Implement Makie 0.25's layout_text protocol

[dawbarton-ai]

Implements the public Makie.layout_text(handler, source, attributes) -> Makie.TextLayout protocol from MakieOrg/Makie.jl#5717, so Makie 0.25 users select TeXLayout explicitly instead of relying on the type piracy the legacy adapter needs.

with_theme(text_handler = TeXLayoutHandler()) do
    fig = Figure()
    Axis(fig[1, 1]; xlabel = L"x", ylabel = L"f(x)")
    fig
end

TeXLayoutHandler emits glyph IDs, exact FreeType faces, origins, extents, scales, block bounds, and LineSegments specs for horizontal and vertical rules. Makie keeps ownership of alignment, rotation, offset, validation, placement, and batching, so moving or rotating a label no longer re-runs layout. The handler claims only LaTeXString; plain strings and rich text fall through to Makie. A font family and LayoutOptions can be pinned per handler or left to resolve the session defaults.

Makie 0.24 keeps working through MathTeXEngineExt. Once the handler interface is present, its generate_tex_elements(::LaTeXString) specialisation delegates to MathTeXEngine's own implementation, so merely loading TeXLayout no longer changes Makie's default renderer.

Glyph and block metrics

Metrics follow Makie's contract rather than TeXLayout's ink bounds. Makie turns every GlyphExtent into (0, descender)–(hadvance, ascender) and expects the font's line metrics there, so a block's height does not depend on which characters it holds. MathTeXEngine.TeXChar pads the same way, which is why the legacy path never showed this.

Reporting bare ink bounds made L"$x$" measure 9.06 px against Makie's 20.0 px at fontsize 20, scattered baselines under align = (:*, :center), and made Axis tick-label space depend on whether a label happened to have a descender. Extents are now padded to max(ink_top, font_ascender) / min(ink_bottom, font_descender), and the block bbox is the union of the placed padded glyph boxes and rule bounds — exactly what raw_string_boundingboxes unions downstream, so align and measurement cannot disagree.

Structure

Source routing and glyph resolution moved into src/render_support.jl, so both adapters share one implementation and one per-FontFamily runtime cache instead of carrying ~120 duplicated lines each. FontFamilyKey names the cache-key type so _font_family_key's arity is stated once.

Makie joins [extras]/[targets]: the handler tests were silently skipped because nothing in CI loaded MakieExt at all. Until Makie 0.25 is released only the 0.24 branch runs there, so handler changes still need a manual run against a PR checkout.

Also fixes inline-math delimiter stripping to use valid UTF-8 indices, so $α$ no longer raises a StringIndexError, and corrects a docs example that passed text_handler to Label, which rejects it.

Verification

• Pkg.test(): 1571/1571 with Makie 0.24
• Makie PR head 727b340b: 11/11 handler assertions, 9/9 routing
• CairoMakie render pass covering fractions, radicals, mixed text/math, plain-string fall-through, and matrix rules
• Runic clean; Documenter builds clean

Stress-suite makie_cairo references still need regenerating, since changing alignment is the point of the metric fix.

🤖 Generated with Claude Code

https://claude.ai/code/session_01BYXUGdHB9mLnZemWvtkZo1

[codecov]

Codecov Report

❌ Patch coverage is 31.72043% with 127 lines in your changes missing coverage. Please review.
✅ Project coverage is 86.09%. Comparing base (eac6b8b) to head (ae10d2c).

Files with missing lines	Patch %	Lines
ext/MakieExt.jl	0.00%	111 Missing ⚠️
src/render_support.jl	76.78%	13 Missing ⚠️
src/TeXLayout.jl	0.00%	2 Missing ⚠️
ext/MathTeXEngineExt.jl	93.75%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #34      +/-   ##
==========================================
- Coverage   89.39%   86.09%   -3.31%     
==========================================
  Files          21       23       +2     
  Lines        2915     3034     +119     
==========================================
+ Hits         2606     2612       +6     
- Misses        309      422     +113     

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