Plot option smooth and decorations.markings

[ghost]

There is an interesting interplay between the plot option smooth and decorations.marking (but most likely not only for markings decorations). Consider the MWE

\documentclass[tikz,border=3.14mm]{standalone}
\usetikzlibrary{calc,decorations.markings}
\begin{document}
\begin{tikzpicture}[scale=2,pics/coordsys/.style = {
    code = {
        \draw [->,pic actions] (0,0) -- +(1,0)[red] node[pos=1.1]
		{$x$};
        \draw [->,pic actions] (0,0) -- +(0,1)[blue] node[pos=1.1,
		%rotate=00,
		%transform shape,
		%transform shape=false
		]
		{$y$};
    }},rotated coordsys at/.style={postaction={decorate,decoration={markings,
mark=at position #1 with {
\path (0,0) coordinate (O') (1,0) coordinate (X');
\path let \p1=($(X)-(O)$),\p2=($(X')-(O')$) in \pgfextra{%
\pgfmathsetmacro{\myangle}{atan2(\y1,\x1)-atan2(\y2,\x2)}
\xdef\myangle{\myangle}};
\pgftransformresetnontranslations
 \path (O') pic[solid,rotate=-\myangle]{coordsys};
}}}}]
 \path (0,0) coordinate (O) (1,0) coordinate (X);
 \draw[rotated coordsys at/.list={0.1,0.3,0.5,0.7,0.9}] 
	plot[variable=\x,domain=-2:2] (\x,{sin(\x*45)});
 \draw[rotated coordsys at/.list={0.1,0.3,0.5,0.7,0.9}] 
  plot[variable=\x,domain=-2:2,samples=25,smooth] (\x+5,{sin(\x*45)});
\end{tikzpicture}
\end{document}

As one can see, on the left side, where a nonsmooth plot is employed, the y is upright. On the other hand, on the right side where the plot has the smooth key, it is not. The difference in behavior is already surprising to me. However, what is worse, I am unable to cure it (other than explicitly computing the rotation angle that rotates it back to upright). I played with the usual suspects like tansform shape, rotate, \pgftransformresetnontranslations in all combinations I could think of but could not fix it.

P.S. It does not seem to be related to the usage of a pic.

\documentclass[tikz,border=3.14mm]{standalone}
\usetikzlibrary{calc,decorations.markings}
\begin{document}
\begin{tikzpicture}[scale=2,rotated coordsys at/.style={postaction={decorate,decoration={markings,
mark=at position #1 with {
\path (0,0) coordinate (O') (1,0) coordinate (X');
\path let \p1=($(X)-(O)$),\p2=($(X')-(O')$) in \pgfextra{%
\pgfmathsetmacro{\myangle}{atan2(\y1,\x1)-atan2(\y2,\x2)}
\xdef\myangle{\myangle}};
%\pgftransformresetnontranslations
 \draw [->] (O') -- +(1,0)[red] node[pos=1.1]
		{$x$};
 \draw [->] (O') -- +(0,1)[blue] node[pos=1.1,
		%rotate=00,
		%transform shape,
		%transform shape=false
		]
		{$y$};
}}}}]
 \path (0,0) coordinate (O) (1,0) coordinate (X);
 \draw[rotated coordsys at/.list={0.1,0.3,0.5,0.7,0.9}] 
	plot[variable=\x,domain=-2:2] (\x,{sin(\x*45)});
 \draw[rotated coordsys at/.list={0.1,0.3,0.5,0.7,0.9}] 
  plot[variable=\x,domain=-2:2,samples=25,smooth] (\x+5,{sin(\x*45)});
 \draw[rotated coordsys at/.list={0.1,0.3,0.5,0.7,0.9}]  (-2,-1) to[bend right] 
  (2,-1);
\end{tikzpicture}
\end{document}

has the same issue.

[hmenke]

I don't remember touching any decorations or plot code, so if this is a regression it must be really old.

[ghost]

@hmenke OK, I remove the parentheses.

[hmenke]

This is the plot handler that is used when the smooth option is active:

pgf/tex/generic/pgf/libraries/pgflibraryplothandlers.code.tex

Lines 13 to 88 in ee17ca5

	% This handler converts each plot stream command into a curveto
	% command, except for the first, which is converted to the previously
	% specified action.
	%
	% Example:
	%
	% \pgfpathmoveto{\pgfpointorigin}
	% \pgfsetlinetofirstplotpoint
	% \pgfplothandlercurveto
	% \pgfplotxyfile{mytable}
	\pgfdeclareplothandler{\pgfplothandlercurveto}{}{%
	point macro=\pgf@plot@curveto@handler@initial,
	jump macro=\pgf@plot@smooth@next@moveto,
	end macro=\pgf@plot@curveto@handler@finish
	}%
	\def\pgf@plot@smooth@next@moveto{%
	\pgf@plot@curveto@handler@finish%
	\global\pgf@plot@startedfalse%
	\global\let\pgf@plotstreampoint\pgf@plot@curveto@handler@initial%
	}%
	\def\pgf@plot@curveto@handler@initial#1{%
	\pgf@process{#1}%
	\pgf@xa=\pgf@x%
	\pgf@ya=\pgf@y%
	\pgf@plot@first@action{\pgfqpoint{\pgf@xa}{\pgf@ya}}%
	\xdef\pgf@plot@curveto@first{\noexpand\pgfqpoint{\the\pgf@xa}{\the\pgf@ya}}%
	\global\let\pgf@plot@curveto@first@support=\pgf@plot@curveto@first%
	\global\let\pgf@plotstreampoint=\pgf@plot@curveto@handler@second%
	}%
	\def\pgf@plot@curveto@handler@second#1{%
	\pgf@process{#1}%
	\xdef\pgf@plot@curveto@second{\noexpand\pgfqpoint{\the\pgf@x}{\the\pgf@y}}%
	\global\let\pgf@plotstreampoint=\pgf@plot@curveto@handler@third%
	\global\pgf@plot@startedtrue%
	}%
	\def\pgf@plot@curveto@handler@third#1{%
	\pgf@process{#1}%
	\xdef\pgf@plot@curveto@current{\noexpand\pgfqpoint{\the\pgf@x}{\the\pgf@y}}%
	% compute difference vector:
	\pgf@xa=\pgf@x%
	\pgf@ya=\pgf@y%
	\pgf@process{\pgf@plot@curveto@first}
	\advance\pgf@xa by-\pgf@x%
	\advance\pgf@ya by-\pgf@y%
	% compute support directions:
	\pgf@xa=\pgf@plottension\pgf@xa%
	\pgf@ya=\pgf@plottension\pgf@ya%
	% first marshal:
	\pgf@process{\pgf@plot@curveto@second}%
	\pgf@xb=\pgf@x%
	\pgf@yb=\pgf@y%
	\pgf@xc=\pgf@x%
	\pgf@yc=\pgf@y%
	\advance\pgf@xb by-\pgf@xa%
	\advance\pgf@yb by-\pgf@ya%
	\advance\pgf@xc by\pgf@xa%
	\advance\pgf@yc by\pgf@ya%
	\edef\pgf@marshal{\noexpand\pgfpathcurveto{\noexpand\pgf@plot@curveto@first@support}%
	{\noexpand\pgfqpoint{\the\pgf@xb}{\the\pgf@yb}}{\noexpand\pgf@plot@curveto@second}}%
	{\pgf@marshal}%
	% Prepare next:
	\global\let\pgf@plot@curveto@first=\pgf@plot@curveto@second%
	\global\let\pgf@plot@curveto@second=\pgf@plot@curveto@current%
	\xdef\pgf@plot@curveto@first@support{\noexpand\pgfqpoint{\the\pgf@xc}{\the\pgf@yc}}%
	}%
	\def\pgf@plot@curveto@handler@finish{%
	\ifpgf@plot@started%
	\pgfpathcurveto{\pgf@plot@curveto@first@support}{\pgf@plot@curveto@second}{\pgf@plot@curveto@second}%
	\fi%
	}%

[ghost]

@hmenke I do not think it is the plot handler but Bezier vs. straight lines.

 \draw[rotated coordsys at/.list={0.1,0.3,0.5,0.7,0.9}]  (-2,-1) to[bend right] 
  (2,-1);

has the same issue.

[hmenke]

Which is kind of the same statement, because the plot handler looks pretty innocent, so it probably comes from \pgfpathcurveto. Do you have an old version at hand with which you could test whether this is a regression?

[ghost]

@hmenke I agree that it is the same thing. All I wanted to say is that it is not the plot handler but the way TikZ switches to the tangent system. And I do not have an old version at hand at the moment.

[hmenke]

I quickly tested with TeX Live 2015 and 2016 and they both exhibit the same broken behaviour as the latest master.

[ghost]

@hmenke OK, thanks! (I did not see this issue in the various tangent solutions on the TeX-SE site.)

[hmenke]

I just realized that you are using a pic. There are some known issues with pic, so that might be the source of the problem.

[ghost]

@hmenke Does not seem like it. If you replace the pic by its code , the same issue arises.

[Mo-Gul]

Regarding "old versions": You can find all -- or at least most of them -- on https://sourceforge.net/projects/pgf/files/pgf/.

[hmenke]

Here is your fix.

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{decorations.markings}
\begin{document}
\begin{tikzpicture}[
    rotated coordsys at/.style={
        postaction={
            decorate,
            decoration={
                markings,
                mark=at position #1 with {
                    \pgfslopedattimefalse % <---
                    \draw (0,0) -- (1,0) node[pos=1.1] {$x$};
                    \draw (0,0) -- (0,1) node[pos=1.1] {$y$};
                }
            }
        }
    }]
    \draw[rotated coordsys at/.list={0.1,0.3,0.5,0.7,0.9}]  (-2,-1) .. controls (0,-2) .. (2,-1);
\end{tikzpicture}
\end{document}

[hmenke]

Possible patch, please test.

diff --git a/tex/generic/pgf/libraries/decorations/pgflibrarydecorations.markings.code.tex b/tex/generic/pgf/libraries/decorations/pgflibrarydecorations.markings.code.tex
index 9d18797d..23b7ff67 100644
--- a/tex/generic/pgf/libraries/decorations/pgflibrarydecorations.markings.code.tex
+++ b/tex/generic/pgf/libraries/decorations/pgflibrarydecorations.markings.code.tex
@@ -89,6 +89,7 @@
     \pgfinterruptpath%
       \pgfscope%
         \let\pgf@lib@dec@mark@marks=\pgfutil@empty%
+        \pgfslopedattimefalse
         \pgf@lib@dec@computed@action%
       \endpgfscope%
     \endpgfinterruptpath%