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[Bug]: Inconsistent pgf backend results from text.usetex flag #28131
Description
Bug summary
The text.usetex rcParam flag can be used to enable TeX rendering on all Text elements instead of Mathtext. When using the pgf backend, I would expect this flag to have no effect and for the Text elements to be rendered identically since pgf also uses TeX to render.
The problem is that the usetex renderer seems to have a different implementation than the pgf renderer.
Code for reproduction
import matplotlib.pyplot as plt
import matplotlib as mpl
mpl.use('pgf')
plt.rcParams.update({
'figure.dpi': 400,
'text.usetex': True, # TODO: comment this out to get different results
'ytick.labelsize': 1,
})
# Create the figure and axis objects
fig, ax = plt.subplots(figsize=(2, 1.5))
# Plot the data
x = [1, 2, 3, 4, 5]
y = [2, 4, 6, 8, 10]
ax.plot(x, y)
# Set the title and axis labels
ax.set_title('My Plot')
ax.set_xlabel('X-axis')
ax.set_ylabel('Y-axis')
# Save the plot to a file
plt.savefig('my_plot.png')
plt.savefig('my_plot.pgf')Actual outcome
When text.usetex is True, the tick labels use display math font to render in Tex.
When text.usetex is False, the tick labels use the regular text font to render in Tex.
Expected outcome
When using the pgf backend, I would expect enabling/disabling text.usetex to have no effect on the output.
Additional information
From what I understand, the text.usetex implementation has an unofficially supported rcParam for the preamble named text.latex.preamble. On the other hand, the pgf implementation has an officially supported rcParam for the preamble named pgf.preamble. From the documentation it's unclear to me which renderer/preamble takes precedence when both pgf and usetex are enabled.
The text.usetex renderer also does not support XeLaTeX/LuaLaTeX according to the documentation.
In conclusion:
Is there any reason why these two rendering engines can not (or should not) be unified? I suspect this is also the root cause of a lot of confusion and consistency errors people have.
Related:
#28084
Operating system
Ubuntu
Matplotlib Version
3.7.5
Matplotlib Backend
pgf
Python version
3.8.10
Jupyter version
No response
Installation
pip
Activity
anntzer commentedon Apr 25, 2024
See #20262 (comment) regarding difficulties of moving to using xe/luatex everywhere.
voidstarstar commentedon Apr 25, 2024
Thanks for that info. It sounds like unifying everything using xe/lualatex is desired, but would be a difficult transition.
voidstarstar commentedon Apr 25, 2024
I think I might understand what's going on now. The documentation was a bit unclear about what
text.usetexactually does and how it's behavior changes slightly based on the backend.With the agg backend:
text.usetex=True, it will use the latex compiler to render text with theTexManagerclass.text.usetex=True, it will use the preamble intext.latex.preamble.text.usetex=True, it will use TeX math mode to render text.text.usetex=False, it will use Mathtext to render text.With the pgf backend:
pgf.texsystemcompiler to render everything.pgf.preamble.text.usetex=True, it will use TeX math mode to render text.text.usetex=False, it will use TeX text mode to render text.In my original post, I had mistakenly assumed that
text.usetex=Falseshould never be possible when using the pgf backend. In general, I think most users will want to enable this flag when using pgf.(This is because
text.usetexchanges the behavior of theFormatters, and this behavior is interpreted differently by Mathtext and TeX. For example,ScalarFormatterwill output$\\mathdefault{4.0}$whentext.usetex=Trueand4.0whentext.usetex=False.)References:
https://matplotlib.org/stable/users/explain/text/mathtext.html
https://matplotlib.org/stable/users/explain/text/usetex.html
https://matplotlib.org/stable/users/explain/text/pgf.html