Fix recursive computation of filter bounds for drop shadow,

morphology, blur.

Because we're computing "backwards" from a clip rect of destination
pixels to be filled to the required source pixels, we should use tail
recursion rather than head recursion in onFilterBounds().

This actually only makes a difference for drop-shadow, where
the computation is non-commutative. Blur and morphology commute, but I
moved them to tail recursion anyway for clarity (so all onFilterBounds
use tail recursion).

BUG=skia:
R=bsalomon@google.com

Author: senorblanco@chromium.org

Review URL: https://codereview.chromium.org/481273005

3 files changed, 9 insertions, 9 deletions

diff --git a/src/effects/SkBlurImageFilter.cpp b/src/effects/SkBlurImageFilter.cpp
index 71bc8114df..8787ccec8c 100644
--- a/src/effects/SkBlurImageFilter.cpp
+++ b/src/effects/SkBlurImageFilter.cpp
@@ -253,13 +253,13 @@ void SkBlurImageFilter::computeFastBounds(const SkRect& src, SkRect* dst) const
 bool SkBlurImageFilter::onFilterBounds(const SkIRect& src, const SkMatrix& ctm,
                                        SkIRect* dst) const {
     SkIRect bounds = src;
-    if (getInput(0) && !getInput(0)->filterBounds(src, ctm, &bounds)) {
-        return false;
-    }
     SkVector sigma = SkVector::Make(fSigma.width(), fSigma.height());
     ctm.mapVectors(&sigma, 1);
     bounds.outset(SkScalarCeilToInt(SkScalarMul(sigma.x(), SkIntToScalar(3))),
                   SkScalarCeilToInt(SkScalarMul(sigma.y(), SkIntToScalar(3))));
+    if (getInput(0) && !getInput(0)->filterBounds(bounds, ctm, &bounds)) {
+        return false;
+    }
     *dst = bounds;
     return true;
 }
diff --git a/src/effects/SkDropShadowImageFilter.cpp b/src/effects/SkDropShadowImageFilter.cpp
index f1ebae8d97..29d685becc 100644
--- a/src/effects/SkDropShadowImageFilter.cpp
+++ b/src/effects/SkDropShadowImageFilter.cpp
@@ -121,9 +121,6 @@ void SkDropShadowImageFilter::computeFastBounds(const SkRect& src, SkRect* dst)
 bool SkDropShadowImageFilter::onFilterBounds(const SkIRect& src, const SkMatrix& ctm,
                                              SkIRect* dst) const {
     SkIRect bounds = src;
-    if (getInput(0) && !getInput(0)->filterBounds(src, ctm, &bounds)) {
-        return false;
-    }
     SkVector offsetVec = SkVector::Make(fDx, fDy);
     ctm.mapVectors(&offsetVec, 1);
     bounds.offset(-SkScalarCeilToInt(offsetVec.x()),
@@ -133,6 +130,9 @@ bool SkDropShadowImageFilter::onFilterBounds(const SkIRect& src, const SkMatrix&
     bounds.outset(SkScalarCeilToInt(SkScalarMul(sigma.x(), SkIntToScalar(3))),
                   SkScalarCeilToInt(SkScalarMul(sigma.y(), SkIntToScalar(3))));
     bounds.join(src);
+    if (getInput(0) && !getInput(0)->filterBounds(bounds, ctm, &bounds)) {
+        return false;
+    }
     *dst = bounds;
     return true;
 }
diff --git a/src/effects/SkMorphologyImageFilter.cpp b/src/effects/SkMorphologyImageFilter.cpp
index eef2a7d623..6a6dd4d451 100644
--- a/src/effects/SkMorphologyImageFilter.cpp
+++ b/src/effects/SkMorphologyImageFilter.cpp
@@ -248,13 +248,13 @@ void SkMorphologyImageFilter::computeFastBounds(const SkRect& src, SkRect* dst)
 bool SkMorphologyImageFilter::onFilterBounds(const SkIRect& src, const SkMatrix& ctm,
                                              SkIRect* dst) const {
     SkIRect bounds = src;
-    if (getInput(0) && !getInput(0)->filterBounds(src, ctm, &bounds)) {
-        return false;
-    }
     SkVector radius = SkVector::Make(SkIntToScalar(this->radius().width()),
                                      SkIntToScalar(this->radius().height()));
     ctm.mapVectors(&radius, 1);
     bounds.outset(SkScalarCeilToInt(radius.x()), SkScalarCeilToInt(radius.y()));
+    if (getInput(0) && !getInput(0)->filterBounds(bounds, ctm, &bounds)) {
+        return false;
+    }
     *dst = bounds;
     return true;
 }