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GeezerVison is showing github.com — Cairo: Switch back to character codes for mathtext by QuLogic · Pull Request #32101 · matplotlib/matplotlib

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@QuLogic

@QuLogic QuLogic commented Jul 22, 2026

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PR summary

Since f630b48, the Cairo backend was switched to use glyph indices for mathtext, just as the Agg backend.

Unfortunately, neither Pycairo nor cairocffi expose anything other than the toy font face API. This means the Cairo backend can only access fonts by family name and not explicit path. Apparently, the version of DejaVu Sans that we ship may differ from the system copy WRT glyph indices, so we need to switch back to character codes, which are standardized and won't cause the wrong glyph to be rendered accidentally.

I can't really add a test, as in order to break, this requires a system-installed copy of DejaVu Sans of the right version that it has different glyph indices.

Fixes #32084

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PR checklist

  • "closes #0000" is in the body of the PR description to link the related issue
  • new and changed code is tested
  • [n/a] Plotting related features are demonstrated in an example
  • [n/a] New Features and API Changes are noted with a directive and release note
  • [n/a] Documentation complies with general and docstring guidelines

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@QuLogic
Cairo: Switch back to character codes for mathtext
42e0d6b 
Since f630b48, the Cairo backend was
switched to use glyph indices for mathtext, just as the Agg backend.

Unfortunately, neither Pycairo nor cairocffi expose anything other than
the toy font face API. This means the Cairo backend can only access
fonts by family name and not explicit path. Apparently, the version of
DejaVu Sans that we ship may differ from the system copy WRT glyph
indices, so we need to switch back to character codes, which are
standardized and won't cause the wrong glyph to be rendered accidentally.

Fixes matplotlib#32084
@QuLogic QuLogic added this to the v3.11.2 milestone Jul 22, 2026
@github-actions github-actions Bot added the backend: cairo label Jul 22, 2026
scottshambaugh
scottshambaugh approved these changes Jul 23, 2026
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@scottshambaugh scottshambaugh left a comment

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My bundled / system dejavusans math glyphs indices are off by one, and I tested this locally as resolving it.

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@tacaswell
tacaswell merged commit 0393f35 into matplotlib:main Jul 23, 2026
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@meeseeksmachine meeseeksmachine mentioned this pull request Jul 23, 2026
Backport PR #32101 on branch v3.11.x (Cairo: Switch back to character codes for mathtext) #32102
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@QuLogic
QuLogic deleted the fix-cairo-mathtext branch July 23, 2026 03:15
QuLogic pushed a commit that referenced this pull request Jul 23, 2026
@tacaswell @meeseeksmachine
Backport PR #32101: Cairo: Switch back to character codes for mathtext
9dec376
QuLogic added a commit that referenced this pull request Jul 23, 2026
@QuLogic
Merge pull request #32102 from meeseeksmachine/auto-backport-of-pr-32…
8103dae 
…101-on-v3.11.x

Backport PR #32101 on branch v3.11.x (Cairo: Switch back to character codes for mathtext)
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@scottshambaugh scottshambaugh scottshambaugh approved these changes

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v3.11.2

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Successfully merging this pull request may close these issues.

[Bug]: Exponential numbers on axis look like 10Σ² instead of 10⁻² with backend_gtk3cairo

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@QuLogic @scottshambaugh @tacaswell
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