allow sloped/transform shape with non-identity transformation

[Qrrbrbirlbel]

This applies the fixes of @thinbold and @muzimuzhi also to curves and arc while not globalize xc/yc for the line function.

In my opinion, this is not a breaking change because the previous behavior was never the intended way.

Motivation for this change

Fixes #1058

Checklist

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• Code changes are licensed under GPLv2 + LPPLv1.3c
• Documentation changes are licensed under FDLv1.2

[muzimuzhi]

Only reviewed the styling. I already forgot my own patches. :)

A new test is needed, though it could be added after #1116 is handled first, which has blocked all PRs more than just typo fixes for a while.

[muzimuzhi]

I was already listed on line 30. 🤔

[Qrrbrbirlbel]

Whoops, I didn't realize that. The recent update only had your nickname so I didn't even scan past the m …

[muzimuzhi]

The three pair of additions to \pgftransformlineattime, \pgftransformarcaxesattime, and \pgftransformcurveattime are so similar that maybe two new macros abstracting them correspondingly can be provided.

[Qrrbrbirlbel]

Good idea, unfortunately \pgftransformlineattime uses \pgf@xc/\pgf@yc and \pgf@x/\pgf@y isn't save to use inbetween. I would just refactor that so that it uses x/y instead of xc/yc. (Too big of a change?)

That said, there's a lot more that they have in common.

[Qrrbrbirlbel]

A new test is needed, though it could be added after #1116 is handled first, which has blocked all PRs more than just typo fixes for a while.

I do know that there's that big #1116 delaying everything else (but I got impatient because it really gets in the way oftentimes – xscale and yscale as in #1287's source is probably rare [and avoidable by scaling via x and y keys] – but just rotating, a very common transformation, is also broken this way).

I do not know much about “a new test”, though, and what is required from me.

[Qrrbrbirlbel]

Here's a \pgftransform@commonattime macro that combines all the common parts of the \pgftransform…attime commands:

• #1 needs to setup \pgf@x and \pgf@y for the position, i.e. the \pgftransformshift, which is done by the corresponding \pgfpoint…attime.
• #2 needs to setup \pgf@x and \pgf@y to be the tangent vector.

The, probably, legacy code of \pgftransformlineattime calculated the tangent again; this is now extracted from \pgfpointlineattime – just as it is with the others.

Here's a testfile with many transformations and all three types of paths (following the example of #1287).
It also contains an adjustment to the \tikz@timer@line timer that would allow distances for the pos key, which then uses a new \pgftransformlineatdistance macro whose definition is now just as easy as for the …attime macros.

(And, as I now realize, this also shows that the name \pgftransform@commonattime isn't really correct, either.)

I've also adjusted the examples in the source since they either used deprecated macros (\pgfxy) or were simply wrong.

\documentclass[tikz]{standalone}
\begin{document}
\tikzset{
  every picture/.append style={
    xscale=2,    yscale=3,
    xshift=40pt, yshift=50pt,
    xslant=.2,   yslant=-.3,
    rotate=-35,
    nodes=above,
    execute at begin picture={
      \draw[help lines, step=1] (0,0) grid (7,3);
      \draw[thick, <->] (0,1) |- (1,0);}}}
%\makeatletter
%\let\iftikz@time@isdistance\iffalse
%\tikzset{
%  pos/.code=\edef\tikz@time{#1}\pgfutil@ifxempty\tikz@time{}{%
%              \pgfmathsetmacro\tikz@time{\tikz@time}%
%              \let\iftikz@time@isdistance\ifpgfmathunitsdeclared}}
%\def\tikz@timer@line{%
%  \iftikz@time@isdistance
%    \pgftransformlineatdistance{\tikz@time pt}{\tikz@timer@start}{\tikz@timer@end}%
%  \else
%    \pgftransformlineattime{\tikz@time}{\tikz@timer@start}{\tikz@timer@end}%
%  \fi}%
%\def\pgftransformlineatdistance#1#2#3{%
%  \pgftransform@commonattime{\pgfpointlineatdistance{#1}{#2}{#3}}{\pgf@x=\pgf@xa\pgf@y=\pgf@ya}}
%\makeatother
\begin{tikzpicture}
\draw (0, 0) -- node[sloped                 ] {\texttt{sloped} only}                         +(2, 2);
\draw (2, 0) -- node[        transform shape] {\texttt{transform shape} only}                +(2, 2);
\draw (4, 0) -- node[sloped, transform shape] {\texttt{sloped} and \texttt{transform shape}} +(2, 2);
\end{tikzpicture}
%\begin{tikzpicture}[pos=2cm]
%\draw (0, 0) -- node[sloped                 ] {\texttt{sloped} only}                         +(2, 2);
%\draw (2, 0) -- node[        transform shape] {\texttt{transform shape} only}                +(2, 2);
%\draw (4, 0) -- node[sloped, transform shape] {\texttt{sloped} and \texttt{transform shape}} +(2, 2);
%\end{tikzpicture}
\begin{tikzpicture}
\draw (0, 0) to[bend left] node[sloped                 ] {\texttt{sloped} only}                         +(2, 2);
\draw (2, 0) to[bend left] node[        transform shape] {\texttt{transform shape} only}                +(2, 2);
\draw (4, 0) to[bend left] node[sloped, transform shape] {\texttt{sloped} and \texttt{transform shape}} +(2, 2);
\end{tikzpicture}
\begin{tikzpicture}[start angle=180, delta angle=-120, x radius=1.5, y radius=.75, nodes=midway]
\draw (0, 0) arc[] node[sloped                 ] {\texttt{sloped} only}                        ;
\draw (2, 0) arc[] node[        transform shape] {\texttt{transform shape} only}               ;
\draw (4, 0) arc[] node[sloped, transform shape] {\texttt{sloped} and \texttt{transform shape}};
\end{tikzpicture}
\end{document}