Fix table text not scaling with device font scale on mobile (LEMS-3885)#3771
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Fix table text not scaling with device font scale on mobile (LEMS-3885)#3771SonicScrewdriver wants to merge 2 commits into
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The mobile apps honor the device font scale by applying CSS zoom to the page body. Under zoom z, Zoomable measured its container as z times narrower while the child's intrinsic width was unchanged, so its fit-to-width transform scale shrank by exactly z — the net visual size of fitted tables (and block math) was identical to unzoomed, cancelling the font enlargement entirely. Zoomable now fits content to the zoom-adjusted container width (parentWidth × effective zoom), so the fitted content's visual size grows with the font scale like all other text. Overflow at the enlarged size is handled by the existing tap-to-zoom and overflowX scrolling. The effective zoom is read from currentCSSZoom where available (Chrome/Android WebView 128+, Safari/iOS 18.4+) with a fallback to the computed zoom of document.body for older webviews. When no zoom is applied the behavior is unchanged. https://claude.ai/code/session_013e7u2DvJ4UxdpmYC5qsVHL
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Size Change: +26 B (+0.01%) Total Size: 508 kB 📦 View Changed
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npm Snapshot: PublishedGood news!! We've packaged up the latest commit from this PR (6aa3e38) and published it to npm. You Example: pnpm add @khanacademy/perseus@PR3771If you are working in Khan Academy's frontend, you can run the below command. ./dev/tools/bump_perseus_version.ts -t PR3771If you are working in Khan Academy's webapp, you can run the below command. ./dev/tools/bump_perseus_version.js -t PR3771 |
Interactive graphs already solve zoom detection for the mobile font scale with getCSSZoomFactor, which accumulates the computed CSS zoom across all ancestors. Move it from interactive-graphs/utils to a shared util module, use it in Zoomable in place of the newly-added getEffectiveZoom (which depended on currentCSSZoom browser support with a body-only fallback), and give the shared helper its own unit tests. https://claude.ai/code/session_013e7u2DvJ4UxdpmYC5qsVHL
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Summary:
The mobile apps honor the device font scale by applying CSS zoom to the
page body. Under zoom z, Zoomable measured its container as z times
narrower while the child's intrinsic width was unchanged, so its
fit-to-width transform scale shrank by exactly z — the net visual size
of fitted tables (and block math) was identical to unzoomed, cancelling
the font enlargement entirely.
Zoomable now fits content to the zoom-adjusted container width
(parentWidth × effective zoom), so the fitted content's visual size
grows with the font scale like all other text. Overflow at the enlarged
size is handled by the existing tap-to-zoom and overflowX scrolling.
The effective zoom is read from currentCSSZoom where available
(Chrome/Android WebView 128+, Safari/iOS 18.4+) with a fallback to the
computed zoom of document.body for older webviews. When no zoom is
applied the behavior is unchanged.
Issue: LEMS-3885
Test plan: