Remove concatAlpha() and concatBlendMode() from Canvas.

Author: domchen

Diff for: src/rendering/graphics/Modifier.cpp

@@ -200,8 +200,11 @@ bool BlendModifier::hitTest(RenderCache*, float, float) const {
 void BlendModifier::applyToGraphic(Canvas* canvas, RenderCache* cache,
                                    std::shared_ptr<Graphic> graphic) const {
   canvas->save();
-  canvas->concatAlpha(alpha);
-  canvas->concatBlendMode(ToBlend(blendMode));
+  auto newAlpha = OpacityConcat(canvas->getAlpha(), alpha);
+  canvas->setAlpha(newAlpha);
+  if (blendMode != BlendMode::Normal) {
+    canvas->setBlendMode(ToBlend(blendMode));
+  }
   graphic->draw(canvas, cache);
   canvas->restore();
 }

Diff for: tgfx/include/gpu/Canvas.h

@@ -95,14 +95,24 @@ class Canvas {
   void concat(const Matrix& matrix);
 
   /**
-   * Replaces the global alpha with specified alpha premultiplied with existing alpha.
+   * Returns the current global alpha.
    */
-  void concatAlpha(Opacity alpha);
+  Opacity getAlpha() const;
 
   /**
-   * Replaces the global blend mode with specified blend mode if it is not BlendMode::Normal.
+   * Replaces the global alpha with specified newAlpha.
    */
-  void concatBlendMode(Blend blendMode);
+  void setAlpha(Opacity newAlpha);
+
+  /**
+   * Returns the current global blend mode.
+   */
+  Blend getBlendMode() const;
+
+  /**
+   * Replaces the global blend mode with specified new blend mode.
+   */
+  void setBlendMode(Blend blendMode);
 
   /**
    * Returns the current total clip.

Diff for: tgfx/src/gpu/Canvas.cpp

@@ -61,14 +61,19 @@ void Canvas::concat(const Matrix& matrix) {
   onSetMatrix(globalPaint.matrix);
 }
 
-void Canvas::concatAlpha(Opacity alpha) {
-  globalPaint.alpha = OpacityConcat(globalPaint.alpha, alpha);
+Opacity Canvas::getAlpha() const {
+  return globalPaint.alpha;
 }
 
-void Canvas::concatBlendMode(Blend blendMode) {
-  if (blendMode == Blend::SrcOver) {
-    return;
-  }
+void Canvas::setAlpha(Opacity newAlpha) {
+  globalPaint.alpha = newAlpha;
+}
+
+Blend Canvas::getBlendMode() const {
+  return globalPaint.blendMode;
+}
+
+void Canvas::setBlendMode(Blend blendMode) {
   globalPaint.blendMode = blendMode;
 }
 

Diff for: tgfx/src/gpu/opengl/GLCanvas.cpp

@@ -260,7 +260,7 @@ void GLCanvas::drawColorGlyphs(const GlyphID glyphIDs[], const Point positions[]
     glyphMatrix.postTranslate(position.x, position.y);
     save();
     concat(glyphMatrix);
-    concatAlpha(paint.getAlpha());
+    globalPaint.alpha = OpacityConcat(globalPaint.alpha, paint.getAlpha());
     auto texture = glyphBuffer->makeTexture(getContext());
     drawTexture(texture.get(), nullptr, false);
     restore();