Add longest-line sizing for wrapped Text (#58351)

Summary:
Pull Request resolved: #58351

Add `textWidthMode="longest-line"` to size wrapped `Text` to its widest rendered line on Android and iOS. This keeps content-proportional spacing in horizontal layouts without an `onTextLayout` round trip; the default measurement behavior is unchanged.

Changelog:
[General][Added] - Add `textWidthMode="longest-line"` for sizing wrapped `Text` to its widest rendered line.

Differential Revision: D118718410

Author: Abbondanzo

packages/react-native/Libraries/Text/TextNativeComponent.js

@@ -44,6 +44,7 @@ const textViewConfig = {
     adjustsFontSizeToFit: true,
     minimumFontScale: true,
     textBreakStrategy: true,
+    textWidthMode: true,
     onTextLayout: true,
     dataDetectorType: true,
     android_hyphenationFrequency: true,

packages/react-native/Libraries/Text/TextProps.js

@@ -181,6 +181,15 @@ type TextBaseProps = Readonly<{
    */
   numberOfLines?: ?number,
 
+  /**
+   * Controls how wrapped text contributes its width to layout. `longest-line`
+   * uses the width of the longest rendered line instead of the wrapping
+   * constraint.
+   *
+   * @default `'default'`
+   */
+  textWidthMode?: ?('default' | 'longest-line'),
+
   onLayout?: ?(event: LayoutChangeEvent) => unknown,
 
   /** Called on long press. */

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/views/text/TextLayoutManager.kt

@@ -96,6 +96,7 @@ internal object TextLayoutManager {
   const val PA_KEY_MINIMUM_FONT_SIZE: Int = 6
   const val PA_KEY_MAXIMUM_FONT_SIZE: Int = 7
   const val PA_KEY_TEXT_ALIGN_VERTICAL: Int = 8
+  const val PA_KEY_TEXT_WIDTH_MODE: Int = 9
 
   private val TAG: String = TextLayoutManager::class.java.simpleName
 
@@ -110,6 +111,8 @@ internal object TextLayoutManager {
 
   private const val DEFAULT_ADJUST_FONT_SIZE_TO_FIT = false
 
+  private const val TEXT_WIDTH_MODE_LONGEST_LINE = "longest-line"
+
   private val tagToSpannableCache = ConcurrentHashMap<Int, Spannable>()
 
   // Lazily cached Method for StaticLayout.Builder.setUseBoundsForWidth (API 35+).
@@ -1065,21 +1068,48 @@ internal object TextLayoutManager {
       )
     }
 
+    var layout = createLayout(
+        text,
+        boring,
+        width,
+        widthYogaMeasureMode,
+        includeFontPadding,
+        textBreakStrategy,
+        hyphenationFrequency,
+        alignment,
+        justificationMode,
+        ellipsizeMode,
+        maximumNumberOfLines,
+        paint,
+    )
+
+    if (
+        widthYogaMeasureMode == YogaMeasureMode.AT_MOST &&
+            paragraphAttributes.contains(PA_KEY_TEXT_WIDTH_MODE) &&
+            paragraphAttributes.getString(PA_KEY_TEXT_WIDTH_MODE) == TEXT_WIDTH_MODE_LONGEST_LINE
+    ) {
+      val lineCount = calculateLineCount(layout, maximumNumberOfLines)
+      val longestLineWidth = longestLineWidth(layout, lineCount)
+      val tightenedWidth = max(1, ceil(longestLineWidth).toInt())
+      if (tightenedWidth < layout.width) {
+        layout =
+            buildLayout(
+                text,
+                tightenedWidth,
+                includeFontPadding,
+                textBreakStrategy,
+                hyphenationFrequency,
+                alignment,
+                justificationMode,
+                ellipsizeMode,
+                maximumNumberOfLines,
+                paint,
+            )
+      }
+    }
+
     return CreateLayoutResult(
-        createLayout(
-            text,
-            boring,
-            width,
-            widthYogaMeasureMode,
-            includeFontPadding,
-            textBreakStrategy,
-            hyphenationFrequency,
-            alignment,
-            justificationMode,
-            ellipsizeMode,
-            maximumNumberOfLines,
-            paint,
-        ),
+        layout,
         textBreakStrategy,
         justificationMode,
     )
@@ -1471,6 +1501,18 @@ internal object TextLayoutManager {
           layout.lineCount
       else min(maximumNumberOfLines, layout.lineCount)
 
+  @VisibleForTesting
+  internal fun longestLineWidth(layout: Layout, lineCount: Int): Float {
+    var longestLineWidth = 0f
+    for (line in 0 until lineCount) {
+      val lineEnd = layout.getLineEnd(line)
+      val endsWithNewLine = lineEnd > 0 && layout.text[lineEnd - 1] == '\n'
+      val lineWidth = if (endsWithNewLine) layout.getLineMax(line) else layout.getLineWidth(line)
+      longestLineWidth = max(longestLineWidth, lineWidth)
+    }
+    return longestLineWidth
+  }
+
   private fun calculateWidth(
       layout: Layout,
       text: Spanned,

packages/react-native/ReactAndroid/src/test/java/com/facebook/react/views/text/TextLayoutManagerLongestLineWidthTest.kt

@@ -0,0 +1,47 @@
+/*
+ * 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.text.Layout
+import android.text.SpannableString
+import android.text.StaticLayout
+import android.text.TextPaint
+import kotlin.math.ceil
+import org.assertj.core.api.Assertions.assertThat
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.robolectric.RobolectricTestRunner
+import org.robolectric.annotation.Config
+
+@RunWith(RobolectricTestRunner::class)
+@Config(sdk = [34])
+class TextLayoutManagerLongestLineWidthTest {
+
+  @Test
+  fun `longest line width tightens a wrapped layout without adding a line`() {
+    val text = SpannableString("Sitting, Standing,\nRoomscale")
+    val paint = TextPaint(TextPaint.ANTI_ALIAS_FLAG).apply { textSize = 16f }
+    val layout = createLayout(text, paint, 20)
+
+    assertThat(layout.lineCount).isGreaterThan(1)
+
+    val tightenedWidth = ceil(TextLayoutManager.longestLineWidth(layout, layout.lineCount)).toInt()
+    val tightenedLayout = createLayout(text, paint, tightenedWidth)
+
+    assertThat(tightenedWidth).isLessThan(layout.width)
+    assertThat(tightenedLayout.lineCount).isEqualTo(layout.lineCount)
+    assertThat(TextLayoutManager.longestLineWidth(tightenedLayout, tightenedLayout.lineCount))
+        .isLessThanOrEqualTo(tightenedWidth.toFloat())
+  }
+
+  private fun createLayout(text: SpannableString, paint: TextPaint, width: Int): Layout =
+      StaticLayout.Builder.obtain(text, 0, text.length, paint, width)
+          .setBreakStrategy(Layout.BREAK_STRATEGY_HIGH_QUALITY)
+          .setHyphenationFrequency(Layout.HYPHENATION_FREQUENCY_NONE)
+          .build()
+}

packages/react-native/ReactCommon/react/renderer/attributedstring/ParagraphAttributes.cpp

@@ -19,6 +19,7 @@ bool ParagraphAttributes::operator==(const ParagraphAttributes& rhs) const {
              maximumNumberOfLines,
              ellipsizeMode,
              textBreakStrategy,
+             textWidthMode,
              adjustsFontSizeToFit,
              includeFontPadding,
              android_hyphenationFrequency,
@@ -27,6 +28,7 @@ bool ParagraphAttributes::operator==(const ParagraphAttributes& rhs) const {
              rhs.maximumNumberOfLines,
              rhs.ellipsizeMode,
              rhs.textBreakStrategy,
+             rhs.textWidthMode,
              rhs.adjustsFontSizeToFit,
              rhs.includeFontPadding,
              rhs.android_hyphenationFrequency,
@@ -52,6 +54,8 @@ SharedDebugStringConvertibleList ParagraphAttributes::getDebugProps() const {
           "textBreakStrategy",
           textBreakStrategy,
           paragraphAttributes.textBreakStrategy),
+      debugStringConvertibleItem(
+          "textWidthMode", textWidthMode, paragraphAttributes.textWidthMode),
       debugStringConvertibleItem(
           "adjustsFontSizeToFit",
           adjustsFontSizeToFit,

packages/react-native/ReactCommon/react/renderer/attributedstring/ParagraphAttributes.h

@@ -48,6 +48,8 @@ class ParagraphAttributes : public DebugStringConvertible {
    */
   TextBreakStrategy textBreakStrategy{TextBreakStrategy::HighQuality};
 
+  TextWidthMode textWidthMode{TextWidthMode::Default};
+
   /*
    * Enables font size adjustment to fit constrained boundaries.
    */
@@ -105,6 +107,7 @@ struct hash<facebook::react::ParagraphAttributes> {
         attributes.maximumNumberOfLines,
         attributes.ellipsizeMode,
         attributes.textBreakStrategy,
+        attributes.textWidthMode,
         attributes.adjustsFontSizeToFit,
         attributes.minimumFontSize,
         attributes.maximumFontSize,

packages/react-native/ReactCommon/react/renderer/attributedstring/conversions.h

@@ -204,6 +204,42 @@ inline void fromRawValue(const PropsParserContext &context, const RawValue &valu
   result = TextBreakStrategy::HighQuality;
 }
 
+inline std::string toString(const TextWidthMode &textWidthMode)
+{
+  switch (textWidthMode) {
+    case TextWidthMode::Default:
+      return "default";
+    case TextWidthMode::LongestLine:
+      return "longest-line";
+  }
+
+  LOG(ERROR) << "Unsupported TextWidthMode value";
+  react_native_expect(false);
+  return "default";
+}
+
+inline void fromRawValue(const PropsParserContext & /*context*/, const RawValue &value, TextWidthMode &result)
+{
+  react_native_expect(value.hasType<std::string>());
+  if (value.hasType<std::string>()) {
+    auto string = (std::string)value;
+    if (string == "default") {
+      result = TextWidthMode::Default;
+    } else if (string == "longest-line") {
+      result = TextWidthMode::LongestLine;
+    } else {
+      LOG(ERROR) << "Unsupported TextWidthMode value: " << string;
+      react_native_expect(false);
+      result = TextWidthMode::Default;
+    }
+    return;
+  }
+
+  LOG(ERROR) << "Unsupported TextWidthMode type";
+  react_native_expect(false);
+  result = TextWidthMode::Default;
+}
+
 inline void fromRawValue(const PropsParserContext &context, const RawValue &value, FontWeight &result)
 {
   react_native_expect(value.hasType<std::string>() || value.hasType<int>());
@@ -1031,6 +1067,12 @@ inline ParagraphAttributes convertRawProp(
       "textBreakStrategy",
       sourceParagraphAttributes.textBreakStrategy,
       defaultParagraphAttributes.textBreakStrategy);
+  paragraphAttributes.textWidthMode = convertRawProp(
+      context,
+      rawProps,
+      "textWidthMode",
+      sourceParagraphAttributes.textWidthMode,
+      defaultParagraphAttributes.textWidthMode);
   paragraphAttributes.adjustsFontSizeToFit = convertRawProp(
       context,
       rawProps,
@@ -1160,13 +1202,15 @@ constexpr static MapBuffer::Key PA_KEY_HYPHENATION_FREQUENCY = 5;
 constexpr static MapBuffer::Key PA_KEY_MINIMUM_FONT_SIZE = 6;
 constexpr static MapBuffer::Key PA_KEY_MAXIMUM_FONT_SIZE = 7;
 constexpr static MapBuffer::Key PA_KEY_TEXT_ALIGN_VERTICAL = 8;
+constexpr static MapBuffer::Key PA_KEY_TEXT_WIDTH_MODE = 9;
 
 inline MapBuffer toMapBuffer(const ParagraphAttributes &paragraphAttributes)
 {
   auto builder = MapBufferBuilder();
   builder.putInt(PA_KEY_MAX_NUMBER_OF_LINES, paragraphAttributes.maximumNumberOfLines);
   builder.putString(PA_KEY_ELLIPSIZE_MODE, toString(paragraphAttributes.ellipsizeMode));
   builder.putString(PA_KEY_TEXT_BREAK_STRATEGY, toString(paragraphAttributes.textBreakStrategy));
+  builder.putString(PA_KEY_TEXT_WIDTH_MODE, toString(paragraphAttributes.textWidthMode));
   builder.putBool(PA_KEY_ADJUST_FONT_SIZE_TO_FIT, paragraphAttributes.adjustsFontSizeToFit);
   builder.putBool(PA_KEY_INCLUDE_FONT_PADDING, paragraphAttributes.includeFontPadding);
   builder.putString(PA_KEY_HYPHENATION_FREQUENCY, toString(paragraphAttributes.android_hyphenationFrequency));

packages/react-native/ReactCommon/react/renderer/attributedstring/primitives.h

@@ -94,6 +94,11 @@ enum class TextBreakStrategy {
   Balanced // Balances line lengths.
 };
 
+enum class TextWidthMode {
+  Default,
+  LongestLine,
+};
+
 enum class TextAlignment {
   Natural, // Indicates the default alignment for script.
   Left, // Visually left aligned.

packages/react-native/ReactCommon/react/renderer/attributedstring/tests/ParagraphAttributesTest.cpp

@@ -70,4 +70,12 @@ TEST(
   EXPECT_FALSE(unset == set);
 }
 
+TEST(ParagraphAttributesTest, testOperatorEqualsIncludesTextWidthMode) {
+  ParagraphAttributes defaultWidth{};
+  ParagraphAttributes longestLineWidth{};
+  longestLineWidth.textWidthMode = TextWidthMode::LongestLine;
+
+  EXPECT_FALSE(defaultWidth == longestLineWidth);
+}
+
 } // namespace facebook::react

packages/react-native/ReactCommon/react/renderer/components/text/BaseParagraphProps.cpp

@@ -80,6 +80,8 @@ void BaseParagraphProps::setProp(
         paragraphAttributes,
         textBreakStrategy,
         "textBreakStrategy");
+    REBUILD_FIELD_SWITCH_CASE(
+        paDefaults, value, paragraphAttributes, textWidthMode, "textWidthMode");
     REBUILD_FIELD_SWITCH_CASE(
         paDefaults,
         value,