Expose foreground property of TextStyle in Icon widget (flutter#150315)

Expose foreground property to icon. See issues:

- flutter#139411

Author: evan361425

packages/flutter/lib/src/widgets/icon.dart

@@ -86,9 +86,10 @@ class Icon extends StatelessWidget {
     this.semanticLabel,
     this.textDirection,
     this.applyTextScaling,
-  }) : assert(fill == null || (0.0 <= fill && fill <= 1.0)),
-       assert(weight == null || (0.0 < weight)),
-       assert(opticalSize == null || (0.0 < opticalSize));
+    this.blendMode,
+  })  : assert(fill == null || (0.0 <= fill && fill <= 1.0)),
+        assert(weight == null || (0.0 < weight)),
+        assert(opticalSize == null || (0.0 < opticalSize));
 
   /// The icon to display. The available icons are described in [Icons].
   ///
@@ -247,6 +248,11 @@ class Icon extends StatelessWidget {
   /// [IconThemeData.applyTextScaling].
   final bool? applyTextScaling;
 
+  /// The [BlendMode] to apply to the foreground of the icon.
+  ///
+  /// Defaults to [BlendMode.srcOver]
+  final BlendMode? blendMode;
+
   @override
   Widget build(BuildContext context) {
     assert(this.textDirection != null || debugCheckHasDirectionality(context));
@@ -279,10 +285,18 @@ class Icon extends StatelessWidget {
     }
 
     final double iconOpacity = iconTheme.opacity ?? 1.0;
-    Color iconColor = color ?? iconTheme.color!;
+    Color? iconColor = color ?? iconTheme.color!;
+    Paint? foreground;
     if (iconOpacity != 1.0) {
       iconColor = iconColor.withOpacity(iconColor.opacity * iconOpacity);
     }
+    if (blendMode != null) {
+      foreground = Paint()
+        ..blendMode = blendMode!
+        ..color = iconColor;
+      // Cannot provide both a color and a foreground.
+      iconColor = null;
+    }
 
     final TextStyle fontStyle = TextStyle(
       fontVariations: <FontVariation>[
@@ -298,8 +312,9 @@ class Icon extends StatelessWidget {
       package: icon.fontPackage,
       fontFamilyFallback: icon.fontFamilyFallback,
       shadows: iconShadows,
-      height: 1.0,  // Makes sure the font's body is vertically centered within the iconSize x iconSize square.
+      height: 1.0, // Makes sure the font's body is vertically centered within the iconSize x iconSize square.
       leadingDistribution: TextLeadingDistribution.even,
+      foreground: foreground,
     );
 
     Widget iconWidget = RichText(

packages/flutter/test/widgets/icon_test.dart

@@ -358,7 +358,6 @@ void main() {
     expect(const IconData(123).toString(), 'IconData(U+0007B)');
   });
 
-
   testWidgets('Fill, weight, grade, and optical size variations are passed', (WidgetTester tester) async {
     await tester.pumpWidget(
       const Directionality(
@@ -443,6 +442,27 @@ void main() {
     ]);
   });
 
+  testWidgets("TextStyle's blendMode should bind in foreground property", (WidgetTester tester) async {
+    await tester.pumpWidget(
+      const Directionality(
+        textDirection: TextDirection.ltr,
+        child: Center(
+          child: IconTheme(
+            data: IconThemeData(opacity: 0.5),
+            child: Icon(
+              IconData(0x41),
+              blendMode: BlendMode.clear,
+            ),
+          ),
+        ),
+      ),
+    );
+
+    final RichText richText = tester.firstWidget(find.byType(RichText));
+    expect(richText.text.style?.color, isNull);
+    expect(richText.text.style?.foreground?.blendMode, BlendMode.clear);
+  });
+
   test('Throws if given invalid values', () {
     expect(() => Icon(Icons.abc, fill: -0.1), throwsAssertionError);
     expect(() => Icon(Icons.abc, fill: 1.1), throwsAssertionError);