toolkit: make font metrics runtime-pluggable (Font interface)#17
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Completes the last pre-1.0 model-edge item. Introduces a Font interface
(Advance/Height/Draw) with a scalable built-in bitmap font: SetFont(
NewBitmapFont(2)) doubles all text ('retina' rendering), and every widget
re-lays-out because GlyphHeight/GlyphAdvance are now read from the active
font at draw time instead of being compile-time constants.
BREAKING (pre-1.0): GlyphHeight and GlyphAdvance become functions, as do the
six metric-derived dimensions (CardHeaderH, CardFooterH, DatePickerFieldH,
DiffLineH, FormFieldLabelH, TimelineEventH) — a const can't call a function.
All 197 internal call sites updated; consumers append () when upgrading.
The default (scale-1) bitmap renders pixel-identical to before, so no golden
regressions. 100% coverage retained; go vet clean; 6 arches + wasm build.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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The final pre-1.0 "model edge" item, and the one invasive refactor of the set — done as a single atomic PR (a half-conversion won't compile).
What
Fontinterface (Advance/Height/Draw) + a scalable built-in bitmap font.SetFont(NewBitmapFont(2))doubles all text ("retina");SetFont(nil)restores the default.GlyphHeight/GlyphAdvancebecame functions returning the active font's metrics.Breaking change (pre-1.0, 0.x)
A
constcan't call a function, soGlyphHeight/GlyphAdvanceand the six metric-derived dimensions —CardHeaderH,CardFooterH,DatePickerFieldH,DiffLineH,FormFieldLabelH,TimelineEventH— are now functions. All 197 internal call sites were updated; downstream consumers append()when they adopt v0.20. (The only sibling that references these,gallery, pinsv0.6.2and is unaffected until it bumps.)Safety
The default scale-1 bitmap renders pixel-identical to the old fixed font (each lit bit is a 1×1 block), so there are no golden regressions. 100% coverage retained (added a font-metrics test covering
SetFont/CurrentFont/NewBitmapFont+ scaled rendering + the clamp + cell-painter delegation);go vetclean; builds on all 6 arches + js/wasm.🤖 Generated with Claude Code