SPv2: Use GeometryMapper to implement PaintLayerClipper.

third_party/WebKit/Source/core/paint/PaintLayerClipper.h

 /*
  * Copyright (C) 2003, 2009, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2013 Intel Corporation. All rights reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@web.de>
@@ skipping 30 matching lines @@
  * If you do not delete the provisions above, a recipient may use your
  * version of this file under any of the LGPL, the MPL or the GPL.
  */
 
 #ifndef PaintLayerClipper_h
 #define PaintLayerClipper_h
 
 #include "core/CoreExport.h"
 #include "core/layout/ClipRectsCache.h"
 #include "core/layout/ScrollEnums.h"
+
+#include "platform/graphics/paint/ClipPaintPropertyNode.h"

[Xianzhu, 2016/08/15 17:09:04]

Nit: The XXXPaintPropertyNode.h headers are actually required by
PropertyTreeState.h so they should be included in that file.
https://codereview.chromium.org/2238853005/ does that.

[chrishtr, 2016/10/05 23:28:32]

Done.

+#include "platform/graphics/paint/EffectPaintPropertyNode.h"
+#include "platform/graphics/paint/GeometryMapper.h"
+#include "platform/graphics/paint/TransformPaintPropertyNode.h"
+
 #include "wtf/Allocator.h"
 
 namespace blink {
 
 class PaintLayer;
 
 enum ShouldRespectOverflowClipType {
     IgnoreOverflowClip,
     RespectOverflowClip
 };
@@ skipping 38 matching lines @@
 
     ClipRectsCacheSlot m_cacheSlot;
     LayoutSize subPixelAccumulation;
     ShouldRespectOverflowClipType respectOverflowClip;
     ShouldRespectOverflowClipType respectOverflowClipForViewport;
 };
 
 // PaintLayerClipper is responsible for computing and caching clip
 // rects.
 //
+// These clip rects have two types: background and foreground.
+//
+// The "background rect" for a PaintLayer is almost the same as its visual
+// rect in the space of some ancestor PaintLayer (specified by a parameter).
+// The only difference is that unclipped rect at the start is LayoutRect::infiniteIntRect,
+// rather than the local overflow bounds of the PaintLayer. Thus, for example
+// if there are no clips then the background rect will be infinite.
+// Also, whether overflow clip of the ancestor should be applied is a parameter.
+//
+// The "foreground rect" for a PaintLayer is its "background rect", intersected
+// with any clip applied by this PaintLayer to its children.
+
+// Motivation for this class:
+//
 // The main reason for this cache is that we compute the clip rects during
 // a layout tree walk but need them during a paint tree walk (see example
 // below for some explanations).
 //
 // A lot of complexity in this class come from the difference in inheritance
 // between 'overflow' and 'clip':
 // * 'overflow' applies based on the containing blocks chain.
 //    (http://www.w3.org/TR/CSS2/visufx.html#propdef-overflow)
 // * 'clip' applies to all descendants.
 //    (http://www.w3.org/TR/CSS2/visufx.html#propdef-clip)
@@ skipping 25 matching lines @@
 //
 // Now instead if we add "clip: rect(0px, 100px, 100px, 0px)" to #container,
 // the clip will apply to both #inflow and #fixed. That's because 'clip'
 // applies to any descendant, regardless of containing blocks. Note that
 // #container and #fixed are siblings in the paint tree but #container does
 // clip #fixed. This is the reason why we compute the painting clip rects during
 // a layout tree walk and cache them for painting.
 class CORE_EXPORT PaintLayerClipper {
     DISALLOW_NEW();
 public:
-    explicit PaintLayerClipper(const PaintLayer& layer) : m_layer(layer) { }
+    explicit PaintLayerClipper(const PaintLayer&);
 
     void clearClipRectsIncludingDescendants();
     void clearClipRectsIncludingDescendants(ClipRectsCacheSlot);
 
     // Returns the background clip rect of the layer in the local coordinate space. Only looks for clips up to the given ancestor.
     LayoutRect localClipRect(const PaintLayer* ancestorLayer) const;
 
     ClipRect backgroundClipRect(const ClipRectsContext&) const;
 
     // This method figures out our layerBounds in coordinates relative to
     // |rootLayer|. It also computes our background and foreground clip rects
     // for painting/event handling.
     // Pass offsetFromRoot if known.
     void calculateRects(const ClipRectsContext&, const LayoutRect& paintDirtyRect, LayoutRect& layerBounds,
         ClipRect& backgroundRect, ClipRect& foregroundRect, const LayoutPoint* offsetFromRoot = 0) const;
 
     ClipRects& paintingClipRects(const PaintLayer* rootLayer, ShouldRespectOverflowClipType, const LayoutSize& subpixelAccumulation) const;
 
 private:
     ClipRects& getClipRects(const ClipRectsContext&) const;
 
     void calculateClipRects(const ClipRectsContext&, ClipRects&) const;
     ClipRects* clipRectsIfCached(const ClipRectsContext&) const;
     ClipRects& storeClipRectsInCache(const ClipRectsContext&, ClipRects* parentClipRects, const ClipRects&) const;
 
     void getOrCalculateClipRects(const ClipRectsContext&, ClipRects&) const;
 
     bool shouldRespectOverflowClip(const ClipRectsContext&) const;
 
+    ClipRect clipRectWithGeometryMapper(const ClipRectsContext&, bool isForeground) const;
+
     const PaintLayer& m_layer;
+    std::unique_ptr<GeometryMapper> m_geometryMapper;
 };
 
 } // namespace blink
 
 #endif // LayerClipper_h