_eval:n {#3} , \fp_eval:n {#4} ,
+               0pt , 0pt
+             )
+         "
+      }
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_backend_box_use:Nnnnn}
+%   No special savings can be made here: simply displace the box inside
+%   a scope. As there is nothing to re-box, just make the box passed of
+%   zero size.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_box_use:Nnnnn #1#2#3#4#5#6#7
+  {
+    \__kernel_backend_scope_begin:
+    \@@_backend_cm:nnnn {#2} {#3} {#4} {#5}
+    \__kernel_backend_literal_svg:n
+      {
+        < g~
+            stroke="none"~
+            transform="scale(-1,1)~translate({?x},{?y})~scale(-1,-1)"
+        >
+      }
+    \box_set_wd:Nn #1 { 0pt }
+    \box_set_ht:Nn #1 { 0pt }
+    \box_set_dp:Nn #1 { 0pt }
+    \box_use:N #1
+    \__kernel_backend_literal_svg:n { </g> }
+    \__kernel_backend_scope_end:
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+%    \begin{macrocode}
+%</dvisvgm>
+%    \end{macrocode}
+%
+%    \begin{macrocode}
+%</initex|package>
+%    \end{macrocode}
+%
+% \end{implementation}
+%
+% \PrintIndex
diff --git a/Master/texmf-dist/source/latex/l3backend/l3backend-graphics.dtx b/Master/texmf-dist/source/latex/l3backend/l3backend-graphics.dtx
new file mode 100644
index 00000000000..b146bcdae69
--- /dev/null
+++ b/Master/texmf-dist/source/latex/l3backend/l3backend-graphics.dtx
@@ -0,0 +1,612 @@
+% \iffalse meta-comment
+%
+%% File: l3backend-graphics.dtx
+%
+% Copyright (C) 2019 The LaTeX3 Project
+%
+% It may be distributed and/or modified under the conditions of the
+% LaTeX Project Public License (LPPL), either version 1.3c of this
+% license or (at your option) any later version.  The latest version
+% of this license is in the file
+%
+%    https://www.latex-project.org/lppl.txt
+%
+% This file is part of the "l3backend bundle" (The Work in LPPL)
+% and all files in that bundle must be distributed together.
+%
+% -----------------------------------------------------------------------
+%
+% The development version of the bundle can be found at
+%
+%    https://github.com/latex3/latex3
+%
+% for those people who are interested.
+%
+%<*driver>
+\documentclass[full,kernel]{l3doc}
+\begin{document}
+  \DocInput{\jobname.dtx}
+\end{document}
+%</driver>
+% \fi
+%
+% \title{^^A
+%   The \textsf{l3backend-graphics} package\\ Backend graphics support^^A
+% }
+%
+% \author{^^A
+%  The \LaTeX3 Project\thanks
+%    {^^A
+%      E-mail:
+%        \href{mailto:latex-team@latex-project.org}
+%          {latex-team@latex-project.org}^^A
+%    }^^A
+% }
+%
+% \date{Released 2019-07-01}
+%
+% \maketitle
+%
+% \begin{documentation}
+%
+% \end{documentation}
+%
+% \begin{implementation}
+%
+% \section{\pkg{l3backend-graphics} Implementation}
+%
+%    \begin{macrocode}
+%<*initex|package>
+%<@@=graphics>
+%    \end{macrocode}
+%
+% \subsection{\texttt{dvips} backend}
+%
+%    \begin{macrocode}
+%<*dvips>
+%    \end{macrocode}
+%
+% \begin{macro}{\@@_backend_getbb_eps:n}
+%   Simply use the generic function.
+%    \begin{macrocode}
+%<*initex>
+\use:n
+%</initex>
+%<*package>
+\AtBeginDocument
+%</package>
+  { \cs_new_eq:NN \@@_backend_getbb_eps:n \graphics_read_bb:n }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_backend_include_eps:n}
+%  The special syntax is relatively clear here: remember we need PostScript
+%  sizes here.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_include_eps:n #1
+  {
+    \__kernel_backend_literal:x
+      {
+        PSfile = #1 \c_space_tl
+        llx = \dim_to_decimal_in_bp:n \l_graphics_llx_dim \c_space_tl
+        lly = \dim_to_decimal_in_bp:n \l_graphics_lly_dim \c_space_tl
+        urx = \dim_to_decimal_in_bp:n \l_graphics_urx_dim \c_space_tl
+        ury = \dim_to_decimal_in_bp:n \l_graphics_ury_dim
+      }
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+%    \begin{macrocode}
+%</dvips>
+%    \end{macrocode}
+%
+% \subsection{\texttt{pdfmode} backend}
+%
+%    \begin{macrocode}
+%<*pdfmode>
+%    \end{macrocode}
+%
+% \begin{variable}{\l_@@_graphics_attr_tl}
+%   In PDF mode, additional attributes of an graphic (such as page number) are
+%   needed both to obtain the bounding box and when inserting the graphic: this
+%   occurs as the graphic dictionary approach means they are read as part of
+%   the bounding box operation. As such, it is easier to track additional
+%   attributes using a dedicated |tl| rather than build up the same data
+%   twice.
+%    \begin{macrocode}
+\tl_new:N \l_@@_graphics_attr_tl
+%    \end{macrocode}
+% \end{variable}
+%
+% \begin{macro}
+%   {
+%     \@@_backend_getbb_jpg:n,
+%     \@@_backend_getbb_pdf:n,
+%     \@@_backend_getbb_png:n
+%   }
+% \begin{macro}
+%   {\@@_backend_getbb_auxi:n, \@@_backend_getbb_auxii:n}
+%   Getting the bounding box here requires us to box up the graphic and
+%   measure it. To deal with the difference in feature support in bitmap
+%   and vector graphics but keeping the common parts, there is a little work
+%   to do in terms of auxiliaries. The key here is to notice that we need
+%   two forms of the attributes: a \enquote{short} set to allow us to
+%   track for caching, and the full form to pass to the primitive.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_getbb_jpg:n #1
+  {
+    \int_zero:N \l_graphics_page_int
+    \tl_clear:N \l_graphics_pagebox_tl
+    \tl_set:Nx \l_@@_graphics_attr_tl
+      {
+        \tl_if_empty:NF \l_graphics_decodearray_tl
+          { :D \l_graphics_decodearray_tl }
+        \bool_if:NT \l_graphics_interpolate_bool
+          { :I }
+      }
+    \tl_clear:N \l_@@_graphics_attr_tl
+    \@@_backend_getbb_auxi:n {#1}
+  }
+\cs_new_eq:NN \@@_backend_getbb_png:n \@@_backend_getbb_jpg:n
+\cs_new_protected:Npn \@@_backend_getbb_pdf:n #1
+  {
+    \tl_clear:N \l_graphics_decodearray_tl
+    \bool_set_false:N \l_graphics_interpolate_bool
+    \tl_set:Nx \l_@@_graphics_attr_tl
+      {
+        : \l_graphics_pagebox_tl
+        \int_compare:nNnT \l_graphics_page_int > 1
+          { :P \int_use:N \l_graphics_page_int }
+      }
+    \@@_backend_getbb_auxi:n {#1}
+  }
+\cs_new_protected:Npn \@@_backend_getbb_auxi:n #1
+  {
+    \graphics_bb_restore:xF { #1 \l_@@_graphics_attr_tl }
+      { \@@_backend_getbb_auxii:n {#1} }
+  }
+%    \begin{macrocode}
+%   Measuring the graphic is done by boxing up: for PDF graphics we could
+%   use |\tex_pdfximagebbox:D|, but if doesn't work for other types.
+%   As the box always starts at $(0,0)$ there is no need to worry about
+%   the lower-left position.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_getbb_auxii:n #1
+  {
+    \tex_immediate:D \tex_pdfximage:D
+      \bool_lazy_or:nnT
+        { \l_graphics_interpolate_bool }
+        { ! \tl_if_empty_p:N \l_graphics_decodearray_tl }
+        {
+          attr ~
+            {
+              \tl_if_empty:NF \l_graphics_decodearray_tl
+                { /Decode~[ \l_graphics_decodearray_tl ] }
+              \bool_if:NT \l_graphics_interpolate_bool
+                { /Interpolate~true }
+            }
+        }
+      \int_compare:nNnT \l_graphics_page_int > 0
+        { page ~ \int_use:N \l_graphics_page_int }
+      \tl_if_empty:NF \l_graphics_pagebox_tl
+        { \l_graphics_pagebox_tl }
+      {#1}
+    \hbox_set:Nn \l_@@_internal_box
+      { \tex_pdfrefximage:D \tex_pdflastximage:D }
+    \dim_set:Nn \l_graphics_urx_dim { \box_wd:N \l_@@_internal_box }
+    \dim_set:Nn \l_graphics_ury_dim { \box_ht:N \l_@@_internal_box }
+    \int_const:cn { c_@@_graphics_ #1 \l_@@_graphics_attr_tl _int }
+      { \tex_the:D \tex_pdflastximage:D }
+    \graphics_bb_save:x { #1 \l_@@_graphics_attr_tl }
+  }
+%    \end{macrocode}
+% \end{macro}
+% \end{macro}
+%
+% \begin{macro}
+%   {
+%     \@@_backend_include_jpg:n,
+%     \@@_backend_include_pdf:n,
+%     \@@_backend_include_png:n
+%   }
+%   Images are already loaded for the measurement part of the code, so
+%   inclusion is straight-forward, with only any attributes to worry about. The
+%   latter carry through from determination of the bounding box.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_include_jpg:n #1
+  {
+    \tex_pdfrefximage:D
+      \int_use:c { c_@@_graphics_ #1 \l_@@_graphics_attr_tl _int }
+  }
+\cs_new_eq:NN \@@_backend_include_pdf:n \@@_backend_include_jpg:n
+\cs_new_eq:NN \@@_backend_include_png:n \@@_backend_include_jpg:n
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_backend_getbb_eps:n}
+% \begin{macro}{\@@_backend_getbb_eps:nm}
+% \begin{macro}{\@@_backend_include_eps:n}
+% \begin{variable}
+%   {\l_@@_backend_dir_str, \l_@@_backend_name_str, \l_@@_backend_ext_str}
+%   EPS graphics may be included in \texttt{pdfmode} by conversion to
+%   PDF: this requires restricted shell escape. Modelled on the \pkg{epstopdf}
+%   \LaTeXe{} package, but simplified, conversion takes place here if we have
+%   shell access.
+%    \begin{macrocode}
+\sys_if_shell:T
+  {
+    \str_new:N \l_@@_backend_dir_str
+    \str_new:N \l_@@_backend_name_str
+    \str_new:N \l_@@_backend_ext_str
+    \cs_new_protected:Npn \@@_backend_getbb_eps:n #1
+      {
+        \file_parse_full_name:nNNN {#1}
+          \l_@@_backend_dir_str
+          \l_@@_backend_name_str
+          \l_@@_backend_ext_str
+        \exp_args:Nx \@@_backend_getbb_eps:nn
+          {
+            \l_@@_backend_name_str - \str_tail:N \l_@@_backend_ext_str
+            -converted-to.pdf
+          }
+          {#1}
+     }
+    \cs_new_protected:Npn \@@_backend_getbb_eps:nn #1#2
+      {
+        \file_compare_timestamp:nNnT {#2} > {#1}
+          {
+            \sys_shell_now:n
+              { repstopdf ~ #2 ~ #1 }
+          }
+        \tl_set:Nn \l_graphics_name_tl {#1}
+        \@@_backend_getbb_pdf:n {#1}
+      }
+    \cs_new_protected:Npn \@@_backend_include_eps:n #1
+      {
+        \file_parse_full_name:nNNN {#1}
+          \l_@@_backend_dir_str \l_@@_backend_name_str \l_@@_backend_ext_str
+        \exp_args:Nx \@@_backend_include_pdf:n
+          {
+            \l_@@_backend_name_str - \str_tail:N \l_@@_backend_ext_str
+            -converted-to.pdf
+          }
+      }
+  }
+%    \end{macrocode}
+% \end{variable}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+%
+%    \begin{macrocode}
+%</pdfmode>
+%    \end{macrocode}
+%
+% \subsection{\texttt{dvipdfmx} backend}
+%
+%    \begin{macrocode}
+%<*dvipdfmx|xdvipdfmx>
+%    \end{macrocode}
+%
+% \begin{macro}
+%   {
+%     \@@_backend_getbb_eps:n, \@@_backend_getbb_jpg:n,
+%     \@@_backend_getbb_pdf:n, \@@_backend_getbb_png:n
+%   }
+%   Simply use the generic functions: only for \texttt{dvipdfmx} in the
+%   extraction cases.
+%    \begin{macrocode}
+%<*initex>
+\use:n
+%</initex>
+%<*package>
+\AtBeginDocument
+%</package>
+  { \cs_new_eq:NN \@@_backend_getbb_eps:n \graphics_read_bb:n }
+%<*dvipdfmx>
+\cs_new_protected:Npn \@@_backend_getbb_jpg:n #1
+  {
+    \int_zero:N \l_graphics_page_int
+    \tl_clear:N \l_graphics_pagebox_tl
+    \graphics_extract_bb:n {#1}
+  }
+\cs_new_eq:NN \@@_backend_getbb_png:n \@@_backend_getbb_jpg:n
+\cs_new_protected:Npn \@@_backend_getbb_pdf:n #1
+  {
+    \tl_clear:N \l_graphics_decodearray_tl
+    \bool_set_false:N \l_graphics_interpolate_bool
+    \graphics_extract_bb:n {#1}
+  }
+%</dvipdfmx>
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{variable}{\g_@@_track_int}
+%   Used to track the object number associated with each graphic.
+%    \begin{macrocode}
+\int_new:N \g_@@_track_int
+%    \end{macrocode}
+% \end{variable}
+%
+% \begin{macro}
+%   {
+%     \@@_backend_include_eps:n, \@@_backend_include_jpg:n,
+%     \@@_backend_include_pdf:n, \@@_backend_include_png:n
+%   }
+%  \begin{macro}{\@@_backend_include_auxi:nn}
+%  \begin{macro}{\@@_backend_include_auxii:nnn, \@@_backend_include_auxii:xnn}
+%  \begin{macro}{\@@_backend_include_auxiii:nnn}
+%   The special syntax depends on the file type. There is a difference in
+%   how PDF graphics are best handled between |dvipdfmx| and |xdvipdfmx|: for
+%   the latter it is better to use the primitive route. The relevant code for
+%   that is included later in this file.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_include_eps:n #1
+  {
+    \__kernel_backend_literal:x
+      {
+        PSfile = #1 \c_space_tl
+        llx = \dim_to_decimal_in_bp:n \l_graphics_llx_dim \c_space_tl
+        lly = \dim_to_decimal_in_bp:n \l_graphics_lly_dim \c_space_tl
+        urx = \dim_to_decimal_in_bp:n \l_graphics_urx_dim \c_space_tl
+        ury = \dim_to_decimal_in_bp:n \l_graphics_ury_dim
+      }
+  }
+\cs_new_protected:Npn \@@_backend_include_jpg:n #1
+  { \@@_backend_include_auxi:nn {#1} { image } }
+\cs_new_eq:NN \@@_backend_include_png:n \@@_backend_include_jpg:n
+%<*dvipdfmx>
+\cs_new_protected:Npn \@@_backend_include_pdf:n #1
+  { \@@_backend_include_auxi:nn {#1} { epdf } }
+%</dvipdfmx>
+%    \end{macrocode}
+%   Graphic inclusion is set up to use the fact that each image is stored in
+%   the PDF as an XObject. This means that we can include repeated images
+%   only once and refer to them. To allow that, track the nature of each
+%   image: much the same as for the direct PDF mode case.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_include_auxi:nn #1#2
+  {
+    \@@_backend_include_auxii:xnn
+      {
+        \tl_if_empty:NF \l_graphics_pagebox_tl
+          { : \l_graphics_pagebox_tl }
+        \int_compare:nNnT \l_graphics_page_int > 1
+          { :P \int_use:N \l_graphics_page_int }
+        \tl_if_empty:NF \l_graphics_decodearray_tl
+          { :D \l_graphics_decodearray_tl }
+        \bool_if:NT \l_graphics_interpolate_bool
+           { :I }
+      }
+      {#1} {#2}
+  }
+\cs_new_protected:Npn \@@_backend_include_auxii:nnn #1#2#3
+  {
+    \int_if_exist:cTF { c_@@_graphics_ #2#1 _int }
+      {
+        \__kernel_backend_literal:x
+          { pdf:usexobj~@graphic \int_use:c { c_@@_graphics_ #2#1 _int } }
+      }
+      { \@@_backend_include_auxiii:nnn {#2} {#1} {#3} }
+  }
+\cs_generate_variant:Nn \@@_backend_include_auxii:nnn { x }
+%    \end{macrocode}
+%  Inclusion using the specials is relatively straight-forward, but there
+%  is one wrinkle. To get the |pagebox| correct for PDF graphics in all cases,
+%  it is necessary to provide both that information and the |bbox| argument:
+%  odd things happen otherwise!
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_include_auxiii:nnn #1#2#3
+  {
+    \int_gincr:N \g_@@_track_int
+    \int_const:cn { c_@@_graphics_ #1#2 _int } { \g_@@_track_int }
+    \__kernel_backend_literal:x
+      {
+        pdf:#3~
+        @graphic \int_use:c { c_@@_graphics_ #1#2 _int } ~
+        \int_compare:nNnT \l_graphics_page_int > 1
+          { page ~ \int_use:N \l_graphics_page_int \c_space_tl }
+        \tl_if_empty:NF \l_graphics_pagebox_tl
+          {
+            pagebox ~ \l_graphics_pagebox_tl \c_space_tl
+            bbox ~
+              \dim_to_decimal_in_bp:n \l_graphics_llx_dim \c_space_tl
+              \dim_to_decimal_in_bp:n \l_graphics_lly_dim \c_space_tl
+              \dim_to_decimal_in_bp:n \l_graphics_urx_dim \c_space_tl
+              \dim_to_decimal_in_bp:n \l_graphics_ury_dim \c_space_tl
+          }
+        (#1)
+        \bool_lazy_or:nnT
+          { \l_graphics_interpolate_bool }
+          { ! \tl_if_empty_p:N \l_graphics_decodearray_tl }
+          {
+            <<
+              \tl_if_empty:NF \l_graphics_decodearray_tl
+                { /Decode~[ \l_graphics_decodearray_tl ] }
+              \bool_if:NT \l_graphics_interpolate_bool
+                { /Interpolate~true> }
+            >>
+          }
+      }
+  }
+%    \end{macrocode}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+%
+%    \begin{macrocode}
+%</dvipdfmx|xdvipdfmx>
+%    \end{macrocode}
+%
+% \subsection{\texttt{xdvipdfmx} backend}
+%
+%    \begin{macrocode}
+%<*xdvipdfmx>
+%    \end{macrocode}
+%
+% \subsubsection{Images}
+%
+% \begin{macro}
+%   {
+%     \@@_backend_getbb_jpg:n,
+%     \@@_backend_getbb_pdf:n,
+%     \@@_backend_getbb_png:n
+%   }
+% \begin{macro}{\@@_backend_getbb_auxi:nN}
+% \begin{macro}{\@@_backend_getbb_auxii:nnN, \@@_backend_getbb_auxii:VnN}
+% \begin{macro}{\@@_backend_getbb_auxiii:nNnn}
+% \begin{macro}{\@@_backend_getbb_auxiv:nnNnn, \@@_backend_getbb_auxiv:VnNnn}
+% \begin{macro}{\@@_backend_getbb_auxv:nNnn, \@@_backend_getbb_auxv:nNnn}
+% \begin{macro}[EXP]{\@@_backend_getbb_pagebox:w}
+%   For \texttt{xdvipdfmx}, there are two primitives that allow us to obtain
+%   the bounding box without needing \texttt{extractbb}. The only complexity
+%   is passing the various minor variations to a common core process. The
+%   \XeTeX{} primitive omits the text |box| from the page box specification,
+%   so there is also some \enquote{trimming} to do here.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_getbb_jpg:n #1
+  {
+    \int_zero:N \l_graphics_page_int
+    \tl_clear:N \l_graphics_pagebox_tl
+    \@@_backend_getbb_auxi:nN {#1} \tex_XeTeXpicfile:D
+  }
+\cs_new_eq:NN \@@_backend_getbb_png:n \@@_backend_getbb_jpg:n
+\cs_new_protected:Npn \@@_backend_getbb_pdf:n #1
+  {
+    \tl_clear:N \l_graphics_decodearray_tl
+    \bool_set_false:N \l_graphics_interpolate_bool
+    \@@_backend_getbb_auxi:nN {#1} \tex_XeTeXpdffile:D
+  }
+\cs_new_protected:Npn \@@_backend_getbb_auxi:nN #1#2
+  {
+    \int_compare:nNnTF \l_graphics_page_int > 1
+      { \@@_backend_getbb_auxii:VnN \l_graphics_page_int {#1} #2  }
+      { \@@_backend_getbb_auxiii:nNnn {#1} #2 { :P 1 } { page 1 } }
+  }
+\cs_new_protected:Npn \@@_backend_getbb_auxii:nnN #1#2#3
+  { \@@_backend_getbb_auxiii:nNnn {#2} #3 { :P #1 } { page #1 } }
+\cs_generate_variant:Nn \@@_backend_getbb_auxii:nnN { V }
+\cs_new_protected:Npn \@@_backend_getbb_auxiii:nNnn #1#2#3#4
+  {
+    \tl_if_empty:NTF \l_graphics_pagebox_tl
+      { \@@_backend_getbb_auxiv:VnNnn \l_graphics_pagebox_tl }
+      { \@@_backend_getbb_auxv:nNnn }
+      {#1} #2 {#3} {#4}
+  }
+\cs_new_protected:Npn \@@_backend_getbb_auxiv:nnNnn #1#2#3#4#5
+  {
+    \use:x
+      {
+        \@@_backend_getbb_auxv:nNnn {#2} #3 { : #1 #4 }
+          { #5 ~ \@@_backend_getbb_pagebox:w #1 }
+      }
+  }
+\cs_generate_variant:Nn \@@_backend_getbb_auxiv:nnNnn { V }
+\cs_new_protected:Npn \@@_backend_getbb_auxv:nNnn #1#2#3#4
+  {
+    \graphics_bb_restore:nF {#1#3}
+      { \@@_backend_getbb_auxvi:nNnn {#1} #2 {#3} {#4} }
+  }
+\cs_new_protected:Npn \@@_backend_getbb_auxvi:nNnn #1#2#3#4
+  {
+    \hbox_set:Nn \l_@@_internal_box { #2 #1 ~ #4 }
+    \dim_set:Nn \l_graphics_urx_dim { \box_wd:N \l_@@_internal_box }
+    \dim_set:Nn \l_graphics_ury_dim { \box_ht:N \l_@@_internal_box }
+    \graphics_bb_save:n {#1#3}
+  }
+\cs_new:Npn \@@_backend_getbb_pagebox:w #1 box {#1}
+%    \end{macrocode}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+%
+% \begin{macro}{\@@_backend_include_pdf:n}
+% \begin{macro}{\@@_backend_include_bitmap_quote:w}
+%   For PDF graphics, properly supporting the |pagebox| concept in \XeTeX{}
+%   is best done using the |\tex_XeTeXpdffile:D| primitive. The syntax here
+%   is the same as for the graphic measurement part, although we know at this
+%   stage that there must be some valid setting for \cs{l_graphics_pagebox_tl}.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_include_pdf:n #1
+  {
+    \tex_XeTeXpdffile:D
+      \@@_backend_include_pdf_quote:w #1 "#1" \q_stop \c_space_tl
+      \int_compare:nNnT \l_graphics_page_int > 0
+        { page ~ \int_use:N \l_graphics_page_int \c_space_tl }
+        \exp_after:wN \@@_backend_getbb_pagebox:w \l_graphics_pagebox_tl
+  }
+\cs_new:Npn \@@_backend_include_pdf_quote:w #1 " #2 " #3 \q_stop
+  { " #2 " }
+%    \end{macrocode}
+% \end{macro}
+% \end{macro}
+%
+%    \begin{macrocode}
+%</xdvipdfmx>
+%    \end{macrocode}
+%
+% \subsection{\texttt{dvisvgm} backend}
+%
+%    \begin{macrocode}
+%<*dvisvgm>
+%    \end{macrocode}
+%
+% \begin{macro}{\@@_backend_getbb_png:n, \@@_backend_getbb_jpg:n}
+%   These can be included by extracting the bounding box data.
+%    \begin{macrocode}
+%<*initex>
+\use:n
+%</initex>
+%<*package>
+\AtBeginDocument
+%</package>
+  {
+    \cs_new_eq:NN \@@_backend_getbb_png:n \graphics_extract_bb:n
+    \cs_new_eq:NN \@@_backend_getbb_jpg:n \graphics_extract_bb:n
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_backend_include_png:n, \@@_backend_include_jpg:n}
+% \begin{macro}{\@@_backend_include_bitmap_quote:w}
+%   The backend here has built-in support for basic graphic inclusion (see
+%   \texttt{dvisvgm.def} for a more complex approach, needed if clipping,
+%   \emph{etc.}, is covered at the graphic backend level). The only issue is
+%   that |#1| must be quote-corrected. The \texttt{dvisvgm:img} operation
+%   quotes the file name, but if it is already quoted (contains spaces)
+%   then we have an issue: we simply strip off any quotes as a result.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_include_png:n #1
+  {
+     \__kernel_backend_literal:x
+       {
+         dvisvgm:img~
+         \dim_to_decimal:n { \l_graphics_ury_dim } ~
+         \dim_to_decimal:n { \l_graphics_ury_dim } ~
+         \@@_backend_include_bitmap_quote:w #1 " #1 " \q_stop
+       }
+  }
+\cs_new_eq:NN \@@_backend_include_jpg:n \@@_backend_include_png:n
+\cs_new:Npn \@@_backend_include_bitmap_quote:w #1 " #2 " #3 \q_stop
+  { " #2 " }
+%    \end{macrocode}
+% \end{macro}
+% \end{macro}
+%
+%    \begin{macrocode}
+%</dvisvgm>
+%    \end{macrocode}
+%
+%    \begin{macrocode}
+%</initex|package>
+%    \end{macrocode}
+%
+% \end{implementation}
+%
+% \PrintIndex
diff --git a/Master/texmf-dist/source/latex/l3backend/l3backend-pdf.dtx b/Master/texmf-dist/source/latex/l3backend/l3backend-pdf.dtx
new file mode 100644
index 00000000000..63e993e16ea
--- /dev/null
+++ b/Master/texmf-dist/source/latex/l3backend/l3backend-pdf.dtx
@@ -0,0 +1,2106 @@
+% \iffalse meta-comment
+%
+%% File: l3backend-pdf.dtx
+%
+% Copyright (C) 2019 The LaTeX3 Project
+%
+% It may be distributed and/or modified under the conditions of the
+% LaTeX Project Public License (LPPL), either version 1.3c of this
+% license or (at your option) any later version.  The latest version
+% of this license is in the file
+%
+%    https://www.latex-project.org/lppl.txt
+%
+% This file is part of the "l3backend bundle" (The Work in LPPL)
+% and all files in that bundle must be distributed together.
+%
+% -----------------------------------------------------------------------
+%
+% The development version of the bundle can be found at
+%
+%    https://github.com/latex3/latex3
+%
+% for those people who are interested.
+%
+%<*driver>
+\documentclass[full,kernel]{l3doc}
+\begin{document}
+  \DocInput{\jobname.dtx}
+\end{document}
+%</driver>
+% \fi
+%
+% \title{^^A
+%   The \textsf{l3backend-pdf} package\\ Backend PDF features^^A
+% }
+%
+% \author{^^A
+%  The \LaTeX3 Project\thanks
+%    {^^A
+%      E-mail:
+%        \href{mailto:latex-team@latex-project.org}
+%          {latex-team@latex-project.org}^^A
+%    }^^A
+% }
+%
+% \date{Released 2019-07-01}
+%
+% \maketitle
+%
+% \begin{documentation}
+%
+% \end{documentation}
+%
+% \begin{implementation}
+%
+% \section{\pkg{l3backend-pdf} Implementation}
+%
+%    \begin{macrocode}
+%<*initex|package>
+%<@@=pdf>
+%    \end{macrocode}
+%
+% Setting up PDF resources is a complex area with only limited documentation
+% in the engine manuals. The following code builds heavily on existing ideas
+% from \pkg{hyperref} work by Sebastian Rahtz and Heiko Oberdiek, and
+% significant contributions by Alexander Grahn, in addition to the specific
+% code referenced a various points.
+%
+% \subsection{Shared code}
+%
+% A very small number of items that belong at the backend level but which
+% are common to all backends.
+%
+% \begin{variable}{\l_@@_internal_boxf}
+%    \begin{macrocode}
+\box_new:N \l_@@_internal_box
+%    \end{macrocode}
+% \end{variable}
+%
+% \subsection{\texttt{dvips} backend}
+%
+%    \begin{macrocode}
+%<*dvips>
+%    \end{macrocode}
+%
+% \begin{macro}{\@@_backend_pdfmark:n, \@@_backend_pdfmark:x}
+%   Used often enough it should be a separate function.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_pdfmark:n #1
+  { \__kernel_backend_postscript:n { mark #1 ~ pdfmark } }
+\cs_generate_variant:Nn \@@_backend_pdfmark:n { x }
+%    \end{macrocode}
+% \end{macro}
+%
+% \subsubsection{Catalogue entries}
+%
+% \begin{macro}{\@@_backend_catalog_gput:nn, \@@_backend_info_gput:nn}
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_catalog_gput:nn #1#2
+  { \@@_backend_pdfmark:n { { Catalog } << /#1 ~ #2 >> /PUT } }
+\cs_new_protected:Npn \@@_backend_info_gput:nn #1#2
+  { \@@_backend_pdfmark:n { /#1 ~ #2 /DOCINFO } }
+%    \end{macrocode}
+% \end{macro}
+%
+% \subsubsection{Objects}
+%
+% \begin{variable}{\g_@@_backend_object_int, \g_@@_backend_object_prop}
+%   For tracking objects to allow finalisation.
+%    \begin{macrocode}
+\int_new:N \g_@@_backend_object_int
+\prop_new:N \g_@@_backend_object_prop
+%    \end{macrocode}
+% \end{variable}
+%
+% \begin{macro}{\@@_backend_object_new:nn}
+% \begin{macro}[EXP]{\@@_backend_object_ref:n}
+%   Tracking objects is similar to \texttt{dvipdfmx}.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_object_new:nn #1#2
+  {
+    \int_gincr:N \g_@@_backend_object_int
+    \int_const:cn
+      { c_@@_backend_object_ \tl_to_str:n {#1} _int }
+      { \g_@@_backend_object_int }
+    \prop_gput:Nnn \g_@@_backend_object_prop {#1} {#2}
+  }
+\cs_new:Npn \@@_backend_object_ref:n #1
+  { { pdf.obj \int_use:c { c_@@_backend_object_ \tl_to_str:n {#1} _int } } }
+%    \end{macrocode}
+% \end{macro}
+% \end{macro}
+%
+% \begin{macro}{\@@_backend_object_write:nn, \@@_backend_object_write:nx}
+% \begin{macro}
+%   {
+%     \@@_backend_object_write_array:nn ,
+%     \@@_backend_object_write_dict:nn  ,
+%     \@@_backend_object_write_stream:nn
+%   }
+% \begin{macro}{\@@_backend_object_write_stream:nnn}
+%   This is where we choose the actual type: some work to get things
+%   right.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_object_write:nn #1#2
+  {
+    \@@_backend_pdfmark:x
+      {
+        /_objdef ~ \@@_backend_object_ref:n {#1}
+        /type
+        \str_case_e:nn
+          { \prop_item:Nn \g_@@_backend_object_prop {#1} }
+          {
+            { array }   { /array }
+            { dict }    { /dict }
+            { fstream } { /stream }
+            { stream }  { /stream }
+          }
+        /OBJ
+      }
+    \use:c
+      { @@_backend_object_write_ \prop_item:Nn \g_@@_backend_object_prop {#1} :nn }
+      { \@@_backend_object_ref:n {#1} } {#2}
+  }
+\cs_generate_variant:Nn \@@_backend_object_write:nn { nx }
+\cs_new_protected:Npn \@@_backend_object_write_array:nn #1#2
+  {
+    \@@_backend_pdfmark:x
+      { #1 [ ~ \exp_not:n {#2} ~ ] ~ /PUTINTERVAL }
+  }
+\cs_new_protected:Npn \@@_backend_object_write_dict:nn #1#2
+  {
+    \@@_backend_pdfmark:x
+      { #1 << \exp_not:n {#2} >> /PUT }
+  }
+\cs_new_protected:Npn \@@_backend_object_write_stream:nn #1#2
+  {
+    \exp_args:Nx
+      \@@_backend_object_write_stream:nnn {#1} #2
+  }
+\cs_new_protected:Npn \@@_backend_object_write_stream:nnn #1#2#3
+  {
+    \@@_postscript:n
+      {
+        [nobreak]
+        mark ~ #1 ~ ( #3 ) /PUT ~ pdfmark ~
+        mark ~ #1 ~ << #2 >> /PUT ~ pdfmark
+      }
+  }
+%    \end{macrocode}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+%
+% \begin{macro}{\@@_backend_object_now:nn, \@@_backend_object_now:nx}
+%   No anonymous objects, so things are done manually.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_object_now:nn #1#2
+  {
+    \int_gincr:N \g_@@_backend_object_int
+    \@@_backend_pdfmark:x
+      {
+        /_objdef ~ { pdf.obj \int_use:N \g_@@_backend_object_int }
+        /type
+        \str_case:nn
+          {#1}
+          {
+            { array }   { /array }
+            { dict }    { /dict }
+            { fstream } { /stream }
+            { stream }  { /stream }
+          }
+        /OBJ
+      }
+    \exp_args:Nnx \use:c { @@_backend_object_write_ #1 :nn }
+      { { pdf.obj \int_use:N \g_@@_backend_object_int } } {#2}
+  }
+\cs_generate_variant:Nn \@@_backend_object_now:nn { nx }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}[EXP]{\@@_backend_object_last:}
+%   Much like the annotation version.
+%    \begin{macrocode}
+\cs_new:Npn \@@_backend_object_last:
+  { { pdf.obj \int_use:N \g_@@_backend_object_int } }
+%    \end{macrocode}
+% \end{macro}
+%
+% \subsubsection{Annotations}
+%
+% In \texttt{dvips}, annotations have to be constructed manually. As such,
+% we need the object code above for some definitions.
+%
+% \begin{macro}{pdf.globaldict}
+%   A small global dictionary for backend use.
+%    \begin{macrocode}
+\__kernel_backend_postscript_header:n
+  {
+    true ~ setglobal ~
+    /pdf.globaldict ~ 4 ~ dict ~ def ~
+    false ~ setglobal
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}
+%   {
+%     pdf.cvs     ,
+%     pdf.dvi.pt  ,
+%     pdf.pt.dvi  ,
+%     pdf.rect.ht
+%   }
+%   Small utilities for PostScript manipulations. Conversion to DVI dimensions
+%   is done here to allow for |Resolution|. The total height of a rectangle
+%   (an array) needs a little maths, in contrast to simply extracting a value.
+%    \begin{macrocode}
+\__kernel_backend_postscript_header:n
+  {
+    /pdf.cvs { 65534 ~ string ~ cvs } def
+    /pdf.dvi.pt { 72.27 ~ mul ~ Resolution ~ div } def
+    /pdf.pt.dvi { 72.27 ~ div ~ Resolution ~ mul } def
+    /pdf.rect.ht { dup ~ 1 ~ get ~ neg ~ exch ~ 3 ~ get ~ add } def
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{pdf.linkmargin, pdf.linkdp.pad, pdf.linkht.pad}
+%   Settings which are defined up-front in |SDict|.
+%    \begin{macrocode}
+\__kernel_backend_postscript_header:n
+  {
+    /pdf.linkmargin { 1 ~ pdf.pt.dvi } def
+    /pdf.linkdp.pad { 0 } def 
+    /pdf.linkht.pad { 0 } def
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}
+%   {
+%     pdf.rect        ,
+%     pdf.save.ll     ,
+%     pdf.save.ur     ,
+%     pdf.save.linkll ,
+%     pdf.save.linkur ,
+%     pdf.llx         ,
+%     pdf.lly         ,
+%     pdf.urx         ,
+%     pdf.ury
+%   }
+%   Functions for marking the limits of an annotation/link, plus drawing the
+%   border. We separate links for generic annotations to support adding a
+%   margin and setting a minimal size.
+%    \begin{macrocode}
+\__kernel_backend_postscript_header:n
+  {
+    /pdf.rect
+      { /Rect [ pdf.llx ~ pdf.lly ~ pdf.urx ~ pdf.ury ] } def
+    /pdf.save.ll
+      {
+        currentpoint
+        /pdf.lly ~ exch ~ def
+        /pdf.llx ~ exch ~ def
+      }
+        def
+    /pdf.save.ur
+      {
+        currentpoint
+        /pdf.ury ~ exch ~ def
+        /pdf.urx ~ exch ~ def
+      }
+        def
+    /pdf.save.linkll
+      {
+        currentpoint ~
+        pdf.linkmargin ~ add ~
+        pdf.linkdp.pad ~ add
+        /pdf.lly ~ exch ~ def ~
+        pdf.linkmargin ~ sub
+        /pdf.llx ~ exch ~ def
+      }
+        def
+    /pdf.save.linkur
+      {
+        currentpoint ~
+        pdf.linkmargin ~ sub ~
+        pdf.linkht.pad ~ sub
+        /pdf.ury ~ exch ~ def ~
+        pdf.linkmargin ~ add
+        /pdf.urx ~ exch ~ def
+      }
+        def
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}
+%   {
+%     pdf.dest.anchor ,
+%     pdf.dest.x      ,
+%     pdf.dest.y      ,
+%     pdf.dest.point  ,
+%     pdf.dest2device ,
+%     pdf.dev.x       ,
+%     pdf.dev.y       ,
+%     pdf.tmpa        ,
+%     pdf.tmpb        ,
+%     pdf.tmpc        ,
+%     pdf.tmpd
+%   }
+%   For finding the anchor point of a destination link. We make the use case
+%   a separate function as it comes up a lot, and as this makes it easier to
+%   adjust if we need additional effects. We also need a more complex approach
+%   to convert a co-ordinate pair correctly when defining a rectangle: this
+%   can otherwise be out when using a landscape page. (Thanks to Alexander
+%   Grahn for the approach here.)
+%    \begin{macrocode}
+\__kernel_backend_postscript_header:n
+  {
+    /pdf.dest.anchor
+      {
+        currentpoint ~ exch ~
+        pdf.dvi.pt ~ 72 ~ add ~
+        /pdf.dest.x ~ exch ~ def ~
+        pdf.dvi.pt ~
+        vsize ~ 72 ~ sub ~ exch ~ sub ~
+        /pdf.dest.y ~ exch ~ def
+      }
+        def
+    /pdf.dest.point
+      { pdf.dest.x ~ pdf.dest.y } def
+   /pdf.dest2device
+     {
+       /pdf.dest.y ~ exch ~ def
+       /pdf.dest.x ~ exch ~ def ~
+       matrix ~ currentmatrix ~
+       matrix ~ defaultmatrix ~
+       matrix ~ invertmatrix ~
+       matrix ~ concatmatrix ~
+       cvx ~ exec
+       /pdf.dev.y ~ exch ~ def
+       /pdf.dev.x ~ exch ~ def
+       /pdf.tmpd ~ exch ~ def
+       /pdf.tmpc ~ exch ~ def
+       /pdf.tmpb ~ exch ~ def
+       /pdf.tmpa ~ exch ~ def ~
+       pdf.dest.x ~ pdf.tmpa ~ mul ~
+         pdf.dest.y ~ pdf.tmpc ~ mul ~ add ~
+         pdf.dev.x ~ add ~
+       pdf.dest.x ~ pdf.tmpb ~ mul ~
+         pdf.dest.y ~ pdf.tmpd ~ mul ~ add ~
+         pdf.dev.y ~ add
+     }
+       def
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}
+%   {
+%     pdf.bordertracking          ,
+%     pdf.bordertracking.begin    ,
+%     pdf.bordertracking.end      ,
+%     pdf.leftboundary            ,
+%     pdf.rightboundary           ,
+%     pdf.brokenlink.rect         ,
+%     pdf.brokenlink.skip         ,
+%     pdf.brokenlink.dict         ,
+%     pdf.bordertracking.endpage  ,
+%     pdf.bordertracking.continue ,
+%     pdf.originx                 ,
+%     pdf.originy
+%   }
+%    To know where a breakable link can go, we need to track the boundary
+%    rectangle. That can be done by hooking into |a| and |x| operations:
+%    those names have to be retained. The boundary is stored at the end of
+%    the operation. Special effort is needed at the start and end of pages
+%    (or rather galleys), such that everything works properly.
+%    \begin{macrocode}
+\__kernel_backend_postscript_header:n
+  {
+    /pdf.bordertracking ~ false ~ def
+    /pdf.bordertracking.begin
+      {
+        SDict ~ /pdf.bordertracking ~ true ~ put ~
+        SDict ~ /pdf.leftboundary ~ undef ~
+        SDict ~ /pdf.rightboundary ~ undef ~
+        /a ~ where
+          {
+            /a
+              {
+                currentpoint ~ pop ~
+                SDict /pdf.rightboundary ~ known ~ dup
+                  {
+                    SDict /pdf.rightboundary ~ get ~ 2 ~ index ~ lt
+                      { not }
+                    if
+                  }
+                if
+                  { pop }
+                  { SDict ~ exch /pdf.rightboundary ~ exch ~ put }
+                ifelse ~
+                moveto ~
+                currentpoint ~ pop ~
+                SDict /pdf.leftboundary ~ known ~ dup
+                  {
+                    SDict /pdf.leftboundary ~ get ~ 2 ~ index ~ gt
+                      { not }
+                    if
+                  }
+                if
+                  { pop }
+                  { SDict ~ exch /pdf.leftboundary ~ exch ~ put }
+                ifelse
+              }
+            put
+          }
+        if
+      }
+        def
+    /pdf.bordertracking.end
+      {
+        /a ~ where { /a { moveto } put } if
+        /x ~ where { /x { 0 ~ exch ~ rmoveto } put } if ~
+        SDict /pdf.leftboundary ~ known
+          { pdf.outerbox ~ 0 ~ pdf.leftboundary ~ put }
+        if ~
+        SDict /pdf.rightboundary ~ known
+          { pdf.outerbox ~ 2 ~ pdf.rightboundary ~ put }
+        if ~
+        SDict /pdf.bordertracking ~ false ~ put
+      }
+        def
+  /pdf.bordertracking.endpage
+    {
+      pdf.bordertracking
+        {
+          pdf.bordertracking.end ~
+          true ~ setglobal ~
+          pdf.globaldict
+            /pdf.brokenlink.rect [ pdf.outerbox ~ aload ~ pop ] put ~
+          pdf.globaldict
+            /pdf.brokenlink.skip ~ pdf.baselineskip ~ put ~
+          pdf.globaldict
+            /pdf.brokenlink.dict ~
+              pdf.link.dict ~ pdf.cvs ~ put ~
+          false ~ setglobal ~
+          mark ~ pdf.link.dict ~ cvx ~ exec ~ /Rect
+            [
+              pdf.llx ~
+              pdf.lly ~
+              pdf.outerbox ~ 2 ~ get ~ pdf.linkmargin ~ add ~
+              currentpoint ~ exch ~ pop ~
+              pdf.outerbox ~ pdf.rect.ht ~ sub ~ pdf.linkmargin ~ sub
+            ]
+          /ANN ~ pdf.pdfmark
+        }
+      if
+    }
+      def
+    /pdf.bordertracking.continue
+      {
+        /pdf.link.dict ~ pdf.globaldict
+          /pdf.brokenlink.dict ~ get ~ def
+        /pdf.outerbox ~ pdf.globaldict
+          /pdf.brokenlink.rect ~ get ~ def
+        /pdf.baselineskip ~ pdf.globaldict
+          /pdf.brokenlink.skip ~ get ~ def ~
+        pdf.globaldict ~ dup ~ dup
+        /pdf.brokenlink.dict ~ undef
+        /pdf.brokenlink.skip ~ undef
+        /pdf.brokenlink.rect ~ undef ~
+        currentpoint
+        /pdf.originy ~ exch ~ def
+        /pdf.originx ~ exch ~ def
+        /a ~ where
+          {
+            /a
+              {
+                moveto ~
+                SDict ~
+                begin ~
+                currentpoint ~ pdf.originy ~ ne ~ exch ~
+                  pdf.originx ~ ne ~ or
+                  {
+                    pdf.save.linkll
+                    /pdf.lly ~
+                      pdf.lly ~ pdf.outerbox ~ 1 ~ get ~ sub ~ def ~
+                    pdf.bordertracking.begin
+                  }
+                if ~
+                end
+              }
+            put
+          }
+        if
+        /x ~ where
+          {
+            /x
+              {
+                0 ~ exch ~ rmoveto ~
+                SDict~
+                begin ~
+                currentpoint ~
+                pdf.originy ~ ne ~ exch ~ pdf.originx ~ ne ~ or
+                  {
+                    pdf.save.linkll
+                    /pdf.lly ~
+                      pdf.lly ~ pdf.outerbox ~ 1 ~ get ~ sub ~ def ~
+                    pdf.bordertracking.begin
+                  }
+                if ~
+                end
+              }
+            put
+          }
+        if
+      }
+        def
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}
+%   {
+%     pdf.breaklink       ,
+%     pdf.breaklink.write ,
+%     pdf.count           ,
+%     pdf.currentrect
+%   }
+%   Dealing with link breaking itself has multiple stage. The first step is to
+%   find the |Rect| entry in the dictionary, looping over key--value pairs.
+%   The first line is handled first, adjusting the rectangle to stay inside the
+%   text area. The second phase is a loop over the height of the bulk of the
+%   link area, done on the basis of a number of baselines. Finally, the end of
+%   the link area is tidied up, again from the boundary of the text area.
+%    \begin{macrocode}
+\__kernel_backend_postscript_header:n
+  {
+    /pdf.breaklink
+      {
+        pop ~
+        counttomark ~ 2 ~ mod ~ 0 ~ eq
+          {
+            counttomark /pdf.count ~ exch ~ def
+              {
+               pdf.count ~ 0 ~ eq { exit } if ~
+               counttomark ~ 2 ~ roll ~
+               1 ~ index ~ /Rect ~ eq
+                 {
+                   dup ~ 4 ~ array ~ copy ~
+                   dup ~ dup ~
+                     1 ~ get ~
+                     pdf.outerbox ~ pdf.rect.ht ~
+                     pdf.linkmargin ~ 2 ~ mul ~ add ~ sub ~
+                     3 ~ exch ~ put ~
+                   dup ~
+                     pdf.outerbox ~ 2 ~ get ~
+                     pdf.linkmargin ~ add ~ 
+                     2 ~ exch ~ put ~
+                   dup ~ dup ~
+                     3 ~ get ~
+                     pdf.outerbox ~ pdf.rect.ht ~
+                     pdf.linkmargin ~ 2 ~ mul ~ add ~ add ~
+                     1 ~ exch ~ put
+                   /pdf.currentrect ~ exch ~  def ~
+                   pdf.breaklink.write
+                     {
+                       pdf.currentrect ~
+                       dup ~
+                         pdf.outerbox ~ 0 ~ get ~
+                         pdf.linkmargin ~ sub ~
+                         0 ~ exch ~ put ~
+                       dup ~
+                         pdf.outerbox ~ 2 ~ get ~
+                         pdf.linkmargin ~ add ~
+                         2 ~ exch ~ put ~
+                       dup ~ dup ~
+                         1 ~ get ~
+                         pdf.baselineskip ~ add ~
+                         1 ~ exch ~ put ~
+                       dup ~ dup ~
+                         3 ~ get ~
+                         pdf.baselineskip ~ add ~
+                         3 ~ exch ~ put ~
+                       /pdf.currentrect ~ exch ~ def ~
+                       pdf.breaklink.write
+                      }
+                    1 ~ index ~ 3 ~ get ~
+                    pdf.linkmargin ~ 2 ~ mul ~ add ~
+                    pdf.outerbox ~ pdf.rect.ht ~ add ~
+                    2 ~ index ~ 1 ~ get ~ sub ~
+                    pdf.baselineskip ~ div ~ round ~ cvi ~ 1 ~ sub ~
+                    exch ~
+                  repeat ~
+                  pdf.currentrect ~
+                  dup ~
+                    pdf.outerbox ~ 0 ~ get ~
+                    pdf.linkmargin ~ sub ~
+                    0 ~ exch ~ put ~
+                  dup ~ dup ~
+                    1 ~ get ~
+                    pdf.baselineskip ~ add ~
+                    1 ~ exch ~ put ~
+                  dup ~ dup ~
+                    3 ~ get ~
+                    pdf.baselineskip ~ add ~
+                    3 ~ exch ~ put ~
+                  dup ~ 2 ~ index ~ 2 ~ get ~  2 ~ exch ~ put
+                  /pdf.currentrect ~ exch ~ def ~
+                  pdf.breaklink.write ~
+                  SDict /pdf.pdfmark.good ~ false ~ put ~
+                  exit
+                }
+                { pdf.count ~ 2 ~ sub /pdf.count ~ exch ~ def }
+              ifelse
+            }
+          loop
+        }
+      if
+      /ANN
+    }
+      def
+    /pdf.breaklink.write
+      {
+        counttomark ~ 1 ~ sub ~
+        index /_objdef ~ eq
+          {
+            counttomark ~ -2 ~ roll ~
+            dup ~ wcheck ~
+              {
+                readonly ~
+                counttomark ~ 2 ~ roll
+              }
+              { pop ~ pop }
+            ifelse
+          }
+        if ~
+        counttomark ~ 1 ~ add ~ copy ~
+        pop ~ pdf.currentrect
+        /ANN ~ pdfmark
+      }
+        def
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}
+%   {
+%     pdf.pdfmark      ,
+%     pdf.pdfmark.good ,
+%     pdf.outerbox     ,
+%     pdf.baselineskip ,
+%     pdf.pdfmark.dict
+%   }
+%   The business end of breaking links starts by hooking into |pdfmarks|.
+%   Unlike \pkg{hypdvips}, we avoid altering any links we have not created
+%   by using a copy of the core |pdfmarks| function. Only mark types which
+%   are known are altered. At present, this is purely |ANN| marks, which are
+%   measured relative to the size of the baseline skip. If they are
+%   more than one apparent line high, breaking is applied.
+%    \begin{macrocode}
+\__kernel_backend_postscript_header:n
+  {
+    /pdf.pdfmark
+      {
+        SDict /pdf.pdfmark.good ~ true ~ put ~
+        dup /ANN ~ eq
+          {
+            pdf.pdfmark.store ~
+            pdf.pdfmark.dict ~
+              begin ~
+                Subtype /Link ~ eq ~
+                currentdict /Rect ~ known ~ and ~
+                SDict /pdf.outerbox ~ known ~ and ~
+                SDict /pdf.baselineskip ~ known ~ and ~
+                  {
+                    Rect ~ 3 ~ get ~
+                    pdf.linkmargin ~ 2 ~ mul ~ add ~
+                    pdf.outerbox ~ pdf.rect.ht ~ add ~
+                    Rect ~ 1 ~ get ~ sub ~
+                    pdf.baselineskip ~ div ~ round ~ cvi ~ 0 ~ gt
+                      { pdf.breaklink }
+                    if
+                  }
+                if ~
+              end ~
+            SDict /pdf.outerbox ~ undef ~
+            SDict /pdf.baselineskip ~ undef ~
+            currentdict /pdf.pdfmark.dict ~ undef ~
+          }
+        if ~
+        pdf.pdfmark.good
+          { pdfmark }
+          { cleartomark }
+        ifelse
+      }
+        def
+    /pdf.pdfmark.store
+      {
+        /pdf.pdfmark.dict ~ 65534 ~ dict ~ def ~
+        counttomark ~ 1 ~ add ~ copy ~
+        pop
+          {
+            dup ~ mark ~ eq
+              {
+                pop ~
+                exit
+              }
+              {
+                pdf.pdfmark.dict ~
+                begin ~ def ~ end
+              }
+            ifelse
+          }
+        loop
+    }
+      def
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{variable}{\l_@@_backend_content_box}
+%   The content of an annotation.
+%    \begin{macrocode}
+\box_new:N \l_@@_backend_content_box
+%    \end{macrocode}
+% \end{variable}
+%
+% \begin{variable}{\l_@@_backend_model_box}
+%   For creating model sizing for links.
+%    \begin{macrocode}
+\box_new:N \l_@@_backend_model_box
+%    \end{macrocode}
+% \end{variable}
+%
+% \begin{variable}{\g_@@_backend_annotation_int}
+%   Needed as objects which are not annotations could be created.
+%    \begin{macrocode}
+\int_new:N \g_@@_backend_annotation_int
+%    \end{macrocode}
+% \end{variable}
+%
+% \begin{macro}{\@@_backend_annotation:nnnn, \@@_backend_annotation_aux:nnnn}
+% \begin{macro}{pdf.llx, pdf.lly, pdf.urx, pdf.ury}
+%   Annotations are objects, but we track them separately. Notably, they are
+%   not in the object data lists. Here, to get the co-ordinates of the
+%   annotation, we need to have the data collected at the PostScript level.
+%   That requires a bit of box trickery (effectively a \LaTeXe{} |picture|
+%   of zero size). Once the data is collected, use it to set up the annotation
+%   border. There is a split into two parts here to allow an easy way of
+%   applying the Adobe Reader fix.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_annotation:nnnn #1#2#3#4
+  {
+    \@@_backend_annotation_aux:nnnn {#1} {#2} {#3} {#4}
+    \int_gincr:N \g_@@_backend_object_int
+    \int_gset_eq:NN \g_@@_backend_annotation_int \g_@@_backend_object_int
+    \@@_backend_pdfmark:x
+      {
+      
+        /_objdef { pdf.obj \int_use:N \g_@@_backend_object_int }
+        pdf.rect ~
+        #4 ~
+        /ANN
+      }
+  }
+\cs_new_protected:Npn \@@_backend_annotation_aux:nnnn #1#2#3#4
+  {
+    \box_move_down:nn {#3}
+      { \hbox:n { \@@_postscript:n { pdf.save.ll } } }
+    \hbox:n {#4}
+    \box_move_up:nn {#2}
+      {
+        \hbox:n
+          {
+            \tex_kern:D \dim_eval:n {#1} \scan_stop:
+            \@@_postscript:n { pdf.save.ur }
+          }
+      }
+    \int_gincr:N \g_@@_backend_object_int
+    \int_gset_eq:NN \g_@@_backend_annotation_int \g_@@_backend_object_int
+    \@@_backend_pdfmark:x
+      {
+        /_objdef { pdf.obj \int_use:N \g_@@_backend_object_int }
+        pdf.rect
+        /ANN
+      }
+  }
+%    \end{macrocode}
+% \end{macro}
+% \end{macro}
+%
+% \begin{macro}[EXP]{\@@_backend_annotation_last:}
+%   Provide the last annotation we created: could get tricky of course if
+%   other packages are loaded.
+%    \begin{macrocode}
+\cs_new:Npn \@@_backend_annotation_last:
+  { { pdf.obj \int_use:N \g_@@_backend_annotation_int } }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{variable}{\g_@@_backend_link_int}
+%   To track annotations which are links.
+%    \begin{macrocode}
+\int_new:N \g_@@_backend_link_int
+%    \end{macrocode}
+% \end{variable}
+%
+% \begin{variable}{\g_@@_backend_link_dict_tl}
+%   To pass information to the end-of-link function.
+%    \begin{macrocode}
+\tl_new:N \g_@@_backend_link_dict_tl
+%    \end{macrocode}
+% \end{variable}
+%
+% \begin{variable}{\g_@@_backend_link_sf_int}
+%   Needed to save/restore space factor, which is needed to deal with the face
+%   we need a box.
+%    \begin{macrocode}
+\int_new:N \g_@@_backend_link_sf_int
+%    \end{macrocode}
+% \end{variable}
+%
+% \begin{variable}{\g_@@_backend_link_math_bool}
+%   Needed to save/restore math mode.
+%    \begin{macrocode}
+\bool_new:N \g_@@_backend_link_math_bool
+%    \end{macrocode}
+% \end{variable}
+%
+% \begin{variable}{\g_@@_backend_link_bool}
+%   Track link formation: we cannot nest at all.
+%    \begin{macrocode}
+\bool_new:N \g_@@_backend_link_bool
+%    \end{macrocode}
+% \end{variable}
+%
+% \begin{variable}{\l_@@_breaklink_pdfmark_tl}
+%   Swappable content for link breaking.
+%    \begin{macrocode}
+\tl_new:N \l_@@_breaklink_pdfmark_tl
+\tl_set:Nn \l_@@_breaklink_pdfmark_tl { pdfmark }
+%    \end{macrocode}
+% \end{variable}
+%
+% \begin{macro}{\@@_breaklink_postscript:n}
+%   To allow dropping material unless link breaking is active.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_breaklink_postscript:n #1 { }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_breaklink_usebox:N}
+%   Swappable box unpacking or use.
+%    \begin{macrocode}
+\cs_new_eq:NN \@@_breaklink_usebox:N \box_use:N
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_backend_link_begin_goto:nnw, \@@_backend_link_begin_user:nnw}
+% \begin{macro}{\@@_backend_link:nw, \@@_backend_link_aux:nw}
+% \begin{macro}{\@@_backend_link_end:, \@@_backend_link_end_aux:}
+% \begin{macro}{\@@_backend_link_minima:}
+% \begin{macro}{\@@_backend_link_outerbox:n}
+% \begin{macro}{\@@_backend_link_sf_save:, \@@_backend_link_sf_restore:}
+% \begin{macro}
+%   {
+%     pdf.linkdp.pad      ,
+%     pdf.linkht.pad      ,
+%     pdf.llx, pdf.lly ,
+%     pdf.ury, pdf.ury ,
+%     pdf.link.dict       ,
+%     pdf.outerbox        ,
+%     pdf.baselineskip
+%   }
+%   Links are crated like annotations but with dedicated code to allow for
+%   adjusting the size of the rectangle. In contrast to \pkg{hyperref}, we
+%   grab the link content as a box which can then unbox: this allows the same
+%   interface as for \pdfTeX{}.
+%
+%   Taking the idea of |evenboxes| from \pkg{hypdvips}, we implement a minimum
+%   box height and depth for link placement. This means that \enquote{underlining}
+%   with a hyperlink will generally give an even appearance. However, to ensure
+%   that the full content is always above the link border, we do not allow
+%   this to be negative (contrast \pkg{hypdvips} approach). The result should
+%   be similar to \pdfTeX{} in the vast majority of foreseeable cases.
+%
+%   The object number for a link is saved separately from the rest of the
+%   dictionary as this allows us to insert it just once, at either an
+%   unbroken link or only in the first line of a broken one. That makes the
+%   code clearer but also avoids a low-level PostScript error with the code
+%   as taken from \pkg{hypdvips}.
+%
+%   Getting the outer dimensions of the text area may be better using a two-pass
+%   approach and |\tex_savepos:D|. That plus format mode are still to re-examine.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_link_begin_goto:nnw #1#2
+  { \@@_backend_link_begin:nw { #1 /Subtype /Link /A << /S /GoTo /D ( #2 ) >> } }
+\cs_new_protected:Npn \@@_backend_link_begin_user:nnw #1#2
+  { \@@_backend_link_begin:nw {#1#2} }
+\cs_new_protected:Npn \@@_backend_link_begin:nw #1
+  {
+    \bool_if:NF \g_@@_backend_link_bool
+      { \@@_backend_link_begin_aux:nw {#1} }
+  }
+\cs_new_protected:Npn \@@_backend_link_begin_aux:nw #1
+  {
+    \bool_gset_true:N \g_@@_backend_link_bool
+    \@@_postscript:n
+      { /pdf.link.dict ( #1 ) def }
+    \tl_gset:Nn \g_@@_backend_link_dict_tl {#1}
+    \@@_backend_link_sf_save:
+    \mode_if_math:TF
+      { \bool_gset_true:N \g_@@_backend_link_math_bool }
+      { \bool_gset_false:N \g_@@_backend_link_math_bool }
+    \hbox_set:Nw \l_@@_backend_content_box
+      \@@_backend_link_sf_restore:
+      \bool_if:NT \g_@@_backend_link_math_bool
+        { \c_math_toggle_token }
+  }
+\cs_new_protected:Npn \@@_backend_link_end:
+  {
+    \bool_if:NT \g_@@_backend_link_bool
+      { \@@_backend_link_end_aux: }
+  }
+\cs_new_protected:Npn \@@_backend_link_end_aux:
+  {
+      \bool_if:NT \g_@@_backend_link_math_bool
+        { \c_math_toggle_token }
+      \@@_backend_link_sf_save:
+    \hbox_set_end:
+    \@@_backend_link_minima:
+    \hbox_set:Nn \l_@@_backend_model_box { Gg }
+    \exp_args:Nx \@@_backend_link_outerbox:n
+      {
+%<*initex>
+         \l_galley_total_left_margin_dim
+%</initex>
+%<*package>
+         \int_if_odd:nTF { \value { page } }
+           { \oddsidemargin }
+           { \evensidemargin }
+%</package>
+      }
+    \box_move_down:nn { \box_dp:N \l_@@_backend_content_box }
+      { \hbox:n { \@@_postscript:n { pdf.save.linkll } } }
+    \@@_breaklink_postscript:n { pdf.bordertracking.begin }
+    \@@_breaklink_usebox:N \l_@@_backend_content_box
+    \@@_breaklink_postscript:n { pdf.bordertracking.end }
+    \box_move_up:nn { \box_ht:N \l_@@_backend_content_box }
+      {
+        \hbox:n
+          { \@@_postscript:n { pdf.save.linkur } }
+      }
+    \int_gincr:N \g_@@_backend_object_int
+    \int_gset_eq:NN \g_@@_backend_link_int \g_@@_backend_object_int
+    \@@_postscript:x
+      {
+        mark
+        /_objdef { pdf.obj \int_use:N \g_@@_backend_link_int }
+        \g_@@_backend_link_dict_tl \c_space_tl
+        pdf.rect
+        /ANN ~ \l_@@_breaklink_pdfmark_tl
+      }
+    \@@_backend_link_sf_restore:
+    \bool_gset_false:N \g_@@_backend_link_bool
+  }
+\cs_new_protected:Npn \@@_backend_link_minima:
+  {
+    \hbox_set:Nn \l_@@_backend_model_box { Gg }
+    \@@_postscript:x
+      {
+        /pdf.linkdp.pad ~
+          \dim_to_decimal:n
+            {
+              \dim_max:nn
+                {
+                    \box_dp:N \l_@@_backend_model_box
+                  - \box_dp:N \l_@@_backend_content_box
+                }
+                { 0pt }
+            } ~
+              pdf.pt.dvi ~ def
+        /pdf.linkht.pad ~
+          \dim_to_decimal:n
+            {
+              \dim_max:nn
+                {
+                    \box_ht:N \l_@@_backend_model_box
+                  - \box_ht:N \l_@@_backend_content_box
+                }
+                { 0pt }
+            } ~
+              pdf.pt.dvi ~ def
+      }
+  }
+\cs_new_protected:Npn \@@_backend_link_outerbox:n #1
+  {
+    \@@_postscript:x
+      {
+        /pdf.outerbox
+          [
+            \dim_to_decimal:n {#1} ~
+            \dim_to_decimal:n { -\box_dp:N \l_@@_backend_model_box } ~
+%<*initex>
+            \dim_to_decimal:n { #1 + \l_galley_text_width_dim } ~
+%</initex>
+%<*package>
+            \dim_to_decimal:n { #1 + \textwidth } ~
+%</package>
+            \dim_to_decimal:n { \box_ht:N \l_@@_backend_model_box }
+          ]
+          [ exch { pdf.pt.dvi } forall ] def
+        /pdf.baselineskip ~
+          \dim_to_decimal:n { \tex_baselineskip:D } ~ dup ~ 0 ~ gt
+            { pdf.pt.dvi ~ def }
+            { pop ~ pop }
+          ifelse 
+      }
+  }
+\cs_new_protected:Npn \@@_backend_link_sf_save:
+  {
+    \int_gset:Nn \g_@@_backend_link_sf_int
+      {
+        \mode_if_horizontal:TF
+          { \tex_spacefactor:D }
+          { 0 }
+      }
+  }
+\cs_new_protected:Npn \@@_backend_link_sf_restore:
+  {
+    \mode_if_horizontal:T
+      {
+        \int_compare:nNnT \g_@@_backend_link_sf_int > { 0 }
+          { \int_set_eq:NN \tex_spacefactor:D \g_@@_backend_link_sf_int }
+      }
+  }
+%    \end{macrocode}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+%
+% \begin{macro}{\@makecol@hook}
+%   Hooks to allow link breaking: something will be needed in format mode
+%   at some stage. At present this code is disabled as there is an open
+%   question about the name of the hook: to be resolved at the \LaTeXe{}
+%   end.
+%    \begin{macrocode}
+%<*package>
+\use_none:n
+  {
+    \cs_if_exist:NT \@makecol@hook
+      {
+        \tl_put_right:Nn \@makecol@hook
+          {
+            \box_if_empty:NF \@cclv
+              {
+                \vbox_set:Nn \@cclv
+                  {
+                    \@@_postscript:n
+                      {
+                        pdf.globaldict /pdf.brokenlink.rect ~ known
+                          { pdf.bordertracking.continue }
+                        if
+                      }
+                    \vbox_unpack_drop:N \@cclv
+                    \@@_postscript:n
+                      { pdf.bordertracking.endpage }
+                  }
+              }
+          }
+        \tl_set:Nn \l_@@_breaklink_pdfmark_tl { pdf.pdfmark }
+        \cs_set_eq:NN \@@_breaklink_postscript:n \@@_postscript:n
+        \cs_set_eq:NN \@@_breaklink_usebox:N \hbox_unpack:N
+      }
+  }
+%</package>
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_backend_link_last:}
+%   The same as annotations, but with a custom integer.
+%    \begin{macrocode}
+\cs_new:Npn \@@_backend_link_last:
+  { { pdf.obj \int_use:N \g_@@_backend_link_int } }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_backend_link_margin:n}
+%   Convert to big points and pass to PostScript.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_link_margin:n #1
+  {
+    \@@_postscript:x
+      {
+        /pdf.linkmargin { \dim_to_decimal:n {#1} ~ pdf.pt.dvi } def
+      }
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_backend_destination:nn, \@@_backend_destination_rectangle:nn}
+%   Here, we need to turn the zoom into a scale. We also need to know where
+%   the current anchor point actually is: worked out in PostScript. For the
+%   rectangle version, we have a bit more PostScript: we need two points.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_destination:nn #1#2
+  {
+    \@@_postscript:n { pdf.dest.anchor }
+    \@@_backend_pdfmark:x
+      {
+        /View
+        [
+          \str_case:nnF {#2}
+            {
+              { xyz }   { /XYZ ~ pdf.dest.point ~ null }
+              { fit }   { /Fit }
+              { fitb }  { /FitB }
+              { fitbh } { /FitBH ~ pdf.dest.y }
+              { fitbv } { /FitBV ~ pdf.dest.x }
+              { fith }  { /FitH ~ pdf.dest.y }
+              { fitv }  { /FitV ~ pdf.dest.x }
+            }
+            {
+              /XYZ ~ pdf.dest.point ~ \fp_eval:n { (#2) / 100 }
+            }
+        ]
+        /Dest ( \exp_not:n {#1} ) cvn
+        /DEST
+      }
+  }
+\cs_new_protected:Npn \@@_backend_destination_rectangle:nn #1#2
+  {
+    \group_begin:
+      \hbox_set:Nn \l_@@_internal_box {#2}
+      \box_move_down:nn
+        { \box_dp:N \l_@@_internal_box }
+        { \hbox:n { \@@_postscript:n { pdf.save.ll } } }
+      \box_use:N \l_@@_internal_box
+      \box_move_up:nn
+        { \box_ht:N \l_@@_internal_box }
+        { \hbox:n { \@@_postscript:n { pdf.save.ur } } }
+      \@@_backend_pdfmark:n
+        {
+          /View
+          [
+            /FitR ~
+              pdf.llx ~ pdf.lly ~ pdf.dest2device ~
+              pdf.urx ~ pdf.ury ~ pdf.dest2device
+          ]
+          /Dest ( #1 ) cvn
+          /DEST
+        }
+    \group_end:    
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% \subsubsection{Structure}
+%
+% \begin{macro}{\@@_backend_compresslevel:n}
+% \begin{macro}{\@@_backend_compress_objects:n}
+%   These are all no-ops.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_compresslevel:n #1 { }
+\cs_new_protected:Npn \@@_backend_compress_objects:n #1 { }
+%    \end{macrocode}
+% \end{macro}
+% \end{macro}
+%
+% \begin{macro}
+%   {\@@_backend_version_major_gset:n, \@@_backend_version_minor_gset:n}
+%   Data not available!
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_version_major_gset:n #1 { }
+\cs_new_protected:Npn \@@_backend_version_minor_gset:n #1 { }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}[EXP]{\@@_backend_version_major:, \@@_backend_version_minor:}
+%   Data not available!
+%    \begin{macrocode}
+\cs_new:Npn \@@_backend_version_major: { -1 }
+\cs_new:Npn \@@_backend_version_minor: { -1 }
+%    \end{macrocode}
+% \end{macro}
+%
+% \subsubsection{Marked content}
+%
+% \begin{macro}{\@@_backend_bdc:nn}
+% \begin{macro}{\@@_backend_emc:}
+%   Simple wrappers.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_bdc:nn #1#2
+  { \@@_backend_pdfmark:n { /#1 ~ #2 /BDC } }
+\cs_new_protected:Npn \@@_backend_emc:
+  { \@@_backend_pdfmark:n { /EMC } }
+%    \end{macrocode}
+% \end{macro}
+% \end{macro}
+%
+%    \begin{macrocode}
+%</dvips>
+%    \end{macrocode}
+%
+% \subsection{\texttt{pdfmode} backend}
+%
+%    \begin{macrocode}
+%<*pdfmode>
+%    \end{macrocode}
+%
+% \subsubsection{Annotations}
+%
+% \begin{macro}{\@@_backend_annotation:nnnn}
+%   Simply pass the raw data through, just dealing with evaluation of dimensions.
+%    \begin{macrocode}
+\cs_new_protected:Npx \@@_backend_annotation:nnnn #1#2#3#4
+  {
+    \cs_if_exist:NTF \tex_pdfextension:D
+      { \tex_pdfextension:D annot ~ }
+      { \tex_pdfannot:D }
+      width  ~ \exp_not:N \dim_eval:n {#1} ~
+      height ~ \exp_not:N \dim_eval:n {#2} ~
+      depth  ~ \exp_not:N \dim_eval:n {#3} ~
+      {#4}
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}[EXP]{\@@_backend_annotation_last:}
+%   A tiny amount of extra data gets added here.
+%    \begin{macrocode}
+\cs_new:Npx \@@_backend_annotation_last:
+  {
+    \exp_not:N \int_value:w
+    \cs_if_exist:NTF \tex_pdffeedback:D
+      { \exp_not:N \tex_pdffeedback:D lastannot ~ }
+      { \exp_not:N \tex_pdflastannot:D }
+      \c_space_tl 0 ~ R
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}
+%   {\@@_backend_link_begin_goto:nnw, \@@_backend_link_begin_user:nnw}
+% \begin{macro}{\@@_backend_link_begin:nnnw}
+% \begin{macro}{\@@_backend_link_end:}
+%   Links are all created using the same internals.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_link_begin_goto:nnw #1#2
+  { \@@_backend_link_begin:nnnw {#1} { goto~name } {#2} }
+\cs_new_protected:Npn \@@_backend_link_begin_user:nnw #1#2
+  { \@@_backend_link_begin:nnnw {#1} { user } {#2} }
+\cs_new_protected:Npx \@@_backend_link_begin:nnnw #1#2#3
+  {
+    \cs_if_exist:NTF \tex_pdfextension:D
+      { \tex_pdfextension:D startlink ~ }
+      { \tex_pdfstartlink:D }
+        attr {#1}
+        #2 {#3}
+  }
+\cs_new_protected:Npx \@@_backend_link_end:
+  {
+    \cs_if_exist:NTF \tex_pdfextension:D
+      { \tex_pdfextension:D endlink \scan_stop: }
+      { \tex_pdfendlink:D }
+  }
+%    \end{macrocode}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+%
+% \begin{macro}{\@@_backend_link_last:}
+%   Formatted for direct use.
+%    \begin{macrocode}
+\cs_new:Npx \@@_backend_link_last:
+  {
+    \exp_not:N \int_value:w 
+    \cs_if_exist:NTF \tex_pdffeedback:D
+      { \exp_not:N \tex_pdffeedback:D lastlink ~ }
+      { \exp_not:N \tex_pdflastlink:D }
+      \c_space_tl 0 ~ R
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_backend_link_margin:n}
+%   A simple task: pass the data to the primitive.
+%    \begin{macrocode}
+\cs_new_protected:Npx \@@_backend_link_margin:n #1
+  {
+    \cs_if_exist:NTF \tex_pdfvariable:D
+      { \exp_not:N \tex_pdfvariable:D linkmargin }
+      { \exp_not:N \tex_pdflinkmargin:D }
+        \exp_not:N \dim_eval:n {#1} \scan_stop:
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_backend_destination:nn, \@@_backend_destination_rectangle:nn}
+%   A simple task: pass the data to the primitive. The |\scan_stop:| deals
+%   with the danger of an unterminated keyword. The zoom given here is a
+%   percentage, but we need to pass it as \emph{per mille}. The rectangle
+%   version is also easy as everything is build in.
+%    \begin{macrocode}
+\cs_new_protected:Npx \@@_backend_destination:nn #1#2
+  {
+    \cs_if_exist:NTF \tex_pdfextension:D
+      { \exp_not:N \tex_pdfextension:D dest ~ }
+      { \exp_not:N \tex_pdfdest:D }
+        name {#1}
+        \exp_not:N \str_case:nnF {#2}
+          {
+            { xyz }   { xyz }
+            { fit }   { fit }
+            { fitb }  { fitb }
+            { fitbh } { fitbh }
+            { fitbv } { fitbv }
+            { fith }  { fith }
+            { fitv }  { fitv }
+          }
+          { xyz ~ zoom \exp_not:N \fp_eval:n { #2 * 10 } }
+        \scan_stop:
+  }
+\cs_new_protected:Npx \@@_backend_destination_rectangle:nn #1#2
+  {
+    \group_begin:
+      \hbox_set:Nn \l_@@_internal_box {#2}
+     \cs_if_exist:NTF \tex_pdfextension:D
+      { \exp_not:N \tex_pdfextension:D dest ~ }
+      { \exp_not:N \tex_pdfdest:D }  
+      name {#1}
+      fitr ~
+        width  \exp_not:N \box_wd:N \l_@@_internal_box
+        height \exp_not:N \box_ht:N \l_@@_internal_box
+        depth  \exp_not:N \box_dp:N \l_@@_internal_box 
+      \box_use:N \l_@@_internal_box
+    \group_end:    
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% \subsubsection{Catalogue entries}
+%
+% \begin{macro}{\@@_backend_catalog_gput:nn, \@@_backend_info_gput:nn}
+%    \begin{macrocode}
+\cs_new_protected:Npx \@@_backend_catalog_gput:nn #1#2
+  {
+    \cs_if_exist:NTF \tex_pdfextension:D
+      { \tex_pdfextension:D catalog }
+      { \tex_pdfcatalog:D }
+        { / #1 ~ #2 }
+  }
+\cs_new_protected:Npx \@@_backend_info_gput:nn #1#2
+  {
+    \cs_if_exist:NTF \tex_pdfextension:D
+      { \tex_pdfextension:D info }
+      { \tex_pdfinfo:D }
+        { / #1 ~ #2 }
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% \subsubsection{Objects}
+%
+% \begin{variable}{\g_@@_backend_object_prop}
+%   For tracking objects to allow finalisation.
+%    \begin{macrocode}
+\prop_new:N \g_@@_backend_object_prop
+%    \end{macrocode}
+% \end{variable}
+%
+% \begin{macro}{\@@_backend_object_new:nn}
+% \begin{macro}[EXP]{\@@_backend_object_ref:n}
+%   Declaring objects means reserving at the PDF level plus starting
+%   tracking.
+%    \begin{macrocode}
+\group_begin:
+  \cs_set_protected:Npn \@@_tmp:w #1#2
+    {
+      \cs_new_protected:Npx \@@_backend_object_new:nn ##1##2
+        {
+          #1 reserveobjnum ~
+          \int_const:cn
+            { c_@@_backend_object_ \exp_not:N \tl_to_str:n {##1} _int }
+            {#2}
+          \prop_gput:Nnn \exp_not:N \g_@@_backend_object_prop {##1} {##2}
+        }
+    }
+  \cs_if_exist:NTF \tex_pdfextension:D
+    {
+      \@@_tmp:w
+        { \tex_pdfextension:D obj ~ }
+        { \exp_not:N \tex_pdffeedback:D lastobj }
+    }
+    { \@@_tmp:w { \tex_pdfobj:D } { \tex_pdflastobj:D } }
+\group_end:
+\cs_new:Npn \@@_backend_object_ref:n #1
+  { \int_use:c { c_@@_backend_object_ \tl_to_str:n {#1} _int } ~ 0 ~ R }
+%    \end{macrocode}
+% \end{macro}
+% \end{macro}
+%
+% \begin{macro}{\@@_backend_object_write:nn,\@@_backend_object_write:nx}
+% \begin{macro}[EXP]{\@@_exp_not_i:nn, \@@_exp_not_ii:nn}
+%   Writing the data needs a little information about the structure of the
+%   object.
+%    \begin{macrocode}
+\group_begin:
+  \cs_set_protected:Npn \@@_tmp:w #1
+    {
+      \cs_new_protected:Npn \@@_backend_object_write:nn ##1##2
+        {
+          \tex_immediate:D #1 useobjnum ~
+          \int_use:c
+            { c_@@_backend_object_ \tl_to_str:n {##1} _int }
+            \str_case_e:nn
+              { \prop_item:Nn \g_@@_backend_object_prop {##1} }
+              {
+                { array } { { [ ~ \exp_not:n {##2} ~ ] } }
+                { dict }  { { << ~ \exp_not:n {##2} ~ >> } }
+                { fstream }
+                  {
+                    stream ~ attr ~ { \@@_exp_not_i:nn ##2 } ~
+                      file ~ { \@@_exp_not_ii:nn ##2 }
+                  }
+                { stream }
+                  {
+                    stream ~ attr ~ { \@@_exp_not_i:nn ##2 } ~ 
+                      { \@@_exp_not_ii:nn ##2 }
+                  }
+              }
+        }
+    }
+  \cs_if_exist:NTF \tex_pdfextension:D
+    { \@@_tmp:w { \tex_pdfextension:D obj ~ } }
+    { \@@_tmp:w { \tex_pdfobj:D } }
+\group_end:
+\cs_generate_variant:Nn \@@_backend_object_write:nn { nx }
+\cs_new:Npn \@@_exp_not_i:nn #1#2 { \exp_not:n {#1} }
+\cs_new:Npn \@@_exp_not_ii:nn #1#2 { \exp_not:n {#2} }
+%    \end{macrocode}
+% \end{macro}
+% \end{macro}
+%
+% \begin{macro}{\@@_backend_object_now:nn, \@@_backend_object_now:nx}
+%   Much like writing, but direct creation.
+%    \begin{macrocode}
+\group_begin:
+  \cs_set_protected:Npn \@@_tmp:w #1
+    {
+      \cs_new_protected:Npn \@@_backend_object_now:nn ##1##2
+        {
+          \tex_immediate:D #1
+            \str_case:nn
+              {##1}
+              {
+                { array } { { [ ~ \exp_not:n {##2} ~ ] } }
+                { dict }  { { << ~ \exp_not:n {##2} ~ >> } }
+                { fstream }
+                  {
+                    stream ~ attr ~ { \@@_exp_not_i:nn ##2 } ~
+                      file ~ { \@@_exp_not_ii:nn ##2 }
+                  }
+                { stream }
+                  {
+                    stream ~ attr ~ { \@@_exp_not_i:nn ##2 } ~ 
+                      { \@@_exp_not_ii:nn ##2 }
+                  }
+              }
+        }
+    }
+  \cs_if_exist:NTF \tex_pdfextension:D
+    { \@@_tmp:w { \tex_pdfextension:D obj ~ } }
+    { \@@_tmp:w { \tex_pdfobj:D } }
+\group_end:
+\cs_generate_variant:Nn \@@_backend_object_now:nn { nx }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}[EXP]{\@@_backend_object_last:}
+%   Much like annotation.
+%    \begin{macrocode}
+\cs_new:Npx \@@_backend_object_last:
+  {
+    \exp_not:N \int_value:w
+    \cs_if_exist:NTF \tex_pdffeedback:D
+      { \exp_not:N \tex_pdffeedback:D lastobj ~ }
+      { \exp_not:N \tex_pdflastobj:D }
+      \c_space_tl 0 ~ R
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% \subsubsection{Structure}
+%
+% \begin{macro}{\@@_backend_compresslevel:n}
+% \begin{macro}{\@@_backend_compress_objects:n}
+% \begin{macro}{\@@_backend_objcompresslevel:n}
+%   Simply pass data to the engine.
+%    \begin{macrocode}
+\cs_new_protected:Npx \@@_backend_compresslevel:n #1
+  {
+    \exp_not:N \tex_global:D
+    \cs_if_exist:NTF \tex_pdfcompresslevel:D
+      { \tex_pdfcompresslevel:D }
+      { \tex_pdfvariable:D compresslevel }
+      \exp_not:N \int_value:w \exp_not:N \int_eval:n {#1} \scan_stop:
+  }
+\cs_new_protected:Npn \@@_backend_compress_objects:n #1
+  {
+    \bool_if:nTF {#1}
+      { \@@_backend_objcompresslevel:n { 2 } }
+      { \@@_backend_objcompresslevel:n { 0 } }
+  }
+\cs_new_protected:Npx \@@_backend_objcompresslevel:n #1
+  {
+    \exp_not:N \tex_global:D
+    \cs_if_exist:NTF \tex_pdfobjcompresslevel:D
+      { \tex_pdfobjcompresslevel:D }
+      { \tex_pdfvariable:D objcompresslevel }
+      #1 \scan_stop:
+  }
+%    \end{macrocode}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+%
+% \begin{macro}
+%   {\@@_backend_version_major_gset:n, \@@_backend_version_minor_gset:n}
+%   At present, we don't have a primitive for the major version in \pdfTeX{},
+%   but we anticipate one \ldots
+%    \begin{macrocode}
+\cs_new_protected:Npx \@@_backend_version_major_gset:n #1
+  {
+    \cs_if_exist:NTF \tex_pdfvariable:D
+      {
+        \int_compare:nNnT \tex_luatexversion:D > { 106 }
+          {
+            \exp_not:N \tex_global:D \tex_pdfvariable:D majorversion
+              \exp_not:N \int_eval:n {#1} \scan_stop:
+          }
+      }
+      {
+        \cs_if_exist:NT \tex_pdfmajorversion:D
+          {
+            \exp_not:N \tex_global:D \tex_pdfmajorversion:D
+              \exp_not:N \int_eval:n {#1} \scan_stop:
+          }
+      }
+  }
+\cs_new_protected:Npx \@@_backend_version_minor_gset:n #1
+  {
+    \exp_not:N \tex_global:D
+    \cs_if_exist:NTF \tex_pdfminorversion:D
+      { \exp_not:N \tex_pdfminorversion:D }
+      { \tex_pdfvariable:D minorversion }
+        \exp_not:N \int_eval:n {#1} \scan_stop:
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}[EXP]{\@@_backend_version_major:, \@@_backend_version_minor:}
+%   At present, we don't have a primitive for the major version!
+%    \begin{macrocode}
+\cs_new:Npx \@@_backend_version_major:
+  {
+    \cs_if_exist:NTF \tex_pdfvariable:D
+      {
+        \int_compare:nNnTF \tex_luatexversion:D > { 106 }
+          { \exp_not:N \tex_the:D \tex_pdfvariable:D majorversion }
+          { 1 }
+      }
+      {
+        \cs_if_exist:NTF \tex_pdfmajorversion:D
+          { \exp_not:N \tex_the:D \tex_pdfmajorversion:D }
+          { 1 }
+      }
+  }
+\cs_new:Npx \@@_backend_version_minor:
+  {
+    \exp_not:N \tex_the:D
+    \cs_if_exist:NTF \tex_pdfminorversion:D
+      { \exp_not:N \tex_pdfminorversion:D }
+      { \tex_pdfvariable:D minorversion }
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% \subsubsection{Marked content}
+%
+% \begin{macro}{\@@_backend_bdc:nn}
+% \begin{macro}{\@@_backend_emc:}
+%   Simple wrappers. May need refinement: see
+%   \url{https://chat.stackexchange.com/transcript/message/49970158#49970158}.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_bdc:nn #1#2
+  { \__kernel_backend_literal_page:n { /#1 ~ #2 ~ BDC } }
+\cs_new_protected:Npn \@@_backend_emc:
+  { \__kernel_backend_literal_page:n { EMC } }
+%    \end{macrocode}
+% \end{macro}
+% \end{macro}
+%
+%    \begin{macrocode}
+%</pdfmode>
+%    \end{macrocode}
+%
+% \subsection{\texttt{dvipdfmx} backend}
+%
+%    \begin{macrocode}
+%<*dvipdfmx|xdvipdfmx>
+%    \end{macrocode}
+%
+% \begin{macro}{\@@_backend:n, \@@_backend:x}
+%   A generic function for the backend PDF specials: used where we can.
+%    \begin{macrocode}
+\cs_new_protected:Npx \@@_backend:n #1
+  { \__kernel_backend_literal:n { pdf: #1 } }
+\cs_generate_variant:Nn \@@_backend:n { x }
+%    \end{macrocode}
+% \end{macro}
+%
+% \subsubsection{Catalogue entries}
+%
+% \begin{macro}{\@@_backend_catalog_gput:nn, \@@_backend_info_gput:nn}
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_catalog_gput:nn #1#2
+  { \@@_backend:n { put ~ @catalog << /#1 ~ #2 >> } }
+\cs_new_protected:Npn \@@_backend_info_gput:nn #1#2
+  { \@@_backend:n { docinfo << /#1 ~ #2 >> } }
+%    \end{macrocode}
+% \end{macro}
+%
+% \subsubsection{Objects}
+%
+% \begin{variable}{\g_@@_backend_object_int, \g_@@_backend_object_prop}
+%   For tracking objects to allow finalisation.
+%    \begin{macrocode}
+\int_new:N \g_@@_backend_object_int
+\prop_new:N \g_@@_backend_object_prop
+%    \end{macrocode}
+% \end{variable}
+%
+% \begin{macro}{\@@_backend_object_new:nn}
+% \begin{macro}[EXP]{\@@_backend_object_ref:n}
+%   Objects are tracked at the macro level, but we don't have to do anything
+%   at this stage.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_object_new:nn #1#2
+  {
+    \int_gincr:N \g_@@_backend_object_int
+    \int_const:cn
+      { c_@@_backend_object_ \tl_to_str:n {#1} _int }
+      { \g_@@_backend_object_int }
+    \prop_gput:Nnn \g_@@_backend_object_prop {#1} {#2}
+  }
+\cs_new:Npn \@@_backend_object_ref:n #1
+  { @pdf.obj \int_use:c { g_@@_backend_object_ \tl_to_str:n {#1} _int } }
+%    \end{macrocode}
+% \end{macro}
+% \end{macro}
+%
+% \begin{macro}{\@@_backend_object_write:nn, \@@_backend_object_write:nx}
+% \begin{macro}{\@@_backend_object_write:nnn}
+% \begin{macro}
+%   {
+%     \@@_backend_object_write_array:nn   ,
+%     \@@_backend_object_write_dict:nn    ,
+%     \@@_backend_object_write_fstream:nn ,
+%     \@@_backend_object_write_stream:nn
+%   }
+% \begin{macro}{\@@_backend_object_write_stream:nnnn}
+%   This is where we choose the actual type.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_object_write:nn #1#2
+  {
+    \exp_args:Nx \@@_backend_object_write:nnn
+      { \prop_item:Nn \g_@@_backend_object_prop {#1} } {#1} {#2}
+  }
+\cs_generate_variant:Nn \@@_backend_object_write:nn { nx }
+\cs_new_protected:Npn \@@_backend_object_write:nnn #1#2#3
+  {
+    \use:c { @@_backend_object_write_ #1 :nn }
+      { \@@_backend_object_ref:n {#2} } {#3}
+  }
+\cs_new_protected:Npn \@@_backend_object_write_array:nn #1#2
+  {
+    \@@_backend:x
+      { obj ~ #1 ~ [ ~ \exp_not:n {#2} ~ ] }
+  }
+\cs_new_protected:Npn \@@_backend_object_write_dict:nn #1#2
+  {
+    \@@_backend:x
+      { obj ~ #1 ~ << ~ \exp_not:n {#2} ~ >> }
+  }
+\cs_new_protected:Npn \@@_backend_object_write_fstream:nn #1#2
+  { \@@_backend_object_write_stream:nnnn { f } {#1} #2 }
+\cs_new_protected:Npn \@@_backend_object_write_stream:nn #1#2
+  { \@@_backend_object_write_stream:nnnn { } {#1} #2 }
+\cs_new_protected:Npn \@@_backend_object_write_stream:nnnn #1#2#3#4
+  {
+    \@@_backend:x
+      {
+        #1 stream ~ #2 ~
+          ( \exp_not:n {#4} ) ~ << \exp_not:n {#3} >>
+      }
+  }
+%    \end{macrocode}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+%
+% \begin{macro}{\@@_backend_object_now:nn, \@@_backend_object_now:nx}
+%   No anonymous objects with \texttt{dvipdfmx} so we have to give an
+%   object name.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_object_now:nn #1#2
+  {
+    \int_gincr:N \g_@@_backend_object_int
+    \exp_args:Nnx \use:c { @@_backend_object_write_ #1 :nn }
+      { @pdf.obj \int_use:N \g_@@_backend_object_int }
+      {#2}
+  }
+\cs_generate_variant:Nn \@@_backend_object_now:nn { nx }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_backend_object_last:}
+%    \begin{macrocode}
+\cs_new:Npn \@@_backend_object_last:
+ { @pdf.obj \int_use:N \g_@@_backend_object_int }
+%    \end{macrocode}
+% \end{macro}
+%
+% \subsubsection{Annotations}
+%
+% \begin{variable}{\g_@@_landscape_bool}
+%   There is a bug in \texttt{(x)dvipdfmx} which means annotations do
+%   not rotate. As such, we need to know if landscape is active.
+%    \begin{macrocode}
+\bool_new:N \g_@@_landscape_bool
+%<*package>
+\AtBeginDocument
+  {
+    \cs_if_exist:NT \landscape
+      {
+        \tl_put_right:Nn \landscape
+          { \bool_gset_true:N \g_@@_landscape_bool }
+        \tl_put_left:Nn \endlandscape
+          { \bool_gset_false:N \g_@@_landscape_bool }
+      }
+  }
+%</package>
+%    \end{macrocode}
+% \end{variable}
+%
+% \begin{variable}{\g_@@_backend_annotation_int}
+%   Needed as objects which are not annotations could be created.
+%    \begin{macrocode}
+\int_new:N \g_@@_backend_annotation_int
+%    \end{macrocode}
+% \end{variable}
+%
+% \begin{macro}{\@@_backend_annotation:nnnn, \@@_backend_annotation_aux:nnnn}
+%   Simply pass the raw data through, just dealing with evaluation of dimensions.
+%   The only wrinkle is landscape: we have to adjust by hand.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_annotation:nnnn #1#2#3#4
+  {
+    \bool_if:NTF \g_@@_landscape_bool
+      {
+         \box_move_up:nn {#2}
+           {
+             \vbox:n
+               {
+                 \@@_backend_annotation_aux:nnnn
+                   { #2 + #3 } {#1} { 0pt } {#4}
+               }
+           }
+      }
+      { \@@_backend_annotation_aux:nnnn {#1} {#2} {#3} {#4} }
+  }
+\cs_new_protected:Npn \@@_backend_annotation_aux:nnnn #1#2#3#4
+  {
+    \int_gincr:N \g_@@_backend_object_int
+    \int_gset_eq:NN \g_@@_backend_annotation_int \g_@@_backend_object_int
+    \@@_backend:x
+      {
+        ann ~ @pdf.obj \int_use:N \g_@@_backend_object_int \c_space_tl
+        width  ~ \dim_eval:n {#1} ~
+        height ~ \dim_eval:n {#2} ~
+        depth  ~ \dim_eval:n {#3} ~
+        << #4 >>
+      }
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_backend_annotation_last:}
+%    \begin{macrocode}
+\cs_new:Npn \@@_backend_annotation_last:
+ { @pdf.obj \int_use:N \g_@@_backend_annotation_int }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}
+%   {\@@_backend_link_begin_goto:nnw, \@@_backend_link_begin_user:nnw}
+% \begin{macro}{\@@_backend_link_begin:n}
+% \begin{macro}{\@@_backend_link_end:}
+%   All created using the same internals.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_link_begin_goto:nnw #1#2
+  { \@@_backend_link_begin:n { #1 /Subtype /Link /A << /S /GoTo /D ( #2 ) >> } }
+\cs_new_protected:Npn \@@_backend_link_begin_user:nnw #1#2
+  { \@@_backend_link_begin:n {#1#2} }
+\cs_new_protected:Npn \@@_backend_link_begin:n #1
+  {
+    \@@_backend:n
+      {
+         bann
+         <<
+           /Type /Annot
+           #1
+         >>
+      }
+  }
+\cs_new_protected:Npn \@@_backend_link_end:
+  { \@@_backend:n { eann } }
+%    \end{macrocode}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+%
+% \begin{macro}{\@@_backend_link_last:}
+%   Data not available.
+%    \begin{macrocode}
+\cs_new:Npn \@@_backend_link_last: { }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_backend_link_margin:n}
+%   Pass to \texttt{dvipdfmx}.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_link_margin:n #1
+  { \__kernel_backend_literal:x { dvipdfmx:config~g~ \dim_eval:n {#1} } }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_backend_destination:nn, \@@_backend_destination_rectangle:nn}
+%   Here, we need to turn the zoom into a scale. The method for \texttt{FitR}
+%   is from Alexander Grahn: the idea is to avoid needing to do any calculations
+%   in \TeX{} by using the backend data for \texttt{@xpos} and \texttt{@ypos}.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_destination:nn #1#2
+  {
+    \@@_backend:x
+      {
+        dest ~ ( \exp_not:n {#1} )
+        [
+          @thispage
+          \str_case:nnF {#2}
+            {
+              { xyz }   { /XYZ ~ @xpos ~ @ypos ~ null }
+              { fit }   { /Fit }
+              { fitb }  { /FitB }
+              { fitbh } { /FitBH }
+              { fitbv } { /FitBV ~ @xpos }
+              { fith }  { /FitH ~ @ypos }
+              { fitv }  { /FitV ~ @xpos }
+            }
+            { /XYZ ~ @xpos ~ @ypos ~ \fp_eval:n { (#2) / 100 } }
+        ]
+      }
+  }
+\cs_new_protected:Npn \@@_backend_destination_rectangle:nn #1#2
+  {
+    \group_begin:
+      \hbox_set:Nn \l_@@_internal_box {#2}
+      \box_move_down:nn { \box_dp:N \l_@@_internal_box }
+        {
+          \hbox:n
+            {
+              \@@_backend:n { obj ~ @pdf_ #1 _llx ~ @xpos }
+              \@@_backend:n { obj ~ @pdf_ #1 _lly ~ @ypos }
+            }
+        }
+      \box_use:N \l_@@_internal_box
+      \box_move_up:nn { \box_ht:N \l_@@_internal_box }
+        {
+          \hbox:n
+            {
+              \@@_backend:n
+                {
+                  dest ~ (#1)
+                  [
+                    @thispage
+                    /FitR ~
+                      @pdf_ #1 _llx ~ @pdf_ #1 _lly ~
+                      @xpos ~ @ypos
+                  ]
+                }
+            }
+        }
+    \group_end:    
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% \subsubsection{Structure}
+%
+% \begin{macro}{\@@_backend_compresslevel:n}
+% \begin{macro}{\@@_backend_compress_objects:n}
+%   Pass data to the backend: these are a one-shot.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_compresslevel:n #1
+  { \__kernel_backend_literal:x { dvipdfmx:config~z~ \int_eval:n {#1} } }
+\cs_new_protected:Npn \@@_backend_compress_objects:n #1
+  {
+    \bool_if:nF {#1}
+      { \__kernel_backend_literal:n { dvipdfmx:config~C~0x40 } }
+  }
+%    \end{macrocode}
+% \end{macro}
+% \end{macro}
+%
+% \begin{macro}
+%   {\@@_backend_version_major_gset:n, \@@_backend_version_minor_gset:n}
+%   We start with the assumption that the default is active.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_version_major:n #1
+  {
+    \cs_gset:Npx \@@_backend_version_major: { \int_eval:n {#1} }
+    \__kernel_backend_literal:x { pdf:majorversion \@@_backend_version_major: }
+  }
+\cs_new_protected:Npn \@@_backend_version_minor:n #1
+  {
+    \cs_gset:Npx \@@_backend_version_minor: { \int_eval:n {#1} }
+    \__kernel_backend_literal:x { pdf:minorversion \@@_backend_version_minor: }
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}[EXP]{\@@_backend_version_major:, \@@_backend_version_minor:}
+%   We start with the assumption that the default is active.
+%    \begin{macrocode}
+\cs_new:Npn \@@_backend_version_major: { 1 }
+\cs_new:Npn \@@_backend_version_minor: { 5 }
+%    \end{macrocode}
+% \end{macro}
+%
+% \subsubsection{Marked content}
+%
+% \begin{macro}{\@@_backend_bdc:nn}
+% \begin{macro}{\@@_backend_emc:}
+%   Simple wrappers. May need refinement: see
+%   \url{https://chat.stackexchange.com/transcript/message/49970158#49970158}.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_bdc:nn #1#2
+  { \__kernel_backend_literal_page:n { /#1 ~ #2 ~ BDC } }
+\cs_new_protected:Npn \@@_backend_emc:
+  { \__kernel_backend_literal_page:n { EMC } }
+%    \end{macrocode}
+% \end{macro}
+% \end{macro}
+%
+%    \begin{macrocode}
+%</dvipdfmx|xdvipdfmx>
+%    \end{macrocode}
+%
+% \subsection{\texttt{dvisvgm} backend}
+%
+%    \begin{macrocode}
+%<*dvisvgm>
+%    \end{macrocode}
+%
+% \subsubsection{Catalogue entries}
+%
+% \begin{macro}{\@@_backend_catalog_gput:nn, \@@_backend_info_gput:nn}
+%   No-op.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_catalog_gput:nn #1#2 { }
+\cs_new_protected:Npn \@@_backend_info_gput:nn #1#2 { }
+%    \end{macrocode}
+% \end{macro}
+%
+% \subsubsection{Objects}
+%
+% \begin{macro}{\@@_backend_object_new:nn}
+% \begin{macro}[EXP]{\@@_backend_object_ref:n}
+% \begin{macro}{\@@_backend_object_write:nn, , \@@_backend_object_write:nx}
+% \begin{macro}{\@@_backend_object_now:nn, , \@@_backend_object_now:nx}
+% \begin{macro}{\@@_backend_object_last:}
+%   All no-ops here.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_object_new:nn #1#2 { }
+\cs_new:Npn \@@_backend_object_ref:n #1 { }
+\cs_new_protected:Npn \@@_backend_object_write:nn #1#2 { }
+\cs_new_protected:Npn \@@_backend_object_write:nx #1#2 { }
+\cs_new_protected:Npn \@@_backend_object_now:nn #1#2 { }
+\cs_new_protected:Npn \@@_backend_object_now:nx #1#2 { }
+\cs_new:Npn \@@_backend_object_last: { }
+%    \end{macrocode}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+%
+% \subsubsection{Structure}
+%
+% \begin{macro}{\@@_backend_compresslevel:n}
+% \begin{macro}{\@@_backend_compress_objects:n}
+%   These are all no-ops.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_compresslevel:n #1 { }
+\cs_new_protected:Npn \@@_backend_compress_objects:n #1 { }
+%    \end{macrocode}
+% \end{macro}
+% \end{macro}
+%
+% \begin{macro}
+%   {\@@_backend_version_major_gset:n, \@@_backend_version_minor_gset:n}
+%   Data not available!
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_version_major_gset:n #1 { }
+\cs_new_protected:Npn \@@_backend_version_minor_gset:n #1 { }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}[EXP]{\@@_backend_version_major:, \@@_backend_version_minor:}
+%   Data not available!
+%    \begin{macrocode}
+\cs_new:Npn \@@_backend_version_major: { -1 }
+\cs_new:Npn \@@_backend_version_minor: { -1 }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\@@_backend_bdc:nn}
+% \begin{macro}{\@@_backend_emc:}
+%   More no-ops.
+%    \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_bdc:nn #1#2 { }
+\cs_new_protected:Npn \@@_backend_emc: { }
+%    \end{macrocode}
+% \end{macro}
+% \end{macro}
+%
+%    \begin{macrocode}
+%</dvisvgm>
+%    \end{macrocode}
+%
+%    \begin{macrocode}
+%</initex|package>
+%    \end{macrocode}
+%
+% \end{implementation}
+%
+% \PrintIndex
diff --git a/Master/texmf-dist/source/latex/l3backend/l3backend.ins b/Master/texmf-dist/source/latex/l3backend/l3backend.ins
new file mode 100644
index 00000000000..149f08b9ee8
--- /dev/null
+++ b/Master/texmf-dist/source/latex/l3backend/l3backend.ins
@@ -0,0 +1,118 @@
+\iffalse meta-comment
+
+File l3backend.ins
+
+Copyright (C) 2019 The LaTeX3 Project
+
+It may be distributed and/or modified under the conditions of the
+LaTeX Project Public License (LPPL), either version 1.3c of this
+license or (at your option) any later version.  The latest version
+of this license is in the file
+
+   https://www.latex-project.org/lppl.txt
+
+This file is part of the "l3backend bundle" (The Work in LPPL)
+and all files in that bundle must be distributed together.
+
+-----------------------------------------------------------------------
+
+The development version of the bundle can be found at
+
+   https://github.com/latex3/latex3
+
+for those people who are interested.
+
+-----------------------------------------------------------------------
+
+Any modification of this file should ensure that the copyright and
+license information is placed in the derived files.
+
+\fi
+
+\let\jobname\relax
+\input l3docstrip.dtx
+\askforoverwritefalse
+
+\preamble
+
+Copyright (C) 1990-2019 The LaTeX3 Project
+
+It may be distributed and/or modified under the conditions of
+the LaTeX Project Public License (LPPL), either version 1.3c of
+this license or (at your option) any later version.  The latest
+version of this license is in the file:
+
+   https://www.latex-project.org/lppl.txt
+
+This file is part of the "l3backend bundle" (The Work in LPPL)
+and all files in that bundle must be distributed together.
+
+\endpreamble
+% stop docstrip adding \endinput
+\postamble
+\endpostamble
+
+\keepsilent
+
+\generate
+  {
+    \file{l3backend-dvipdfmx.def}
+      {
+        \from{l3backend-basics.dtx}  {package,dvipdfmx}
+        \from{l3backend-color.dtx}   {package,dvipdfmx}
+        \from{l3backend-box.dtx}     {package,dvipdfmx}
+        \from{l3backend-draw.dtx}    {package,dvipdfmx}
+        \from{l3backend-graphics.dtx}{package,dvipdfmx}
+        \from{l3backend-pdf.dtx}     {package,dvipdfmx}
+      }
+  }
+\generate
+  {
+    \file{l3backend-dvips.def}
+      {
+        \from{l3backend-basics.dtx}  {package,dvips}
+        \from{l3backend-color.dtx}   {package,dvips}
+        \from{l3backend-box.dtx}     {package,dvips}
+        \from{l3backend-draw.dtx}    {package,dvips}
+        \from{l3backend-graphics.dtx}{package,dvips}
+        \from{l3backend-pdf.dtx}     {package,dvips}
+      }
+  }
+\generate
+  {
+    \file{l3backend-dvisvgm.def}
+      {
+        \from{l3backend-basics.dtx}  {package,dvisvgm}
+        \from{l3backend-color.dtx}   {package,dvisvgm}
+        \from{l3backend-box.dtx}     {package,dvisvgm}
+        \from{l3backend-draw.dtx}    {package,dvisvgm}
+        \from{l3backend-graphics.dtx}{package,dvisvgm}
+        \from{l3backend-pdf.dtx}     {package,dvisvgm}
+      }
+  }
+\generate
+  {
+    \file{l3backend-pdfmode.def}
+      {
+        \from{l3backend-basics.dtx}  {package,pdfmode}
+        \from{l3backend-color.dtx}   {package,pdfmode}
+        \from{l3backend-box.dtx}     {package,pdfmode}
+        \from{l3backend-draw.dtx}    {package,pdfmode}
+        \from{l3backend-graphics.dtx}{package,pdfmode}
+        \from{l3backend-pdf.dtx}     {package,pdfmode}
+      }
+  }
+\generate
+  {
+    \file{l3backend-xdvipdfmx.def}
+      {
+        \from{l3backend-basics.dtx}  {package,xdvipdfmx}
+        \from{l3backend-color.dtx}   {package,xdvipdfmx}
+        \from{l3backend-box.dtx}     {package,xdvipdfmx}
+        \from{l3backend-draw.dtx}    {package,xdvipdfmx}
+        \from{l3backend-graphics.dtx}{package,xdvipdfmx}
+        \from{l3backend-pdf.dtx}     {package,xdvipdfmx}
+      }
+  }
+
+\endbatchfile