Document Android 14+ non-linear font scaling on getFontScale and allowFontScaling - #5205
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Document Android 14+ non-linear font scaling on getFontScale and allowFontScaling#5205sbaiahmed1 wants to merge 1 commit into
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…wFontScaling On Android 14 and newer, the OS scales fonts non-linearly (small sizes grow by the full factor, large sizes progressively less; 30sp is pinned until the setting exceeds 1.5), so PixelRatio.getFontScale() no longer predicts rendered text sizes. Document this on the PixelRatio and Text pages for next and 0.86. Prompted by react/react-native#56961, where the non-linear curve was mistaken for a rendering bug.
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The
PixelRatio.getFontScale()docs currently tell readers the value "is used to calculate the absolute font size", and theallowFontScalingdocs imply a single scale factor. On Android 14 and newer that is no longer accurate: the OS applies non-linear font scaling once the user's font scale is ≥ 1.05 — small fonts grow by roughly the full factor while large fonts grow progressively less, and a 30sp font does not grow at all until the setting exceeds 1.5 (per AOSP'sFontScaleConverterFactorytables). React Native inherits this viaTypedValue.applyDimension(COMPLEX_UNIT_SP, …), sofontSize * getFontScale()overestimates rendered sizes of large text.This mismatch was mistaken for a rendering bug in react/react-native#56961 — I verified there that RN matches the platform tables exactly (measurements in this comment).
Changes:
docs/pixelratio.md: add a note undergetFontScale()explaining non-linear scaling and the caveat about multiplying by the returned value.docs/text.md: add one sentence underallowFontScaling.website/versioned_docs/version-0.86/.