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

1 files changed, 44 insertions, 0 deletions

diff --git a/tests/ImageFilterTest.cpp b/tests/ImageFilterTest.cpp
index f87f99ce98..e7e0f84385 100644
--- a/tests/ImageFilterTest.cpp
+++ b/tests/ImageFilterTest.cpp
@@ -469,6 +469,50 @@ DEF_TEST(ImageFilterDrawMatrixBBH, reporter) {
     }
 }
 
+static SkImageFilter* makeBlur(SkImageFilter* input = NULL) {
+    return SkBlurImageFilter::Create(SK_Scalar1, SK_Scalar1, input);
+}
+
+static SkImageFilter* makeDropShadow(SkImageFilter* input = NULL) {
+    return SkDropShadowImageFilter::Create(
+        SkIntToScalar(100), SkIntToScalar(100),
+        SkIntToScalar(10), SkIntToScalar(10),
+        SK_ColorBLUE, input);
+}
+
+DEF_TEST(ImageFilterBlurThenShadowBounds, reporter) {
+    SkAutoTUnref<SkImageFilter> filter1(makeBlur());
+    SkAutoTUnref<SkImageFilter> filter2(makeDropShadow(filter1.get()));
+
+    SkIRect bounds = SkIRect::MakeXYWH(0, 0, 100, 100);
+    SkIRect expectedBounds = SkIRect::MakeXYWH(-133, -133, 236, 236);
+    filter2->filterBounds(bounds, SkMatrix(), &bounds);
+
+    REPORTER_ASSERT(reporter, bounds == expectedBounds);
+}
+
+DEF_TEST(ImageFilterShadowThenBlurBounds, reporter) {
+    SkAutoTUnref<SkImageFilter> filter1(makeDropShadow());
+    SkAutoTUnref<SkImageFilter> filter2(makeBlur(filter1.get()));
+
+    SkIRect bounds = SkIRect::MakeXYWH(0, 0, 100, 100);
+    SkIRect expectedBounds = SkIRect::MakeXYWH(-133, -133, 236, 236);
+    filter2->filterBounds(bounds, SkMatrix(), &bounds);
+
+    REPORTER_ASSERT(reporter, bounds == expectedBounds);
+}
+
+DEF_TEST(ImageFilterDilateThenBlurBounds, reporter) {
+    SkAutoTUnref<SkImageFilter> filter1(SkDilateImageFilter::Create(2, 2));
+    SkAutoTUnref<SkImageFilter> filter2(makeDropShadow(filter1.get()));
+
+    SkIRect bounds = SkIRect::MakeXYWH(0, 0, 100, 100);
+    SkIRect expectedBounds = SkIRect::MakeXYWH(-132, -132, 234, 234);
+    filter2->filterBounds(bounds, SkMatrix(), &bounds);
+
+    REPORTER_ASSERT(reporter, bounds == expectedBounds);
+}
+
 static void drawBlurredRect(SkCanvas* canvas) {
     SkAutoTUnref<SkImageFilter> filter(SkBlurImageFilter::Create(SkIntToScalar(8), 0));
     SkPaint filterPaint;