commit 3b428cbf8a2f4b8d4fad7f2708e67cf954ba7bf1
author Xianzhu Wang <wangxianzhu@chromium.org> Mon Jan 22 09:51:13 2018 -0800
committer Skia Commit-Bot <skia-commit-bot@chromium.org> Mon Jan 22 19:51:47 2018 +0000
tree ce7c15c645704743ae328abb807fbedcff56dbcd
parent 2cb6cb1f338e655f63fa258efeaa38988ec6a7b3

Set empty device clip when an image filter has zero bounds

When an image filter has zero input bounds, we should not paint any
contents of it, so we should set an empty clip. This is like the
case that the clip rect doesn't intersect with the image filter's
input bounds.

Bug: chromium:771643
Change-Id: I063c14128dacb83e3572bd2ef4dfeee93c871064
Reviewed-on: https://skia-review.googlesource.com/96943
Reviewed-by: Mike Reed <reed@google.com>
Reviewed-by: Stephen White <senorblanco@chromium.org>
Commit-Queue: Mike Reed <reed@google.com>

src/core/SkCanvas.cpp

diff --git a/src/core/SkCanvas.cpp b/src/core/SkCanvas.cpp
index 0f079aa..7fbb952 100644
--- a/src/core/SkCanvas.cpp
+++ b/src/core/SkCanvas.cpp
@@ -953,9 +953,6 @@
 
     if (imageFilter) {
         clipBounds = imageFilter->filterBounds(clipBounds, ctm);
-        if (clipBounds.isEmpty()) {
-            return false;
-        }
         if (bounds && !imageFilter->canComputeFastBounds()) {
             bounds = nullptr;
         }
@@ -963,21 +960,21 @@
     SkIRect ir;
     if (bounds) {
         SkRect r;
-
         ctm.mapRect(&r, *bounds);
         r.roundOut(&ir);
-        // early exit if the layer's bounds are clipped out
-        if (!ir.intersect(clipBounds)) {
-            if (BoundsAffectsClip(saveLayerFlags)) {
-                fMCRec->fTopLayer->fDevice->clipRegion(SkRegion(), SkClipOp::kIntersect); // empty
-                fMCRec->fRasterClip.setEmpty();
-                fDeviceClipBounds.setEmpty();
-            }
-            return false;
-        }
     } else {    // no user bounds, so just use the clip
         ir = clipBounds;
     }
+
+    // early exit if the layer's bounds are clipped out
+    if (!ir.intersect(clipBounds)) {
+        if (BoundsAffectsClip(saveLayerFlags)) {
+            fMCRec->fTopLayer->fDevice->clipRegion(SkRegion(), SkClipOp::kIntersect); // empty
+            fMCRec->fRasterClip.setEmpty();
+            fDeviceClipBounds.setEmpty();
+        }
+        return false;
+    }
     SkASSERT(!ir.isEmpty());
 
     if (BoundsAffectsClip(saveLayerFlags)) {

tests/CanvasTest.cpp

diff --git a/tests/CanvasTest.cpp b/tests/CanvasTest.cpp
index 9b1e0c9..e83777b 100644
--- a/tests/CanvasTest.cpp
+++ b/tests/CanvasTest.cpp
@@ -61,10 +61,11 @@
 #include "SkRect.h"
 #include "SkRegion.h"
 #include "SkShader.h"
+#include "SkSpecialImage.h"
 #include "SkStream.h"
 #include "SkSurface.h"
-#include "SkTemplates.h"
 #include "SkTDArray.h"
+#include "SkTemplates.h"
 #include "SkVertices.h"
 #include "Test.h"
 
@@ -812,3 +813,50 @@
     REPORTER_ASSERT(r, SK_ColorRED == SkSwizzle_BGRA_to_PMColor(*bitmap.getAddr32(0, 0)));
 }
 #endif
+
+namespace {
+
+class ZeroBoundsImageFilter : public SkImageFilter {
+public:
+    static sk_sp<SkImageFilter> Make() { return sk_sp<SkImageFilter>(new ZeroBoundsImageFilter); }
+
+    SK_TO_STRING_OVERRIDE()
+    SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(ZeroBoundsImageFilter)
+
+protected:
+    sk_sp<SkSpecialImage> onFilterImage(SkSpecialImage*, const Context&, SkIPoint*) const override {
+        return nullptr;
+    }
+    sk_sp<SkImageFilter> onMakeColorSpace(SkColorSpaceXformer*) const override { return nullptr; }
+    SkIRect onFilterNodeBounds(const SkIRect&, const SkMatrix&, MapDirection) const override {
+        return SkIRect::MakeEmpty();
+    }
+
+private:
+    ZeroBoundsImageFilter() : INHERITED(nullptr, 0, nullptr) {}
+
+    typedef SkImageFilter INHERITED;
+};
+
+sk_sp<SkFlattenable> ZeroBoundsImageFilter::CreateProc(SkReadBuffer& buffer) {
+    SkDEBUGFAIL("Should never get here");
+    return nullptr;
+}
+
+#ifndef SK_IGNORE_TO_STRING
+void ZeroBoundsImageFilter::toString(SkString* str) const {
+    str->appendf("ZeroBoundsImageFilter: ()");
+}
+#endif
+
+}  // anonymous namespace
+
+DEF_TEST(Canvas_SaveLayerWithNullBoundsAndZeroBoundsImageFilter, r) {
+    SkCanvas canvas(10, 10);
+    SkPaint p;
+    p.setImageFilter(ZeroBoundsImageFilter::Make());
+    // This should not fail any assert.
+    canvas.saveLayer(nullptr, &p);
+    REPORTER_ASSERT(r, canvas.getDeviceClipBounds().isEmpty());
+    canvas.restore();
+}