Implement a computeFastBounds() traversal for SkImageFilter. This allows for correct culling of pri…

src/core/SkImageFilter.cpp

 /*
  * Copyright 2012 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkImageFilter.h"
 
 #include "SkBitmap.h"
@@ skipping 93 matching lines @@
            this->onFilterImage(proxy, src, ctm, result, offset);
 }
 
 bool SkImageFilter::filterBounds(const SkIRect& src, const SkMatrix& ctm,
                                  SkIRect* dst) {
     SkASSERT(&src);
     SkASSERT(dst);
     return this->onFilterBounds(src, ctm, dst);
 }
 
+void SkImageFilter::computeFastBounds(const SkRect& src, SkRect* dst) const {
+    if (0 == fInputCount) {
+        *dst = src;
+        return;
+    }
+    if (this->getInput(0)) {
+        this->getInput(0)->computeFastBounds(src, dst);
+    } else {
+        *dst = src;
+    }
+    for (int i = 1; i < fInputCount; i++) {
+        SkImageFilter* input = this->getInput(i);
+        if (input) {
+            SkRect bounds;
+            input->computeFastBounds(src, &bounds);
+            dst->join(bounds);
+        } else {
+            dst->join(src);
+        }
+    }
+}
+
 bool SkImageFilter::onFilterImage(Proxy*, const SkBitmap&, const SkMatrix&,
                                   SkBitmap*, SkIPoint*) {
     return false;
 }
 
 bool SkImageFilter::canFilterImageGPU() const {
     return this->asNewEffect(NULL, NULL, SkMatrix::I(), SkIRect());
 }
 
 bool SkImageFilter::filterImageGPU(Proxy* proxy, const SkBitmap& src, const SkMatrix& ctm,
@@ skipping 65 matching lines @@
     return true;
 }
 
 bool SkImageFilter::asNewEffect(GrEffectRef**, GrTexture*, const SkMatrix&, const SkIRect&) const {
     return false;
 }
 
 bool SkImageFilter::asColorFilter(SkColorFilter**) const {
     return false;
 }