add `TextLeadingDistribution` to webui `TextStyle` (#25777)

lib/web_ui/dev/goldens_lock.yaml

 repository: https://github.com/flutter/goldens.git
-revision: 4a8da9f65353bda26a73e12838797f20cfdedc40
+revision: 4d00d1a0f1c0bc123814919a45ef2c2f57ed21ec

lib/web_ui/lib/src/engine/canvaskit/canvaskit_api.dart

@@ -1674,6 +1674,7 @@ class SkTextStyleProperties {
   external set letterSpacing(double? value);
   external set wordSpacing(double? value);
   external set heightMultiplier(double? value);
+  external set halfLeading(bool? value);
   external set locale(String? value);
   external set fontFamilies(List<String>? value);
   external set fontStyle(SkFontStyle? value);
@@ -1688,6 +1689,7 @@ class SkStrutStyleProperties {
   external set fontStyle(SkFontStyle? value);
   external set fontSize(double? value);
   external set heightMultiplier(double? value);
+  external set halfLeading(bool? value);
   external set leading(double? value);
   external set strutEnabled(bool? value);
   external set forceStrutHeight(bool? value);

lib/web_ui/lib/src/engine/canvaskit/text.dart

@@ -37,6 +37,7 @@ class CkParagraphStyle implements ui.ParagraphStyle {
         _fontFamily = fontFamily,
         _fontSize = fontSize,
         _height = height,
+        _leadingDistribution = textHeightBehavior?.leadingDistribution,
         _fontWeight = fontWeight,
         _fontStyle = fontStyle;
 
@@ -47,6 +48,7 @@ class CkParagraphStyle implements ui.ParagraphStyle {
   final double? _height;
   final ui.FontWeight? _fontWeight;
   final ui.FontStyle? _fontStyle;
+  final ui.TextLeadingDistribution? _leadingDistribution;
 
   static SkTextStyleProperties toSkTextStyleProperties(
     String? fontFamily,
@@ -73,7 +75,7 @@ class CkParagraphStyle implements ui.ParagraphStyle {
     return skTextStyle;
   }
 
-  static SkStrutStyleProperties toSkStrutStyleProperties(ui.StrutStyle value) {
+  static SkStrutStyleProperties toSkStrutStyleProperties(ui.StrutStyle value, ui.TextHeightBehavior? paragraphHeightBehavior) {
     EngineStrutStyle style = value as EngineStrutStyle;
     final SkStrutStyleProperties skStrutStyle = SkStrutStyleProperties();
     skStrutStyle.fontFamilies =
@@ -87,6 +89,18 @@ class CkParagraphStyle implements ui.ParagraphStyle {
       skStrutStyle.heightMultiplier = style._height;
     }
 
+    final ui.TextLeadingDistribution? effectiveLeadingDistribution = style._leadingDistribution ?? paragraphHeightBehavior?.leadingDistribution;
+    switch (effectiveLeadingDistribution) {
+      case null:
+        break;
+      case ui.TextLeadingDistribution.even:
+        skStrutStyle.halfLeading = true;
+        break;
+      case ui.TextLeadingDistribution.proportional:
+        skStrutStyle.halfLeading = false;
+        break;
+    }
+
     if (style._leading != null) {
       skStrutStyle.leading = style._leading;
     }
@@ -147,7 +161,7 @@ class CkParagraphStyle implements ui.ParagraphStyle {
     }
 
     if (strutStyle != null) {
-      properties.strutStyle = toSkStrutStyleProperties(strutStyle);
+      properties.strutStyle = toSkStrutStyleProperties(strutStyle, textHeightBehavior);
     }
 
     properties.textStyle = toSkTextStyleProperties(
@@ -161,6 +175,7 @@ class CkParagraphStyle implements ui.ParagraphStyle {
       fontFamily: _fontFamily,
       fontSize: _fontSize,
       height: _height,
+      leadingDistribution: _leadingDistribution,
       fontWeight: _fontWeight,
       fontStyle: _fontStyle,
     );
@@ -184,6 +199,7 @@ class CkTextStyle implements ui.TextStyle {
     double? letterSpacing,
     double? wordSpacing,
     double? height,
+    ui.TextLeadingDistribution? leadingDistribution,
     ui.Locale? locale,
     CkPaint? background,
     CkPaint? foreground,
@@ -205,6 +221,7 @@ class CkTextStyle implements ui.TextStyle {
       letterSpacing,
       wordSpacing,
       height,
+      leadingDistribution,
       locale,
       background,
       foreground,
@@ -228,6 +245,7 @@ class CkTextStyle implements ui.TextStyle {
     this.letterSpacing,
     this.wordSpacing,
     this.height,
+    this.leadingDistribution,
     this.locale,
     this.background,
     this.foreground,
@@ -249,6 +267,7 @@ class CkTextStyle implements ui.TextStyle {
   final double? letterSpacing;
   final double? wordSpacing;
   final double? height;
+  final ui.TextLeadingDistribution? leadingDistribution;
   final ui.Locale? locale;
   final CkPaint? background;
   final CkPaint? foreground;
@@ -275,6 +294,7 @@ class CkTextStyle implements ui.TextStyle {
       letterSpacing: other.letterSpacing ?? letterSpacing,
       wordSpacing: other.wordSpacing ?? wordSpacing,
       height: other.height ?? height,
+      leadingDistribution: other.leadingDistribution ?? leadingDistribution,
       locale: other.locale ?? locale,
       background: other.background ?? background,
       foreground: other.foreground ?? foreground,
@@ -367,6 +387,17 @@ class CkTextStyle implements ui.TextStyle {
       properties.heightMultiplier = height;
     }
 
+    switch (leadingDistribution) {
+      case null:
+        break;
+      case ui.TextLeadingDistribution.even:
+        properties.halfLeading = true;
+        break;
+      case ui.TextLeadingDistribution.proportional:
+        properties.halfLeading = false;
+        break;
+    }
+
     if (locale != null) {
       properties.locale = locale.toLanguageTag();
     }

lib/web_ui/lib/src/engine/text/paragraph.dart

@@ -1210,7 +1210,6 @@ class EngineStrutStyle implements ui.StrutStyle {
     List<String>? fontFamilyFallback,
     double? fontSize,
     double? height,
-    //TODO(LongCatIsLooong): implement leadingDistribution.
     ui.TextLeadingDistribution? leadingDistribution,
     double? leading,
     ui.FontWeight? fontWeight,

lib/web_ui/lib/src/ui/text.dart

@@ -285,6 +285,7 @@ abstract class TextStyle {
         letterSpacing: letterSpacing,
         wordSpacing: wordSpacing,
         height: height,
+        leadingDistribution: leadingDistribution,
         locale: locale,
         background: background as engine.CkPaint?,
         foreground: foreground as engine.CkPaint?,

lib/web_ui/test/canvaskit/canvas_golden_test.dart

@@ -357,6 +357,27 @@ void testMain() {
       await testTextStyle('height', height: 2);
     });
 
+    test('text styles - leading distribution', () async {
+      await testTextStyle('half leading', height: 20, fontSize: 10, leadingDistribution: ui.TextLeadingDistribution.even);
+      await testTextStyle(
+        'half leading inherited from paragraph',
+        height: 20,
+        fontSize: 10,
+        paragraphTextHeightBehavior: ui.TextHeightBehavior(
+          leadingDistribution: ui.TextLeadingDistribution.even,
+        ),
+      );
+      await testTextStyle(
+        'text style half leading overrides paragraph style half leading',
+        height: 20,
+        fontSize: 10,
+        leadingDistribution: ui.TextLeadingDistribution.proportional,
+        paragraphTextHeightBehavior: ui.TextHeightBehavior(
+          leadingDistribution: ui.TextLeadingDistribution.even,
+        ),
+      );
+    });
+
     // TODO(yjbanov): locales specified in text styles don't work:
     //                https://github.com/flutter/flutter/issues/74687
     // TODO(yjbanov): spaces are not rendered correctly:
@@ -1118,6 +1139,7 @@ Future<void> testTextStyle(
   double? letterSpacing,
   double? wordSpacing,
   double? height,
+  ui.TextLeadingDistribution? leadingDistribution,
   ui.Locale? locale,
   CkPaint? background,
   CkPaint? foreground,
@@ -1169,6 +1191,7 @@ Future<void> testTextStyle(
       letterSpacing: letterSpacing,
       wordSpacing: wordSpacing,
       height: height,
+      leadingDistribution: leadingDistribution,
       locale: locale,
       background: background,
       foreground: foreground,

lib/web_ui/test/canvaskit/canvaskit_api_test.dart

@@ -1289,6 +1289,7 @@ void _paragraphTests() {
       ..letterSpacing = 5
       ..wordSpacing = 10
       ..heightMultiplier = 2.5
+      ..halfLeading = true
       ..locale = 'en_CA'
       ..fontFamilies = <String>['Roboto', 'serif']
       ..fontStyle = (SkFontStyle()
@@ -1310,6 +1311,7 @@ void _paragraphTests() {
         ..weight = canvasKit.FontWeight.Bold)
       ..fontSize = 23
       ..heightMultiplier = 5
+      ..halfLeading = true
       ..leading = 6
       ..strutEnabled = true
       ..forceStrutHeight = false;
@@ -1338,6 +1340,8 @@ void _paragraphTests() {
         SkPaint());
     builder.addText('!');
     builder.pop();
+    builder.pushStyle(canvasKit.TextStyle(SkTextStyleProperties()..halfLeading = true));
+    builder.pop();
     final SkParagraph paragraph = builder.build();
     paragraph.layout(55);
     expect(paragraph.getAlphabeticBaseline(),