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I'm trying to override the color key within a pic but not within the enclosing scope (That is the path/draw/fill instruction).

My objective is to be able to set the colour for a path and have this affect the pic as well. That is the pic might have a custom shading and I would like this shading to adopt the paths colour as a tint. One should, however, still be allowed to override the local colour for the pic.

The example shows how I think it should be coded based upon the documentation but the filter is not working as I'd expected. Within the example I create a local name space /tikz/example as originally the 'color' style was clobbering the /tikz/color key. Filtering also needs a family to work with.

My understanding of filtering is that one ought to create/register the filter, in this case tikz/example, and then activate it when necessary i.e. before and after pic actions is executed.

The output I expect to see is the backround block in white with a blue line, overlaid by the three smaller blocks each shaded in blue, red and green.

\documentclass[tikz]{standalone}

\usetikzlibrary{calc}

\tikzset{
 basis/.initial=1em,
 block/.is family,
 /tikz/pic actions/.install key filter=block,
 block/.pic={
  \draw[block/.activate family, pic actions, block/.deactivate family]
    let \n{basis}={\pgfkeysvalueof{/tikz/basis}} in 
      (-\n{basis},-\n{basis}) rectangle  (\n{basis},\n{basis});
 },
 block/.cd,
 colour/.style={/tikz/top color   =#1!50!white,
                /tikz/bottom color=#1!50!black},
}

\begin{document}

\begin{tikzpicture}
\draw[color=blue] 
     ( 0, 0) pic               {block}
     (-1,-1) pic[color=green]  {block}
      rectangle
      (1,1)  pic[color=red]    {block};
\end{tikzpicture}

\end{document}
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1 Answer 1

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2

Sorry but I do not understand why you need all this "block family". Inside a picture the pic actions contains the current color settings, that are by default the path's one, but you can overwrite them inside the pic style. 

\documentclass[tikz]{standalone}
\usetikzlibrary{calc}

\tikzset{
 basis/.initial=1em,
 block/.pic={
  \draw[pic actions]
    let \n{basis}={\pgfkeysvalueof{/tikz/basis}} in
      (-\n{basis},-\n{basis}) rectangle  (\n{basis},\n{basis});
 },
 colour/.style={top color   =#1!50!white,
                bottom color=#1!50!black},
}

\begin{document}

  \begin{tikzpicture}
    \draw[blue]
      ( 0, 0) pic                         {block}
      (-1,-1) pic[colour=green, draw=red] {block}
        rectangle
      (1,1)  pic[colour=red]              {block};
  \end{tikzpicture}

\end{document}

enter image description here

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2
  • Thanks for the response, my actual aim is to use the filter mechanism. I suspect one may be able to intercept keys within the /tikz/block family and use them to manipulate those in the /tikz family. This would allow me to do things like intercept certain keys, for example intercepting fill to providing a shaded fill in place of a flat fill. it's a bit of an over complication for a pic but I'm trying more exotic things. I've seen /.search also used in this way but it acts later.
    – Carel
    Oct 14, 2016 at 15:40
  • Sorry but I do not understand what you really want. My be you just want to replace (-1,-1) pic[color=green] {block} by (-1,-1) pic[block\colour=green] {block} in your original code ?
    – Kpym
    Oct 15, 2016 at 10:25

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