Optimization of alpha with DisplayList properties

Some views (such as ImageView and TextView) handle non-opaque alpha
values directly. This was originally an optimization, but we can handle it faster
in many cases without this optimization when DisplayList properties are enabled.
Basically, if a view has non-overlapping rendering, we set the alpha value directly
on the renderer (the equivalent of setting it on the Paint object) and draw each
primitive with that alpha value. Doing it this way avoids re-creating DisplayLists
while getting the same speedup that onSetAlpha() used to get pre-DisplayList properties.

Change-Id: I0f7827f075d3b35093a882d4adbb300a1063c288

1 files changed, 2 insertions, 0 deletions

diff --git a/libs/hwui/OpenGLRenderer.cpp b/libs/hwui/OpenGLRenderer.cpp
index 115787c..ec9b56b 100644
--- a/libs/hwui/OpenGLRenderer.cpp
+++ b/libs/hwui/OpenGLRenderer.cpp
@@ -1101,6 +1101,7 @@ void OpenGLRenderer::setupDrawColor(int color) {
 
 void OpenGLRenderer::setupDrawColor(int color, int alpha) {
     mColorA = alpha / 255.0f;
+    mColorA *= mSnapshot->alpha;
     // Second divide of a by 255 is an optimization, allowing us to simply multiply
     // the rgb values by a instead of also dividing by 255
     const float a = mColorA / 255.0f;
@@ -2800,6 +2801,7 @@ void OpenGLRenderer::getAlphaAndMode(SkPaint* paint, int* alpha, SkXfermode::Mod
         *mode = SkXfermode::kSrcOver_Mode;
         *alpha = 255;
     }
+    *alpha *= mSnapshot->alpha;
 }
 
 SkXfermode::Mode OpenGLRenderer::getXfermode(SkXfermode* mode) {