Optimize FBOs composition

Change-Id: Ifc8eada8922509373c0e4c3b2ed75b6f08d098de

Author: Romain Guy

graphics/java/android/graphics/Canvas.java

@@ -40,14 +40,8 @@ public class Canvas {
     // assigned in constructors, freed in finalizer
     final int mNativeCanvas;
 
-    /*  Our native canvas can be either a raster, gl, or picture canvas.
-        If we are raster, then mGL will be null, and mBitmap may or may not be
-        present (our default constructor creates a raster canvas but no
-        java-bitmap is). If we are a gl-based, then mBitmap will be null, and
-        mGL will not be null. Thus both cannot be non-null, but its possible
-        for both to be null.
-    */
-    private Bitmap  mBitmap;    // if not null, mGL must be null
+    // may be null
+    private Bitmap mBitmap;
 
     // optional field set by the caller
     private DrawFilter mDrawFilter;
@@ -66,7 +60,7 @@ public class Canvas {
 
     // Used by native code
     @SuppressWarnings({"UnusedDeclaration"})
-    private int         mSurfaceFormat;
+    private int mSurfaceFormat;
 
     /**
      * Flag for drawTextRun indicating left-to-right run direction.

libs/hwui/OpenGLRenderer.cpp

@@ -594,6 +594,9 @@ void OpenGLRenderer::composeLayer(sp<Snapshot> current, sp<Snapshot> previous) {
     const bool fboLayer = current->flags & Snapshot::kFlagIsFboLayer;
 
     if (fboLayer) {
+        // Detach the texture from the FBO
+        glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, 0, 0);
+
         // Unbind current FBO and restore previous one
         glBindFramebuffer(GL_FRAMEBUFFER, previous->fbo);
     }
@@ -634,11 +637,6 @@ void OpenGLRenderer::composeLayer(sp<Snapshot> current, sp<Snapshot> previous) {
         //       code path
         // See LayerRenderer::destroyLayer(Layer*)
 
-        // Detach the texture from the FBO
-        glBindFramebuffer(GL_FRAMEBUFFER, current->fbo);
-        glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, 0, 0);
-        glBindFramebuffer(GL_FRAMEBUFFER, previous->fbo);
-
         // Put the FBO name back in the cache, if it doesn't fit, it will be destroyed
         mCaches.fboCache.put(current->fbo);
         layer->setFbo(0);