feat: OpacityEffect support on text components

examples/lib/stories/rendering/text_example.dart

@@ -1,6 +1,7 @@
 import 'dart:async';
 
 import 'package:flame/components.dart';
+import 'package:flame/effects.dart';
 import 'package:flame/game.dart';
 import 'package:flame/palette.dart';
 import 'package:flame/text.dart';
@@ -82,6 +83,20 @@ class TextExample extends FlameGame {
             margins: EdgeInsets.fromLTRB(10, 10, 10, 10),
           ),
         ),
+        TextComponent(
+          text: 'I fade in and fade out',
+          anchor: Anchor.topRight,
+          position: Vector2(size.x - 50, 20),
+          children: [
+            SequenceEffect(
+              [
+                OpacityEffect.fadeIn(LinearEffectController(1.5)),
+                OpacityEffect.fadeOut(LinearEffectController(1.5)),
+              ],
+              infinite: true,
+            ),
+          ],
+        ),
       ],
     );
   }

packages/flame/lib/src/components/text_component.dart

@@ -1,11 +1,13 @@
 import 'dart:ui';
 
 import 'package:flame/components.dart';
+import 'package:flame/effects.dart';
 import 'package:flame/text.dart';
 import 'package:flutter/painting.dart';
 import 'package:meta/meta.dart';
 
-class TextComponent<T extends TextRenderer> extends PositionComponent {
+class TextComponent<T extends TextRenderer> extends PositionComponent
+    implements OpacityProvider {
   TextComponent({
     String? text,
     T? textRenderer,
@@ -52,4 +54,14 @@ class TextComponent<T extends TextRenderer> extends PositionComponent {
   void render(Canvas canvas) {
     _textElement.draw(canvas);
   }
+
+  @override
+  set opacity(double opacity) {
+    textRenderer = textRenderer.copyWithOpacity(opacity) as T;
+  }
+
+  @override
+  double get opacity {
+    return textRenderer.opacity;
+  }
 }

packages/flame/lib/src/text/renderers/sprite_font_renderer.dart

@@ -56,4 +56,14 @@ class SpriteFontRenderer extends TextRenderer {
       ),
     );
   }
+
+  @override
+  TextRenderer copyWithOpacity(double opacity) {
+    // TODO(erickzanardo): Implement this, keeping as noop for now
+    return this;
+  }
+
+  @override
+  // TODO(erickzanardo): Implement this, keeping as noop for now
+  double get opacity => 1;
 }

packages/flame/lib/src/text/renderers/text_paint.dart

@@ -54,6 +54,17 @@ class TextPaint extends TextRenderer {
     return _textPainterCache.getValue(text)!;
   }
 
+  @override
+  TextRenderer copyWithOpacity(double opacity) {
+    return copyWith(
+      (style) {
+        return style.copyWith(
+          color: style.color?.withValues(alpha: opacity),
+        );
+      },
+    );
+  }
+
   TextPaint copyWith(
     TextStyle Function(TextStyle) transform, {
     TextDirection? textDirection,
@@ -96,4 +107,7 @@ class TextPaint extends TextRenderer {
     }
     return null;
   }
+
+  @override
+  double get opacity => style.color?.a ?? 0;
 }

packages/flame/lib/src/text/renderers/text_renderer.dart

@@ -11,6 +11,10 @@ abstract class TextRenderer {
     return format(text).metrics;
   }
 
+  TextRenderer copyWithOpacity(double opacity);
+
+  double get opacity;
+
   void render(
     Canvas canvas,
     String text,