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+% \iffalse meta-comment
+%
+%% File: l3backend-opacity.dtx
+%
+% Copyright (C) 2021-2024 The LaTeX 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 \pkg{l3backend-opacity} module\\ Backend opacity support^^A
+% }
+%
+% \author{^^A
+% The \LaTeX{} Project\thanks
+% {^^A
+% E-mail:
+% \href{mailto:latex-team@latex-project.org}
+% {latex-team@latex-project.org}^^A
+% }^^A
+% }
+%
+% \date{Released 2024-04-11}
+%
+% \maketitle
+%
+% \begin{documentation}
+%
+% \end{documentation}
+%
+% \begin{implementation}
+%
+% \section{\pkg{l3backend-opacity} implementation}
+%
+% \begin{macrocode}
+%<*package>
+%<@@=opacity>
+% \end{macrocode}
+%
+% Although opacity is not color, it needs to be managed in a somewhat
+% similar way: using a dedicated stack if possible. Depending on the backend,
+% that may not be possible. There is also the need to cover fill/stroke setting
+% as well as more general running opacity. It is easiest to describe the value
+% used in terms of opacity, although commonly this is referred to as
+% transparency.
+%
+% \begin{macrocode}
+%<*dvips>
+% \end{macrocode}
+%
+% \begin{macro}{\@@_backend_select:n}
+% \begin{macro}{\@@_backend_fill:n, \@@_backend_stroke:n}
+% \begin{macro}{\@@_backend:nnn}
+% No stack so set values directly. The need to deal with Distiller and
+% Ghostscript separately means we use a common auxiliary: the two
+% systems require different PostScript for transparency. This is
+% of course not quite as efficient as doing one test for setting all
+% transparency, but it keeps things clearer here. Thanks to Alex Grahn
+% for the detail on testing for GhostScript.
+% \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_select:n #1
+ {
+ \@@_backend:nnn {#1} { fill } { ca }
+ \@@_backend:nnn {#1} { stroke } { CA }
+ }
+\cs_new_protected:Npn \@@_backend_fill:n #1
+ {
+ \@@_backend:nnn
+ { #1 }
+ { fill }
+ { ca }
+ }
+\cs_new_protected:Npn \@@_backend_stroke:n #1
+ {
+ \@@_backend:nnn
+ { #1 }
+ { stroke }
+ { CA }
+ }
+\cs_new_protected:Npn \@@_backend:nnn #1#2#3
+ {
+ \__kernel_backend_postscript:n
+ {
+ product ~ (Ghostscript) ~ search
+ {
+ pop ~ pop ~ pop ~
+ #1 ~ .set #2 constantalpha
+ }
+ {
+ pop ~
+ mark ~
+ /#3 ~ #1
+ /SetTransparency ~
+ pdfmark
+ }
+ ifelse
+ }
+ }
+% \end{macrocode}
+% \end{macro}
+% \end{macro}
+% \end{macro}
+%
+% \begin{macrocode}
+%</dvips>
+% \end{macrocode}
+%
+% \begin{macrocode}
+%<*dvipdfmx|luatex|pdftex|xetex>
+% \end{macrocode}
+%
+% \begin{variable}{\c_@@_backend_stack_int}
+% Set up a stack, where that is applicable.
+% \begin{macrocode}
+\bool_lazy_and:nnT
+ { \cs_if_exist_p:N \pdfmanagement_if_active_p: }
+ { \pdfmanagement_if_active_p: }
+ {
+%<*luatex|pdftex>
+ \__kernel_color_backend_stack_init:Nnn \c_@@_backend_stack_int
+ { page ~ direct } { /opacity 1 ~ gs }
+%</luatex|pdftex>
+ \pdfmanagement_add:nnn { Page / Resources / ExtGState }
+ { opacity 1 } { << /ca ~ 1 /CA ~ 1 >> }
+ }
+% \end{macrocode}
+% \end{variable}
+%
+% \begin{variable}{\l_@@_backend_fill_tl, \l_@@_backend_stroke_tl}
+% We use |tl| here for speed: at the backend, this should be reasonable.
+% Both need to start off fully opaque.
+% \begin{macrocode}
+\tl_new:N \l_@@_backend_fill_tl
+\tl_new:N \l_@@_backend_stroke_tl
+\tl_set:Nn \l_@@_backend_fill_tl { 1 }
+\tl_set:Nn \l_@@_backend_stroke_tl { 1 }
+% \end{macrocode}
+% \end{variable}
+%
+% \begin{macro}{\@@_backend_select:n}
+% \begin{macro}{\@@_backend_reset:}
+% Much the same as color.
+% \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_select:n #1
+ {
+ \tl_set:Nn \l_@@_backend_fill_tl {#1}
+ \tl_set:Nn \l_@@_backend_stroke_tl {#1}
+ \pdfmanagement_add:nnn { Page / Resources / ExtGState }
+ { opacity #1 }
+ { << /ca ~ #1 /CA ~ #1 >> }
+%<*dvipdfmx|xetex>
+ \__kernel_backend_literal_pdf:n
+%</dvipdfmx|xetex>
+%<*luatex|pdftex>
+ \__kernel_color_backend_stack_push:nn \c_@@_backend_stack_int
+%</luatex|pdftex>
+ { /opacity #1 ~ gs }
+ \group_insert_after:N \@@_backend_reset:
+ }
+\cs_new_protected:Npn \@@_backend_reset:
+ {
+%<*dvipdfmx|xetex>
+ \__kernel_backend_literal_pdf:n
+ { /opacity1 ~ gs }
+%</dvipdfmx|xetex>
+%<*luatex|pdftex>
+ \__kernel_color_backend_stack_pop:n \c_@@_backend_stack_int
+%</luatex|pdftex>
+ }
+% \end{macrocode}
+% \end{macro}
+% \end{macro}
+%
+% \begin{macro}{\@@_backend_fill:n, \@@_backend_stroke:n}
+% \begin{macro}{\@@_backend_fill_stroke:nn}
+% For separate fill and stroke, we need to work out if we need to do
+% more work or if we can stick to a single setting.
+% \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_fill:n #1
+ {
+ \exp_args:Nno \@@_backend_fill_stroke:nn
+ { #1 }
+ { \l_@@_backend_stroke_tl }
+ }
+\cs_new_protected:Npn \@@_backend_stroke:n #1
+ {
+ \exp_args:No \@@_backend_fill_stroke:nn
+ { \l_@@_backend_fill_tl }
+ { #1 }
+ }
+\cs_new_protected:Npn \@@_backend_fill_stroke:nn #1#2
+ {
+ \str_if_eq:nnTF {#1} {#2}
+ { \@@_backend_select:n {#1} }
+ {
+ \tl_set:Nn \l_@@_backend_fill_tl {#1}
+ \tl_set:Nn \l_@@_backend_stroke_tl {#2}
+ \pdfmanagement_add:nnn { Page / Resources / ExtGState }
+ { opacity.fill #1 }
+ { << /ca ~ #1 >> }
+ \pdfmanagement_add:nnn { Page / Resources / ExtGState }
+ { opacity.stroke #2 }
+ { << /CA ~ #2 >> }
+%<*dvipdfmx|xetex>
+ \__kernel_backend_literal_pdf:n
+%</dvipdfmx|xetex>
+%<*luatex|pdftex>
+ \__kernel_color_backend_stack_push:nn \c_@@_backend_stack_int
+%</luatex|pdftex>
+ { /opacity.fill #1 ~ gs /opacity.stroke #2 ~ gs }
+ \group_insert_after:N \@@_backend_reset:
+ }
+ }
+% \end{macrocode}
+% \end{macro}
+% \end{macro}
+%
+% \begin{macro}{\@@_backend_select:n, \@@_backend_fill_stroke:nn}
+% Redefine them to stubs if pdfmanagement is either not loaded or
+% deactivated.
+% \begin{macrocode}
+\bool_lazy_and:nnF
+ { \cs_if_exist_p:N \pdfmanagement_if_active_p: }
+ { \pdfmanagement_if_active_p: }
+ {
+ \cs_gset_protected:Npn \@@_backend_select:n #1 { }
+ \cs_gset_protected:Npn \@@_backend_fill_stroke:nn #1#2 { }
+ }
+% \end{macrocode}
+% \end{macro}
+%
+% \begin{macrocode}
+%</dvipdfmx|luatex|pdftex|xetex>
+% \end{macrocode}
+%
+% \begin{macrocode}
+%<*dvisvgm>
+% \end{macrocode}
+%
+% \begin{macro}{\@@_backend_select:n, \@@_backend_fill:n, \@@_backend_stroke:n}
+% \begin{macro}{\@@_backend:nn}
+% Once again, we use a scope here. There is a general opacity function for
+% SVG, but that is of course not set up using the stack.
+% \begin{macrocode}
+\cs_new_protected:Npn \@@_backend_select:n #1
+ { \@@_backend:nn {#1} { } }
+\cs_new_protected:Npn \@@_backend_fill:n #1
+ { \@@_backend:nn {#1} { fill- } }
+\cs_new_protected:Npn \@@_backend_stroke:n #1
+ { \@@_backend:nn {#1} { stroke- } }
+\cs_new_protected:Npn \@@_backend:nn #1#2
+ { \__kernel_backend_scope:e { #2 opacity = " #1 " } }
+% \end{macrocode}
+% \end{macro}
+% \end{macro}
+%
+% \begin{macrocode}
+%</dvisvgm>
+% \end{macrocode}
+%
+% \begin{macrocode}
+%</package>
+% \end{macrocode}
+%
+% \subsection{Font handling integration}
+%
+% In \LuaTeX{} we want to use these functions also for transparent fonts
+% to avoid interference between both uses of transparency.
+%
+% \begin{macrocode}
+%<*lua>
+% \end{macrocode}
+%
+% First we need to check if pdfmanagement is active from Lua.
+% \begin{macrocode}
+local pdfmanagement_active do
+ local pdfmanagement_if_active_p = token.create'pdfmanagement_if_active_p:'
+ local cmd = pdfmanagement_if_active_p.cmdname
+ if cmd == 'undefined_cs' then
+ pdfmanagement_active = false
+ else
+ token.put_next(pdfmanagement_if_active_p)
+ pdfmanagement_active = token.scan_int() ~= 0
+ end
+end
+
+if pdfmanagement_active and luaotfload and luaotfload.set_transparent_colorstack then
+ luaotfload.set_transparent_colorstack(function() return token.create'c_@@_backend_stack_int'.index end)
+
+ local transparent_register = {
+ token.create'pdfmanagement_add:nnn',
+ token.new(0, 1),
+ 'Page/Resources/ExtGState',
+ token.new(0, 2),
+ token.new(0, 1),
+ '',
+ token.new(0, 2),
+ token.new(0, 1),
+ '<</ca ',
+ '',
+ '/CA ',
+ '',
+ '>>',
+ token.new(0, 2),
+ }
+ luatexbase.add_to_callback('luaotfload.parse_transparent', function(value)
+ value = (octet * -1):match(value)
+ if not value then
+ tex.error'Invalid transparency value'
+ return
+ end
+ value = value:sub(1, -2)
+ local result = 'opacity' .. value
+ tex.runtoks(function()
+ transparent_register[6], transparent_register[10], transparent_register[12] = result, value, value
+ tex.sprint(-2, transparent_register)
+ end)
+ return '/' .. result .. ' gs'
+ end, 'l3opacity')
+end
+% \end{macrocode}
+%
+% \begin{macrocode}
+%</lua>
+% \end{macrocode}
+%
+%
+% \end{implementation}
+%
+% \PrintIndex