Add backgroundColor argument to TextStyle for convenience (#28172)

packages/flutter/lib/src/painting/text_style.dart

@@ -12,7 +12,10 @@ import 'strut_style.dart';
 const String _kDefaultDebugLabel = 'unknown';
 
 const String _kColorForegroundWarning = 'Cannot provide both a color and a foreground\n'
-         'The color argument is just a shorthand for "foreground: new Paint()..color = color".';
+    'The color argument is just a shorthand for "foreground: new Paint()..color = color".';
+
+const String _kColorBackgroundWarning = 'Cannot provide both a backgroundColor and a background\n'
+    'The backgroundColor argument is just a shorthand for "background: new Paint()..color = color".';
 
 // Examples can assume:
 // BuildContext context;
@@ -60,6 +63,10 @@ const String _kColorForegroundWarning = 'Cannot provide both a color and a foreg
 /// If [color] is specified, [foreground] must be null and vice versa. [color] is
 /// treated as a shorthand for `Paint()..color = color`.
 ///
+/// If [backgroundColor] is specified, [background] must be null and vice versa.
+/// The [backgroundColor] is treated as a shorthand for
+/// `background: Paint()..color = backgroundColor`.
+///
 /// ```dart
 /// RichText(
 ///   text: TextSpan(
@@ -295,6 +302,7 @@ class TextStyle extends Diagnosticable {
   const TextStyle({
     this.inherit = true,
     this.color,
+    this.backgroundColor,
     this.fontSize,
     this.fontWeight,
     this.fontStyle,
@@ -317,7 +325,8 @@ class TextStyle extends Diagnosticable {
        _fontFamilyFallback = fontFamilyFallback,
        _package = package,
        assert(inherit != null),
-       assert(color == null || foreground == null, _kColorForegroundWarning);
+       assert(color == null || foreground == null, _kColorForegroundWarning),
+       assert(backgroundColor == null || background == null, _kColorBackgroundWarning);
 
 
   /// Whether null values are replaced with their value in an ancestor text
@@ -338,6 +347,17 @@ class TextStyle extends Diagnosticable {
   /// specified in one place, it will dominate [color] in another.
   final Color color;
 
+  /// The color to use as the background for the text.
+  ///
+  /// If [background] is specified, this value must be null. The
+  /// [backgroundColor] property is shorthand for
+  /// `background: Paint()..color = backgroundColor`.
+  ///
+  /// In [merge], [apply], and [lerp], conflicts between [backgroundColor] and [background]
+  /// specification are resolved in [background]'s favor - i.e. if [background] is
+  /// specified in one place, it will dominate [color] in another.
+  final Color backgroundColor;
+
   /// The name of the font to use when painting the text (e.g., Roboto). If the
   /// font is defined in a package, this will be prefixed with
   /// 'packages/package_name/' (e.g. 'packages/cool_fonts/Roboto'). The
@@ -450,6 +470,15 @@ class TextStyle extends Diagnosticable {
   /// styles are created with the same paint settings. Otherwise, each time it
   /// will appear like the style changed, which will result in unnecessary
   /// updates all the way through the framework.
+  ///
+  /// If [backgroundColor] is specified, this value must be null. The
+  /// [backgroundColor] property is shorthand for
+  /// `background: Paint()..color = backgroundColor`.
+  ///
+  /// In [merge], [apply], and [lerp], conflicts between [backgroundColor] and
+  /// [background] specification are resolved in [background]'s favor - i.e. if
+  /// [background] is specified in one place, it will dominate [backgroundColor]
+  /// in another.
   final Paint background;
 
   /// The decorations to paint near the text (e.g., an underline).
@@ -488,8 +517,13 @@ class TextStyle extends Diagnosticable {
   ///
   /// One of [color] or [foreground] must be null, and if this has [foreground]
   /// specified it will be given preference over any color parameter.
+  ///
+  /// One of [backgroundColor] or [background] must be null, and if this has
+  /// [background] specified it will be given preference over any
+  /// backgroundColor parameter.
   TextStyle copyWith({
     Color color,
+    Color backgroundColor,
     String fontFamily,
     List<String> fontFamilyFallback,
     double fontSize,
@@ -509,6 +543,7 @@ class TextStyle extends Diagnosticable {
     String debugLabel,
   }) {
     assert(color == null || foreground == null, _kColorForegroundWarning);
+    assert(backgroundColor == null || background == null, _kColorBackgroundWarning);
     String newDebugLabel;
     assert(() {
       if (this.debugLabel != null)
@@ -518,6 +553,7 @@ class TextStyle extends Diagnosticable {
     return TextStyle(
       inherit: inherit,
       color: this.foreground == null && foreground == null ? color ?? this.color : null,
+      backgroundColor: this.background == null && background == null ? backgroundColor ?? this.backgroundColor : null,
       fontFamily: fontFamily ?? this.fontFamily,
       fontFamilyFallback: fontFamilyFallback ?? this.fontFamilyFallback,
       fontSize: fontSize ?? this.fontSize,
@@ -544,7 +580,9 @@ class TextStyle extends Diagnosticable {
   /// The non-numeric properties [color], [fontFamily], [decoration],
   /// [decorationColor] and [decorationStyle] are replaced with the new values.
   ///
-  /// [foreground] will be given preference over [color] if it is not null.
+  /// [foreground] will be given preference over [color] if it is not null and
+  /// [background] will be given preference over [backgroundColor] if it is not
+  /// null.
   ///
   /// The numeric properties are multiplied by the given factors and then
   /// incremented by the given deltas.
@@ -563,9 +601,11 @@ class TextStyle extends Diagnosticable {
   /// deltas must not be specified.
   ///
   /// If [foreground] is specified on this object, then applying [color] here
-  /// will have no effect.
+  /// will have no effect and if [background] is specified on this object, then
+  /// applying [backgroundColor] here will have no effect either.
   TextStyle apply({
     Color color,
+    Color backgroundColor,
     TextDecoration decoration,
     Color decorationColor,
     TextDecorationStyle decorationStyle,
@@ -606,6 +646,7 @@ class TextStyle extends Diagnosticable {
     return TextStyle(
       inherit: inherit,
       color: foreground == null ? color ?? this.color : null,
+      backgroundColor: background == null ? backgroundColor ?? this.backgroundColor : null,
       fontFamily: fontFamily ?? this.fontFamily,
       fontFamilyFallback: fontFamilyFallback ?? this.fontFamilyFallback,
       fontSize: fontSize == null ? null : fontSize * fontSizeFactor + fontSizeDelta,
@@ -616,7 +657,7 @@ class TextStyle extends Diagnosticable {
       textBaseline: textBaseline,
       height: height == null ? null : height * heightFactor + heightDelta,
       locale: locale,
-      foreground: foreground != null ? foreground : null,
+      foreground: foreground,
       background: background,
       shadows: shadows,
       decoration: decoration ?? this.decoration,
@@ -643,6 +684,10 @@ class TextStyle extends Diagnosticable {
   ///
   /// One of [color] or [foreground] must be null, and if this or `other` has
   /// [foreground] specified it will be given preference over any color parameter.
+  ///
+  /// Similarly, One of [backgroundColor] or [background] must be null, and if
+  /// this or `other` has [background] specified it will be given preference
+  /// over any backgroundColor parameter.
   TextStyle merge(TextStyle other) {
     if (other == null)
       return this;
@@ -658,6 +703,7 @@ class TextStyle extends Diagnosticable {
 
     return copyWith(
       color: other.color,
+      backgroundColor: other.backgroundColor,
       fontFamily: other.fontFamily,
       fontFamilyFallback: other.fontFamilyFallback,
       fontSize: other.fontSize,
@@ -687,6 +733,10 @@ class TextStyle extends Diagnosticable {
   /// If [foreground] is specified on either of `a` or `b`, both will be treated
   /// as if they have a [foreground] paint (creating a new [Paint] if necessary
   /// based on the [color] property).
+  ///
+  /// If [background] is specified on either of `a` or `b`, both will be treated
+  /// as if they have a [background] paint (creating a new [Paint] if necessary
+  /// based on the [backgroundColor] property).
   static TextStyle lerp(TextStyle a, TextStyle b, double t) {
     assert(t != null);
     assert(a == null || b == null || a.inherit == b.inherit);
@@ -704,6 +754,7 @@ class TextStyle extends Diagnosticable {
       return TextStyle(
         inherit: b.inherit,
         color: Color.lerp(null, b.color, t),
+        backgroundColor: Color.lerp(null, b.backgroundColor, t),
         fontFamily: t < 0.5 ? null : b.fontFamily,
         fontFamilyFallback: t < 0.5 ? null : b.fontFamilyFallback,
         fontSize: t < 0.5 ? null : b.fontSize,
@@ -728,6 +779,7 @@ class TextStyle extends Diagnosticable {
       return TextStyle(
         inherit: a.inherit,
         color: Color.lerp(a.color, null, t),
+        backgroundColor: Color.lerp(null, a.backgroundColor, t),
         fontFamily: t < 0.5 ? a.fontFamily : null,
         fontFamilyFallback: t < 0.5 ? a.fontFamilyFallback : null,
         fontSize: t < 0.5 ? a.fontSize : null,
@@ -751,6 +803,7 @@ class TextStyle extends Diagnosticable {
     return TextStyle(
       inherit: b.inherit,
       color: a.foreground == null && b.foreground == null ? Color.lerp(a.color, b.color, t) : null,
+      backgroundColor: a.background == null && b.background == null ? Color.lerp(a.backgroundColor, b.backgroundColor, t) : null,
       fontFamily: t < 0.5 ? a.fontFamily : b.fontFamily,
       fontFamilyFallback: t < 0.5 ? a.fontFamilyFallback : b.fontFamilyFallback,
       fontSize: ui.lerpDouble(a.fontSize ?? b.fontSize, b.fontSize ?? a.fontSize, t),
@@ -766,7 +819,11 @@ class TextStyle extends Diagnosticable {
           ? a.foreground ?? (Paint()..color = a.color)
           : b.foreground ?? (Paint()..color = b.color)
         : null,
-      background: t < 0.5 ? a.background : b.background,
+      background: (a.background != null || b.background != null)
+        ? t < 0.5
+          ? a.background ?? (Paint()..color = a.backgroundColor)
+          : b.background ?? (Paint()..color = b.backgroundColor)
+        : null,
       shadows: t < 0.5 ? a.shadows : b.shadows,
       decoration: t < 0.5 ? a.decoration : b.decoration,
       decorationColor: Color.lerp(a.decorationColor, b.decorationColor, t),
@@ -793,7 +850,10 @@ class TextStyle extends Diagnosticable {
       height: height,
       locale: locale,
       foreground: foreground,
-      background: background,
+      background: background ?? (backgroundColor != null
+        ? (Paint()..color = backgroundColor)
+        : null
+      ),
       shadows: shadows,
     );
   }
@@ -873,6 +933,7 @@ class TextStyle extends Diagnosticable {
         !listEquals(fontFamilyFallback, other.fontFamilyFallback))
       return RenderComparison.layout;
     if (color != other.color ||
+        backgroundColor != other.backgroundColor ||
         decoration != other.decoration ||
         decorationColor != other.decorationColor ||
         decorationStyle != other.decorationStyle)
@@ -889,6 +950,7 @@ class TextStyle extends Diagnosticable {
     final TextStyle typedOther = other;
     return inherit == typedOther.inherit &&
            color == typedOther.color &&
+           backgroundColor == typedOther.backgroundColor &&
            fontFamily == typedOther.fontFamily &&
            fontSize == typedOther.fontSize &&
            fontWeight == typedOther.fontWeight &&
@@ -912,6 +974,7 @@ class TextStyle extends Diagnosticable {
     return hashValues(
       inherit,
       color,
+      backgroundColor,
       fontFamily,
       fontFamilyFallback,
       fontSize,
@@ -942,6 +1005,7 @@ class TextStyle extends Diagnosticable {
       properties.add(MessageProperty('${prefix}debugLabel', debugLabel));
     final List<DiagnosticsNode> styles = <DiagnosticsNode>[];
     styles.add(DiagnosticsProperty<Color>('${prefix}color', color, defaultValue: null));
+    styles.add(DiagnosticsProperty<Color>('${prefix}backgroundColor', backgroundColor, defaultValue: null));
     styles.add(StringProperty('${prefix}family', fontFamily, defaultValue: null, quoted: false));
     styles.add(IterableProperty<String>('${prefix}familyFallback', fontFamilyFallback, defaultValue: null));
     styles.add(DoubleProperty('${prefix}size', fontSize, defaultValue: null));

packages/flutter/test/material/theme_test.dart

@@ -666,6 +666,7 @@ class _TextStyleProxy implements TextStyle {
 
   // Do make sure that all the properties correctly forward to the _delegate.
   @override Color get color => _delegate.color;
+  @override Color get backgroundColor => _delegate.backgroundColor;
   @override String get debugLabel => _delegate.debugLabel;
   @override TextDecoration get decoration => _delegate.decoration;
   @override Color get decorationColor => _delegate.decorationColor;
@@ -700,7 +701,7 @@ class _TextStyleProxy implements TextStyle {
   }
 
   @override
-  TextStyle apply({ Color color, TextDecoration decoration, Color decorationColor, TextDecorationStyle decorationStyle, String fontFamily, List<String> fontFamilyFallback, double fontSizeFactor = 1.0, double fontSizeDelta = 0.0, int fontWeightDelta = 0, double letterSpacingFactor = 1.0, double letterSpacingDelta = 0.0, double wordSpacingFactor = 1.0, double wordSpacingDelta = 0.0, double heightFactor = 1.0, double heightDelta = 0.0 }) {
+  TextStyle apply({ Color color, Color backgroundColor, TextDecoration decoration, Color decorationColor, TextDecorationStyle decorationStyle, String fontFamily, List<String> fontFamilyFallback, double fontSizeFactor = 1.0, double fontSizeDelta = 0.0, int fontWeightDelta = 0, double letterSpacingFactor = 1.0, double letterSpacingDelta = 0.0, double wordSpacingFactor = 1.0, double wordSpacingDelta = 0.0, double heightFactor = 1.0, double heightDelta = 0.0 }) {
     throw UnimplementedError();
   }
 
@@ -710,7 +711,7 @@ class _TextStyleProxy implements TextStyle {
   }
 
   @override
-  TextStyle copyWith({ Color color, String fontFamily, List<String> fontFamilyFallback, double fontSize, FontWeight fontWeight, FontStyle fontStyle, double letterSpacing, double wordSpacing, TextBaseline textBaseline, double height, Locale locale, ui.Paint foreground, ui.Paint background, List<Shadow> shadows, TextDecoration decoration, Color decorationColor, TextDecorationStyle decorationStyle, String debugLabel }) {
+  TextStyle copyWith({ Color color, Color backgroundColor, String fontFamily, List<String> fontFamilyFallback, double fontSize, FontWeight fontWeight, FontStyle fontStyle, double letterSpacing, double wordSpacing, TextBaseline textBaseline, double height, Locale locale, ui.Paint foreground, ui.Paint background, List<Shadow> shadows, TextDecoration decoration, Color decorationColor, TextDecorationStyle decorationStyle, String debugLabel }) {
     throw UnimplementedError();
   }
 

packages/flutter/test/painting/text_style_test.dart

@@ -294,4 +294,58 @@ void main() {
     expect(TextStyle.lerp(redPaintTextStyle, bluePaintTextStyle, .25).foreground.color, red);
     expect(TextStyle.lerp(redPaintTextStyle, bluePaintTextStyle, .75).foreground.color, blue);
   });
+
+  test('backgroundColor', () {
+    const TextStyle s1 = TextStyle();
+    expect(s1.backgroundColor, isNull);
+    expect(s1.toString(), 'TextStyle(<all styles inherited>)');
+
+    const TextStyle s2 = TextStyle(backgroundColor: Color(0xFF00FF00));
+    expect(s2.backgroundColor, const Color(0xFF00FF00));
+    expect(s2.toString(), 'TextStyle(inherit: true, backgroundColor: Color(0xff00ff00))');
+
+    final ui.TextStyle ts2 = s2.getTextStyle();
+    expect(ts2.toString(), contains('background: Paint(Color(0xff00ff00))'));
+  });
+
+  test('TextStyle background and backgroundColor combos', () {
+    const Color red = Color.fromARGB(255, 255, 0, 0);
+    const Color blue = Color.fromARGB(255, 0, 0, 255);
+    const TextStyle redTextStyle = TextStyle(backgroundColor: red);
+    const TextStyle blueTextStyle = TextStyle(backgroundColor: blue);
+    final TextStyle redPaintTextStyle = TextStyle(background: Paint()..color = red);
+    final TextStyle bluePaintTextStyle = TextStyle(background: Paint()..color = blue);
+
+    // merge/copyWith
+    final TextStyle redBlueBothForegroundMerged = redTextStyle.merge(blueTextStyle);
+    expect(redBlueBothForegroundMerged.backgroundColor, blue);
+    expect(redBlueBothForegroundMerged.foreground, isNull);
+
+    final TextStyle redBlueBothPaintMerged = redPaintTextStyle.merge(bluePaintTextStyle);
+    expect(redBlueBothPaintMerged.backgroundColor, null);
+    expect(redBlueBothPaintMerged.background, bluePaintTextStyle.background);
+
+    final TextStyle redPaintBlueColorMerged = redPaintTextStyle.merge(blueTextStyle);
+    expect(redPaintBlueColorMerged.backgroundColor, null);
+    expect(redPaintBlueColorMerged.background, redPaintTextStyle.background);
+
+    final TextStyle blueColorRedPaintMerged = blueTextStyle.merge(redPaintTextStyle);
+    expect(blueColorRedPaintMerged.backgroundColor, null);
+    expect(blueColorRedPaintMerged.background, redPaintTextStyle.background);
+
+    // apply
+    expect(redPaintTextStyle.apply(backgroundColor: blue).backgroundColor, isNull);
+    expect(redPaintTextStyle.apply(backgroundColor: blue).background.color, red);
+    expect(redTextStyle.apply(backgroundColor: blue).backgroundColor, blue);
+
+    // lerp
+    expect(TextStyle.lerp(redTextStyle, blueTextStyle, .25).backgroundColor, Color.lerp(red, blue, .25));
+    expect(TextStyle.lerp(redTextStyle, bluePaintTextStyle, .25).backgroundColor, isNull);
+    expect(TextStyle.lerp(redTextStyle, bluePaintTextStyle, .25).background.color, red);
+    expect(TextStyle.lerp(redTextStyle, bluePaintTextStyle, .75).background.color, blue);
+
+    expect(TextStyle.lerp(redPaintTextStyle, bluePaintTextStyle, .25).backgroundColor, isNull);
+    expect(TextStyle.lerp(redPaintTextStyle, bluePaintTextStyle, .25).background.color, red);
+    expect(TextStyle.lerp(redPaintTextStyle, bluePaintTextStyle, .75).background.color, blue);
+  });
 }