Moving updateClipConservativelyUsingBounds into SkCanvas

src/core/SkCanvas.cpp

Index: src/core/SkCanvas.cpp
===================================================================
--- src/core/SkCanvas.cpp	(revision 9298)
+++ src/core/SkCanvas.cpp	(working copy)
@@ -1279,6 +1279,74 @@
     return clipPathHelper(this, fMCRec->fRasterClip, devPath, op, doAA);
 }
 
+bool SkCanvas::updateClipConservativelyUsingBounds(const SkRect& bounds, SkRegion::Op op,

[reed1, 2013/05/29 18:54:01]

/**
 * 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.
 */

+                                                   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).
+    if (inverseFilled) {
+        switch (op) {
+            case SkRegion::kIntersect_Op:
+            case SkRegion::kDifference_Op:
+                // These ops can only shrink the current clip. So leaving
+                // the clip unchanges conservatively respects the contract.
+                return this->getClipDeviceBounds(NULL);
+            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::MakeFromIRect(deviceIBounds);
+                    this->SkCanvas::save(SkCanvas::kMatrix_SaveFlag);
+                    // set the clip in device space
+                    this->SkCanvas::setMatrix(SkMatrix::I());
+                    bool result = this->SkCanvas::clipRect(deviceBounds,
+                        SkRegion::kReplace_Op, false);
+                    this->SkCanvas::restore(); //pop the matrix, but keep the clip
+                    return result;
+                }
+            default:
+                SkASSERT(0); // unhandled op?
+        }
+    } else {
+        // Not inverse filled
+        switch (op) {
+            case SkRegion::kIntersect_Op:
+            case SkRegion::kUnion_Op:
+            case SkRegion::kReplace_Op:
+                return this->SkCanvas::clipRect(bounds, op, false);
+            case SkRegion::kDifference_Op:
+                // Difference can only shrink the current clip.
+                // Leaving clip unchanged conservatively fullfills the contract.
+                return this->getClipDeviceBounds(NULL);
+            case SkRegion::kReverseDifference_Op:
+                // To reverse, we swap in the bounds with a replace op.
+                // As with difference, leave it unchanged.
+                return this->SkCanvas::clipRect(bounds, SkRegion::kReplace_Op, false);
+            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))
+                return this->SkCanvas::clipRect(bounds, SkRegion::kUnion_Op, false);
+            default:
+                SkASSERT(0); // unhandled op?
+        }
+    }
+    return true;
+}
+
 bool SkCanvas::clipRegion(const SkRegion& rgn, SkRegion::Op op) {
     AutoValidateClip avc(this);