commit 6452f12c95e855a96ab8f690f28914cd37de762b
author Robert Carr <racarr@google.com> Tue Mar 21 10:41:29 2017 -0700
committer Robert Carr <racarr@google.com> Wed Mar 22 13:47:34 2017 -0700
tree c217f4dd107ac8b4723be9030725026219e94b2f
parent 8b71dc3c7e57c2cbed47934c00bb440ac43f3832

SurfaceFlinger: Inherit Alpha for child surfaces.

Necessary for various animations to work correctly and
for the general goal of treating child surfaces like
pixels in the parent surface.

Test: Includes new test in SurfaceFlinger_test
Bug: None yet ;)
Change-Id: Ic8309518bd327bbba6ad2f79f265e24cf37898e7

services/surfaceflinger/Layer.cpp

diff --git a/services/surfaceflinger/Layer.cpp b/services/surfaceflinger/Layer.cpp
index adfff96..ac7e083 100644
--- a/services/surfaceflinger/Layer.cpp
+++ b/services/surfaceflinger/Layer.cpp
@@ -595,7 +595,7 @@
     const State& s(getDrawingState());
 #ifdef USE_HWC2
     auto blendMode = HWC2::BlendMode::None;
-    if (!isOpaque(s) || s.alpha != 1.0f) {
+    if (!isOpaque(s) || getAlpha() != 1.0f) {
         blendMode = mPremultipliedAlpha ?
                 HWC2::BlendMode::Premultiplied : HWC2::BlendMode::Coverage;
     }
@@ -604,7 +604,7 @@
              " %s (%d)", mName.string(), to_string(blendMode).c_str(),
              to_string(error).c_str(), static_cast<int32_t>(error));
 #else
-    if (!isOpaque(s) || s.alpha != 0xFF) {
+    if (!isOpaque(s) || getAlpha() != 0xFF) {
         layer.setBlending(mPremultipliedAlpha ?
                 HWC_BLENDING_PREMULT :
                 HWC_BLENDING_COVERAGE);
@@ -678,9 +678,10 @@
         hwcInfo.sourceCrop = sourceCrop;
     }
 
-    error = hwcLayer->setPlaneAlpha(s.alpha);
+    float alpha = getAlpha();
+    error = hwcLayer->setPlaneAlpha(alpha);
     ALOGE_IF(error != HWC2::Error::None, "[%s] Failed to set plane alpha %.3f: "
-            "%s (%d)", mName.string(), s.alpha, to_string(error).c_str(),
+            "%s (%d)", mName.string(), alpha, to_string(error).c_str(),
             static_cast<int32_t>(error));
 
     error = hwcLayer->setZOrder(z);
@@ -698,7 +699,7 @@
     const Transform& tr(hw->getTransform());
     layer.setFrame(tr.transform(frame));
     layer.setCrop(computeCrop(hw));
-    layer.setPlaneAlpha(s.alpha);
+    layer.setPlaneAlpha(getAlpha());
 #endif
 
     /*
@@ -1147,7 +1148,7 @@
     texCoords[3] = vec2(right, 1.0f - top);
 
     RenderEngine& engine(mFlinger->getRenderEngine());
-    engine.setupLayerBlending(mPremultipliedAlpha, isOpaque(s), s.alpha);
+    engine.setupLayerBlending(mPremultipliedAlpha, isOpaque(s), getAlpha());
     engine.drawMesh(mMesh);
     engine.disableBlending();
 }
@@ -1961,12 +1962,11 @@
 }
 
 bool Layer::isVisible() const {
-    const Layer::State& s(mDrawingState);
 #ifdef USE_HWC2
-    return !(isHiddenByPolicy()) && s.alpha > 0.0f
+    return !(isHiddenByPolicy()) && getAlpha() > 0.0f
             && (mActiveBuffer != NULL || mSidebandStream != NULL);
 #else
-    return !(isHiddenByPolicy()) && s.alpha
+    return !(isHiddenByPolicy()) && getAlpha()
             && (mActiveBuffer != NULL || mSidebandStream != NULL);
 #endif
 }
@@ -2523,6 +2523,24 @@
     return t * getDrawingState().active.transform;
 }
 
+#ifdef USE_HWC2
+float Layer::getAlpha() const {
+    const auto& p = getParent();
+
+    float parentAlpha = (p != nullptr) ? p->getAlpha() : 1.0;
+    return parentAlpha * getDrawingState().alpha;
+}
+#else
+uint8_t Layer::getAlpha() const {
+    const auto& p = getParent();
+
+    float parentAlpha = (p != nullptr) ? (p->getAlpha() / 255.0f) : 1.0;
+    float drawingAlpha = getDrawingState().alpha / 255.0f;
+    drawingAlpha = drawingAlpha * parentAlpha;
+    return static_cast<uint8_t>(std::round(drawingAlpha * 255));
+}
+#endif
+
 void Layer::commitChildList() {
     for (size_t i = 0; i < mCurrentChildren.size(); i++) {
         const auto& child = mCurrentChildren[i];