wip

Author: LongCatIsLooong

lib/ui/text.dart

@@ -3,6 +3,11 @@
 // found in the LICENSE file.
 part of dart.ui;
 
+/// A [TextStyle.height] value that indicates the text span should take
+/// the height defined by the font, which may not be exactly the height of
+/// [TextStyle.fontSize].
+const double kTextHeightNone = 0.0;
+
 /// Whether to use the italic type variation of glyphs in the font.
 ///
 /// Some modern fonts allow this to be selected in a more fine-grained manner.
@@ -1687,10 +1692,10 @@ class TextStyle {
   /// * `letterSpacing`: The amount of space (in logical pixels) to add between each letter.
   /// * `wordSpacing`: The amount of space (in logical pixels) to add at each sequence of white-space (i.e. between each word).
   /// * `textBaseline`: The common baseline that should be aligned between this text span and its parent text span, or, for the root text spans, with the line box.
-  /// * `height`: The height of this text span, as a multiplier of the font size. Omitting `height` will allow the line height
+  /// * `height`: The height of this text span, as a multiplier of the font size. Setting the `height` to `kTextHeightNone` will allow the line height
   ///   to take the height as defined by the font, which may not be exactly the height of the fontSize.
-  /// * `leadingDistribution`: When `height` is specified, how the extra vertical space should be distributed over and under the text. Defaults
-  ///   to the paragraph's [TextHeightBehavior] if left unspecified.
+  /// * `leadingDistribution`: When `height` is set to a non-null that is not `kTextHeightNone`, how the extra vertical space should be distributed over and under the text.
+  ///   Defaults to the paragraph's [TextHeightBehavior] if left unspecified.
   /// * `locale`: The locale used to select region-specific glyphs.
   /// * `background`: The paint drawn as a background for the text.
   /// * `foreground`: The paint used to draw the text. If this is specified, `color` must be null.
@@ -1923,7 +1928,9 @@ Int32List _encodeParagraphStyle(
     result[0] |= 1 << 8;
     // Passed separately to native.
   }
-  if (height != null) {
+  // Paragraph styles are unique in a paragraph, there is no inheriting so
+  // height == null and height == kTextHeightNone are semantically equivalent.
+  if (height != null && height != kTextHeightNone) {
     result[0] |= 1 << 9;
     // Passed separately to native.
   }
@@ -1973,9 +1980,10 @@ class ParagraphStyle {
   ///
   /// * `height`: The fallback height of the spans as a multiplier of the font
   ///   size. The fallback height is used when no height is provided through
-  ///   [TextStyle.height]. Omitting `height` here and in [TextStyle] will allow
-  ///   the line height to take the height as defined by the font, which may not
-  ///   be exactly the height of the `fontSize`.
+  ///   [TextStyle.height]. Omitting `height` here (or setting it to
+  ///   [kTextHeightNone]) and in [TextStyle] will allow the line height to take
+  ///   the height as defined by the font, which may not be exactly the height of
+  ///   the `fontSize`.
   ///
   /// * `textHeightBehavior`: Specifies how the `height` multiplier is
   ///   applied to ascent of the first line and the descent of the last line.
@@ -2110,9 +2118,12 @@ ByteData _encodeStrut(
   FontWeight? fontWeight,
   FontStyle? fontStyle,
   bool? forceStrutHeight) {
+  // Strut styles are unique in a paragraph, there is no inheriting so
+  // height == null and height == kTextHeightNone are semantically equivalent.
+  final bool hasHeightOverride = height != null && height != kTextHeightNone;
   if (fontFamily == null &&
     fontSize == null &&
-    height == null &&
+    !hasHeightOverride &&
     leadingDistribution == null &&
     leading == null &&
     fontWeight == null &&
@@ -2146,7 +2157,7 @@ ByteData _encodeStrut(
     data.setFloat32(byteCount, fontSize, _kFakeHostEndian);
     byteCount += 4;
   }
-  if (height != null) {
+  if (hasHeightOverride) {
     bitmask |= 1 << 5;
     data.setFloat32(byteCount, height, _kFakeHostEndian);
     byteCount += 4;
@@ -2186,12 +2197,13 @@ class StrutStyle {
   /// * `height`: The minimum height of the line boxes, as a multiplier of the
   ///   font size. The lines of the paragraph will be at least
   ///   `(height + leading) * fontSize` tall when `fontSize` is not null. Omitting
-  ///   `height` will allow the minimum line height to take the height as defined
-  ///   by the font, which may not be exactly the height of the `fontSize`. When
-  ///   `fontSize` is null, there is no minimum line height. Tall glyphs due to
-  ///   baseline alignment or large [TextStyle.fontSize] may cause the actual line
-  ///   height after layout to be taller than specified here. The `fontSize` must
-  ///   be provided for this property to take effect.
+  ///   `height` (or setting it to [kTextHeightNone]) will allow the minimum line
+  ///   height to take the height as defined by the font, which may not be exactly
+  ///   the height of the `fontSize`. When `fontSize` is null, there is no minimum
+  ///   line height. Tall glyphs due to baseline alignment or large
+  ///   [TextStyle.fontSize] may cause the actual line height after layout to be
+  ///   taller than specified here. The `fontSize` must be provided for
+  ///   this property to take effect.
   ///
   /// * `leading`: The minimum amount of leading between lines as a multiple of
   ///   the font size. `fontSize` must be provided for this property to take

lib/ui/text/paragraph_builder.cc

@@ -445,7 +445,7 @@ void ParagraphBuilder::pushStyle(const tonic::Int32List& encoded,
 
   if (mask & kTSHeightMask) {
     style.height = height;
-    style.has_height_override = true;
+    style.has_height_override = style.height != 0;
   }
 
   if (mask & kTSLocaleMask) {

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

@@ -39,7 +39,7 @@ class CkParagraphStyle implements ui.ParagraphStyle {
           maxLines,
           _computeEffectiveFontFamily(fontFamily),
           fontSize,
-          height,
+          height == ui.kTextHeightNone ? null : height,
           textHeightBehavior,
           fontWeight,
           fontStyle,
@@ -55,7 +55,7 @@ class CkParagraphStyle implements ui.ParagraphStyle {
         _originalFontFamily = fontFamily,
         _effectiveFontFamily = _computeEffectiveFontFamily(fontFamily),
         _fontSize = fontSize,
-        _height = height,
+        _height = height == ui.kTextHeightNone ? null : height,
         _textHeightBehavior = textHeightBehavior,
         _strutStyle = strutStyle,
         _ellipsis = ellipsis,
@@ -413,6 +413,9 @@ class CkTextStyle implements ui.TextStyle {
   /// The values in this text style are used unless [other] specifically
   /// overrides it.
   CkTextStyle mergeWith(CkTextStyle other) {
+    final double? textHeight = other.height == ui.kTextHeightNone
+      ? null
+      : (other.height ?? height);
     return CkTextStyle._(
       color: other.color ?? color,
       decoration: other.decoration ?? decoration,
@@ -429,7 +432,7 @@ class CkTextStyle implements ui.TextStyle {
       fontSize: other.fontSize ?? fontSize,
       letterSpacing: other.letterSpacing ?? letterSpacing,
       wordSpacing: other.wordSpacing ?? wordSpacing,
-      height: other.height ?? height,
+      height: textHeight,
       leadingDistribution: other.leadingDistribution ?? leadingDistribution,
       locale: other.locale ?? locale,
       background: other.background ?? background,
@@ -699,7 +702,7 @@ class CkStrutStyle implements ui.StrutStyle {
   })  : _fontFamily = _computeEffectiveFontFamily(fontFamily),
         _fontFamilyFallback = ui_web.debugEmulateFlutterTesterEnvironment ? null : fontFamilyFallback,
         _fontSize = fontSize,
-        _height = height,
+        _height = height == ui.kTextHeightNone ? null : height,
         _leadingDistribution = leadingDistribution,
         _leading = leading,
         _fontWeight = fontWeight,

lib/web_ui/lib/src/engine/skwasm/skwasm_impl/paragraph.dart

@@ -594,7 +594,7 @@ final class SkwasmStrutStyle extends SkwasmObjectWrapper<RawStrutStyle> implemen
     if (fontSize != null) {
       strutStyleSetFontSize(handle, fontSize);
     }
-    if (height != null) {
+    if (height != null || height == kTextHeightNone) {
       strutStyleSetHeight(handle, height);
     }
     if (leadingDistribution != null) {
@@ -734,7 +734,7 @@ class SkwasmParagraphStyle extends SkwasmObjectWrapper<RawParagraphStyle> implem
     if (maxLines != null) {
       paragraphStyleSetMaxLines(handle, maxLines);
     }
-    if (height != null) {
+    if (height != null || height != kTextHeightNone) {
       paragraphStyleSetHeight(handle, height);
     }
     if (textHeightBehavior != null) {

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

@@ -401,33 +401,29 @@ abstract class StyleNode {
   /// The resolved text style is equivalent to the entire ascendent chain of
   /// parent style nodes.
   EngineTextStyle resolveStyle() {
-    final EngineTextStyle? style = _cachedStyle;
-    if (style == null) {
-      return _cachedStyle ??= EngineTextStyle(
-        color: _color,
-        decoration: _decoration,
-        decorationColor: _decorationColor,
-        decorationStyle: _decorationStyle,
-        decorationThickness: _decorationThickness,
-        fontWeight: _fontWeight,
-        fontStyle: _fontStyle,
-        textBaseline: _textBaseline,
-        fontFamily: _fontFamily,
-        fontFamilyFallback: _fontFamilyFallback,
-        fontFeatures: _fontFeatures,
-        fontVariations: _fontVariations,
-        fontSize: _fontSize,
-        letterSpacing: _letterSpacing,
-        wordSpacing: _wordSpacing,
-        height: _height,
-        leadingDistribution: _leadingDistribution,
-        locale: _locale,
-        background: _background,
-        foreground: _foreground,
-        shadows: _shadows,
-      );
-    }
-    return style;
+    return _cachedStyle ??= EngineTextStyle(
+      color: _color,
+      decoration: _decoration,
+      decorationColor: _decorationColor,
+      decorationStyle: _decorationStyle,
+      decorationThickness: _decorationThickness,
+      fontWeight: _fontWeight,
+      fontStyle: _fontStyle,
+      textBaseline: _textBaseline,
+      fontFamily: _fontFamily,
+      fontFamilyFallback: _fontFamilyFallback,
+      fontFeatures: _fontFeatures,
+      fontVariations: _fontVariations,
+      fontSize: _fontSize,
+      letterSpacing: _letterSpacing,
+      wordSpacing: _wordSpacing,
+      height: _height,
+      leadingDistribution: _leadingDistribution,
+      locale: _locale,
+      background: _background,
+      foreground: _foreground,
+      shadows: _shadows,
+    );
   }
 
   ui.Color? get _color;
@@ -510,7 +506,9 @@ class ChildStyleNode extends StyleNode {
   double? get _wordSpacing => style.wordSpacing ?? parent._wordSpacing;
 
   @override
-  double? get _height => style.height ?? parent._height;
+  double? get _height {
+    return style.height == ui.kTextHeightNone ? null : (style.height ?? parent._height);
+  }
 
   @override
   ui.TextLeadingDistribution? get _leadingDistribution => style.leadingDistribution ?? parent._leadingDistribution;

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

@@ -435,7 +435,7 @@ class EngineParagraphStyle implements ui.ParagraphStyle {
     this.maxLines,
     this.fontFamily,
     this.fontSize,
-    this.height,
+    double? height,
     ui.TextHeightBehavior? textHeightBehavior,
     this.fontWeight,
     this.fontStyle,
@@ -444,7 +444,8 @@ class EngineParagraphStyle implements ui.ParagraphStyle {
     this.locale,
   })  : _textHeightBehavior = textHeightBehavior,
         // TODO(mdebbar): add support for strut style., b/128317744
-        _strutStyle = strutStyle as EngineStrutStyle?;
+        _strutStyle = strutStyle as EngineStrutStyle?,
+        this.height = height == ui.kTextHeightNone ? null : height;
 
   final ui.TextAlign? textAlign;
   final ui.TextDirection? textDirection;
@@ -808,7 +809,7 @@ class EngineStrutStyle implements ui.StrutStyle {
   })  : _fontFamily = fontFamily,
         _fontFamilyFallback = fontFamilyFallback,
         _fontSize = fontSize,
-        _height = height,
+        _height = height == ui.kTextHeightNone ? null : height,
         _leadingDistribution = leadingDistribution,
         _leading = leading,
         _fontWeight = fontWeight,

lib/web_ui/lib/text.dart

@@ -4,6 +4,10 @@
 
 part of ui;
 
+// This constant must be consistent with `kTextHeightNone` defined in
+// flutter/lib/ui/text.dart.
+const double kTextHeightNone = 0.0;
+
 enum FontStyle {
   normal,
   italic,

lib/web_ui/skwasm/text/text_style.cpp

@@ -96,7 +96,7 @@ SKWASM_EXPORT void textStyle_setWordSpacing(TextStyle* style,
 
 SKWASM_EXPORT void textStyle_setHeight(TextStyle* style, SkScalar height) {
   style->setHeight(height);
-  style->setHeightOverride(true);
+  style->setHeightOverride(height != 0.0);
 }
 
 SKWASM_EXPORT void textStyle_setHalfLeading(TextStyle* style,