Fixed Shadow blur for transparent objects

Source/platform/graphics/GraphicsContext.cpp

 /*
  * Copyright (C) 2003, 2004, 2005, 2006, 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 33 matching lines @@
 #include "third_party/skia/include/core/SkColorFilter.h"
 #include "third_party/skia/include/core/SkData.h"
 #include "third_party/skia/include/core/SkDevice.h"
 #include "third_party/skia/include/core/SkPicture.h"
 #include "third_party/skia/include/core/SkPictureRecorder.h"
 #include "third_party/skia/include/core/SkRRect.h"
 #include "third_party/skia/include/core/SkRefCnt.h"
 #include "third_party/skia/include/core/SkSurface.h"
 #include "third_party/skia/include/effects/SkBlurMaskFilter.h"
 #include "third_party/skia/include/effects/SkCornerPathEffect.h"
+#include "third_party/skia/include/effects/SkDropShadowImageFilter.h"
 #include "third_party/skia/include/effects/SkLumaColorFilter.h"
 #include "third_party/skia/include/effects/SkMatrixImageFilter.h"
 #include "third_party/skia/include/effects/SkPictureImageFilter.h"
 #include "third_party/skia/include/gpu/GrRenderTarget.h"
 #include "third_party/skia/include/gpu/GrTexture.h"
 #include "wtf/Assertions.h"
 #include "wtf/MathExtras.h"
 
 namespace {
 
@@ skipping 255 matching lines @@
         }
         clearShadow();
         return;
     }
 
     drawLooperBuilder->addShadow(offset, blur, color, shadowTransformMode, shadowAlphaMode);
     if (shadowMode == DrawShadowAndForeground) {
         drawLooperBuilder->addUnmodifiedContent();
     }
     setDrawLooper(drawLooperBuilder.release());
+
+    if (shadowTransformMode == DrawLooperBuilder::ShadowIgnoresTransforms

[Justin Novosad, 2014/11/28 23:20:39]

This is wrong by the way. SkDropShadowImageFilter Does not ignore transforms. It
applies the CTM to sigma and to the offset.  This CL causes a regression that
was not caught because of incomplete test coverage. There are no tests that draw
semi-transparent images with a shadow with a transform (other than translation)
applied.  crbug.com/437112

+        && shadowAlphaMode == DrawLooperBuilder::ShadowRespectsAlpha) {
+        // This image filter will be used in place of the drawLooper created above but only for drawing non-opaque bitmaps;
+        // see preparePaintForDrawRectToRect().
+        SkColor skColor = color.rgb();
+        // These constants are from RadiusToSigma() from DrawLooperBuilder.cpp.
+        const SkScalar sigma = 0.288675f * blur + 0.5f;
+        SkDropShadowImageFilter::ShadowMode dropShadowMode = shadowMode == DrawShadowAndForeground ? SkDropShadowImageFilter::kDrawShadowAndForeground_ShadowMode : SkDropShadowImageFilter::kDrawShadowOnly_ShadowMode;
+        RefPtr<SkImageFilter> filter = adoptRef(SkDropShadowImageFilter::Create(offset.width(), offset.height(), sigma, sigma, skColor, dropShadowMode));
+        setDropShadowImageFilter(filter);
+    }
 }
 
 void GraphicsContext::setDrawLooper(PassOwnPtr<DrawLooperBuilder> drawLooperBuilder)
 {
     if (contextDisabled())
         return;
 
     mutableState()->setDrawLooper(drawLooperBuilder->detachDrawLooper());
 }
 
 void GraphicsContext::clearDrawLooper()
 {
     if (contextDisabled())
         return;
 
     mutableState()->clearDrawLooper();
 }
 
+void GraphicsContext::setDropShadowImageFilter(PassRefPtr<SkImageFilter> imageFilter)
+{
+    if (contextDisabled())
+        return;
+
+    mutableState()->setDropShadowImageFilter(imageFilter);
+}
+
+void GraphicsContext::clearDropShadowImageFilter()
+{
+    if (contextDisabled())
+        return;
+
+    mutableState()->clearDropShadowImageFilter();
+}
+
 bool GraphicsContext::hasShadow() const
 {
-    return !!immutableState()->drawLooper();
+    return !!immutableState()->drawLooper() || !!immutableState()->dropShadowImageFilter();
 }
 
 bool GraphicsContext::getTransformedClipBounds(FloatRect* bounds) const
 {
     if (contextDisabled())
         return false;
     ASSERT(m_canvas);
     SkIRect skIBounds;
     if (!m_canvas->getClipDeviceBounds(&skIBounds))
         return false;
@@ skipping 1600 matching lines @@
         m_textRegion.join(textRect);
     }
 }
 
 void GraphicsContext::preparePaintForDrawRectToRect(
     SkPaint* paint,
     const SkRect& srcRect,
     const SkRect& destRect,
     CompositeOperator compositeOp,
     WebBlendMode blendMode,
+    bool isBitmapWithAlpha,
     bool isLazyDecoded,
     bool isDataComplete) const
 {
     paint->setXfermodeMode(WebCoreCompositeToSkiaComposite(compositeOp, blendMode));
     paint->setColorFilter(this->colorFilter());
     paint->setAlpha(this->getNormalizedAlpha());
-    paint->setLooper(this->drawLooper());
+    if (this->dropShadowImageFilter() && isBitmapWithAlpha) {
+        paint->setImageFilter(this->dropShadowImageFilter());
+    } else {
+        paint->setLooper(this->drawLooper());
+    }
     paint->setAntiAlias(shouldDrawAntiAliased(this, destRect));
 
     InterpolationQuality resampling;
     if (this->isAccelerated()) {
         resampling = InterpolationLow;
     } else if (this->printing()) {
         resampling = InterpolationNone;
     } else if (isLazyDecoded) {
         resampling = InterpolationHigh;
     } else {
@@ skipping 13 matching lines @@
         // FIXME: This is to not break tests (it results in the filter bitmap flag
         // being set to true). We need to decide if we respect InterpolationNone
         // being returned from computeInterpolationQuality.
         resampling = InterpolationLow;
     }
     resampling = limitInterpolationQuality(this, resampling);
     paint->setFilterLevel(static_cast<SkPaint::FilterLevel>(resampling));
 }
 
 } // namespace blink