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|
% Copyright 2006 by Till Tantau
%
% This file may be distributed and/or modified
%
% 1. under the LaTeX Project Public License and/or
% 2. under the GNU Free Documentation License.
%
% See the file doc/generic/pgf/licenses/LICENSE for more details.
\section{Commands of the System Layer}
\makeatletter
\subsection{Beginning and Ending a Stream of System Commands}
A ``user'' of the \pgfname\ system layer (like the basic layer or a
frontend) will interface with the system layer by calling a stream of
commands starting with |\pgfsys@|. From the system layer's point of
view, these commands form a long stream. Between calls to the system
layer, control goes back to the user.
The driver files implement system layer commands by inserting
|\special| commands that implement the desired operation. For example,
|\pgfsys@stroke| will be mapped to |\special{pdf: S}| by the driver
file for |pdftex|.
For many drivers, when such a stream of specials starts, it is
necessary to install an appropriate transformation and perhaps perform
some more bureaucratic tasks. For this reason, every stream will start
with a |\pgfsys@beginpicture| and will end with a corresponding ending
command.
\begin{command}{\pgfsys@beginpicture}
Called at the beginning of a |{pgfpicture}|. This command should
``set up things.''
Most drivers will need to implement this command.
\end{command}
\begin{command}{\pgfsys@endpicture}
Called at the end of a |{pgfpicture}|.
Most drivers will need to implement this command.
\end{command}
\begin{command}{\pgfsys@typesetpicturebox\marg{box}}
Called \emph{after} a |{pgfpicture}| has been typeset. The picture
will have been put in box \meta{box}. This command should insert the
box into the normal text. The box \meta{box} will still be a ``raw''
box that contains only the |\special|'s that make up the description
of the picture. The job of this command is to resize and shift
\meta{box} according to the baseline shift and the size of the
box.
This command has a default implementation and need not be
implemented by a driver file.
\end{command}
\begin{command}{\pgfsys@beginpurepicture}
This version of the |\pgfsys@beginpicture| picture command can be
used for pictures that are guaranteed not to contain any escaped
boxes (see below). In this case, a driver might provide a more
compact version of the command.
This command has a default implementation and need not be
implemented by a driver file.
\end{command}
\begin{command}{\pgfsys@endpurepicture}
Called at the end of a ``pure'' |{pgfpicture}|.
This command has a default implementation and need not be
implemented by a driver file.
\end{command}
Inside a stream it is sometimes necessary to ``escape'' back into
normal typesetting mode; for example to insert some normal text, but
with all of the current transformations and clippings being in
force. For this escaping, the following command is used:
\begin{command}{\pgfsys@hbox\marg{box number}}
Called to insert a (horizontal) TeX box inside a
|{pgfpicture}|.
Most drivers will need to (re-)implement this command.
\end{command}
\begin{command}{\pgfsys@hboxsynced\marg{box number}}
Called to insert a (horizontal) TeX box inside a
|{pgfpicture}|, but with the current coordinate transformation
matrix synced with the canvas transformation matrix.
This command should do the same as if you used
|\pgflowlevelsynccm| followed by |\pgfsys@hbox|. However, the default
implementation of this command will use a ``TeX-translation'' for
the translation part of the transformation matrix. This will ensure
that hyperlinks ``survive'' at least translations. On the other
hand, a driver may choose to revert to a simpler
implementation. This is done, for example, for the \textsc{svg}
implementation, where a \TeX-translation makes no sense.
\end{command}
\begin{command}{\pgfsys@pictureboxsynced\marg{box number}}
Basically, this should do the same as doing a (scoped) low level sync
followed by inserting the box \meta{box number} directly into the
output stream. However, the default implementation uses
|\pgfsys@hboxsynced| in conjunction with |\pgfsys@beginpicture| to
ensure that, if possible, hyperlinks survive in
\textsc{pdf}s. Drivers that are sensitive to picture-in-picture
scopes should replace this implementation by
\begin{codeexample}[code only]
\pgfsys@beginscope\pgflowlevelsynccm\box#1\pgfsys@endscope
\end{codeexample}
\end{command}
\subsection{Path Construction System Commands}
\begin{command}{\pgfsys@moveto\marg{x}\marg{y}}
This command is used to start a path at a specific point
$(x,y)$ or to move the current point of the current path to $(x,y)$
without drawing anything upon stroking (the current path is
``interrupted'').
Both \meta{x} and \meta{y} are given as \TeX\ dimensions. It is the
driver's job to transform these to the coordinate system of the
backend. Typically, this means converting the \TeX\ dimension into a
dimensionless multiple of $\frac{1}{72}\mathrm{in}$. The function
|\pgf@sys@bp| helps with this conversion.
\example Draw a line from $(10\mathrm{pt},10\mathrm{pt})$ to the
origin of the picture.
\begin{codeexample}[code only]
\pgfsys@moveto{10pt}{10pt}
\pgfsys@lineto{0pt}{0pt}
\pgfsys@stroke
\end{codeexample}
This command is protocolled, see Section~\ref{section-protocols}.
\end{command}
\begin{command}{\pgfsys@lineto\marg{x}\marg{y}}
Continue the current path to $(x,y)$ with
a straight line.
This command is protocolled, see Section~\ref{section-protocols}.
\end{command}
\begin{command}{\pgfsys@curveto\marg{$x_1$}\marg{$y_1$}\marg{$x_2$}\marg{$y_2$}\marg{$x_3$}\marg{$y_3$}}
Continue the current path to $(x_3,y_3)$
with a B\'ezier curve that has the two control points $(x_1,y_1)$ and $(x_2,y_2)$.
\example Draw a good approximation of a quarter circle:
\begin{codeexample}[code only]
\pgfsys@moveto{10pt}{0pt}
\pgfsys@curveto{10pt}{5.55pt}{5.55pt}{10pt}{0pt}{10pt}
\pgfsys@stroke
\end{codeexample}
This command is protocolled, see Section~\ref{section-protocols}.
\end{command}
\begin{command}{\pgfsys@rect\marg{x}\marg{y}\marg{width}\marg{height}}
Append a rectangle to the current path whose lower left corner is
at $(x,y)$ and whose width and height in
big points are given by \meta{width} and \meta{height}.
This command can be ``mapped back'' to |\pgfsys@moveto| and
|\pgfsys@lineto| commands, but it is included since \pdf\ has a
special, quick version of this command.
This command is protocolled, see Section~\ref{section-protocols}.
\end{command}
\begin{command}{\pgfsys@closepath}
Close the current path. This results in joining the current point of
the path with the point specified by the last |\pgfsys@moveto|
operation. Typically, this is preferable over using |\pgfsys@lineto|
to the last point specified by a |\pgfsys@moveto|, since the line
starting at this point and the line ending at this point will be
smoothly joined by |\pgfsys@closepath|.
\example Consider
\begin{codeexample}[code only]
\pgfsys@moveto{0pt}{0pt}
\pgfsys@lineto{10bp}{10bp}
\pgfsys@lineto{0bp}{10bp}
\pgfsys@closepath
\pgfsys@stroke
\end{codeexample}
and
\begin{codeexample}[code only]
\pgfsys@moveto{0bp}{0bp}
\pgfsys@lineto{10bp}{10bp}
\pgfsys@lineto{0bp}{10bp}
\pgfsys@lineto{0bp}{0bp}
\pgfsys@stroke
\end{codeexample}
The difference between the above will be that in the second triangle
the corner at the origin will be wrong; it will just be the overlay
of two lines going in different directions, not a sharp pointed
corner.
This command is protocolled, see Section~\ref{section-protocols}.
\end{command}
\subsection{Canvas Transformation System Commands}
\begin{command}{\pgfsys@transformcm\marg{a}\marg{b}\marg{c}\marg{d}\marg{e}\marg{f}}
Perform a concatenation of the canvas transformation matrix with the
matrix given by the values \meta{a} to \meta{f}, see the \pdf\ or
PostScript manual for details. The values \meta{a} to \meta{d} are
dimensionless factors, \meta{e} and \meta{f} are \TeX\ dimensions
\example |\pgfsys@transformcm{1}{0}{0}{1}{1cm}{1cm}|.
This command is protocolled, see Section~\ref{section-protocols}.
\end{command}
\begin{command}{\pgfsys@transformshift\marg{x displacement}\marg{y displacement}}
This command will change the origin of the canvas to $(x,y)$.
This command has a default implementation and need not be
implemented by a driver file.
This command is protocolled, see Section~\ref{section-protocols}.
\end{command}
\begin{command}{\pgfsys@transformxyscale\marg{x scale}\marg{y scale}}
This command will scale the canvas (and everything that is drawn)
by a factor of \meta{x scale} in the $x$-direction and \meta{y
scale} in the $y$-direction. Note that this applies to
everything, including lines. So a scaled line will have a different
width and may even have a different width when going along the
$x$-axis and when going along the $y$-axis, if the scaling is
different in these directions. Usually, you do not want this.
This command has a default implementation and need not be
implemented by a driver file.
This command is protocolled, see Section~\ref{section-protocols}.
\end{command}
\subsection{Stroking, Filling, and Clipping System Commands}
\begin{command}{\pgfsys@stroke}
Stroke the current path (as if it were drawn with a pen). A number
of graphic state parameters influence this, which can be
set using appropriate system commands described later.
\begin{description}
\item[Line width]
The ``thickness'' of the line. A width of 0 is the thinnest width
renderable on the device. On a high-resolution printer this may
become invisible and should be avoided. A good choice is 0.4pt,
which is the default.
\item[Stroke color]
This special color is used for stroking. If it is not set, the
current color is used.
\item[Cap]
The cap describes how the endings of lines are drawn. A round cap
adds a little half circle to these endings. A butt cap ends the
lines exactly at the end (or start) point without anything
added. A rectangular cap ends the lines like the butt cap, but the
lines protrude over the endpoint by the line thickness. (See also
the \pdf\ manual.) If the path has been closed, no cap
is drawn.
\item[Join]
This describes how a bend (a join) in a path is rendered. A round
join draws bends using small arcs. A bevel join just draws the two
lines and then fills the join minimally so that it becomes
convex. A miter join extends the lines so that they form a single
sharp corner, but only up to a certain miter limit. (See the \pdf\
manual once more.)
\item[Dash]
The line may be dashed according to a dashing pattern.
\item[Clipping area]
If a clipping area is established, only those parts of the path
that are inside the clipping area will be drawn.
\end{description}
In addition to stroking a path, the path may also be used for
clipping after it has been stroked. This will happen if the
|\pgfsys@clipnext| is used prior to this command, see there for
details.
This command is protocolled, see Section~\ref{section-protocols}.
\end{command}
\begin{command}{\pgfsys@closestroke}
This command should have the same effect as first closing the path
and then stroking it.
This command has a default implementation and need not be
implemented by a driver file.
This command is protocolled, see Section~\ref{section-protocols}.
\end{command}
\begin{command}{\pgfsys@fill}
This command fills the area surrounded by the current path. If the
path has not yet been closed, it is closed prior to filling. The
path itself is not stroked. For self-intersecting paths or paths
consisting of multiple parts, the nonzero winding number rule is
used to determine whether a point is inside or outside the
path, except if |\ifpgfsys@eorule| holds -- in which case the
even-odd rule should be used. (See the \pdf\ or PostScript manual
for details.)
The following graphic state parameters influence the filling:
\begin{description}
\item[Interior rule]
If |\ifpgfsys@eorule| is set, the even-odd rule is used, otherwise
the non-zero winding number rule.
\item[Fill color]
If the fill color is not especially set, the current color is
used.
\item[Clipping area]
If a clipping area is established, only those parts of the filling
area that are inside the clipping area will be drawn.
\end{description}
In addition to filling the path, the path will also be used for
clipping if |\pgfsys@clipnext| is used prior to this command.
This command is protocolled, see Section~\ref{section-protocols}.
\end{command}
\begin{command}{\pgfsys@fillstroke}
First, the path is filled, then the path is stroked. If the fill and
stroke colors are the same (or if they are not specified and the
current color is used), this yields almost the same as a
|\pgfsys@fill|. However, due to the line thickness of the stroked
path, the fill-stroked area will be slightly larger.
In addition to stroking and filling the path, the path will also be
used for clipping if |\pgfsys@clipnext| is used prior to this command.
This command is protocolled, see Section~\ref{section-protocols}.
\end{command}
\begin{command}{\pgfsys@discardpath}
Normally, this command should ``throw away'' the current path.
However, after |\pgfsys@clipnext| has been called, the current path
should subsequently be used for clipping. See |\pgfsys@clipnext| for
details.
This command is protocolled, see Section~\ref{section-protocols}.
\end{command}
\begin{command}{\pgfsys@clipnext}
This command should be issued after a path has been constructed, but
before it has been stroked and/or filled or discarded. When the
command is used, the next stroking/filling/discarding command will
first be executed normally. Then, afterwards, the just-used path
will be used for subsequent clipping. If there has already been a
clipping region, this region is intersected with the new clipping
path (the clipping cannot get bigger). The nonzero winding number
rule is used to determine whether a point is inside or outside the
clipping area or the even-odd rule, depending on whether
|\ifpgfsys@eorule| holds.
\end{command}
\subsection{Graphic State Option System Commands}
\begin{command}{\pgfsys@setlinewidth\marg{width}}
Sets the width of lines, when stroked, to \meta{width}, which must
be a \TeX\ dimension.
This command is protocolled, see Section~\ref{section-protocols}.
\end{command}
\begin{command}{\pgfsys@buttcap}
Sets the cap to a butt cap. See |\pgfsys@stroke|.
This command is protocolled, see Section~\ref{section-protocols}.
\end{command}
\begin{command}{\pgfsys@roundcap}
Sets the cap to a round cap. See |\pgfsys@stroke|.
This command is protocolled, see Section~\ref{section-protocols}.
\end{command}
\begin{command}{\pgfsys@rectcap}
Sets the cap to a rectangular cap. See |\pgfsys@stroke|.
This command is protocolled, see Section~\ref{section-protocols}.
\end{command}
\begin{command}{\pgfsys@miterjoin}
Sets the join to a miter join. See |\pgfsys@stroke|.
This command is protocolled, see Section~\ref{section-protocols}.
\end{command}
\begin{command}{\pgfsys@setmiterlimit\marg{factor}}
Sets the miter limit of lines to \meta{factor}. See
the \pdf\ or PostScript for details on what the miter limit is.
This command is protocolled, see Section~\ref{section-protocols}.
\end{command}
\begin{command}{\pgfsys@roundjoin}
Sets the join to a round join. See |\pgfsys@stroke|.
This command is protocolled, see Section~\ref{section-protocols}.
\end{command}
\begin{command}{\pgfsys@beveljoin}
Sets the join to a bevel join. See |\pgfsys@stroke|.
This command is protocolled, see Section~\ref{section-protocols}.
\end{command}
\begin{command}{\pgfsys@setdash\marg{pattern}\marg{phase}}
Sets the dashing patter. \meta{pattern} should be a list of \TeX\
dimensions separated by commas. \meta{phase} should be a
single dimension.
\example |\pgfsys@setdash{3pt,3pt}{0pt}|
The list of values in \meta{pattern} is used to determine the
lengths of the ``on'' and ``off'' phases of the dashing. For example, if \meta{pattern} is |3bp,4bp|, then the dashing
pattern is ``3bp on followed by 4bp off, followed by 3bp on,
followed by 4bp off, and so on.'' A pattern of |.5pt,4pt,3pt,1.5pt| means
``.5pt on, 4pt off, 3pt on, 1.5pt off, .5pt on, \dots'' If the
number of entries is odd, the last one is used twice, so |3pt| means
``3pt on, 3pt off, 3pt on, 3pt off, \dots'' An empty list
means ``always on.''
The second argument determines the ``phase'' of the pattern. For
example, for a pattern of |3bp,4bp| and a phase of |1bp|, the pattern
would start: ``2bp on, 4bp off, 3bp on, 4bp off, 3bp on, 4bp off,
\dots''
This command is protocolled, see Section~\ref{section-protocols}.
\end{command}
{\let\ifpgfsys@eorule=\relax
\begin{command}{\ifpgfsys@eorule}
Determines whether the even odd rule is used for filling and
clipping or not.
\end{command}
}
\subsection{Color System Commands}
The \pgfname\ system layer provides a number of system commands for
setting colors. These command coexist with commands from the |color|
and |xcolor| package, which perform similar functions. However, the
|color| package does not support having two different colors for
stroking and filling, which is a useful feature that is supported by
\pgfname. For this reason, the \pgfname\ system layer offers commands for
setting these colors separately. Also, plain \TeX\ profits from the
fact that \pgfname\ can set colors.
For \pdf, implementing these color commands is easy since \pdf\
supports different stroking and filling colors directly. For
PostScript, a more complicated approach is needed in which the colors
need to be stored in special PostScript variables that are set
whenever a stroking or a filling operation is done.
\begin{command}{\pgfsys@color@rgb\marg{red}\marg{green}\marg{blue}}
Sets the color used for stroking and filling operations to the given
red/green/blue tuple (numbers between 0 and 1).
This command is protocolled, see Section~\ref{section-protocols}.
\end{command}
\begin{command}{\pgfsys@color@rgb@stroke\marg{red}\marg{green}\marg{blue}}
Sets the color used for stroking operations to the given
red/green/blue tuple (numbers between 0 and 1).
\example Make stroked text dark red: |\pgfsys@color@rgb@stroke{0.5}{0}{0}|
The special stroking color is only used if the stroking color has
been set since the last |\color| or |\pgfsys@color@xxx|
command. Thus, each |\color| command will reset both the stroking
and filling colors by calling |\pgfsys@color@reset|.
This command is protocolled, see Section~\ref{section-protocols}.
\end{command}
\begin{command}{\pgfsys@color@rgb@fill\marg{red}\marg{green}\marg{blue}}
Sets the color used for filling operations to the given
red/green/blue tuple (numbers between 0 and 1). This color may be
different from the stroking color.
This command is protocolled, see Section~\ref{section-protocols}.
\end{command}
\begin{command}{\pgfsys@color@cmyk\marg{cyan}\marg{magenta}\marg{yellow}\marg{black}}
Sets the color used for stroking and filling operations to the given
cmyk tuple (numbers between 0 and 1).
This command is protocolled, see Section~\ref{section-protocols}.
\end{command}
\begin{command}{\pgfsys@color@cmyk@stroke\marg{cyan}\marg{magenta}\marg{yellow}\marg{black}}
Sets the color used for stroking operations to the given cmyk tuple
(numbers between 0 and 1).
This command is protocolled, see Section~\ref{section-protocols}.
\end{command}
\begin{command}{\pgfsys@color@cmyk@fill\marg{cyan}\marg{magenta}\marg{yellow}\marg{black}}
Sets the color used for filling operations to the given cmyk tuple
(numbers between 0 and 1).
This command is protocolled, see Section~\ref{section-protocols}.
\end{command}
\begin{command}{\pgfsys@color@cmy\marg{cyan}\marg{magenta}\marg{yellow}}
Sets the color used for stroking and filling operations to the given
cmy tuple (numbers between 0 and 1).
This command is protocolled, see Section~\ref{section-protocols}.
\end{command}
\begin{command}{\pgfsys@color@cmy@stroke\marg{cyan}\marg{magenta}\marg{yellow}}
Sets the color used for stroking operations to the given cmy tuple
(numbers between 0 and 1).
This command is protocolled, see Section~\ref{section-protocols}.
\end{command}
\begin{command}{\pgfsys@color@cmy@fill\marg{cyan}\marg{magenta}\marg{yellow}}
Sets the color used for filling operations to the given cmy tuple
(numbers between 0 and 1).
This command is protocolled, see Section~\ref{section-protocols}.
\end{command}
\begin{command}{\pgfsys@color@gray\marg{black}}
Sets the color used for stroking and filling operations to the given
black value, where 0 means black and 1 means white.
This command is protocolled, see Section~\ref{section-protocols}.
\end{command}
\begin{command}{\pgfsys@color@gray@stroke\marg{black}}
Sets the color used for stroking operations to the given black value,
where 0 means black and 1 means white.
This command is protocolled, see Section~\ref{section-protocols}.
\end{command}
\begin{command}{\pgfsys@color@gray@fill\marg{black}}
Sets the color used for filling operations to the given black value,
where 0 means black and 1 means white.
This command is protocolled, see Section~\ref{section-protocols}.
\end{command}
\begin{command}{\pgfsys@color@reset}
This command will be called when the |\color| command is used. It
should purge any internal settings of stroking and filling
color. After this call, till the next use of a command like
|\pgfsys@color@rgb@fill|, the current color installed by the
|\color| command should be used.
If the \TeX-if |\pgfsys@color@reset@inorder| is set to true, this
command may ``assume'' that any call to a color command that sets
the fill or stroke color came ``before'' the call to this command
and may try to optimize the output accordingly.
An example of an incorrect ``out of order'' call would be using
|\pgfsys@color@reset| at the beginning of a box that is constructed
using |\setbox|. Then, when the box is constructed, no special fill
or stroke color might be in force. However, when the box is later on
inserted at some point, a special fill color might already have been
set. In this case, this command is not guaranteed to reset the color
correctly.
\end{command}
\begin{command}{\pgfsys@color@reset@inordertrue}
Sets the optimized ``in order'' version of the color resetting. This
is the default.
\end{command}
\begin{command}{\pgfsys@color@reset@inorderfalse}
Switches off the optimized color resetting.
\end{command}
\begin{command}{\pgfsys@color@unstacked\marg{\LaTeX\ color}}
This slightly obscure command causes the color stack to be
tricked. When called, this command should set the current color to
\meta{\LaTeX\ color} without causing any change in the color stack.
\example |\pgfsys@color@unstacked{red}|
\end{command}
\subsection{Pattern System Commands}
\begin{command}{\pgfsys@declarepattern
\marg{name}\marg{$x_1$}\marg{$y_1$}\marg{$x_2$}\marg{$y_2$}
\marg{$x$ step}\marg{$y$ step}\marg{code}\marg{flag}}
This command declares a new colored or uncolored pattern, depending
on whether \meta{flag} is |0|, which means uncolored, or |1|, which
means colored. Uncolored patterns have no inherent color, the color
is provided when they are set. Colored patters have an inherent
color.
The \meta{name} is a name for later use when the pattern is to be
shown. The pairs $(x_1,y_1)$ and $(x_2,y_2)$ must describe a
bounding box of the pattern \meta{code}.
The tiling step of the pattern is given by \meta{$x$ step} and
\meta{$y$ step}.
\example
\begin{codeexample}[code only]
\pgfsys@declarepattern{hori}{-.5pt}{0pt}{.5pt}{3pt}{3pt}{3pt}
{\pgfsys@moveto{0pt}{0pt}\pgfsys@lineto{0pt}{3pt}\pgfsys@stroke}
{0}
\end{codeexample}
\end{command}
\begin{command}{\pgfsys@setpatternuncolored\marg{name}\marg{red}\marg{green}\marg{blue}}
Sets the fill color to the pattern named \meta{name}. This pattern
must previously have been declared with \meta{flag} set to |0|. The
color of the pattern is given in the parameters \meta{red},
\meta{green}, and \meta{blue} in the usual way.
The fill color ``pattern'' will persist till the next color command
that modifies the fill color.
\end{command}
\begin{command}{\pgfsys@setpatterncolored\marg{name}}
Sets the fill color to the pattern named \meta{name}. This pattern
must have been declared with the |1| flag.
\end{command}
\subsection{Scoping System Commands}
The scoping commands are used to keep changes of the graphics state
local.
\begin{command}{\pgfsys@beginscope}
Saves the current graphic state on a graphic state stack. All
changes to the graphic state parameters mentioned for |\pgfsys@stroke|
and |\pgfsys@fill| will be local to the current graphic state and
the old values will be restored after |\pgfsys@endscope| is used.
\emph{Warning:} \pdf\ and PostScript differ with respect to the
question of whether the current path is part of the graphic state or
not. For this reason, you should never use this command unless the
path is currently empty. For example, it might be a good idea to use
|\pgfsys@discardpath| prior to calling this command.
This command is protocolled, see Section~\ref{section-protocols}.
\end{command}
\begin{command}{\pgfsys@endscope}
Restores the last saved graphic state.
This command is protocolled, see Section~\ref{section-protocols}.
\end{command}
\subsection{Image System Commands}
The system layer provides some commands for image inclusion.
\begin{command}{\pgfsys@imagesuffixlist}
This macro should expand to a list of suffixes, separated by `:',
that will be tried when searching for an image.
\example |\def\pgfsys@imagesuffixlist{eps:epsi:ps}|
\end{command}
\begin{command}{\pgfsys@defineimage}
Called, when an image should be defined.
This command does not take any parameters. Instead, certain macros
will be preinstalled with appropriate values when this command is
invoked. These are:
\begin{itemize}
\item\declare{|\pgf@filename|}
File name of the image to be defined.
\item\declare{|\pgf@imagewidth|}
Will be set to the desired (scaled) width of the image.
\item\declare{|\pgf@imageheight|}
Will be set to the desired (scaled) height of the image.
If this macro and also the height macro are empty, the image
should have its ``natural'' size.
If only one of them is specified, the undefined value the
image is scaled so that the aspect ratio is kept.
If both are set, the image is scaled in both directions
independently, possibly changing the aspect ratio.
\end{itemize}
The following macros presumable mostly make sense for drivers that
can handle \pdf:
\begin{itemize}
\item \declare{|\pgf@imagepage|}
The desired page number to be extracted from a multi-page
``image.''
\item\declare{|\pgf@imagemask|}
If set, it will be set to |/SMask x 0 R| where |x| is the \pdf\
object number of a soft mask to be applied to the image.
\item\declare{|\pgf@imageinterpolate|}
If set, it will be set to |/Interpolate true| or
|/Interpolate false|, indicating whether the image should be
interpolated in \pdf.
\end{itemize}
The command should now set up the macro |\pgf@image| such that calling
this macro will result in typesetting the image. Thus, |\pgf@image| is
the ``return value'' of the command.
This command has a default implementation and need not be
implemented by a driver file.
\end{command}
\subsection{Shading System Commands}
\begin{command}{\pgfsys@horishading\marg{name}\marg{height}\marg{specification}}
Declares a horizontal shading for later use. The effect of this
command should be the definition of a macro called |\@pgfshading|\meta{name}|!|
(or |\csname @pdfshading|\meta{name}|!\endcsname|, to be
precise). When invoked, this new macro should insert a shading at
the current position.
\meta{name} is the name of the shading, which is also used in the
output macro name. \meta{height} is the height of the shading and
must be given as a TeX dimension like |2cm| or
|10pt|. \meta{specification} is a shading color
specification as specified in Section~\ref{section-shadings}. The
shading specification implicitly fixes the width of the shading.
When |\@pgfshading|\meta{name}|!| is invoked, it should insert a box
of height \meta{height} and the width implicit in the shading
declaration.
\end{command}
\begin{command}{\pgfsys@vertshading\marg{name}\marg{width}\marg{specification}}
Like the horizontal version, only for vertical shadings. This time,
the height of the shading is implicit in \meta{specification} and
the width is given as \meta{width}.
\end{command}
\begin{command}{\pgfsys@radialshading\marg{name}\marg{starting point}\marg{specification}}
Declares a radial shading. Like the previous macros, this command
should set up the macro |\@pgfshading|\meta{name}|!|, which upon
invocation should insert a radial shading whose size is implicit in
\meta{specification}.
The parameter \meta{starting point} is a \pgfname\ point
specifying the inner starting point of the shading.
\end{command}
\begin{command}{\pgfsys@functionalshading\marg{name}\marg{lower left
corner}\meta{upper right corner}\marg{type 4 function}}
Declares a shading using a PostScript-like function that provides a
color for each point. Like the previous macros, this command
should set up the macro |\@pgfshading|\meta{name}|!| so that it will
produce a box containing the desired shading.
Parameter \meta{name} is the name of the shading. Parameter
\meta{type 4 function} is a
Postscript-like function (type 4 function of the PDF specification)
as described in Section 3.9.4 of the PDF specification version 1.7.
Parameters \meta{lower left corner} and \meta{upper right corner} are
\pgfname\ points that specifies the lower left and upper right
corners of the shading, respectively.
When \meta{type 4 function} is evaluated, the coordinate of the current
point will be on the (virtual) PostScript stack in bp units. After
the function has been evaluated, the stack should consist of three
numbers (not integers! -- the Apple PDF renderer is broken in this
regard, so add cvrs at the end if needed) that represent the red,
green, and blue components of the color.
A buggy function will result is \emph{totally unpredictable chaos} during
rendering.
\end{command}
\subsection{Transparency System Commands}
\begin{command}{\pgfsys@stroke@opacity\marg{value}}
Sets the opacity of stroking operations.
\end{command}
\begin{command}{\pgfsys@fill@opacity\marg{value}}
Sets the opacity of filling operations.
\end{command}
\begin{command}{\pgfsys@blend@mode\marg{value}}
Sets the blend mode, see Section 7.2.4 of the \textsc{pdf}
Specification, Version 1.7.
\end{command}
\begin{command}{\pgfsys@transparencygroupfrombox\marg{box}}
This takes a \TeX\ box and converts it into a transparency
group. This means that any transparency settings apply to the box as
a whole. For instance, if a box contains two overlapping black
circles and you draw the box and, thus, the two circles normally
with 50\% transparency, then the overlap will be darker than the
rest. By comparison, if the circles are part of a transparency
group, the overlap will get the same color as the rest.
\end{command}
A transparency group can be \emph{isolated} and/or a \emph{knockout}
group (see Sections 7.3.4 and 7.3.5 of the \textsc{pdf}
Specification Version 1.7). Which of these is the case is dictated
by the current settings of the following two ifs, which must be set
before the above command is called:
{\let\ifpgfsys@transparency@group@isolated=\relax
\begin{command}{\ifpgfsys@transparency@group@isolated}
Determines whether a transparency group should be isolated.
\end{command}
}
{\let\ifpgfsys@transparency@group@knockout=\relax
\begin{command}{\ifpgfsys@transparency@group@knockout}
Determines whether a transparency group is a knockout group or not.
\end{command}
}
\begin{command}{\pgfsys@fadingfrombox\marg{name}\marg{box}}
Declares the fading \meta{name}. The \meta{box} is a \TeX-box. Its
content's luminosity determines the opacity of the resulting
fading. This means that the lighter a pixel inside the box, the more
opaque the fading will be at this position.
\end{command}
\begin{command}{\pgfsys@usefading\meta{name}\marg{a}\marg{b}\marg{c}\marg{d}\marg{e}\marg{f}}
Installs a previously declared fading \meta{name} in the current
graphics state. Afterwards, all drawings will be masked by the
fading. The fading should be centered on the origin and have its
original size, except that the parameters \meta{a} to \meta{f}
specify a transformation matrix that should be applied additionally
to the fading before it is installed. The transformation should not
apply to the following graphics, however.
\end{command}
\begin{command}{\pgfsys@definemask}
This command declares a fading (known as a soft mask in this
context) based on an image and for usage with images. It
works similar to |\pgfsys@defineimage|: Certain macros are set when
the command is called. The result should be to set the macro
|\pgf@mask| to a pdf object count that can subsequently be used as a
transparency mask. The following macros will be set when this command is
invoked:
\begin{itemize}
\item \declare{|\pgf@filename|}
File name of the mask to be defined.
\item \declare{|\pgf@maskmatte|}
The so-called matte of the mask (see the \pdf\ documentation for
details). The matte is a color specification consisting of 1, 3 or
4 numbers between 0 and 1. The number of numbers depends on the
number of color channels in the image (not in the mask!). It will
be assumed that the image has been preblended with this color.
\end{itemize}
\end{command}
\subsection{Reusable Objects System Commands}
\begin{command}{\pgfsys@invoke\marg{literals}}
This command gets protocolled literals and should insert them into
the |.pdf| or |.dvi| file using an appropriate |\special|.
\end{command}
\begin{command}{\pgfsys@defobject\marg{name}\marg{lower
left}\marg{upper right}\marg{code}}
Declares an object for later use. The idea is that the object can be
precached in some way and then be rendered more quickly when used
several times. For example, an arrow head might be defined and
prerendered in this way.
The parameter \meta{name} is the name for later use. \meta{lower
left} and \meta{upper right} are \pgfname\ points specifying a bounding
box for the object. \meta{code} is the code for the object. The code
should not be too fancy.
This command has a default implementation and need not be
implemented by a driver file.
\end{command}
\begin{command}{\pgfsys@useobject\marg{name}\marg{extra code}}
Renders a previously declared object. The first parameter is the
name of the object. The second parameter is extra code that
should be executed right \emph{before} the object is
rendered. Typically, this will be some transformation code.
This command has a default implementation and need not be
implemented by a driver file.
\end{command}
\subsection{Invisibility System Commands}
All drawing or stroking or text rendering between calls of the
following commands should be suppressed. A similar effect can be
achieved by clipping against an empty region, but the following
commands do not open a graphics scope and can be opened and closed
``orthogonally'' to other scopes.
\begin{command}{\pgfsys@begininvisible}
Between this command and the closing |\pgfsys@endinvisible| all
output should be suppressed. Nothing should be drawn at all, which
includes all paths, images and shadings. However, no groups (neither
\TeX\ groups nor graphic state groups) should be opened by this
command.
This command has a default implementation and need not be
implemented by a driver file.
This command is protocolled, see Section~\ref{section-protocols}.
\end{command}
\begin{command}{\pgfsys@endinvisible}
Ends the invisibility section, unless invisibility blocks have been
nested. In this case, only the ``last'' one restores visibility.
This command has a default implementation and need not be
implemented by a driver file.
This command is protocolled, see Section~\ref{section-protocols}.
\end{command}
\subsection{Page Size Commands}
The following commands can be used to set the page size of a document
in a ``portable'' way. Note, however, that many packages also (try to)
set the page size.
These commands are typically not given inside a |{pgfpicture}|, but on
the outer level of compilation.
\begin{command}{\pgfsys@papersize\marg{width}\marg{height}}
Inserts the necessary |\special|s for the current driver into the
output stream to ``locally'' change the page size. Whether such a
``local'' change is possible depends strongly on the driver. For
instance, |dvips| will honor the first call to this command that is
part of the shipped-out document and will ignore all other uses. In
contrast, |pdftex| will use the current value of the paper size for
each page and, additionally, setting the papersize is local to the
current \TeX\ group.
\end{command}
\begin{command}{\pgfsys@global@papersize\marg{width}\marg{height}}
Like the previous command, only for drivers where setting the paper
size parameters is a \TeX-group-local operation, |\global| is
prefixed to the setting of the page sizes.
\end{command}
\begin{command}{\pgfsys@thepageheight}
This macro expands to the current page's height, provided \LaTeX\ is
used, otherwise a best guess is returned (currently just |\the\vsize|).
\end{command}
\begin{command}{\pgfsys@thepagewidth}
As above.
\end{command}
\subsection{Position Tracking Commands}
The following commands are used to determine the position of text on a
page. This is a rather complicated process in general since at the
moment when the text is read by \TeX, the final position cannot be
determined, yet. For example, the text might be put in a box which is
later put in the headline or perhaps in the footline or perhaps even
on a different page.
For these reasons, position tracking is typically a two-stage
process. In a first stage you indicate that a certain position is of
interest by \emph{marking} it. This will (depending on the details of
the backend driver) cause page coordinates or this position to be
written to an |.aux| file when the page is shipped. Possibly, the
position might also be determined at an even later stage. Then, on a
second run of \TeX, the position is read from the |.aux| file and can
be used.
\begin{command}{\pgfsys@markposition\marg{name}}
Marks a position on the page. This command should be given while
normal typesetting is done such as in
\begin{codeexample}[code only]
The value of $x$ is \pgfsys@markposition{here}important.
\end{codeexample}
It causes the position |here| to be saved when the page is shipped
out.
\end{command}
\begin{command}{\pgfsys@getposition\marg{name}\marg{macro}}
This command retrieves a position that has been marked on an earlier
run of \TeX\ on the current file. The \meta{macro} must be a macro
name such as |\mymacro|. It will be redefined such that it is
\begin{itemize}
\item either just |\relax| or
\item a |\pgfpoint...| command.
\end{itemize}
The first case will happen when the position has not been marked at
all or when the file is typeset for the first time, when the
coordinates are not yet available.
In the second case, executing \meta{macro} yields the position on
the page that is to be interpreted as follows: A coordinate like
|\pgfpoint{2cm}{3cm}| means ``2cm to the right and 3cm up from the
origin of the page.'' The position of the origin of the page is not
guaranteed to be at the lower left corner, it is only guaranteed
that all pictures on a page use the same origin.
To determine the lower left corner of a page, you can call
|\pgfsys@getposition| with \meta{name} set to the special name
|pgfpageorigin|. By shifting all positions by the amount returned by
this call you can position things absolutely on a page.
\example Referencing a point of the page:
\begin{codeexample}[code only]
The value of $x$ is \pgfsys@markposition{here}important.
Lots of text.
\hbox{\pgfsys@markposition{myorigin}%
\begin{pgfpicture}
% Switch of size protocol
\pgfpathmoveto{\pgfpointorigin}
\pgfusepath{use as bounding box}
\pgfsys@getposition{here}{\hereposition}
\pgfsys@getposition{myorigin}{\thispictureposition}
\pgftransformshift{\pgfpointscale{-1}{\thispictureposition}}
\pgftransformshift{\hereposition}
\pgfpathcircle{\pgfpointorigin}{1cm}
\pgfusepath{draw}
\end{pgfpicture}}
\end{codeexample}
\end{command}
\subsection{Internal Conversion Commands}
The system commands take \TeX\ dimensions as input, but the dimensions
that have to be inserted into \pdf\ and PostScript files need to be
dimensionless values that are interpreted as multiples of
$\frac{1}{72}\mathrm{in}$. For example, the \TeX\ dimension $2bp$
should be inserted as |2| into a \pdf\ file and the \TeX\ dimension
$10\mathrm{pt}$ as |9.9626401|. To make this conversion easier, the following
command may be useful:
\begin{command}{\pgf@sys@bp\marg{dimension}}
Inserts how many multiples of $\frac{1}{72}\mathrm{in}$ the
\meta{dimension} is into the current protocol stream (buffered).
\example |\pgf@sys@bp{\pgf@x}| or |\pgf@sys@bp{1cm}|.
\end{command}
Note that this command is \emph{not} a system command that can/needs
to be overwritten by a driver.
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