commit 24443ea3992e372e47daa50266b0f2ec38cac388
author Romain Guy <romainguy@android.com> Mon May 11 11:56:30 2009 -0700
committer Romain Guy <romainguy@android.com> Mon May 11 14:03:52 2009 -0700
tree 4aaf21a24e198686cc0715cbdac62bfeb809d698
parent c825d3ebd6ca66e65e63fdc76f032e08aa2a8e22

Fixes #1596240. Optimize invalidate/draw passes by marking opaque views and avoiding drawing them. Whenever a View requests an invalidate its parent check whether the view is opaque or not. When the view is not opaque, the framework behaves as it used to. However, when a view is opaque, the parent marks itself as being dirty because of an opaque view. Its parent then does the same, and so on. When the framework then starts drawing the views, it does not draw views marked as dirty opaque. If a view is dirty opaque and receives an invalidate request from a non-opaque view, it then clears the dirty opaque flag and behaves as before.

core/java/android/view/View.java

diff --git a/core/java/android/view/View.java b/core/java/android/view/View.java
index d042f28d..753cdf2 100644
--- a/core/java/android/view/View.java
+++ b/core/java/android/view/View.java
@@ -850,6 +850,28 @@
     public static final int HAPTIC_FEEDBACK_ENABLED = 0x10000000;
 
     /**
+     * View flag indicating whether this view was invalidated (fully or partially.)
+     *
+     * @hide
+     */
+    static final int DIRTY = 0x20000000;
+
+    /**
+     * View flag indicating whether this view was invalidated by an opaque
+     * invalidate request.
+     *
+     * @hide
+     */
+    static final int DIRTY_OPAQUE = 0x40000000;
+
+    /**
+     * Mask for {@link #DIRTY} and {@link #DIRTY_OPAQUE}.
+     *
+     * @hide
+     */
+    static final int DIRTY_MASK = 0x60000000;
+
+    /**
      * Use with {@link #focusSearch}. Move focus to the previous selectable
      * item.
      */
@@ -4522,6 +4544,23 @@
     }
 
     /**
+     * Indicates whether this View is opaque. An opaque View guarantees that it will
+     * draw all the pixels overlapping its bounds using a fully opaque color.
+     *
+     * Subclasses of View should override this method whenever possible to indicate
+     * whether an instance is opaque. Opaque Views are treated in a special way by
+     * the View hierarchy, possibly allowing it to perform optimizations during
+     * invalidate/draw passes.
+     * 
+     * @return True if this View is guaranteed to be fully opaque, false otherwise.
+     *
+     * @hide Pending API council approval
+     */
+    public boolean isOpaque() {
+        return mBGDrawable != null && mBGDrawable.getOpacity() == PixelFormat.OPAQUE;
+    }
+
+    /**
      * @return A handler associated with the thread running the View. This
      * handler can be used to pump events in the UI events queue.
      */
@@ -5687,7 +5726,7 @@
             final int restoreCount = canvas.save();
             canvas.translate(-mScrollX, -mScrollY);
 
-            mPrivateFlags |= DRAWN;
+            mPrivateFlags = (mPrivateFlags & ~DIRTY_MASK) | DRAWN; 
 
             // Fast path for layouts with no backgrounds
             if ((mPrivateFlags & SKIP_DRAW) == SKIP_DRAW) {
@@ -5875,7 +5914,10 @@
             ViewDebug.trace(this, ViewDebug.HierarchyTraceType.DRAW);
         }
 
-        mPrivateFlags |= DRAWN;                    
+        final boolean dirtyOpaque = (mPrivateFlags & DIRTY_MASK) == DIRTY_OPAQUE;
+        mPrivateFlags = (mPrivateFlags & ~DIRTY_MASK) | DRAWN;
+
+        if (dirtyOpaque) android.util.Log.d("View", "Skipping draw in " + this);
 
         /*
          * Draw traversal performs several drawing steps which must be executed
@@ -5892,22 +5934,24 @@
         // Step 1, draw the background, if needed
         int saveCount;
 
-        final Drawable background = mBGDrawable;
-        if (background != null) {
-            final int scrollX = mScrollX;
-            final int scrollY = mScrollY;
+        if (!dirtyOpaque) {
+            final Drawable background = mBGDrawable;
+            if (background != null) {
+                final int scrollX = mScrollX;
+                final int scrollY = mScrollY;
 
-            if (mBackgroundSizeChanged) {
-                background.setBounds(0, 0,  mRight - mLeft, mBottom - mTop);
-                mBackgroundSizeChanged = false;
-            }
+                if (mBackgroundSizeChanged) {
+                    background.setBounds(0, 0,  mRight - mLeft, mBottom - mTop);
+                    mBackgroundSizeChanged = false;
+                }
 
-            if ((scrollX | scrollY) == 0) {
-                background.draw(canvas);
-            } else {
-                canvas.translate(scrollX, scrollY);
-                background.draw(canvas);
-                canvas.translate(-scrollX, -scrollY);
+                if ((scrollX | scrollY) == 0) {
+                    background.draw(canvas);
+                } else {
+                    canvas.translate(scrollX, scrollY);
+                    background.draw(canvas);
+                    canvas.translate(-scrollX, -scrollY);
+                }
             }
         }
 
@@ -5917,7 +5961,7 @@
         boolean verticalEdges = (viewFlags & FADING_EDGE_VERTICAL) != 0;
         if (!verticalEdges && !horizontalEdges) {
             // Step 3, draw the content
-            onDraw(canvas);
+            if (!dirtyOpaque) onDraw(canvas);
 
             // Step 4, draw the children
             dispatchDraw(canvas);
@@ -6020,7 +6064,7 @@
         }
 
         // Step 3, draw the content
-        onDraw(canvas);
+        if (!dirtyOpaque) onDraw(canvas);
 
         // Step 4, draw the children
         dispatchDraw(canvas);