Fix pie labels and boxed text [mpl compatibility]

[sselvakumaran]

Summary

Fix the Matplotlib 3.11 pie-label and text-command gallery paths:

• preserve integer pie input dtype so {absval:d} formatting works
• implement pie_label(..., rotate=True) alignment and radial label geometry
• support named font sizes, weight, family, style, alignment, and rotation in pie text properties
• support Axes.text(style="italic", bbox=...) across browser, SVG, and native PNG rendering
• keep figure suptitles in positioned/native PNG figures after subplots_adjust(...)

This is separate from #240 and does not change autoscale margins, ticks, or bar extents.

Gallery references

• Pie label
• Text commands

Pie labels — before / Matplotlib / after

Before, the gallery aborts as soon as it requests rotated labels. After, all eight gallery figures complete. SVG keeps the radial text rotations; native PNG currently renders arbitrary-angle glyphs upright, which is a small renderer-specific text variation.

Text commands — before / Matplotlib / after

Before, the first italic boxed label aborts the example. After, the full annotated figure renders, including the box, font styling, and figure suptitle.

Verification

• 547 passed, 65 skipped in tests/pyplot
• pie_label.py: all 8 PNG captures complete
• text_commands.py: PNG capture completes
• Ruff, format check, and git diff --check pass

[codspeed-hq]

Merging this PR will degrade performance by 23.82%

⚠️ Different runtime environments detected

Some benchmarks with significant performance changes were compared across different runtime environments,
which may affect the accuracy of the results.

Open the report in CodSpeed to investigate

❌ 1 regressed benchmark
✅ 101 untouched benchmarks
⏩ 1 skipped benchmark¹

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Benchmark	BASE	HEAD	Efficiency
❌	test_select_lasso_message_1m	93.3 ms	122.4 ms	-23.82%

Tip

Investigate this regression by commenting @codspeedbot fix this regression on this PR, or directly use the CodSpeed MCP with your agent.

---

_{Comparing agent/gallery-compat-pie-text-vector (2946fc6) with main (960e132)}

Footnotes

1. 1 benchmark was skipped, so the baseline result was used instead. If it was deleted from the codebase, click here and archive it to remove it from the performance reports. ↩

[sselvakumaran]

pie chart:

• add the rotated labels, this version adds the labels but does not rotate them.
• the pie chart is not circular (maybe another PR fixes this)
• the axes, ticks are not hidden (maybe another PR fixes this)
• pie chart has visual artifacts of thin white spokes going out of the pie, probably due to piece-wise rendering of the segments - these should not be visible and/or removed.
• the xy pie chart does not actually rotate the items (this should be fixed). the pie chart is actually circular (a different PR probably fixes this), and axes are hidden (hopefully another PR fixes this).
  text commands:
• annotations do not respect italics, mathtext italics (e=mc^2)
• box 'boxed italics text in data coords' seems to over-extend instead of cleanly wrapping the text with some padding (maybe another PR fixes this?)
• figure suptitle (subtitle?) does not respect bold (or bold at all) - also both axes title and subtitle are not centered correctly (maybe another PR fixes this?)
• arrow seems to not be large enough (maybe this is due to 2x scale?)

[sselvakumaran]

I worked through each visual point in the comparison and pushed 0ca6b78.

The comparison uses the same pie_label gallery capture at normalized 640×480 resolution.

What changed:

• Pie axes now use equal aspect, hide axes/spines for the default frameless pie, and cover triangle-fan antialiasing seams with same-face strokes.
• Native PNG text now supports arbitrary rotation, italic shear, and bold emphasis, so rotated pie labels, explicit italics, and the bold suptitle are preserved in static exports.
• Simple mathtext now retains italic spans only for the math variables (E, mc), across browser, SVG, and PNG.
• Text-bbox width/padding is tightened to the Matplotlib reference.
• The legacy arrowprops={facecolor: ..., shrink: ...} arrowhead is enlarged to match Matplotlib's YAArrow proportions.
• startangle was already reaching wedge geometry; it is now regression-pinned together with the corrected label rotation.

The axes title and suptitle did not need a centering change. Pixel measurement against the Matplotlib 3.11 reference puts the XY centers at 324.75/320.5 px versus 324.5/320.0 px, respectively. The apparent offset was under 0.5 px, not a 2x-DPI error.

Verification:

• 178 relevant Python/export tests passed, 3 skipped.
• 115 Rust library tests passed.
• Ruff, JS typecheck/build, Rust clippy, and diff checks passed.
• Full exact Matplotlib 3.11 scoped rerender: all 54 examples / 82 figures remain paired; automatic similarity improves from 30/82 before these fixes to 38/82 after them.

[sselvakumaran]

I also checked the refreshed CodSpeed red on 0ca6b78. It is the same cross-runtime lasso outlier appearing on several unrelated gallery PRs, not a code-path regression from this change:

• CodSpeed explicitly reports different runtime environments.
• The only reported row is test_select_lasso_message_1m (93.3 ms → 122.4 ms).
• The benchmark and its complete timed Python/Rust path are unchanged versus main: benchmarks/test_codspeed_selection.py, python/xy/channel.py, python/xy/_figure.py, python/xy/interaction.py, python/xy/kernels.py, and src/kernels.rs have no diff.
• This PR changes annotation rendering, pyplot pie/text translation, and the static raster text opcode; none are invoked inside benchmark(channel.handle_message, uniform_figure, message).
• The full benchmark workflow passed; 101 other CodSpeed rows are unchanged.

So there is no causal performance fix to make in #243. The actionable rendering checks, including Matplotlib 3.11 compatibility and the full Rust/Python/JS test job, are green.