Merge "Discard framebuffer commands when we redraw the entire buffer" into jb-mr1-dev

Author: Romain Guy

libs/hwui/DisplayListRenderer.cpp

@@ -1412,8 +1412,12 @@ int DisplayListRenderer::prepareDirty(float left, float top,
     mSnapshot = new Snapshot(mFirstSnapshot,
             SkCanvas::kMatrix_SaveFlag | SkCanvas::kClip_SaveFlag);
     mSaveCount = 1;
+
     mSnapshot->setClip(0.0f, 0.0f, mWidth, mHeight);
+    mDirtyClip = opaque;
+
     mRestoreSaveCount = -1;
+
     return DrawGlInfo::kStatusDone; // No invalidate needed at record-time
 }
 

libs/hwui/LayerRenderer.cpp

@@ -332,10 +332,10 @@ void LayerRenderer::flushLayer(Layer* layer) {
         if (Caches::getInstance().extensions.hasDiscardFramebuffer()) {
             GLuint previousFbo;
             glGetIntegerv(GL_FRAMEBUFFER_BINDING, (GLint*) &previousFbo);
-
-            GLenum attachments = GL_COLOR_ATTACHMENT0;
             if (fbo != previousFbo) glBindFramebuffer(GL_FRAMEBUFFER, fbo);
-            glDiscardFramebufferEXT(GL_FRAMEBUFFER, 1, &attachments);
+
+            const GLenum attachments[] = { GL_COLOR_ATTACHMENT0 };
+            glDiscardFramebufferEXT(GL_FRAMEBUFFER, 1, attachments);
 
             if (fbo != previousFbo) glBindFramebuffer(GL_FRAMEBUFFER, previousFbo);
         }

libs/hwui/OpenGLRenderer.cpp

@@ -173,6 +173,15 @@ int OpenGLRenderer::prepareDirty(float left, float top, float right, float botto
     mSnapshot->setClip(left, top, right, bottom);
     mDirtyClip = opaque;
 
+    // If we know that we are going to redraw the entire framebuffer,
+    // perform a discard to let the driver know we don't need to preserve
+    // the back buffer for this frame.
+    if (mCaches.extensions.hasDiscardFramebuffer() &&
+            left <= 0.0f && top <= 0.0f && right >= mWidth && bottom >= mHeight) {
+        const GLenum attachments[] = { getTargetFbo() == 0 ? GL_COLOR_EXT : GL_COLOR_ATTACHMENT0 };
+        glDiscardFramebufferEXT(GL_FRAMEBUFFER, 1, attachments);
+    }
+
     syncState();
 
     if (!opaque) {