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fix: remove fontScale from CSS relative units to prevent double scaling #447

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fix: remove fontScale from CSS relative units to prevent double scaling #447

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6 changes: 2 additions & 4 deletions packages/react-strict-dom/src/native/css/CSSLengthUnitValue.js
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Original file line number Diff line number Diff line change
Expand Up @@ -14,7 +14,6 @@ const LENGTH_REGEX = /^(-?[0-9]*[.]?[0-9]+)(em|px|rem|vh|vmax|vmin|vw)$/;
type CSSLengthUnitType = 'em' | 'px' | 'rem' | 'vh' | 'vmax' | 'vmin' | 'vw';

type ResolvePixelValueOptions = $ReadOnly<{
fontScale: number | void,
inheritedFontSize: ?number,
viewportHeight: number,
viewportScale: number,
Expand Down Expand Up @@ -54,7 +53,6 @@ export class CSSLengthUnitValue {

resolvePixelValue(options: ResolvePixelValueOptions): number {
const {
fontScale = 1,
inheritedFontSize,
viewportHeight,
viewportScale = 1,
Expand All @@ -66,7 +64,7 @@ export class CSSLengthUnitValue {
switch (unit) {
case 'em': {
if (inheritedFontSize == null) {
return fontScale * 16 * value * viewportScale;
return 16 * value * viewportScale;
} else {
return inheritedFontSize * value;
}
Expand All @@ -75,7 +73,7 @@ export class CSSLengthUnitValue {
return value * viewportScale;
}
case 'rem': {
return fontScale * 16 * value * viewportScale;
return 16 * value * viewportScale;
}
case 'vh': {
return viewportHeight * valuePercent;
Expand Down
4 changes: 0 additions & 4 deletions packages/react-strict-dom/src/native/css/index.js
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Expand Up @@ -119,7 +119,6 @@ type ResolveStyleOptions = $ReadOnly<{
colorScheme: ?('light' | 'dark'),
customProperties: CustomProperties,
focus?: ?boolean,
fontScale: number | void,
fontSize?: ?number,
hover?: ?boolean,
inheritedFontSize: ?number,
Expand All @@ -142,7 +141,6 @@ function resolveStyle(
const {
active,
focus,
fontScale,
fontSize: _fontSize,
hover,
inheritedFontSize,
Expand Down Expand Up @@ -183,7 +181,6 @@ function resolveStyle(
// we use the inherited fontSize.
if (propName === 'fontSize' || fontSize == null) {
result[propName] = styleValue.resolvePixelValue({
fontScale,
inheritedFontSize: inheritedFontSize,
viewportHeight,
viewportScale,
Expand All @@ -196,7 +193,6 @@ function resolveStyle(
// used as the "inherited" value to resolve other lengths correctly.
if (typeof fontSize === 'number') {
result[propName] = styleValue.resolvePixelValue({
fontScale,
inheritedFontSize: fontSize,
viewportHeight,
viewportScale,
Expand Down
3 changes: 1 addition & 2 deletions packages/react-strict-dom/src/native/modules/useStyleProps.js
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Expand Up @@ -95,7 +95,7 @@ export function useStyleProps(
writingDirection: dir
} = options;

const { fontScale, height, width } = ReactNative.useWindowDimensions();
const { height, width } = ReactNative.useWindowDimensions();
const colorScheme = ReactNative.useColorScheme();
const { scale: viewportScale } = useViewportScale();

Expand Down Expand Up @@ -130,7 +130,6 @@ export function useStyleProps(
colorScheme: colorScheme === 'unspecified' ? 'light' : colorScheme,
customProperties: customProperties ?? emptyObject,
focus,
fontScale,
hover,
inheritedFontSize:
typeof inheritedFontSize === 'number' ? inheritedFontSize : undefined,
Expand Down
23 changes: 8 additions & 15 deletions packages/react-strict-dom/tests/css/__snapshots__/css-create-test.native.js.snap
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Expand Up @@ -346,13 +346,6 @@ exports[`css.create() properties fontSize 1`] = `
}
`;

exports[`css.create() properties fontSize scaling fontScale:2 1`] = `
{
"boxSizing": "content-box",
"fontSize": 80,
"position": "static",
}
`;

exports[`css.create() properties fontVariant 1`] = `
{
Expand Down Expand Up @@ -2077,35 +2070,35 @@ exports[`css.create() values: length units 10 "rem" units are resolved to pixels
exports[`css.create() values: length units 10 "vh" units are resolved to pixels: vh 1`] = `
{
"boxSizing": "content-box",
"height": NaN,
"height": -100,
"position": "static",
"width": NaN,
"width": 100,
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@axyz axyz Jan 28, 2026

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it seems that removing the fontScale accidentally fixed this preexisting bug where the resolved value was NAN, I'm assuming it could have been a lack of mocking in the test though?

}
`;

exports[`css.create() values: length units 10 "vmax" units are resolved to pixels: vmax 1`] = `
{
"boxSizing": "content-box",
"height": NaN,
"height": -200,
"position": "static",
"width": NaN,
"width": 200,
}
`;

exports[`css.create() values: length units 10 "vmin" units are resolved to pixels: vmin 1`] = `
{
"boxSizing": "content-box",
"height": NaN,
"height": -100,
"position": "static",
"width": NaN,
"width": 100,
}
`;

exports[`css.create() values: length units 10 "vw" units are resolved to pixels: vw 1`] = `
{
"boxSizing": "content-box",
"height": NaN,
"height": -200,
"position": "static",
"width": NaN,
"width": 200,
}
`;
23 changes: 0 additions & 23 deletions packages/react-strict-dom/tests/css/css-create-test.native.js
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Expand Up @@ -497,29 +497,6 @@ describe('css.create()', () => {
expect(root.toJSON().props.style).toMatchSnapshot();
});

describe('fontSize scaling', () => {
const ReactNative = require('../../src/native/react-native');
beforeEach(() => {
ReactNative.useWindowDimensions.mockReturnValue({ fontScale: 2 });
});
afterEach(() => {
ReactNative.useWindowDimensions.mockReturnValue({ fontScale: 1 });
});

test('fontScale:2', () => {
const styles = css.create({
root: {
fontSize: '2.5rem'
}
});
let root;
act(() => {
root = create(<html.span style={styles.root} />);
});
expect(root.toJSON().props.style).toMatchSnapshot();
});
});

test('fontVariant', () => {
const styles = css.create({
root: {
Expand Down