Revert of Revert of allow canvas to force conservative clips (for speed)

src/core/SkRasterClip.cpp

Index: src/core/SkRasterClip.cpp
diff --git a/src/core/SkRasterClip.cpp b/src/core/SkRasterClip.cpp
index dab91d8f4ce31434af80839208961509e5746761..f820c5a0a44154389b5cea7521eaef7b1b3aad42 100644
--- a/src/core/SkRasterClip.cpp
+++ b/src/core/SkRasterClip.cpp
@@ -6,34 +6,37 @@
  */
 
 #include "SkRasterClip.h"
-
-
-SkRasterClip::SkRasterClip() {
+#include "SkPath.h"
+
+SkRasterClip::SkRasterClip(const SkRasterClip& src) {
+    AUTO_RASTERCLIP_VALIDATE(src);
+
+    fForceConservativeRects = src.fForceConservativeRects;
+    fIsBW = src.fIsBW;
+    if (fIsBW) {
+        fBW = src.fBW;
+    } else {
+        fAA = src.fAA;
+    }
+
+    fIsEmpty = src.isEmpty();
+    fIsRect = src.isRect();
+    SkDEBUGCODE(this->validate();)
+}
+
+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(const SkRasterClip& src) {
-    AUTO_RASTERCLIP_VALIDATE(src);
-
-    fIsBW = src.fIsBW;
-    if (fIsBW) {
-        fBW = src.fBW;
-    } else {
-        fAA = src.fAA;
-    }
-
-    fIsEmpty = src.isEmpty();
-    fIsRect = src.isRect();
-    SkDEBUGCODE(this->validate();)
-}
-
-SkRasterClip::SkRasterClip(const SkIRect& bounds) : fBW(bounds) {
-    fIsBW = true;
-    fIsEmpty = this->computeIsEmpty();  // bounds might be empty, so compute
-    fIsRect = !fIsEmpty;
     SkDEBUGCODE(this->validate();)
 }
 
@@ -70,8 +73,83 @@
     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);
@@ -90,7 +168,22 @@
     // 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 @@
             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 @@
         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 @@
     return x - SkScalarFloorToScalar(x) < domain;
 }
 
-bool SkRasterClip::op(const SkRect& r, SkRegion::Op op, bool doAA) {
-    AUTO_RASTERCLIP_VALIDATE(*this);
-
+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 @@
 
 void SkRasterClip::convertToAA() {
     AUTO_RASTERCLIP_VALIDATE(*this);
-
+    
+    SkASSERT(!fForceConservativeRects);
+    
     SkASSERT(fIsBW);
     fAA.setRegion(fBW);
     fIsBW = false;