Enter RectangleMode when the clip region is a rectangle

ClipArea's region mode implementation store the region's boundary in
a rectangle, and if the region is that rectangle, set its region to
empty.  This is a bug, since as long as the ClipArea is in region
mode it treats its region as determinitive. When the next clipping
operation comes in, it is tested against the empty region instead of
against the valid rect.

Discovered via Skia GM testing.

Change-Id: I3bbc4e81c8d68636061f830156e017e9b5c7e587

1 files changed, 12 insertions, 7 deletions

diff --git a/libs/hwui/ClipArea.cpp b/libs/hwui/ClipArea.cpp
index 852204a48fae..eb520b48a67a 100644
--- a/libs/hwui/ClipArea.cpp
+++ b/libs/hwui/ClipArea.cpp
@@ -234,7 +234,7 @@ bool ClipArea::clipRectWithTransform(const Rect& r, const mat4* transform,
 bool ClipArea::clipRegion(const SkRegion& region, SkRegion::Op op) {
     enterRegionMode();
     mClipRegion.op(region, op);
-    setClipRectToRegionBounds();
+    onClipRegionUpdated();
     return true;
 }
 
@@ -263,6 +263,9 @@ void ClipArea::enterRectangleMode() {
 bool ClipArea::rectangleModeClipRectWithTransform(const Rect& r,
         const mat4* transform, SkRegion::Op op) {
 
+    // TODO: we should be able to handle kReplace_Op efficiently without
+    // going through RegionMode and later falling back into RectangleMode.
+
     if (op != SkRegion::kIntersect_Op) {
         enterRegionMode();
         return regionModeClipRectWithTransform(r, transform, op);
@@ -324,15 +327,16 @@ bool ClipArea::rectangleListModeClipRectWithTransform(float left, float top,
  */
 
 void ClipArea::enterRegionMode() {
-    if (mMode != kModeRegion) {
-        if (mMode == kModeRectangle) {
+    Mode oldMode = mMode;
+    mMode = kModeRegion;
+    if (oldMode != kModeRegion) {
+        if (oldMode == kModeRectangle) {
             mClipRegion.setRect(mClipRect.left, mClipRect.top,
                     mClipRect.right, mClipRect.bottom);
         } else {
             mClipRegion = mRectangleList.convertToRegion(createViewportRegion());
-            setClipRectToRegionBounds();
+            onClipRegionUpdated();
         }
-        mMode = kModeRegion;
     }
 }
 
@@ -342,7 +346,7 @@ bool ClipArea::regionModeClipRectWithTransform(const Rect& r,
     SkRegion transformedRectRegion;
     regionFromPath(transformedRect, transformedRectRegion);
     mClipRegion.op(transformedRectRegion, op);
-    setClipRectToRegionBounds();
+    onClipRegionUpdated();
     return true;
 }
 
@@ -352,12 +356,13 @@ bool ClipArea::regionModeClipRectWithTransform(float left, float top,
             transform, op);
 }
 
-void ClipArea::setClipRectToRegionBounds() {
+void ClipArea::onClipRegionUpdated() {
     if (!mClipRegion.isEmpty()) {
         mClipRect.set(mClipRegion.getBounds());
 
         if (mClipRegion.isRect()) {
             mClipRegion.setEmpty();
+            enterRectangleMode();
         }
     } else {
         mClipRect.setEmpty();