[SPv2] Create effect nodes for CSS filter

third_party/WebKit/Source/platform/graphics/paint/EffectPaintPropertyNode.h

 // 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.
 
 #ifndef EffectPaintPropertyNode_h
 #define EffectPaintPropertyNode_h
 
 #include "platform/PlatformExport.h"
+#include "platform/graphics/CompositorFilterOperations.h"
 #include "wtf/PassRefPtr.h"
 #include "wtf/RefCounted.h"
 #include "wtf/RefPtr.h"
 
 #include <iosfwd>
 
 namespace blink {
 
-// A paint effect created by the opacity css property along with a reference to
-// the parent effect for inherited effects.
+// Effect nodes are abstraction of isolated groups, along with optional effects
+// that can be applied to the composited output of the group.
 //
 // The effect tree is rooted at a node with no parent. This root node should
 // not be modified.
-//
-// TODO(pdr): Support more effects than just opacity.
 class PLATFORM_EXPORT EffectPaintPropertyNode
     : public RefCounted<EffectPaintPropertyNode> {
  public:
   static PassRefPtr<EffectPaintPropertyNode> create(
       PassRefPtr<const EffectPaintPropertyNode> parent,
-      float opacity) {
-    return adoptRef(new EffectPaintPropertyNode(std::move(parent), opacity));
+      PassRefPtr<const TransformPaintPropertyNode> localTransformSpace,
+      PassRefPtr<const ClipPaintPropertyNode> outputClip,
+      float opacity, CompositorFilterOperations filter) {
+    return adoptRef(new EffectPaintPropertyNode(std::move(parent), std::move(localTransformSpace), std::move(outputClip), opacity, std::move(filter)));
   }
 
-  void update(PassRefPtr<const EffectPaintPropertyNode> parent, float opacity) {
+  void update(PassRefPtr<const EffectPaintPropertyNode> parent,
+      PassRefPtr<const TransformPaintPropertyNode> localTransformSpace,
+      PassRefPtr<const ClipPaintPropertyNode> outputClip,
+      float opacity, CompositorFilterOperations filter) {
     DCHECK(!isRoot());
     DCHECK(parent != this);
     m_parent = parent;
+    m_localTransformSpace = localTransformSpace;
+    m_outputClip = outputClip;
     m_opacity = opacity;
+    m_filter = std::move(filter);
   }
 
+  const TransformPaintPropertyNode* localTransformSpace() const { return m_localTransformSpace.get(); }
+  const ClipPaintPropertyNode* outputClip() const { return m_outputClip.get(); }
+
   float opacity() const { return m_opacity; }
+  const CompositorFilterOperations& filter() const { return m_filter; }
 
   // Parent effect or nullptr if this is the root effect.
   const EffectPaintPropertyNode* parent() const { return m_parent.get(); }
   bool isRoot() const { return !m_parent; }
 
  private:
   EffectPaintPropertyNode(PassRefPtr<const EffectPaintPropertyNode> parent,
-                          float opacity)
-      : m_parent(parent), m_opacity(opacity) {}
+      PassRefPtr<const TransformPaintPropertyNode> localTransformSpace,
+      PassRefPtr<const ClipPaintPropertyNode> outputClip,
+      float opacity, CompositorFilterOperations filter)
+      : m_parent(parent), m_localTransformSpace(localTransformSpace), m_outputClip(outputClip), m_opacity(opacity), m_filter(std::move(filter)) {}
 
   RefPtr<const EffectPaintPropertyNode> m_parent;
+  // The local transform space serves two purposes:
+  // 1. Assign a depth mapping for 3D depth sorting against other paint chunks
+  //    and effects under the same parent.
+  // 2. Some effects are spatial (namely blur filter and reflection), the
+  //    effect parameters will be specified in the local space.
+  RefPtr<const TransformPaintPropertyNode> m_localTransformSpace;
+  // The output of the effect can be optionally clipped when composited onto
+  // the current backdrop.
+  RefPtr<const ClipPaintPropertyNode> m_outputClip;
+
+  // Optionally a number of effects can be applied to the composited output.
+  // The chain of effects are applied in reverse order of the following list:

[pdr., 2016/10/19 17:44:43]

Nit: can we list these in order instead of reverse order?

[trchen, 2016/10/21 23:26:39]

Done.

By the way every time we added a new property, all
EffectPaintPropertyNode::create() invocation in the unit tests need to be
updated. This results in O(n^2) effort and won't scale. I think we should adopt
keyword-based optional arguments (which can be implemented with variadic
templates), if that's accepted by style guide.

+  // === Begin of effects ===
   float m_opacity;
+  CompositorFilterOperations m_filter;
+  // === End of effects ===
 };
 
 // Redeclared here to avoid ODR issues.
 // See platform/testing/PaintPrinters.h.
 void PrintTo(const EffectPaintPropertyNode&, std::ostream*);
 
 }  // namespace blink
 
 #endif  // EffectPaintPropertyNode_h