Adds filter support for offscreen canvas

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

Index: third_party/WebKit/Source/modules/canvas2d/CanvasRenderingContext2DState.cpp
diff --git a/third_party/WebKit/Source/modules/canvas2d/CanvasRenderingContext2DState.cpp b/third_party/WebKit/Source/modules/canvas2d/CanvasRenderingContext2DState.cpp
index 4ea962955da8ef164cddfa921b0bb7a8a0a408b4..8eaafb83cb4c1dfc30afd33e90816444410afb75 100644
--- a/third_party/WebKit/Source/modules/canvas2d/CanvasRenderingContext2DState.cpp
+++ b/third_party/WebKit/Source/modules/canvas2d/CanvasRenderingContext2DState.cpp
@@ -279,6 +279,39 @@ static void updateFilterReferences(HTMLCanvasElement* canvasElement,
   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,
@@ -333,6 +366,13 @@ SkImageFilter* CanvasRenderingContext2DState::getFilter(
   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,