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 261 matching lines @@
   m_isTransformInvertible = true;
 }
 
 static void updateFilterReferences(HTMLCanvasElement* canvasElement,
                                    CanvasRenderingContext2D* context,
                                    const FilterOperations& filters) {
   context->clearFilterReferences();
   context->addFilterReferences(filters, canvasElement->document());
 }
 
+SkImageFilter* CanvasRenderingContext2DState::getFilterWithoutDocument(
+    IntSize canvasSize) const {
+  if (!m_filterValue)
+    return nullptr;
+
+  if (m_resolvedFilter)
+    return m_resolvedFilter.get();
+
+  FilterOperations op =
+      FilterOperationResolver::createFilterOperations(nullptr, *m_filterValue);

[meade_UTC10, 2016/10/26 06:57:34]

Nit: don't abbreviate variable names.

[fserb, 2016/10/26 19:08:26]

done

+
+  // 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;
+  m_fillStyle->applyToPaint(fillPaintForFilter);
+  fillPaintForFilter.setColor(m_fillStyle->paintColor());
+  SkPaint strokePaintForFilter;
+  m_strokeStyle->applyToPaint(strokePaintForFilter);
+  strokePaintForFilter.setColor(m_strokeStyle->paintColor());
+
+  FilterEffectBuilder filterEffectBuilder(
+      nullptr, FloatRect((FloatPoint()), FloatSize(canvasSize)),

[Justin Novosad, 2016/10/24 18:51:22]

This nullptr lacks readability.  Please use a temp var or an /*inline comment*/
so we know what it is.

[fserb, 2016/10/26 19:08:26]

done

+      1.0f,  // Deliberately ignore zoom on the canvas element.
+      &fillPaintForFilter, &strokePaintForFilter);

[meade_UTC10, 2016/10/26 06:57:34]

It looks like these get stored in the FilterEffectBuilder. Is it ok that they
are temporary variables?

[fserb, 2016/10/26 19:08:26]

yep. They are used the same way on getFilter(). They are only used on
buildFilterEffect and it doesn't keep anything remotely.

+
+  if (FilterEffect* lastEffect = filterEffectBuilder.buildFilterEffect(op)) {
+    m_resolvedFilter =
+        SkiaImageFilterBuilder::build(lastEffect, ColorSpaceDeviceRGB);
+  }
+
+  return m_resolvedFilter.get();
+}
+
 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())
     return nullptr;
@@ skipping 34 matching lines @@
                                context, filterStyle->filter());
         if (lastEffect->originTainted())
           context->setOriginTainted();
       }
     }
   }
 
   return m_resolvedFilter.get();
 }
 
+bool CanvasRenderingContext2DState::hasFilterWithoutDocument(
+    IntSize canvasSize) const {
+  // Checking for a non-null m_filterValue isn't sufficient, since this value
+  // might refer to a non-existent filter.
+  return !!getFilterWithoutDocument(canvasSize);
+}
+
 bool CanvasRenderingContext2DState::hasFilter(
     Element* styleResolutionHost,
     IntSize canvasSize,
     CanvasRenderingContext2D* context) const {
   // Checking for a non-null m_filterValue isn't sufficient, since this value
   // might refer to a non-existent filter.
   return !!getFilter(styleResolutionHost, canvasSize, context);
 }
 
 void CanvasRenderingContext2DState::clearResolvedFilter() const {
@@ skipping 210 matching lines @@
     paint->setLooper(0);
     paint->setImageFilter(shadowAndForegroundImageFilter());
     return paint;
   }
   paint->setLooper(sk_ref_sp(shadowAndForegroundDrawLooper()));
   paint->setImageFilter(0);
   return paint;
 }
 
 }  // namespace blink