Adds filter support for offscreen canvas

third_party/WebKit/Source/modules/canvas2d/CanvasRenderingContext2DState.cpp

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "modules/canvas2d/CanvasRenderingContext2DState.h"
 
 #include "core/css/CSSFontSelector.h"
 #include "core/css/resolver/FilterOperationResolver.h"
 #include "core/css/resolver/StyleBuilder.h"
 #include "core/css/resolver/StyleResolverState.h"
@@ skipping 277 matching lines @@
     context->clearFilterReferences();
     context->addFilterReferences(filters, canvasElement->document());
 }
 
 SkImageFilter* CanvasRenderingContext2DState::getFilter(Element* styleResolutionHost, IntSize canvasSize, CanvasRenderingContext2D* context) const
 {
     if (!m_filterValue)
         return nullptr;
 
     // StyleResolverState cannot be used in frame-less documents.
-    if (!styleResolutionHost->document().frame())
+    if (styleResolutionHost && !styleResolutionHost->document().frame())
         return nullptr;
 
     if (!m_resolvedFilter) {
         RefPtr<ComputedStyle> filterStyle = ComputedStyle::create();
         // Must set font in case the filter uses any font-relative units (em, ex)
         filterStyle->setFont(m_fontForFilter);
 
-        StyleResolverState resolverState(styleResolutionHost->document(), styleResolutionHost, filterStyle.get());
-        resolverState.setStyle(filterStyle);
+        if (styleResolutionHost) {
+            StyleResolverState resolverState(styleResolutionHost->document(), styleResolutionHost, filterStyle.get());
+            resolverState.setStyle(filterStyle);
 
-        StyleBuilder::applyProperty(CSSPropertyFilter, resolverState, *m_filterValue);
-        resolverState.loadPendingResources();
+            StyleBuilder::applyProperty(CSSPropertyFilter, resolverState, *m_filterValue);
+            resolverState.loadPendingResources();
+        } else {
+            StyleResolverState resolverState(filterStyle.get());
+            resolverState.setStyle(filterStyle);
+
+            StyleBuilder::applyProperty(CSSPropertyFilter, resolverState, *m_filterValue);
+            resolverState.loadPendingResources();
+        }
+
+
         FilterEffectBuilder* filterEffectBuilder = FilterEffectBuilder::create();
 
         // We can't reuse m_fillPaint and m_strokePaint for the filter, since these incorporate
         // the global alpha, which isn't applicable here.
         SkPaint fillPaintForFilter;
         SkPaint strokePaintForFilter;
         m_fillStyle->applyToPaint(fillPaintForFilter);
         m_strokeStyle->applyToPaint(strokePaintForFilter);
         fillPaintForFilter.setColor(m_fillStyle->paintColor());
         strokePaintForFilter.setColor(m_strokeStyle->paintColor());
         FloatSize floatCanvasSize(canvasSize);
         const double effectiveZoom = 1.0; // Deliberately ignore zoom on the canvas element
         filterEffectBuilder->build(styleResolutionHost, filterStyle->filter(), effectiveZoom, &floatCanvasSize, &fillPaintForFilter, &strokePaintForFilter);
 
         if (FilterEffect* lastEffect = filterEffectBuilder->lastEffect()) {
             lastEffect->determineMaximumEffectRect(DetermineMaxEffectRectNone);
             m_resolvedFilter = SkiaImageFilterBuilder::build(lastEffect, ColorSpaceDeviceRGB);
-            if (m_resolvedFilter) {
+            if (styleResolutionHost && m_resolvedFilter) {
                 updateFilterReferences(toHTMLCanvasElement(styleResolutionHost), context, filterStyle->filter());
                 if (lastEffect->originTainted())
                     context->setOriginTainted();
             }
         }
     }
 
     return m_resolvedFilter.get();
 }
 
@@ skipping 222 matching lines @@
         paint->setLooper(0);
         paint->setImageFilter(shadowAndForegroundImageFilter());
         return paint;
     }
     paint->setLooper(sk_ref_sp(shadowAndForegroundDrawLooper()));
     paint->setImageFilter(0);
     return paint;
 }
 
 } // namespace blink