Allow SkCanvas to be initialized to force conservative rasterclips. This has the following effects:

1. Queries to the current clip will be conservatively large. This can mean the quickReject may return false more often.

2. The conservative clips mean less work is done.

3. Enabled by default for Gpu, Record, and NoSaveLayer canvases.

4. API is private for now.

R=robertphillips@google.com, bsalomon@google.com, mtklein@google.com, junov@google.com

Author: reed@google.com

Review URL: https://codereview.chromium.org/541593005

12 files changed, 233 insertions, 166 deletions

diff --git a/include/core/SkCanvas.h b/include/core/SkCanvas.h
index f514d18b5e..5088d7ded5 100644
--- a/include/core/SkCanvas.h
+++ b/include/core/SkCanvas.h
@@ -1265,11 +1265,6 @@ protected:
                         SkIRect* intersection,
                         const SkImageFilter* imageFilter = NULL);
 
-    // Called by child classes that override clipPath and clipRRect to only
-    // track fast conservative clip bounds, rather than exact clips.
-    void updateClipConservativelyUsingBounds(const SkRect&, SkRegion::Op,
-                                             bool inverseFilled);
-
     // notify our surface (if we have one) that we are about to draw, so it
     // can perform copy-on-write or invalidate any cached images
     void predrawNotify();
@@ -1309,13 +1304,22 @@ private:
     friend class SkDebugCanvas;     // needs experimental fAllowSimplifyClip
     friend class SkDeferredDevice;  // needs getTopDevice()
     friend class SkSurface_Raster;  // needs getDevice()
+    friend class SkRecorder;        // InitFlags
+    friend class SkNoSaveLayerCanvas;   // InitFlags
     
+    enum InitFlags {
+        kDefault_InitFlags                  = 0,
+        kConservativeRasterClip_InitFlag    = 1 << 0,
+    };
+    SkCanvas(int width, int height, InitFlags flags);
+    SkCanvas(SkBaseDevice*, InitFlags flags);
+
     // needs gettotalclip()
     friend SkCanvasState* SkCanvasStateUtils::CaptureCanvasState(SkCanvas*);
     
     SkBaseDevice* createLayerDevice(const SkImageInfo&);
 
-    SkBaseDevice* init(SkBaseDevice*);
+    SkBaseDevice* init(SkBaseDevice*, InitFlags);
 
     /**
      *  DEPRECATED
@@ -1365,6 +1369,7 @@ private:
     mutable bool   fCachedLocalClipBoundsDirty;
     bool fAllowSoftClip;
     bool fAllowSimplifyClip;
+    bool fConservativeRasterClip;
 
     const SkRect& getLocalClipBounds() const {
         if (fCachedLocalClipBoundsDirty) {
diff --git a/include/core/SkDevice.h b/include/core/SkDevice.h
index aad5bf4737..618431a2de 100644
--- a/include/core/SkDevice.h
+++ b/include/core/SkDevice.h
@@ -372,6 +372,8 @@ private:
     // TODO: move to SkBitmapDevice
     virtual void replaceBitmapBackendForRasterSurface(const SkBitmap&) {}
 
+    virtual bool forceConservativeRasterClip() const { return false; }
+
     // just called by SkCanvas when built as a layer
     void setOrigin(int x, int y) { fOrigin.set(x, y); }
     // just called by SkCanvas for saveLayer
diff --git a/include/gpu/SkGpuDevice.h b/include/gpu/SkGpuDevice.h
index 91fc2f0bb6..5545227129 100644
--- a/include/gpu/SkGpuDevice.h
+++ b/include/gpu/SkGpuDevice.h
@@ -152,6 +152,7 @@ private:
     virtual SkSurface* newSurface(const SkImageInfo&) SK_OVERRIDE;
 
     virtual SkImageFilter::Cache* getImageFilterCache() SK_OVERRIDE;
+    virtual bool forceConservativeRasterClip() const SK_OVERRIDE { return true; }
 
     // sets the render target, clip, and matrix on GrContext. Use forceIdenity to override
     // SkDraw's matrix and draw in device coords.
diff --git a/include/utils/SkNoSaveLayerCanvas.h b/include/utils/SkNoSaveLayerCanvas.h
index 686f179901..56a09622a0 100644
--- a/include/utils/SkNoSaveLayerCanvas.h
+++ b/include/utils/SkNoSaveLayerCanvas.h
@@ -16,7 +16,8 @@
 // It also simplifies the clipping calls to only use rectangles.
 class SK_API SkNoSaveLayerCanvas : public SkCanvas {
 public:
-    SkNoSaveLayerCanvas(SkBaseDevice* device) : INHERITED(device) {}
+    SkNoSaveLayerCanvas(SkBaseDevice* device) : INHERITED(device, kConservativeRasterClip_InitFlag)
+    {}
 
 protected:
     virtual SaveLayerStrategy willSaveLayer(const SkRect* bounds, const SkPaint* paint,
@@ -25,21 +26,6 @@ protected:
         return kNoLayer_SaveLayerStrategy;
     }
 
-    // disable aa for speed
-    virtual void onClipRect(const SkRect& rect, SkRegion::Op op, ClipEdgeStyle) SK_OVERRIDE {
-        this->INHERITED::onClipRect(rect, op, kHard_ClipEdgeStyle);
-    }
-
-    // for speed, just respect the bounds, and disable AA. May give us a few
-    // false positives and negatives.
-    virtual void onClipPath(const SkPath& path, SkRegion::Op op, ClipEdgeStyle) SK_OVERRIDE {
-        this->updateClipConservativelyUsingBounds(path.getBounds(), op,
-                                                  path.isInverseFillType());
-    }
-    virtual void onClipRRect(const SkRRect& rrect, SkRegion::Op op, ClipEdgeStyle) SK_OVERRIDE {
-        this->updateClipConservativelyUsingBounds(rrect.getBounds(), op, false);
-    }
-
 private:
     typedef SkCanvas INHERITED;
 };
diff --git a/src/core/SkCanvas.cpp b/src/core/SkCanvas.cpp
index 99786151ab..62d60da178 100644
--- a/src/core/SkCanvas.cpp
+++ b/src/core/SkCanvas.cpp
@@ -81,9 +81,12 @@ struct DeviceCM {
     const SkMatrix*     fMatrix;
     SkPaint*            fPaint; // may be null (in the future)
 
-    DeviceCM(SkBaseDevice* device, int x, int y, const SkPaint* paint, SkCanvas* canvas)
-            : fNext(NULL) {
-        if (device) {
+    DeviceCM(SkBaseDevice* device, int x, int y, const SkPaint* paint, SkCanvas* canvas,
+             bool conservativeRasterClip)
+        : fNext(NULL)
+        , fClip(conservativeRasterClip)
+    {
+        if (NULL != device) {
             device->ref();
             device->onAttachToCanvas(canvas);
         }
@@ -151,11 +154,10 @@ private:
 */
 class SkCanvas::MCRec {
 public:
-    SkMatrix        fMatrix;
     SkRasterClip    fRasterClip;
+    SkMatrix        fMatrix;
     SkDrawFilter*   fFilter;    // the current filter (or null)
-
-    DeviceCM*   fLayer;
+    DeviceCM*       fLayer;
     /*  If there are any layers in the stack, this points to the top-most
         one that is at or below this level in the stack (so we know what
         bitmap/device to draw into from this level. This value is NOT
@@ -164,22 +166,21 @@ public:
     */
     DeviceCM*   fTopLayer;
 
-    MCRec(const MCRec* prev) {
-        if (prev) {
-            fMatrix = prev->fMatrix;
-            fRasterClip = prev->fRasterClip;
-
-            fFilter = prev->fFilter;
-            SkSafeRef(fFilter);
-
-            fTopLayer = prev->fTopLayer;
-        } else {   // no prev
-            fMatrix.reset();
-            fFilter     = NULL;
-            fTopLayer   = NULL;
-        }
+    MCRec(bool conservativeRasterClip) : fRasterClip(conservativeRasterClip) {
+        fMatrix.reset();
+        fFilter     = NULL;
+        fLayer      = NULL;
+        fTopLayer   = NULL;
+        
+        // don't bother initializing fNext
+        inc_rec();
+    }
+    MCRec(const MCRec& prev) : fRasterClip(prev.fRasterClip) {
+        fMatrix = prev.fMatrix;
+        fFilter = SkSafeRef(prev.fFilter);
         fLayer = NULL;
-
+        fTopLayer = prev.fTopLayer;
+        
         // don't bother initializing fNext
         inc_rec();
     }
@@ -381,7 +382,8 @@ bool AutoDrawLooper::doNext(SkDrawFilter::Type drawType) {
 
 ////////////////////////////////////////////////////////////////////////////
 
-SkBaseDevice* SkCanvas::init(SkBaseDevice* device) {
+SkBaseDevice* SkCanvas::init(SkBaseDevice* device, InitFlags flags) {
+    fConservativeRasterClip = SkToBool(flags & kConservativeRasterClip_InitFlag);
     fCachedLocalClipBounds.setEmpty();
     fCachedLocalClipBoundsDirty = true;
     fAllowSoftClip = true;
@@ -391,10 +393,14 @@ SkBaseDevice* SkCanvas::init(SkBaseDevice* device) {
     fCullCount = 0;
     fMetaData = NULL;
 
+    if (device && device->forceConservativeRasterClip()) {
+        fConservativeRasterClip = true;
+    }
+    
     fMCRec = (MCRec*)fMCStack.push_back();
-    new (fMCRec) MCRec(NULL);
+    new (fMCRec) MCRec(fConservativeRasterClip);
 
-    fMCRec->fLayer = SkNEW_ARGS(DeviceCM, (NULL, 0, 0, NULL, NULL));
+    fMCRec->fLayer = SkNEW_ARGS(DeviceCM, (NULL, 0, 0, NULL, NULL, fConservativeRasterClip));
     fMCRec->fTopLayer = fMCRec->fLayer;
 
     fSurfaceBase = NULL;
@@ -412,25 +418,54 @@ SkCanvas::SkCanvas()
 {
     inc_canvas();
 
-    this->init(NULL);
+    this->init(NULL, kDefault_InitFlags);
 }
 
+static SkBitmap make_nopixels(int width, int height) {
+    SkBitmap bitmap;
+    bitmap.setInfo(SkImageInfo::MakeUnknown(width, height));
+    return bitmap;
+}
+
+class SkNoPixelsBitmapDevice : public SkBitmapDevice {
+public:
+    SkNoPixelsBitmapDevice(int width, int height) : INHERITED(make_nopixels(width, height)) {}
+
+private:
+    
+    typedef SkBitmapDevice INHERITED;
+};
+
 SkCanvas::SkCanvas(int width, int height)
     : fMCStack(sizeof(MCRec), fMCRecStorage, sizeof(fMCRecStorage))
 {
     inc_canvas();
+    
+    this->init(SkNEW_ARGS(SkNoPixelsBitmapDevice, (width, height)), kDefault_InitFlags)->unref();
+}
 
-    SkBitmap bitmap;
-    bitmap.setInfo(SkImageInfo::MakeUnknown(width, height));
-    this->init(SkNEW_ARGS(SkBitmapDevice, (bitmap)))->unref();
+SkCanvas::SkCanvas(int width, int height, InitFlags flags)
+    : fMCStack(sizeof(MCRec), fMCRecStorage, sizeof(fMCRecStorage))
+{
+    inc_canvas();
+    
+    this->init(SkNEW_ARGS(SkNoPixelsBitmapDevice, (width, height)), flags)->unref();
 }
 
-SkCanvas::SkCanvas(SkBaseDevice* device)
+SkCanvas::SkCanvas(SkBaseDevice* device, InitFlags flags)
     : fMCStack(sizeof(MCRec), fMCRecStorage, sizeof(fMCRecStorage))
 {
     inc_canvas();
+    
+    this->init(device, flags);
+}
 
-    this->init(device);
+SkCanvas::SkCanvas(SkBaseDevice* device)
+    : fMCStack(sizeof(MCRec), fMCRecStorage, sizeof(fMCRecStorage))
+{
+    inc_canvas();
+    
+    this->init(device, kDefault_InitFlags);
 }
 
 SkCanvas::SkCanvas(const SkBitmap& bitmap)
@@ -438,7 +473,7 @@ SkCanvas::SkCanvas(const SkBitmap& bitmap)
 {
     inc_canvas();
 
-    this->init(SkNEW_ARGS(SkBitmapDevice, (bitmap)))->unref();
+    this->init(SkNEW_ARGS(SkBitmapDevice, (bitmap)), kDefault_InitFlags)->unref();
 }
 
 SkCanvas::~SkCanvas() {
@@ -734,7 +769,7 @@ int SkCanvas::internalSave() {
     int saveCount = this->getSaveCount(); // record this before the actual save
 
     MCRec* newTop = (MCRec*)fMCStack.push_back();
-    new (newTop) MCRec(fMCRec);    // balanced in restore()
+    new (newTop) MCRec(*fMCRec);    // balanced in restore()
     fMCRec = newTop;
 
     fClipStack.save();
@@ -866,7 +901,8 @@ int SkCanvas::internalSaveLayer(const SkRect* bounds, const SkPaint* paint, Save
     }
 
     device->setOrigin(ir.fLeft, ir.fTop);
-    DeviceCM* layer = SkNEW_ARGS(DeviceCM, (device, ir.fLeft, ir.fTop, paint, this));
+    DeviceCM* layer = SkNEW_ARGS(DeviceCM,
+                                 (device, ir.fLeft, ir.fTop, paint, this, fConservativeRasterClip));
     device->unref();
 
     layer->fNext = fMCRec->fTopLayer;
@@ -1286,7 +1322,7 @@ void SkCanvas::onClipRect(const SkRect& rect, SkRegion::Op op, ClipEdgeStyle edg
 
         fMCRec->fMatrix.mapRect(&r, rect);
         fClipStack.clipDevRect(r, op, kSoft_ClipEdgeStyle == edgeStyle);
-        fMCRec->fRasterClip.op(r, op, kSoft_ClipEdgeStyle == edgeStyle);
+        fMCRec->fRasterClip.op(r, this->getBaseLayerSize(), op, kSoft_ClipEdgeStyle == edgeStyle);
     } else {
         // since we're rotated or some such thing, we convert the rect to a path
         // and clip against that, since it can handle any matrix. However, to
@@ -1421,82 +1457,6 @@ void SkCanvas::onClipPath(const SkPath& path, SkRegion::Op op, ClipEdgeStyle edg
     rasterclip_path(&fMCRec->fRasterClip, this, devPath, op, edgeStyle);
 }
 
-void SkCanvas::updateClipConservativelyUsingBounds(const SkRect& bounds, SkRegion::Op op,
-                                                   bool inverseFilled) {
-    // This is for updating the clip conservatively using only bounds
-    // information.
-    // Contract:
-    //    The current clip must contain the true clip. The true
-    //    clip is the clip that would have normally been computed
-    //    by calls to clipPath and clipRRect
-    // Objective:
-    //    Keep the current clip as small as possible without
-    //    breaking the contract, using only clip bounding rectangles
-    //    (for performance).
-
-    // N.B.: This *never* calls back through a virtual on canvas, so subclasses
-    // don't have to worry about getting caught in a loop. Thus anywhere
-    // we call a virtual method, we explicitly prefix it with
-    // SkCanvas:: to be sure to call the base-class.
-
-    if (inverseFilled) {
-        switch (op) {
-            case SkRegion::kIntersect_Op:
-            case SkRegion::kDifference_Op:
-                // These ops can only shrink the current clip. So leaving
-                // the clip unchanged conservatively respects the contract.
-                break;
-            case SkRegion::kUnion_Op:
-            case SkRegion::kReplace_Op:
-            case SkRegion::kReverseDifference_Op:
-            case SkRegion::kXOR_Op: {
-                    // These ops can grow the current clip up to the extents of
-                    // the input clip, which is inverse filled, so we just set
-                    // the current clip to the device bounds.
-                    SkRect deviceBounds;
-                    SkIRect deviceIBounds;
-                    this->getDevice()->getGlobalBounds(&deviceIBounds);
-                    deviceBounds = SkRect::Make(deviceIBounds);
-
-                    // set the clip in device space
-                    SkMatrix savedMatrix = this->getTotalMatrix();
-                    this->SkCanvas::setMatrix(SkMatrix::I());
-                    this->SkCanvas::onClipRect(deviceBounds, SkRegion::kReplace_Op,
-                                               kHard_ClipEdgeStyle);
-                    this->setMatrix(savedMatrix);
-                    break;
-            }
-            default:
-                SkASSERT(0); // unhandled op?
-        }
-    } else {
-        // Not inverse filled
-        switch (op) {
-            case SkRegion::kIntersect_Op:
-            case SkRegion::kUnion_Op:
-            case SkRegion::kReplace_Op:
-                this->SkCanvas::onClipRect(bounds, op, kHard_ClipEdgeStyle);
-                break;
-            case SkRegion::kDifference_Op:
-                // Difference can only shrink the current clip.
-                // Leaving clip unchanged conservatively fullfills the contract.
-                break;
-            case SkRegion::kReverseDifference_Op:
-                // To reverse, we swap in the bounds with a replace op.
-                // As with difference, leave it unchanged.
-                this->SkCanvas::onClipRect(bounds, SkRegion::kReplace_Op, kHard_ClipEdgeStyle);
-                break;
-            case SkRegion::kXOR_Op:
-                // Be conservative, based on (A XOR B) always included in (A union B),
-                // which is always included in (bounds(A) union bounds(B))
-                this->SkCanvas::onClipRect(bounds, SkRegion::kUnion_Op, kHard_ClipEdgeStyle);
-                break;
-            default:
-                SkASSERT(0); // unhandled op?
-        }
-    }
-}
-
 void SkCanvas::clipRegion(const SkRegion& rgn, SkRegion::Op op) {
     this->onClipRegion(rgn, op);
 }
@@ -1525,7 +1485,7 @@ void SkCanvas::validateClip() const {
 
     SkIRect ir;
     ir.set(0, 0, device->width(), device->height());
-    SkRasterClip tmpClip(ir);
+    SkRasterClip tmpClip(ir, fConservativeRasterClip);
 
     SkClipStack::B2TIter                iter(fClipStack);
     const SkClipStack::Element* element;
@@ -1569,7 +1529,6 @@ bool SkCanvas::isClipRect() const {
 }
 
 bool SkCanvas::quickReject(const SkRect& rect) const {
-
     if (!rect.isFinite())
         return true;
 
diff --git a/src/core/SkDeviceLooper.cpp b/src/core/SkDeviceLooper.cpp
index 9346465dfc..a8350cc027 100644
--- a/src/core/SkDeviceLooper.cpp
+++ b/src/core/SkDeviceLooper.cpp
@@ -10,9 +10,10 @@
 SkDeviceLooper::SkDeviceLooper(const SkBitmap& base,
                                const SkRasterClip& rc,
                                const SkIRect& bounds, bool aa)
-: fBaseBitmap(base)
-, fBaseRC(rc)
-, fDelta(aa ? kAA_Delta : kBW_Delta)
+    : fBaseBitmap(base)
+    , fBaseRC(rc)
+    , fSubsetRC(rc.isForceConservativeRects())
+    , fDelta(aa ? kAA_Delta : kBW_Delta)
 {
     // sentinels that next() has not yet been called, and so our mapper functions
     // should not be called either.
diff --git a/src/core/SkPictureRecord.cpp b/src/core/SkPictureRecord.cpp
index b17169183a..cae8420e95 100644
--- a/src/core/SkPictureRecord.cpp
+++ b/src/core/SkPictureRecord.cpp
@@ -788,7 +788,7 @@ size_t SkPictureRecord::recordClipRect(const SkRect& rect, SkRegion::Op op, bool
 
 void SkPictureRecord::onClipRRect(const SkRRect& rrect, SkRegion::Op op, ClipEdgeStyle edgeStyle) {
     this->recordClipRRect(rrect, op, kSoft_ClipEdgeStyle == edgeStyle);
-    this->updateClipConservativelyUsingBounds(rrect.getBounds(), op, false);
+    this->INHERITED::onClipRRect(rrect, op, edgeStyle);
 }
 
 size_t SkPictureRecord::recordClipRRect(const SkRRect& rrect, SkRegion::Op op, bool doAA) {
@@ -810,9 +810,7 @@ size_t SkPictureRecord::recordClipRRect(const SkRRect& rrect, SkRegion::Op op, b
 void SkPictureRecord::onClipPath(const SkPath& path, SkRegion::Op op, ClipEdgeStyle edgeStyle) {
     int pathID = this->addPathToHeap(path);
     this->recordClipPath(pathID, op, kSoft_ClipEdgeStyle == edgeStyle);
-
-    this->updateClipConservativelyUsingBounds(path.getBounds(), op,
-                                              path.isInverseFillType());
+    this->INHERITED::onClipPath(path, op, edgeStyle);
 }
 
 size_t SkPictureRecord::recordClipPath(int pathID, SkRegion::Op op, bool doAA) {
diff --git a/src/core/SkRasterClip.cpp b/src/core/SkRasterClip.cpp
index dab91d8f4c..f820c5a0a4 100644
--- a/src/core/SkRasterClip.cpp
+++ b/src/core/SkRasterClip.cpp
@@ -6,18 +6,12 @@
  */
 
 #include "SkRasterClip.h"
-
-
-SkRasterClip::SkRasterClip() {
-    fIsBW = true;
-    fIsEmpty = true;
-    fIsRect = false;
-    SkDEBUGCODE(this->validate();)
-}
+#include "SkPath.h"
 
 SkRasterClip::SkRasterClip(const SkRasterClip& src) {
     AUTO_RASTERCLIP_VALIDATE(src);
 
+    fForceConservativeRects = src.fForceConservativeRects;
     fIsBW = src.fIsBW;
     if (fIsBW) {
         fBW = src.fBW;
@@ -30,13 +24,22 @@ SkRasterClip::SkRasterClip(const SkRasterClip& src) {
     SkDEBUGCODE(this->validate();)
 }
 
-SkRasterClip::SkRasterClip(const SkIRect& bounds) : fBW(bounds) {
+SkRasterClip::SkRasterClip(const SkIRect& bounds, bool forceConservativeRects) : fBW(bounds) {
+    fForceConservativeRects = forceConservativeRects;
     fIsBW = true;
     fIsEmpty = this->computeIsEmpty();  // bounds might be empty, so compute
     fIsRect = !fIsEmpty;
     SkDEBUGCODE(this->validate();)
 }
 
+SkRasterClip::SkRasterClip(bool forceConservativeRects) {
+    fForceConservativeRects = forceConservativeRects;
+    fIsBW = true;
+    fIsEmpty = true;
+    fIsRect = false;
+    SkDEBUGCODE(this->validate();)
+}
+
 SkRasterClip::~SkRasterClip() {
     SkDEBUGCODE(this->validate();)
 }
@@ -70,9 +73,84 @@ bool SkRasterClip::setRect(const SkIRect& rect) {
     return fIsRect;
 }
 
+/////////////////////////////////////////////////////////////////////////////////////
+
+bool SkRasterClip::setConservativeRect(const SkRect& r, const SkIRect& clipR, bool isInverse) {
+    SkIRect ir;
+    r.roundOut(&ir);
+
+    SkRegion::Op op;
+    if (isInverse) {
+        op = SkRegion::kDifference_Op;
+    } else {
+        op = SkRegion::kIntersect_Op;
+    }
+    fBW.setRect(clipR);
+    fBW.op(ir, op);
+    return this->updateCacheAndReturnNonEmpty();
+}
+
+/////////////////////////////////////////////////////////////////////////////////////
+
+enum MutateResult {
+    kDoNothing_MutateResult,
+    kReplaceClippedAgainstGlobalBounds_MutateResult,
+    kContinue_MutateResult,
+};
+
+static MutateResult mutate_conservative_op(SkRegion::Op* op, bool inverseFilled) {
+    if (inverseFilled) {
+        switch (*op) {
+            case SkRegion::kIntersect_Op:
+            case SkRegion::kDifference_Op:
+                // These ops can only shrink the current clip. So leaving
+                // the clip unchanged conservatively respects the contract.
+                return kDoNothing_MutateResult;
+            case SkRegion::kUnion_Op:
+            case SkRegion::kReplace_Op:
+            case SkRegion::kReverseDifference_Op:
+            case SkRegion::kXOR_Op: {
+                // These ops can grow the current clip up to the extents of
+                // the input clip, which is inverse filled, so we just set
+                // the current clip to the device bounds.
+                *op = SkRegion::kReplace_Op;
+                return kReplaceClippedAgainstGlobalBounds_MutateResult;
+            }
+        }
+    } else {
+        // Not inverse filled
+        switch (*op) {
+            case SkRegion::kIntersect_Op:
+            case SkRegion::kUnion_Op:
+            case SkRegion::kReplace_Op:
+                return kContinue_MutateResult;
+            case SkRegion::kDifference_Op:
+                // Difference can only shrink the current clip.
+                // Leaving clip unchanged conservatively fullfills the contract.
+                return kDoNothing_MutateResult;
+            case SkRegion::kReverseDifference_Op:
+                // To reverse, we swap in the bounds with a replace op.
+                // As with difference, leave it unchanged.
+                *op = SkRegion::kReplace_Op;
+                return kContinue_MutateResult;
+            case SkRegion::kXOR_Op:
+                // Be conservative, based on (A XOR B) always included in (A union B),
+                // which is always included in (bounds(A) union bounds(B))
+                *op = SkRegion::kUnion_Op;
+                return kContinue_MutateResult;
+        }
+    }
+    SkFAIL("should not get here");
+    return kDoNothing_MutateResult;
+}
+
 bool SkRasterClip::setPath(const SkPath& path, const SkRegion& clip, bool doAA) {
     AUTO_RASTERCLIP_VALIDATE(*this);
 
+    if (fForceConservativeRects) {
+        return this->setConservativeRect(path.getBounds(), clip.getBounds(), path.isInverseFillType());
+    }
+
     if (this->isBW() && !doAA) {
         (void)fBW.setPath(path, clip);
     } else {
@@ -90,7 +168,22 @@ bool SkRasterClip::op(const SkPath& path, const SkISize& size, SkRegion::Op op,
     // base is used to limit the size (and therefore memory allocation) of the
     // region that results from scan converting devPath.
     SkRegion base;
-    
+
+    if (fForceConservativeRects) {
+        SkIRect ir;
+        switch (mutate_conservative_op(&op, path.isInverseFillType())) {
+            case kDoNothing_MutateResult:
+                return !this->isEmpty();
+            case kReplaceClippedAgainstGlobalBounds_MutateResult:
+                ir = SkIRect::MakeSize(size);
+                break;
+            case kContinue_MutateResult:
+                path.getBounds().roundOut(&ir);
+                break;
+        }
+        return this->op(ir, op);
+    }
+
     if (SkRegion::kIntersect_Op == op) {
         // since we are intersect, we can do better (tighter) with currRgn's
         // bounds, than just using the device. However, if currRgn is complex,
@@ -102,7 +195,7 @@ bool SkRasterClip::op(const SkPath& path, const SkISize& size, SkRegion::Op op,
             return this->setPath(path, this->bwRgn(), doAA);
         } else {
             base.setRect(this->getBounds());
-            SkRasterClip clip;
+            SkRasterClip clip(fForceConservativeRects);
             clip.setPath(path, base, doAA);
             return this->op(clip, op);
         }
@@ -112,7 +205,7 @@ bool SkRasterClip::op(const SkPath& path, const SkISize& size, SkRegion::Op op,
         if (SkRegion::kReplace_Op == op) {
             return this->setPath(path, base, doAA);
         } else {
-            SkRasterClip clip;
+            SkRasterClip clip(fForceConservativeRects);
             clip.setPath(path, base, doAA);
             return this->op(clip, op);
         }
@@ -182,9 +275,24 @@ static bool nearly_integral(SkScalar x) {
     return x - SkScalarFloorToScalar(x) < domain;
 }
 
-bool SkRasterClip::op(const SkRect& r, SkRegion::Op op, bool doAA) {
+bool SkRasterClip::op(const SkRect& r, const SkISize& size, SkRegion::Op op, bool doAA) {
     AUTO_RASTERCLIP_VALIDATE(*this);
 
+    if (fForceConservativeRects) {
+        SkIRect ir;
+        switch (mutate_conservative_op(&op, false)) {
+            case kDoNothing_MutateResult:
+                return !this->isEmpty();
+            case kReplaceClippedAgainstGlobalBounds_MutateResult:
+                ir = SkIRect::MakeSize(size);
+                break;
+            case kContinue_MutateResult:
+                r.roundOut(&ir);
+                break;
+        }
+        return this->op(ir, op);
+    }
+    
     if (fIsBW && doAA) {
         // check that the rect really needs aa, or is it close enought to
         // integer boundaries that we can just treat it as a BW rect?
@@ -251,7 +359,9 @@ const SkRegion& SkRasterClip::forceGetBW() {
 
 void SkRasterClip::convertToAA() {
     AUTO_RASTERCLIP_VALIDATE(*this);
-
+    
+    SkASSERT(!fForceConservativeRects);
+    
     SkASSERT(fIsBW);
     fAA.setRegion(fBW);
     fIsBW = false;
diff --git a/src/core/SkRasterClip.h b/src/core/SkRasterClip.h
index ec38990a0c..8a0681805c 100644
--- a/src/core/SkRasterClip.h
+++ b/src/core/SkRasterClip.h
@@ -13,11 +13,13 @@
 
 class SkRasterClip {
 public:
-    SkRasterClip();
-    SkRasterClip(const SkIRect&);
+    SkRasterClip(bool forceConservativeRects = false);
+    SkRasterClip(const SkIRect&, bool forceConservativeRects = false);
     SkRasterClip(const SkRasterClip&);
     ~SkRasterClip();
 
+    bool isForceConservativeRects() const { return fForceConservativeRects; }
+
     bool isBW() const { return fIsBW; }
     bool isAA() const { return !fIsBW; }
     const SkRegion& bwRgn() const { SkASSERT(fIsBW); return fBW; }
@@ -41,7 +43,7 @@ public:
 
     bool op(const SkIRect&, SkRegion::Op);
     bool op(const SkRegion&, SkRegion::Op);
-    bool op(const SkRect&, SkRegion::Op, bool doAA);
+    bool op(const SkRect&, const SkISize&, SkRegion::Op, bool doAA);
     bool op(const SkPath&, const SkISize&, SkRegion::Op, bool doAA);
     
     void translate(int dx, int dy, SkRasterClip* dst) const;
@@ -75,6 +77,7 @@ public:
 private:
     SkRegion    fBW;
     SkAAClip    fAA;
+    bool        fForceConservativeRects;
     bool        fIsBW;
     // these 2 are caches based on querying the right obj based on fIsBW
     bool        fIsEmpty;
@@ -107,6 +110,7 @@ private:
     bool setPath(const SkPath& path, const SkRegion& clip, bool doAA);
     bool setPath(const SkPath& path, const SkIRect& clip, bool doAA);
     bool op(const SkRasterClip&, SkRegion::Op);
+    bool setConservativeRect(const SkRect& r, const SkIRect& clipR, bool isInverse);
 };
 
 class SkAutoRasterClipValidate : SkNoncopyable {
diff --git a/src/core/SkRecorder.cpp b/src/core/SkRecorder.cpp
index 86578a53b8..f6c16d1c30 100644
--- a/src/core/SkRecorder.cpp
+++ b/src/core/SkRecorder.cpp
@@ -11,7 +11,7 @@
 
 // SkCanvas will fail in mysterious ways if it doesn't know the real width and height.
 SkRecorder::SkRecorder(SkRecord* record, int width, int height)
-    : SkCanvas(width, height)
+    : SkCanvas(width, height, SkCanvas::kConservativeRasterClip_InitFlag)
     , fRecord(record)
     , fSaveLayerCount(0) {}
 
@@ -280,12 +280,12 @@ void SkRecorder::onClipRect(const SkRect& rect, SkRegion::Op op, ClipEdgeStyle e
 }
 
 void SkRecorder::onClipRRect(const SkRRect& rrect, SkRegion::Op op, ClipEdgeStyle edgeStyle) {
-    INHERITED(updateClipConservativelyUsingBounds, rrect.getBounds(), op, false);
+    INHERITED(onClipRRect, rrect, op, edgeStyle);
     APPEND(ClipRRect, this->devBounds(), rrect, op, edgeStyle == kSoft_ClipEdgeStyle);
 }
 
 void SkRecorder::onClipPath(const SkPath& path, SkRegion::Op op, ClipEdgeStyle edgeStyle) {
-    INHERITED(updateClipConservativelyUsingBounds, path.getBounds(), op, path.isInverseFillType());
+    INHERITED(onClipPath, path, op, edgeStyle);
     APPEND(ClipPath, this->devBounds(), delay_copy(path), op, edgeStyle == kSoft_ClipEdgeStyle);
 }
 
diff --git a/tests/AAClipTest.cpp b/tests/AAClipTest.cpp
index 776cd5267a..64e378455a 100644
--- a/tests/AAClipTest.cpp
+++ b/tests/AAClipTest.cpp
@@ -371,6 +371,7 @@ static bool operator==(const SkRasterClip& a, const SkRasterClip& b) {
 
 static void did_dx_affect(skiatest::Reporter* reporter, const SkScalar dx[],
                           size_t count, bool changed) {
+    const SkISize baseSize = SkISize::Make(10, 10);
     SkIRect ir = { 0, 0, 10, 10 };
 
     for (size_t i = 0; i < count; ++i) {
@@ -381,11 +382,11 @@ static void did_dx_affect(skiatest::Reporter* reporter, const SkScalar dx[],
         SkRasterClip rc1(ir);
         SkRasterClip rc2(ir);
 
-        rc0.op(r, SkRegion::kIntersect_Op, false);
+        rc0.op(r, baseSize, SkRegion::kIntersect_Op, false);
         r.offset(dx[i], 0);
-        rc1.op(r, SkRegion::kIntersect_Op, true);
+        rc1.op(r, baseSize, SkRegion::kIntersect_Op, true);
         r.offset(-2*dx[i], 0);
-        rc2.op(r, SkRegion::kIntersect_Op, true);
+        rc2.op(r, baseSize, SkRegion::kIntersect_Op, true);
 
         REPORTER_ASSERT(reporter, changed != (rc0 == rc1));
         REPORTER_ASSERT(reporter, changed != (rc0 == rc2));
diff --git a/tests/PictureTest.cpp b/tests/PictureTest.cpp
index 05aec092c3..3bc91d78a7 100644
--- a/tests/PictureTest.cpp
+++ b/tests/PictureTest.cpp
@@ -1570,8 +1570,8 @@ static void test_clip_bound_opt(skiatest::Reporter* reporter) {
     path2.addOval(rect3);
     SkIRect clipBounds;
     SkPictureRecorder recorder;
-    // Minimalist test set for 100% code coverage of
-    // SkPictureRecord::updateClipConservativelyUsingBounds
+
+    // Testing conservative-raster-clip that is enabled by PictureRecord
     {
         SkCanvas* canvas = recorder.beginRecording(10, 10);
         canvas->clipPath(invPath, SkRegion::kIntersect_Op);