Unexpected behavior when using `colorbar as legend` #465

BobYue-01 · 2023-07-28T02:04:49Z

When using the colorbar as legend key, the ticks on colorbar seem to be incorrect: from the third onwards, they are all the same as the second.

The error is already visible in the official manual (1.18.1, page 293).

To make sure that I understood correctly what the key does, I checked version 1.16, which shows the expected result in the manual (1.16, page 290).

The text was updated successfully, but these errors were encountered:

muzimuzhi · 2023-07-28T13:48:46Z

With the help of git bisect, commit d2fbb2a (fixed SIMPLE scientific notation in tick arguments, 2019-05-30) is the first bad commit.

\documentclass{article}
\usepackage{pgfplots}
\pgfplotsset{compat=newest}

\begin{document}
\pgfplotscolorbardrawstandalone[
    colorbar as legend,
    colorbar style={
        ticklabel style={font=\tiny},
    },
    colormap access=const,
    colormap={CM}{
        of colormap={
            viridis,
            target pos={
                0,200,300,350,375,
                400,700,800,850,1000
            },
            sample for=const,
        },
    },
]
\end{document}

muzimuzhi · 2023-07-29T06:14:31Z

This is caused by interactions between the ~~new~~ extended uniform-loop-list optimization for \pgfplotsforeachungrouped, fpu library, and \pgfplotsarrayselect.

If /pgf/fpu is on, \pgfplotsforeachungrouped \x in {<uniform list>} {<body>} will set \x as a number in fpu representation like 1Y2.0e0] (+2.0 * 10^0). With commit d2fbb2a, the form(s) of <uniform list> was extended from 0,1,...,5 to also recognize 0,...,5. This hurt the use of

\pgfplotsforeachungrouped \x in {0,...,\pgfplots@colorcount} {%
  \pgfplotsarrayselect{\x}\of\positions\to\pgfplotsretval
  % ...
}

in colorbar drawing, since \pgfplotsarrayselect\x\of\<list>\to\<return> requires that \x is an integer assignable to a TeX count.

pgfplots/tex/generic/pgfplots/pgfplots.code.tex

Lines 1367 to 1376 in a1fe88f

    
           % accumulate a list of formatted positions into this 
        
           % variable: 
        
           \def\pgfplots@loc@TMPc{}% 
        
           \pgfplotsforeachungrouped \x in {0,...,\pgfplots@colorcount} {% 
        
           	\pgfplotsarrayselect{\x}\of\positions\to\pgfplotsretval 
        
           	\edef\pgfplots@loc@TMPa{\noexpand\pgfmathprintnumber{\pgfplotsretval}} 
        
           	\t@pgfplots@toka=\expandafter{\pgfplots@loc@TMPc}% 
        
           	\t@pgfplots@tokb=\expandafter{\pgfplots@loc@TMPa}% 
        
           	\edef\pgfplots@loc@TMPc{\the\t@pgfplots@toka \the\t@pgfplots@tokb,}% 
        
           }%

pgfplots/tex/generic/pgfplots/liststructure/pgfplotsarray.code.tex

Lines 207 to 225 in a1fe88f

    
           % Returns the #1th element of array #2 into macro #3 
        
           % Arguments: 
        
           % #1: a count 0,...,N-1 where N is the array size. 
        
           %     You may specify a number of a count. 
        
           % #2: a array 
        
           % #3: a macro name 
        
           % Example: 
        
           %   Element 0: 
        
           %   \pgfplotsarrayselect0\of\foo\to\elem 
        
           %   \elem 
        
           %   Element \count1: 
        
           %   \pgfplotsarrayselect\count1\of\foo\to\elem 
        
           \def\pgfplotsarrayselect#1\of#2\to#3{% 
        
           	\c@pgfplotsarray@tmp=#1\relax 
        
           	\expandafter\let\expandafter#3\csname\string#2@\the\c@pgfplotsarray@tmp\endcsname% 
        
           	\ifx#3\relax 
        
           		\pgfplotsthrow{no such element}{#1}{No such element: \string\pgfplotsarrayselect\the\c@pgfplotsarray@tmp\string\of{\string#2}}\pgfeov% 
        
           	\fi 
        
           }

A quick and very specific workaround

diff --git a/tex/generic/pgfplots/pgfplots.code.tex b/tex/generic/pgfplots/pgfplots.code.tex
index 0b4486b..b72bfa6 100644
--- a/tex/generic/pgfplots/pgfplots.code.tex
+++ b/tex/generic/pgfplots/pgfplots.code.tex
@@ -1368,6 +1368,9 @@
 			% variable:
 			\def\pgfplots@loc@TMPc{}%
 			\pgfplotsforeachungrouped \x in {0,...,\pgfplots@colorcount} {%
+				% ensure \x is assignable to a TeX count,
+				% because \pgfplotsarrayselect will assign \x to a TeX count)
+				\pgfmathfloattoint{\x}\let\x=\pgfmathresult
 				\pgfplotsarrayselect{\x}\of\positions\to\pgfplotsretval
 				\edef\pgfplots@loc@TMPa{\noexpand\pgfmathprintnumber{\pgfplotsretval}}
 				\t@pgfplots@toka=\expandafter{\pgfplots@loc@TMPc}%

I believe a thorough solution is to adapt \pgfplotsforeachungrouped (more specifically, \pgfplotsforeachungroupeduniform@ and the ones it calls) to make it's optimization for uniform-loop-list work with fpu.

\documentclass{article}
\usepackage{pgfplots}
\pgfplotsset{compat=1.18}

\usepackage{xpatch}
\makeatletter
% patch /pgfplots/colorbar as legend/.style={...}
\expandafter\xpatchcmd\csname pgfk@/pgfplots/colorbar as legend/.@cmd\endcsname
  {%
    \pgfplotsarrayselect{\x}\of\positions\to\pgfplotsretval
  }{%
    \pgfmathfloattoint{\x}\let\x=\pgfmathresult
    \pgfplotsarrayselect{\x}\of\positions\to\pgfplotsretval
  }{}{\PatchFailed}
\expandafter\xpatchcmd\csname pgfk@/pgfplots/colorbar as legend/.@body\endcsname
  {%
    \pgfplotsarrayselect{\x}\of\positions\to\pgfplotsretval
  }{%
    \pgfmathfloattoint{\x}\let\x=\pgfmathresult
    \pgfplotsarrayselect{\x}\of\positions\to\pgfplotsretval
  }{}{\PatchFailed}
\makeatother

\begin{document}
\pgfplotscolorbardrawstandalone[
    colorbar as legend,
    colorbar style={
        ticklabel style={font=\tiny},
    },
    colormap access=const,
    colormap={CM}{
        of colormap={
            viridis,
            target pos={
                0,200,300,350,375,
                400,700,800,850,1000
            },
            sample for=const,
        },
    },
]

{
  \pgfset{fpu=false}
  \foreach \x in {1,...,5} {\x, }\par
  \pgfplotsforeachungrouped \x in {1,2,...,5} {\x, }\par
  \pgfplotsforeachungrouped \x in {1,...,5} {\x, }
  
  \pgfset{fpu=true}
  \foreach \x in {1,...,5} {\x, }\par
  \pgfplotsforeachungrouped \x in {1,2,...,5} {\x, }\par % \x in fpu forms
  \pgfplotsforeachungrouped \x in {1,...,5} {\x, }       % \x in fpu forms
}
\end{document}

muzimuzhi · 2023-07-30T11:25:59Z

If /pgf/fpu is on, \pgfplotsforeachungrouped \x in {<uniform list>} {<body>} will set \x as a number in fpu representation like 1Y2.0e0] (+2.0 * 10^0).
[...]
I believe a thorough solution is to adapt \pgfplotsforeachungrouped (more specifically, \pgfplotsforeachungroupeduniform@ and the ones it calls) to make it's optimization for uniform-loop-list work with fpu.

It seems this behavior (for <uniform list> with form a,b,...,n) was on purpose, as it was introduced 14 years ago, in commit 063bebf on 2008-12-06. Hence the diff shown in my previous comment is on the right direction.

Alternatively, add a guard at the beginning of \pgfplotsarrayselect? Not necessary. Most uses of \pgfplotsarrayselect don't need such a guard, and there's already a similar fp-to-int guard added in commit 4214bc0 (improved the 'patch table' feature, 2010-06-22).

pgfplots/tex/generic/pgfplots/pgfplotsmeshplothandler.code.tex

Lines 2516 to 2521 in a1fe88f

    
           \pgfmathfloatparsenumber{\pgfplots@current@vertexindex}% 
        
           \pgfmathfloattoint\pgfmathresult 
        
           \let\pgfplots@current@vertexindex=\pgfmathresult 
        
           % 
        
           \let\pgfplotsexceptionmsg=\pgfplotsplothandlermesh@patchtable@rowlistener@exceptionmsg 
        
           \pgfplotsarrayselect\pgfplots@current@vertexindex\of\pgfplots@verts\to\pgfplots@stored@pt

muzimuzhi · 2023-07-30T14:59:07Z

Another option: The \pgfplotsforeachungrouped \x in {0,...,\pgfplots@colorcount} {<loop body>} is so simple that it can be replaced by \pgfutil@loop ... \pgfutil@repeat.

diff --git a/tex/generic/pgfplots/pgfplots.code.tex b/tex/generic/pgfplots/pgfplots.code.tex
index 0b4486b..ba213d0 100644
--- a/tex/generic/pgfplots/pgfplots.code.tex
+++ b/tex/generic/pgfplots/pgfplots.code.tex
@@ -1367,13 +1367,16 @@
 			% accumulate a list of formatted positions into this
 			% variable:
 			\def\pgfplots@loc@TMPc{}%
-			\pgfplotsforeachungrouped \x in {0,...,\pgfplots@colorcount} {%
+			\def\x{0}% or, is \c@pgf@counta safe here?
+			\pgfutil@loop
+			\unless\ifnum\x>\pgfplots@colorcount
 				\pgfplotsarrayselect{\x}\of\positions\to\pgfplotsretval
-				\edef\pgfplots@loc@TMPa{\noexpand\pgfmathprintnumber{\pgfplotsretval}}
+				\edef\pgfplots@loc@TMPa{\noexpand\pgfmathprintnumber{\pgfplotsretval}}%
 				\t@pgfplots@toka=\expandafter{\pgfplots@loc@TMPc}%
 				\t@pgfplots@tokb=\expandafter{\pgfplots@loc@TMPa}%
 				\edef\pgfplots@loc@TMPc{\the\t@pgfplots@toka \the\t@pgfplots@tokb,}%
-			}%
+				\edef\x{\the\numexpr\x+1}%
+			\pgfutil@repeat
 			\t@pgfplots@tokb=\expandafter{\pgfplots@loc@TMPc}%
 			\xdef\pgfplots@glob@TMPa{%
 				\noexpand\pgfplotsset{%

muzimuzhi added fpu utility labels Jul 29, 2023

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Unexpected behavior when using `colorbar as legend` #465

Unexpected behavior when using `colorbar as legend` #465

BobYue-01 commented Jul 28, 2023

muzimuzhi commented Jul 28, 2023

muzimuzhi commented Jul 29, 2023 •

edited

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muzimuzhi commented Jul 30, 2023 •

edited

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muzimuzhi commented Jul 30, 2023

Unexpected behavior when using colorbar as legend #465

Unexpected behavior when using colorbar as legend #465

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BobYue-01 commented Jul 28, 2023

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muzimuzhi commented Jul 30, 2023

Unexpected behavior when using `colorbar as legend` #465

Unexpected behavior when using `colorbar as legend` #465

muzimuzhi commented Jul 29, 2023 •

edited

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muzimuzhi commented Jul 30, 2023 •

edited

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