From 16d1127469a7f0a607af12dc06b519334d13cc96 Mon Sep 17 00:00:00 2001 From: Peter Abbondanzo Date: Fri, 6 Nov 2026 14:24:38 -0800 Subject: [PATCH] Keep adjustsFontSizeToFit from shrinking text at whole-pixel heights on Android Summary: `adjustsFontSizeToFit` shrinks the font while the text layout is taller than its `AT_MOST` height. That height arrives in pixels after Yoga subtracts the container's padding and converts it from DIPs back to pixels, all in 32-bit floats, so a whole number of pixels can come back a fraction short: 46px comes back as 45.999996px. A layout exactly as tall as the space it was given then counts as too tall. When the text sets a `lineHeight`, shrinking the font never makes it shorter, so it shrinks all the way to the minimum font size. Compare the layout height against the `AT_MOST` height with the same 0.001px tolerance the previous change added for widths, now named `PIXEL_SIZE_TOLERANCE`. Adds a unit test and an RNTester example. The example lays out 17 labels, each with a `lineHeight` of a whole number of pixels, in containers that leave exactly that height below their padding. Each row is a pixel taller than the last. Without this change, 11 of them shrink to the minimum font size at 320dpi and 4 at 420dpi. Changelog: [Android][Fixed] - Fix `adjustsFontSizeToFit` shrinking text that exactly fits its container's height Differential Revision: D129533186 --- .../react/views/text/TextLayoutManager.kt | 11 +- ...youtManagerFontSizeToFitPixelHeightTest.kt | 109 ++++++++++++++++++ .../js/examples/Text/TextExample.android.js | 46 ++++++++ 3 files changed, 161 insertions(+), 5 deletions(-) create mode 100644 packages/react-native/ReactAndroid/src/test/java/com/facebook/react/views/text/TextLayoutManagerFontSizeToFitPixelHeightTest.kt diff --git a/packages/react-native/ReactAndroid/src/main/java/com/facebook/react/views/text/TextLayoutManager.kt b/packages/react-native/ReactAndroid/src/main/java/com/facebook/react/views/text/TextLayoutManager.kt index dd3367ed6c56..e30f4dc416fe 100644 --- a/packages/react-native/ReactAndroid/src/main/java/com/facebook/react/views/text/TextLayoutManager.kt +++ b/packages/react-native/ReactAndroid/src/main/java/com/facebook/react/views/text/TextLayoutManager.kt @@ -118,9 +118,9 @@ internal object TextLayoutManager { private const val TEXT_WIDTH_MODE_LONGEST_LINE = "longest-line" - // Widths arrive in pixels converted from Yoga's floating point DIPs, so a width of a whole number - // of pixels can arrive a fraction of a pixel short of it (e.g. 371.99997 instead of 372). - private const val PIXEL_WIDTH_TOLERANCE = 0.001f + // Sizes arrive in pixels converted from Yoga's floating point DIPs, so a whole number of pixels + // can arrive a fraction of a pixel short of it (e.g. 371.99997 instead of 372). + private const val PIXEL_SIZE_TOLERANCE = 0.001f private val tagToSpannableCache = ConcurrentHashMap() @@ -982,7 +982,7 @@ internal object TextLayoutManager { * width back as its constraint once Yoga has converted it to DIPs and back, and flooring that to * one pixel less wraps the text. */ - private fun floorPixelWidth(width: Float): Int = floor(width + PIXEL_WIDTH_TOLERANCE).toInt() + private fun floorPixelWidth(width: Float): Int = floor(width + PIXEL_SIZE_TOLERANCE).toInt() @VisibleForTesting internal fun adjustLayoutForRtlRightOverhang( @@ -1560,7 +1560,8 @@ internal object TextLayoutManager { val singleLineTextExceedsWidth = text.length == 1 && layout.getLineWidth(0) > width val exceedsHeight = - heightYogaMeasureMode != YogaMeasureMode.UNDEFINED && layout.height > height + heightYogaMeasureMode != YogaMeasureMode.UNDEFINED && + layout.height > height + PIXEL_SIZE_TOLERANCE val exceedsMaximumNumberOfLines = maximumNumberOfLines != ReactConstants.UNSET && maximumNumberOfLines != 0 && diff --git a/packages/react-native/ReactAndroid/src/test/java/com/facebook/react/views/text/TextLayoutManagerFontSizeToFitPixelHeightTest.kt b/packages/react-native/ReactAndroid/src/test/java/com/facebook/react/views/text/TextLayoutManagerFontSizeToFitPixelHeightTest.kt new file mode 100644 index 000000000000..ce2669d8b388 --- /dev/null +++ b/packages/react-native/ReactAndroid/src/test/java/com/facebook/react/views/text/TextLayoutManagerFontSizeToFitPixelHeightTest.kt @@ -0,0 +1,109 @@ +/* + * Copyright (c) Meta Platforms, Inc. and affiliates. + * + * This source code is licensed under the MIT license found in the + * LICENSE file in the root directory of this source tree. + */ + +package com.facebook.react.views.text + +import android.annotation.SuppressLint +import android.graphics.text.LineBreakConfig +import android.text.Layout +import android.text.SpannableString +import android.text.Spanned +import android.text.StaticLayout +import android.text.TextPaint +import com.facebook.react.common.ReactConstants +import com.facebook.react.uimanager.DisplayMetricsHolder +import com.facebook.react.views.text.internal.span.ReactAbsoluteSizeSpan +import com.facebook.yoga.YogaMeasureMode +import org.assertj.core.api.Assertions.assertThat +import org.junit.After +import org.junit.Before +import org.junit.Test +import org.junit.runner.RunWith +import org.robolectric.RobolectricTestRunner +import org.robolectric.RuntimeEnvironment +import org.robolectric.annotation.GraphicsMode +import org.robolectric.annotation.TextLayoutMode + +@RunWith(RobolectricTestRunner::class) +@GraphicsMode(GraphicsMode.Mode.NATIVE) +@TextLayoutMode(TextLayoutMode.Mode.REALISTIC) +@SuppressLint("InlinedApi") +class TextLayoutManagerFontSizeToFitPixelHeightTest { + + @Before + fun setUp() { + DisplayMetricsHolder.initDisplayMetricsIfNotInitialized(RuntimeEnvironment.getApplication()) + } + + @After + fun tearDown() { + DisplayMetricsHolder.setScreenDisplayMetrics(null) + } + + @Test + fun `AT_MOST height a floating point error short of the text height keeps the font size`() { + val textHeight = layoutHeight(spannableWithFontSize(FONT_SIZE)) + + for (height in listOf(Math.nextDown(textHeight.toFloat()), textHeight - 0.0004f)) { + val text = spannableWithFontSize(FONT_SIZE) + adjustToFitHeight(text, height) + + assertThat(fontSize(text)).isEqualTo(FONT_SIZE) + } + } + + @Test + fun `AT_MOST height a fraction of a pixel short of the text height shrinks the font`() { + val text = spannableWithFontSize(FONT_SIZE) + adjustToFitHeight(text, layoutHeight(text) - 0.5f) + + assertThat(fontSize(text)).isLessThan(FONT_SIZE) + } + + private fun spannableWithFontSize(fontSize: Int): SpannableString = + SpannableString("Add payment method").apply { + setSpan(ReactAbsoluteSizeSpan(fontSize), 0, length, Spanned.SPAN_INCLUSIVE_INCLUSIVE) + } + + private fun paint(): TextPaint = + TextPaint(TextPaint.ANTI_ALIAS_FLAG).apply { textSize = FONT_SIZE.toFloat() } + + private fun layoutHeight(text: SpannableString): Int = + StaticLayout.Builder.obtain(text, 0, text.length, paint(), WIDTH.toInt()) + .setIncludePad(false) + .build() + .height + + private fun fontSize(text: SpannableString): Int = + text.getSpans(0, text.length, ReactAbsoluteSizeSpan::class.java).single().size + + private fun adjustToFitHeight(text: SpannableString, height: Float) { + TextLayoutManager.adjustSpannableFontToFit( + text, + WIDTH, + YogaMeasureMode.EXACTLY, + height, + YogaMeasureMode.AT_MOST, + /* minimumFontSizeAttr = */ Float.NaN, + /* minimumFontScale = */ Float.NaN, + ReactConstants.UNSET, + /* includeFontPadding = */ false, + Layout.BREAK_STRATEGY_HIGH_QUALITY, + Layout.HYPHENATION_FREQUENCY_NONE, + LineBreakConfig.LINE_BREAK_STYLE_NONE, + LineBreakConfig.LINE_BREAK_WORD_STYLE_NONE, + Layout.Alignment.ALIGN_NORMAL, + /* justificationMode = */ 0, + paint(), + ) + } + + private companion object { + const val FONT_SIZE = 40 + const val WIDTH = 1000f + } +} diff --git a/packages/rn-tester/js/examples/Text/TextExample.android.js b/packages/rn-tester/js/examples/Text/TextExample.android.js index af4c76503899..2bd0b1e07c1c 100644 --- a/packages/rn-tester/js/examples/Text/TextExample.android.js +++ b/packages/rn-tester/js/examples/Text/TextExample.android.js @@ -1415,6 +1415,39 @@ function FitContentWholePixelWidthExample(props: {}): React.Node { return {rows}; } +function AdjustsFontSizeToFitWholePixelHeightExample(props: {}): React.Node { + // Each label's line height is a whole number of pixels, and so is the space + // its container leaves for it below the container's padding. That space + // picks up floating point error from the padding and from the conversion to + // DIPs and back, so it can fall a hair short of the line height. Each row is + // a pixel taller than the last. No label should shrink. + const pixelRatio = PixelRatio.get(); + const rows = []; + for (let i = 0; i < 17; i++) { + const lineHeight = (Math.round(20 * pixelRatio) + i) / pixelRatio; + rows.push( + + + Add payment method + + , + ); + } + return ( + + {rows} + + ); +} + const examples = [ { title: 'Wrapped text width mode', @@ -1516,6 +1549,11 @@ const examples = [ name: 'fitContentWholePixelWidth', render: FitContentWholePixelWidthExample, }, + { + title: 'adjustsFontSizeToFit at whole pixel heights', + name: 'adjustsFontSizeToFitWholePixelHeight', + render: AdjustsFontSizeToFitWholePixelHeightExample, + }, { title: 'Hyphenation', name: 'hyphenation', @@ -2028,6 +2066,14 @@ const styles = StyleSheet.create({ fontSize: 15, maxWidth: '100%', }, + adjustsFontSizeToFitRow: { + backgroundColor: '#E4E6EB', + marginBottom: 2, + paddingTop: 7.1, + }, + adjustsFontSizeToFitLabel: { + fontSize: 16, + }, lineBreakSample: { backgroundColor: '#eee', fontSize: 16,