Support alpha for SurfaceView
Basically, this removes an excuse for apps to use TextureView for video
playback or one-off HDR images prior to HDR UI being ready everywhere.
The idea is that for Z-above, applying alpha is easy, because the
surface just needs to be have alpha modulated. Z-below is a little bit
more creative - the alpha is applied to the hole punch and drawn using
DST_OUT blending semantics. This allows for views underneath the
SurfaceView to blend with surface, while being occluded by views on top
of the SurfaceView.
There may need to be some complex view hierarchies that would be useful
to test, but simple view layouts seem to work.
Note that this is guarded with a target SDK check, to defend against
applications that are propagated alpha to child views while expecting
opaque SurfaceViews.
Bug: 241474646
Test: HWAccelerationTest doesn't look broken
Change-Id: Ibc14b18f1ce6f25250318db50275c6b8c972bade
diff --git a/libs/hwui/pipeline/skia/RenderNodeDrawable.cpp b/libs/hwui/pipeline/skia/RenderNodeDrawable.cpp
index 3bf2b2e..f2282e66 100644
--- a/libs/hwui/pipeline/skia/RenderNodeDrawable.cpp
+++ b/libs/hwui/pipeline/skia/RenderNodeDrawable.cpp
@@ -201,6 +201,7 @@
paint.setAlpha((uint8_t)paint.getAlpha() * mAlpha);
return true;
}
+
void onDrawDrawable(SkDrawable* drawable, const SkMatrix* matrix) override {
// We unroll the drawable using "this" canvas, so that draw calls contained inside will
// get their alpha applied. The default SkPaintFilterCanvas::onDrawDrawable does not unroll.
@@ -292,7 +293,7 @@
// with the same canvas transformation + clip into the target
// canvas then draw the layer on top
if (renderNode->hasHolePunches()) {
- TransformCanvas transformCanvas(canvas, SkBlendMode::kClear);
+ TransformCanvas transformCanvas(canvas, SkBlendMode::kDstOut);
displayList->draw(&transformCanvas);
}
canvas->drawImageRect(snapshotImage, SkRect::Make(srcBounds),