Using \pgftext in \behindbackground{} shape: color problems

colortikz-pgf

I do not know if this is expected or not; this is probably a very dumb operator error, but consider the following MWE:

\documentclass[border=10pt]{standalone}
\usepackage{tikz}
\pgfdeclareshape{sline}{
    \anchor{center}{\pgfpointorigin}%
    \behindbackgroundpath{
        % \pgfsetcolor{.}%       <- line B
        % \pgfsetfillcolor{red}% <- line A
        \pgfpathmoveto{\pgfpoint{-0.3cm}{0pt}}%
        \pgfpathlineto{\pgfpoint{0.3cm}{0pt}}%
        \pgfnode{circle}{center}{}{}{\pgfusepath{stroke,fill}}%
        \pgftext[top,y=0.4cm]{zzz}%
        \pgfusepath{draw}%
    }
}
\begin{document}
Text
\begin{tikzpicture}[]
    \draw[] (0,1)  node [sline]{} (1,1) node{aaa};
    \draw[blue, fill=green] (0,0)  node [sline]{} (1,0) node{aaa};
\end{tikzpicture}
\end{document}

Which result in:

What is quite puzzling is the fact that "zzz" is following the fill color of the shape and not the stroke color. I tried to find something in the manual, to no avail.

What I would like is that the shape could follow the external "fill" parameter (either in the draw, or in the shape itself) but the text should follow the draw color, like "aaa" is doing (or at least following the external current color).

Uncommenting line B gives the "fill and stroke as the current color", as expected (\pgfsetcolor sets both stroke and fill):

…and uncommenting both line A and line B gives a fixed red fill and red text.

Commenting just line B gives:

In conclusion, it seems that the text created by \pgftext is colored with the fill color and colored with the current color only if the fill color is undefined. Is this the expected behavior?

Best Answer

In principal, text is colored with fill color, not stroke color. After all, modern fonts are all outline fonts. Commands like \color and \textcolor set both the fill and stroke color, making the fact that "text is filled" less imperceptible.
Therefore in pgf, each of \pgftext, \pgfnode, and \pgfmultipartnode colors the (node) text with current fill color.
But tikz introduces a new concept "text color" which is set by text=<color> and init to empty per node. If set, for node text both the current fill and stroke color are locally set to the text color. The related code is in \tikz@do@fig:
```
\ifx\tikz@textcolor\pgfutil@empty%
\else%
   \pgfutil@colorlet{.}{\tikz@textcolor}%
   \pgfutil@color{\tikz@textcolor}%
\fi%
```
A slightly different logic can be found in \tikz@nodepart@continue and \tikz@fig@continue which uses \pgfsetcolor{.} after \fi instead of \pgfutil@color{\tikz@textcolor}. The differences I know by far is that \pgfsetcolor will also set named colors pgfstrokecolor and pgffillcolor.
Therefore, through tikz options, one can use up to three different colors for a node:
```
\node[draw=blue, fill=yellow!20, text=cyan] {text};
```
Back to pgf layer, some manual work is needed since option text=<color> is only available in tikz layer and the above code logic is only applied to tikz (not pgf) node text.

The example below provides a \pgf@cir@usetextcolor that sets the current fill and stroke color to text color if the latter is set.

\documentclass[border=10pt]{standalone}
\usepackage{tikz}

\makeatletter
\pgfdeclareshape{sline}{
    \anchor{center}{\pgfpointorigin}%
    \behindbackgroundpath{
        % \pgfsetcolor{.}%       <- line B
        % \pgfsetfillcolor{red}% <- line A
        \pgfpathmoveto{\pgfpoint{-0.3cm}{0pt}}%
        \pgfpathlineto{\pgfpoint{0.3cm}{0pt}}%
        \pgfnode{circle}{center}{}{}{\pgfusepath{stroke,fill}}%
        \pgfusepath{draw}
        % \pgfscope
        \pgf@circ@usetextcolor % if used at last, no need to wrap in pgfscope
        \pgftext[top,y=0.4cm]{zzz}%
        % \endpgfscope
    }
}

\def\pgf@circ@usetextcolor{%
  \ifx\tikz@textcolor\pgfutil@empty
  \else
    \pgfutil@colorlet{.}{\tikz@textcolor}%
    \pgfutil@color{\tikz@textcolor}%
  \fi
}
\makeatother

\begin{document}
Text
\begin{tikzpicture}[]
    \draw[] (0,1)  node [sline]{} (1,1) node{aaa};
    \draw[blue, fill=green] (0,0)  node [sline]{} (1,0) node{aaa};
    \draw[blue, fill=green] (0,-1)  node [sline,text=red]{} (1,-1) node[text=red]{aaa};
\end{tikzpicture}
\end{document}

Related Solutions

[Tex/LaTex] TikZ: Cropping the Bounding Box

The code adds some completely useless invisible (or rather white) stuff. The lines

\clip(0pt,403pt) -- (389.957pt,403pt) -- (389.957pt,99.6166pt) -- (0pt,99.6166pt) -- (0pt,403pt);
\color[rgb]{1,1,1}
\fill(3.76406pt,399.236pt) -- (380.923pt,399.236pt) -- (380.923pt,253.19pt) -- (3.76406pt,253.19pt) -- (3.76406pt,399.236pt);
\fill(53.4497pt,394.719pt) -- (374.901pt,394.719pt) -- (374.901pt,289.325pt) -- (53.4497pt,289.325pt) -- (53.4497pt,394.719pt);

draw a white background that is larger than the actual picture. TikZ sees that and thinks it is part of the picture. Simply removing/uncommenting these lines removes most of the whitespace.

Near the end of the first scope,

\color[rgb]{1,1,1}
\fill(3.76406pt,249.426pt) -- (386.193pt,249.426pt) -- (386.193pt,103.381pt) -- (3.76406pt,103.381pt) -- (3.76406pt,249.426pt);

does the same. Additionally (near the end of the second scope),

\pgftext[center, base, at={\pgfpoint{220.95pt}{106.392pt}}]{\sffamily\fontsize{9}{0}\selectfont{\textbf{ }}}

adds a blank node below the picture, again enlarging the bounding box.

Removing all those lines gives a tight bounding box.

As far as I know, TikZ cannot do the cropping for you, as it can't know whether the white stuff is intentional or not (there might for example be a dark background behind the image so that white is visible).

[Tex/LaTex] Using patterns inside pgf shapes

I don't see a way to get the stroke colour from PGF itself (\pgfgetsstrokecolor isn't a defined macro) but fortunately TikZ stores the colour in its own memory space and so it is possible to use that to get the colour. There are three such storage places:

\tikz@strokecolor
\tikz@fillcolor
tikz@color
.

The first two are macros, the last two are colours. The draw=colour option sets the first, the fill=colour option sets the second, and the color=colour options sets both of the last two.

So one solution is to set the colour to be . unless \tikz@strokecolor is set, whereupon we use that. One way of doing this is the following:

\documentclass{article}
\usepackage{tikz}

\usetikzlibrary{patterns}

\makeatletter
\pgfdeclareshape{test shape}
{
  \inheritsavedanchors[from=rectangle]
  \inheritanchor[from=rectangle]{center}

  \backgroundpath
  {
    \def\my@color{.}%
    \ifx\tikz@strokecolor\pgfutil@empty
    \else
    \let\my@color\tikz@strokecolor
    \fi
    \pgfsetfillpattern{north east lines}{\my@color}
    \pgfpathrectanglecorners{\pgfpoint{0}{0}}{\pgfpoint{1cm}{1cm}}
    \pgfusepath{fill}
  }
}
\makeatother
\begin{document}
\begin{tikzpicture}
\node[draw=red,test shape] at (0,0) {};
\node[fill=red,test shape] at (2cm,0) {};
\node[color=red,test shape] at (4cm,0) {};
\end{tikzpicture}
\end{document}

which results in:

coloured patterns

If you want a different combination then you need to adjust the choices.

Best Answer

Related Solutions

[Tex/LaTex] TikZ: Cropping the Bounding Box

[Tex/LaTex] Using patterns inside pgf shapes

Related Question