Don't clear the framebuffer when not needed.

6 files changed, 15 insertions, 10 deletions

diff --git a/libs/hwui/DisplayListRenderer.cpp b/libs/hwui/DisplayListRenderer.cpp
index ce85d46..61e5408 100644
--- a/libs/hwui/DisplayListRenderer.cpp
+++ b/libs/hwui/DisplayListRenderer.cpp
@@ -342,7 +342,7 @@ void DisplayListRenderer::setViewport(int width, int height) {
     mHeight = height;
 }
 
-void DisplayListRenderer::prepare() {
+void DisplayListRenderer::prepare(bool opaque) {
     mSnapshot = new Snapshot(mFirstSnapshot,
             SkCanvas::kMatrix_SaveFlag | SkCanvas::kClip_SaveFlag);
     mSaveCount = 1;
diff --git a/libs/hwui/DisplayListRenderer.h b/libs/hwui/DisplayListRenderer.h
index 5d02bd7..0fbfce1 100644
--- a/libs/hwui/DisplayListRenderer.h
+++ b/libs/hwui/DisplayListRenderer.h
@@ -209,7 +209,7 @@ public:
     ~DisplayListRenderer();
 
     void setViewport(int width, int height);
-    void prepare();
+    void prepare(bool opaque);
 
     void acquireContext();
     void releaseContext();
diff --git a/libs/hwui/OpenGLDebugRenderer.cpp b/libs/hwui/OpenGLDebugRenderer.cpp
index 4e5123e..b9583e5 100644
--- a/libs/hwui/OpenGLDebugRenderer.cpp
+++ b/libs/hwui/OpenGLDebugRenderer.cpp
@@ -23,10 +23,10 @@
 namespace android {
 namespace uirenderer {
 
-void OpenGLDebugRenderer::prepare() {
+void OpenGLDebugRenderer::prepare(bool opaque) {
     mPrimitivesCount = 0;
     LOGD("========= Frame start =========");
-    OpenGLRenderer::prepare();
+    OpenGLRenderer::prepare(opaque);
 }
 
 void OpenGLDebugRenderer::finish() {
diff --git a/libs/hwui/OpenGLDebugRenderer.h b/libs/hwui/OpenGLDebugRenderer.h
index ce15512..2ac19ae 100644
--- a/libs/hwui/OpenGLDebugRenderer.h
+++ b/libs/hwui/OpenGLDebugRenderer.h
@@ -34,7 +34,7 @@ public:
     ~OpenGLDebugRenderer() {
     }
 
-    void prepare();
+    void prepare(bool opaque);
     void finish();
 
     int saveLayer(float left, float top, float right, float bottom,
diff --git a/libs/hwui/OpenGLRenderer.cpp b/libs/hwui/OpenGLRenderer.cpp
index ee5fe22..5399668 100644
--- a/libs/hwui/OpenGLRenderer.cpp
+++ b/libs/hwui/OpenGLRenderer.cpp
@@ -150,7 +150,7 @@ void OpenGLRenderer::setViewport(int width, int height) {
     mFirstSnapshot->viewport.set(0, 0, width, height);
 }
 
-void OpenGLRenderer::prepare() {
+void OpenGLRenderer::prepare(bool opaque) {
     mSnapshot = new Snapshot(mFirstSnapshot,
             SkCanvas::kMatrix_SaveFlag | SkCanvas::kClip_SaveFlag);
     mSaveCount = 1;
@@ -160,8 +160,10 @@ void OpenGLRenderer::prepare() {
     glDisable(GL_DITHER);
     glDisable(GL_SCISSOR_TEST);
 
-    glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
-    glClear(GL_COLOR_BUFFER_BIT);
+    if (!opaque) {
+        glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
+        glClear(GL_COLOR_BUFFER_BIT);
+    }
 
     glEnable(GL_SCISSOR_TEST);
     glScissor(0, 0, mWidth, mHeight);
@@ -325,7 +327,10 @@ int OpenGLRenderer::saveLayerAlpha(float left, float top, float right, float bot
  *   - Issue the drawing
  *
  * Switching rendering target n + 1 times per drawn primitive is extremely costly.
- * To avoid this, layers are implemented in a different way here.
+ * To avoid this, layers are implemented in a different way here, at least in the
+ * general case. FBOs are used, as an optimization, when the "clip to layer" flag
+ * is set. When this flag is set we can redirect all drawing operations into a
+ * single FBO.
  *
  * This implementation relies on the frame buffer being at least RGBA 8888. When
  * a layer is created, only a texture is created, not an FBO. The content of the
diff --git a/libs/hwui/OpenGLRenderer.h b/libs/hwui/OpenGLRenderer.h
index e3d4653..4caa8fb 100644
--- a/libs/hwui/OpenGLRenderer.h
+++ b/libs/hwui/OpenGLRenderer.h
@@ -67,7 +67,7 @@ public:
 
     virtual void setViewport(int width, int height);
 
-    virtual void prepare();
+    virtual void prepare(bool opaque);
     virtual void finish();
 
     virtual void acquireContext();