Implement clipRect with a transform, clipRegion & clipPath

Bug #7146141

When non-rectangular clipping occurs in a layer the render buffer
used as the stencil buffer is not cached. If this happens on a
View's hardware layer the render buffer will live for as long
as the layer is bound to the view. When a stencil buffer is
required because of a call to Canvas.saveLayer() it will be allocated
on every frame. A future change will address this problem.

If "show GPU overdraw" is enabled, non-rectangular clips are not
supported anymore and we fall back to rectangular clips instead.
This is a limitation imposed by OpenGL ES that cannot be worked
around at this time.

This change also improves the Matrix4 implementation to easily
detect when a rect remains a rect after transform.

Change-Id: I0e69fb901792d38bc0c4ca1bf9fdb02d7db415b9

1 files changed, 16 insertions, 28 deletions

diff --git a/libs/hwui/Snapshot.cpp b/libs/hwui/Snapshot.cpp
index d947299114c1..22c7dde602e0 100644
--- a/libs/hwui/Snapshot.cpp
+++ b/libs/hwui/Snapshot.cpp
@@ -31,7 +31,7 @@ Snapshot::Snapshot(): flags(0), previous(NULL), layer(NULL), fbo(0),
     transform = &mTransformRoot;
     clipRect = &mClipRectRoot;
     region = NULL;
-    clipRegion = NULL;
+    clipRegion = &mClipRegionRoot;
 }
 
 /**
@@ -39,12 +39,10 @@ Snapshot::Snapshot(): flags(0), previous(NULL), layer(NULL), fbo(0),
  * the previous snapshot.
  */
 Snapshot::Snapshot(const sp<Snapshot>& s, int saveFlags):
-        flags(0), previous(s), layer(NULL), fbo(s->fbo),
+        flags(0), previous(s), layer(s->layer), fbo(s->fbo),
         invisible(s->invisible), empty(false),
         viewport(s->viewport), height(s->height), alpha(s->alpha) {
 
-    clipRegion = NULL;
-
     if (saveFlags & SkCanvas::kMatrix_SaveFlag) {
         mTransformRoot.load(*s->transform);
         transform = &mTransformRoot;
@@ -55,17 +53,13 @@ Snapshot::Snapshot(const sp<Snapshot>& s, int saveFlags):
     if (saveFlags & SkCanvas::kClip_SaveFlag) {
         mClipRectRoot.set(*s->clipRect);
         clipRect = &mClipRectRoot;
-#if STENCIL_BUFFER_SIZE
-        if (s->clipRegion) {
+        if (!s->clipRegion->isEmpty()) {
             mClipRegionRoot.op(*s->clipRegion, SkRegion::kUnion_Op);
-            clipRegion = &mClipRegionRoot;
         }
-#endif
+        clipRegion = &mClipRegionRoot;
     } else {
         clipRect = s->clipRect;
-#if STENCIL_BUFFER_SIZE
         clipRegion = s->clipRegion;
-#endif
     }
 
     if (s->flags & Snapshot::kFlagFboTarget) {
@@ -81,41 +75,38 @@ Snapshot::Snapshot(const sp<Snapshot>& s, int saveFlags):
 ///////////////////////////////////////////////////////////////////////////////
 
 void Snapshot::ensureClipRegion() {
-#if STENCIL_BUFFER_SIZE
-    if (!clipRegion) {
-        clipRegion = &mClipRegionRoot;
+    if (clipRegion->isEmpty()) {
         clipRegion->setRect(clipRect->left, clipRect->top, clipRect->right, clipRect->bottom);
     }
-#endif
 }
 
 void Snapshot::copyClipRectFromRegion() {
-#if STENCIL_BUFFER_SIZE
     if (!clipRegion->isEmpty()) {
         const SkIRect& bounds = clipRegion->getBounds();
         clipRect->set(bounds.fLeft, bounds.fTop, bounds.fRight, bounds.fBottom);
 
         if (clipRegion->isRect()) {
             clipRegion->setEmpty();
-            clipRegion = NULL;
         }
     } else {
         clipRect->setEmpty();
-        clipRegion = NULL;
     }
-#endif
 }
 
 bool Snapshot::clipRegionOp(float left, float top, float right, float bottom, SkRegion::Op op) {
-#if STENCIL_BUFFER_SIZE
     SkIRect tmp;
     tmp.set(left, top, right, bottom);
     clipRegion->op(tmp, op);
     copyClipRectFromRegion();
     return true;
-#else
-    return false;
-#endif
+}
+
+bool Snapshot::clipRegionTransformed(const SkRegion& region, SkRegion::Op op) {
+    ensureClipRegion();
+    clipRegion->op(region, op);
+    copyClipRectFromRegion();
+    flags |= Snapshot::kFlagClipSet;
+    return true;
 }
 
 bool Snapshot::clip(float left, float top, float right, float bottom, SkRegion::Op op) {
@@ -129,7 +120,7 @@ bool Snapshot::clipTransformed(const Rect& r, SkRegion::Op op) {
 
     switch (op) {
         case SkRegion::kIntersect_Op: {
-            if (CC_UNLIKELY(clipRegion)) {
+            if (CC_UNLIKELY(!clipRegion->isEmpty())) {
                 ensureClipRegion();
                 clipped = clipRegionOp(r.left, r.top, r.right, r.bottom, SkRegion::kIntersect_Op);
             } else {
@@ -142,7 +133,7 @@ bool Snapshot::clipTransformed(const Rect& r, SkRegion::Op op) {
             break;
         }
         case SkRegion::kUnion_Op: {
-            if (CC_UNLIKELY(clipRegion)) {
+            if (CC_UNLIKELY(!clipRegion->isEmpty())) {
                 ensureClipRegion();
                 clipped = clipRegionOp(r.left, r.top, r.right, r.bottom, SkRegion::kUnion_Op);
             } else {
@@ -171,12 +162,9 @@ bool Snapshot::clipTransformed(const Rect& r, SkRegion::Op op) {
 
 void Snapshot::setClip(float left, float top, float right, float bottom) {
     clipRect->set(left, top, right, bottom);
-#if STENCIL_BUFFER_SIZE
-    if (clipRegion) {
+    if (!clipRegion->isEmpty()) {
         clipRegion->setEmpty();
-        clipRegion = NULL;
     }
-#endif
     flags |= Snapshot::kFlagClipSet;
 }