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[Bug]: leading whitespace in legend and labels ignored with usetex=True #24166

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lukashergt opened this issue Oct 14, 2022 · 5 comments
Open

[Bug]: leading whitespace in legend and labels ignored with usetex=True #24166

lukashergt opened this issue Oct 14, 2022 · 5 comments
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topic: text/usetex

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@lukashergt
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lukashergt commented Oct 14, 2022 •
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Bug summary

As raised in a question on stackoverflow, none of the typical latex commands for horizontal white space (e.g. ~, \,, \quad, \hphantom{whitespace}) seem to work at the start of a text label when using text.usetex=True.

The commands work as expected in the middle of a text label.

Code for reproduction

import matplotlib.pyplot as plt
plt.rcParams['font.family'] = 'serif'
plt.rcParams['text.usetex'] = True
plt.rcParams['mathtext.fontset'] = 'cm'

fig = plt.figure(figsize=(4, 3))
plt.plot([], label="~ tilde $\\sim$")
plt.plot([], label="\, comma \\textbackslash,")
plt.plot([], label="\quad \\textbackslash quad")
plt.plot([], label="\hphantom{whitespace} \\textbackslash hphantom")
plt.plot([], label=".\hphantom{whitespace} ugly leading dot")
plt.plot([], label=".whitespace ugly leading dot")
plt.xlabel("\hphantom{whitespace} xlabel")
plt.legend()

Actual outcome

As you can see in the image below, none of the horizontal white space commands seem to be doing anything as long as they are at the head of the legend label or xlabel.

They all work fine when starting with some other character. Compare legend labels 4, 5, and 6. \hphantom{whitespace} doesn't do anything in label 4, but in label 5 after a leading dot it correctly produces exactly the amount of white space that matches the horizontal space of the word whitespace as shown in label 6.

no leading whitespace

Expected outcome

The latex commands ~, \,, \quad, \hphantom{whitespace} should produce horizontal white space even when at the start of a text label.

System

  • Operating system: Manjaro Linux
  • Matplotlib Version: 3.6.1
  • Matplotlib Backend: module://matplotlib_inline.backend_inline
  • Python version: 3.10.7
  • Jupyter version: 6.4.12 (notebook), 3.4.7 (lab)
  • Installation: pip
@timhoffm
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This is likely due to dvipng -T tight being used in TexManager.make_png()`. My guess is that we are fundamentally not able to preserve leading whitespace. But people with more TeX/dvi knowledge may know better.

@anntzer
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anntzer commented Oct 17, 2022

My guess is that we need to somehow hook the new-paragraph (\everypar) mechanism of tex to make it lay a marker there so that we know where the intended start-of-line is, but there's probably a bit of engineering needed (especially as we don't want this to affect displaymath, which is normally rendered at the center of the page, i.e. very far from the normal paragraph start position).

@zweihuehner
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Is there a update on this? I have a similar problem with adding leading whitespace to the tick labels.

@tacaswell
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@zweihuehner For ticklabels I think you can right-align the text and get the effect I suspect you want.

I do not think this is a regression (it has always been like this) and is unfortunately not a high priority issue. For this to move forward we need someone to look into the latex -> dvi pipeline and sort out how to extract the intended bounding box (including white space).

@pjgorski
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A workaround. I also had a similar issue for axis label. I solved it by moving the whole label.

ax2.set_ylabel('Ylabel', y=0.4)

I guess it is more difficult to do it for legend texts, but maybe it is still possible?

@ksunden ksunden mentioned this issue Jun 9, 2023
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@ksunden ksunden mentioned this issue Sep 25, 2024
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@tacaswell @anntzer @timhoffm @pjgorski @lukashergt @zweihuehner