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fix: Render a loading font face with its family's loaded face - #26059
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Faces of a manifest font now load on first use, so a SemiBold title rendered with the system fallback (monospace on WebAssembly) until its face arrived. Use the family's already-loaded normal face meanwhile. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01TXMNu2RupRy4QPFGK2cmij
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🤖 Your WebAssembly Sample App stage site is ready! Visit it here: |
This was referenced Nov 4, 2026
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The build 243715 found UI Test snapshots differences: Details
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GitHub Issue: part of #24079 (complements #24080; does not close the issue)
PR Type:
🐞 Bugfix
What changed? 🚀
Once faces of a manifest font load on first use (#24080), text in a not-yet-loaded face (e.g. a SemiBold title) renders with the system fallback until the face arrives. On WebAssembly that fallback is a monospace font, which is a visible flash.
FontDetailsCachenow renders such text with the family's already-loaded normal face, so only the weight or style catches up when the face lands.Validation:
Measurements
No download change. The fallback window lasts until the SemiBold face arrives, ~1 RTT plus 68 KB.
How this was measured
A
dotnet new unoapppage with a SemiBold title and a dozen common controls (Skia,net10.0-browserwasm, Release publish), built twice from the same tree: with all six startup PRs (#26054–#26059) plusUnoXamlResourcesTrimming, and with only this PR's change removed. Both builds were served by the same static server (brotli q11, immutable caching for fingerprinted files) and loaded cold in headless Chrome, runs interleaved. "Visually ready" is the first CDP screencast frame identical to the settled final frame. 4G = 9 Mbps down, 85 ms RTT (CDP emulation). Values are medians with (min–max). A difference is only claimed where the ranges don't overlap. Rig: Playwright + Node, available on request.PR Checklist ✅
Screenshots Compare Test Runresults.🤖 Generated with Claude Code
https://claude.ai/code/session_01TXMNu2RupRy4QPFGK2cmij