FIX: Add mtext into RendererBase._draw_as_path() arguments - #31910

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Thanks! Can you please add a test to ensure this works as expected?

Ah yes, sorry! I have included a test below for this:

>>> import matplotlib as mpl
>>> import matplotlib.pyplot as plt
>>> mpl.rcParams['text.usetex'] = True
>>> plt.rcParams['text.latex.preamble'] = r"\usepackage{lmodern}"
>>> x = list(range(5))
>>> plt.plot(x,x)
>>> plt.savefig('test.png', backend='cairo')

Based on the information above, it seems that the error occurs only when the backend='cairo' is called. I was not able to get the error if the backend was not explicitly defined.

Thank you!

it seems that the error occurs only when the backend='cairo'

Any idea why?

And can you add a test to test_text.py, something like:

I think the error occurs mainly because the mtext argument in draw_tex(...) was not passed into the next function self._draw_text_as_path(...) in the RendererBase class:

More specifically, with cairo the figure tries to draw the image with self.figure.draw(self._renderer) in backend_cairo.py:

This then calls the draw() function in text.py, where draw_tex(...) is used in line 905:

The TypeError then occurs after that since mtext was not passed into the next function.

I followed the traceback messages a little bit and tried to identity the root cause. I checked two other backend files backend_agg.py

There, they both have similar calls with self.figure.draw(renderer), but there were no errors with these backends.
I noticed that only the RendererAgg and RendererCairo classes inherit from RendererBase; a different parent is used for RendererPdf.

This is where I noticed that RendererAgg has its own draw_tex(...) method but RendererCairo does not. Furthermore, in RendererAgg, the mtext argument was not used at all, but in RendererBase (and thus RendererCairo), this argument was needed. Which was why only backend=cairo would throw an error, while backend=pdf and backend=agg were fine.

I suspect every backend that has RendererBase as a parent in its renderer class but without its own draw_tex(...) method would thus throw the same error when using LaTeX.

This is my first ever pull request to such a massive repo, so I am still figuring out how and where to write the tests for this according to the docs. Thank you for your patience and understanding! 😄

Thanks for your work on this. Writing a test here might be a bit difficult for a newcomer, since it's not in the standard rendering path. I've gone ahead and written one here, as well as rebased, so that we can get 3.11.1 out soonish.