Track canvas clearing for swap buffers logic.

A previous fix made it necessary for a frame to render something to GL
in order to cause a call to eglSwapBuffers(). Besides the calls being
tracked as part of issuing a DisplayList, there is also a potential call
to clear the canvas (via glClear()) on non-opaque surfaces. This call is also
good to track, since a surface that gets cleared without any other drawing operations
is worth flipping to the screen (to erase old contents on that surface).

This fix tracks the status of the pre-draw operations to find out whether
glClear() was called and then sets the drawing status appropriately.

Issue #6606422 QuickContact dismissal is janky again (Tracking)

Change-Id: I5fcaccfdc9293dd46b83f2fc279730a5d2740ebf

3 files changed, 18 insertions, 16 deletions

diff --git a/core/java/android/view/GLES20Canvas.java b/core/java/android/view/GLES20Canvas.java
index 1631fb34fea5..055aee3e8440 100644
--- a/core/java/android/view/GLES20Canvas.java
+++ b/core/java/android/view/GLES20Canvas.java
@@ -215,16 +215,17 @@ class GLES20Canvas extends HardwareCanvas {
     private static native void nSetViewport(int renderer, int width, int height);
 
     @Override
-    public void onPreDraw(Rect dirty) {
+    public int onPreDraw(Rect dirty) {
         if (dirty != null) {
-            nPrepareDirty(mRenderer, dirty.left, dirty.top, dirty.right, dirty.bottom, mOpaque);
+            return nPrepareDirty(mRenderer, dirty.left, dirty.top, dirty.right, dirty.bottom,
+                    mOpaque);
         } else {
-            nPrepare(mRenderer, mOpaque);
+            return nPrepare(mRenderer, mOpaque);
         }
     }
 
-    private static native void nPrepare(int renderer, boolean opaque);
-    private static native void nPrepareDirty(int renderer, int left, int top, int right, int bottom,
+    private static native int nPrepare(int renderer, boolean opaque);
+    private static native int nPrepareDirty(int renderer, int left, int top, int right, int bottom,
             boolean opaque);
 
     @Override
diff --git a/core/java/android/view/HardwareCanvas.java b/core/java/android/view/HardwareCanvas.java
index ee2dd5928f2c..777552a23b5a 100644
--- a/core/java/android/view/HardwareCanvas.java
+++ b/core/java/android/view/HardwareCanvas.java
@@ -41,8 +41,10 @@ public abstract class HardwareCanvas extends Canvas {
      * Invoked before any drawing operation is performed in this canvas.
      * 
      * @param dirty The dirty rectangle to update, can be null.
+     * @return {@link DisplayList#STATUS_DREW} if anything was drawn (such as a call to clear
+     * the canvas).
      */
-    public abstract void onPreDraw(Rect dirty);
+    public abstract int onPreDraw(Rect dirty);
 
     /**
      * Invoked after all drawing operation have been performed.
@@ -58,8 +60,9 @@ public abstract class HardwareCanvas extends Canvas {
      * @param flags Optional flags about drawing, see {@link DisplayList} for
      *              the possible flags.
      *
-     * @return One of {@link DisplayList#STATUS_DONE}, {@link DisplayList#STATUS_DRAW} or
-     *         {@link DisplayList#STATUS_INVOKE}
+     * @return One of {@link DisplayList#STATUS_DONE}, {@link DisplayList#STATUS_DRAW}, or
+     *         {@link DisplayList#STATUS_INVOKE}, or'd with {@link DisplayList#STATUS_DREW}
+     *         if anything was drawn.
      */
     public abstract int drawDisplayList(DisplayList displayList, Rect dirty, int flags);
 
diff --git a/core/java/android/view/HardwareRenderer.java b/core/java/android/view/HardwareRenderer.java
index 7e86ea3a542e..0ae6b56df6fe 100644
--- a/core/java/android/view/HardwareRenderer.java
+++ b/core/java/android/view/HardwareRenderer.java
@@ -1042,8 +1042,8 @@ public abstract class HardwareRenderer {
             return mGl != null && mCanvas != null;
         }        
         
-        void onPreDraw(Rect dirty) {
-            
+        int onPreDraw(Rect dirty) {
+            return DisplayList.STATUS_DONE;
         }
 
         void onPostDraw() {
@@ -1102,9 +1102,7 @@ public abstract class HardwareRenderer {
                         }
                     }
 
-                    onPreDraw(dirty);
-
-                    int status = DisplayList.STATUS_DONE;
+                    int status = onPreDraw(dirty);
                     int saveCount = canvas.save();
                     callbacks.onHardwarePreDraw(canvas);
 
@@ -1138,7 +1136,7 @@ public abstract class HardwareRenderer {
                                 drawDisplayListStartTime = System.nanoTime();
                             }
 
-                            status = canvas.drawDisplayList(displayList, mRedrawClip,
+                            status |= canvas.drawDisplayList(displayList, mRedrawClip,
                                     DisplayList.FLAG_CLIP_CHILDREN);
 
                             if (mProfileEnabled) {
@@ -1372,8 +1370,8 @@ public abstract class HardwareRenderer {
         }                
 
         @Override
-        void onPreDraw(Rect dirty) {
-            mGlCanvas.onPreDraw(dirty);
+        int onPreDraw(Rect dirty) {
+            return mGlCanvas.onPreDraw(dirty);
         }
 
         @Override