Improve usage of window rectangles

src/gpu/GrReducedClip.h

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrReducedClip_DEFINED
 #define GrReducedClip_DEFINED
 
+#include "GrWindowRectangles.h"
 #include "SkClipStack.h"
 #include "SkTLList.h"
 
 class GrContext;
 class GrDrawContext;
 
 /**
  * This class takes a clip stack and produces a reduced set of elements that are equivalent to
  * applying that full stack within a specified query rectangle.
  */
 class SK_API GrReducedClip {
 public:
-    GrReducedClip(const SkClipStack& stack, const SkRect& queryBounds);
+    GrReducedClip(const SkClipStack&, const SkRect& queryBounds, int maxWindowRectangles = 0);
 
     /**
-     * If hasIBounds() is true, this is the bounding box within which the reduced clip is valid, and
-     * the caller must not modify any pixels outside this box. Undefined if hasIBounds() is false.
+     * If hasIBounds() is true, this is the bounding box within which the clip elements are valid.
+     * The caller must not modify any pixels outside this box. Undefined if hasIBounds() is false.
      */
     const SkIRect& ibounds() const { SkASSERT(fHasIBounds); return fIBounds; }
     int left() const { return this->ibounds().left(); }
     int top() const { return this->ibounds().top(); }
     int width() const { return this->ibounds().width(); }
     int height() const { return this->ibounds().height(); }
 
     /**
      * Indicates whether ibounds() are defined. They will always be defined if the elements() are
      * nonempty.
      */
     bool hasIBounds() const { return fHasIBounds; }
 
+    /**
+     * If nonempty, this is a set of "exclusive" windows within which the clip elements are NOT
+     * valid. The caller must not modify any pixels inside these windows.
+     */
+    const GrWindowRectangles& windowRectangles() const { return fWindowRects; }
+
     typedef SkTLList<SkClipStack::Element, 16> ElementList;
 
     /**
-     * Populated with a minimal list of elements that implement the clip.
+     * Populated with a minimal list of elements required to fully implement the clip.
      */
     const ElementList& elements() const { return fElements; }
 
     /**
      * If elements() are nonempty, uniquely identifies the list of elements within ibounds().
      * Otherwise undefined.
      */
     int32_t elementsGenID() const { SkASSERT(!fElements.isEmpty()); return fElementsGenID; }
 
     /**
      * Indicates whether antialiasing is required to process any of the clip elements.
      */
     bool requiresAA() const { return fRequiresAA; }
 
     enum class InitialState : bool {
         kAllIn,
         kAllOut
     };
 
     InitialState initialState() const { return fInitialState; }
 
     bool drawAlphaClipMask(GrDrawContext*) const;
     bool drawStencilClipMask(GrContext*, GrDrawContext*, const SkIPoint& clipOrigin) const;
 
 private:
-    void walkStack(const SkClipStack&, const SkRect& queryBounds);
+    void walkStack(const SkClipStack&, const SkRect& queryBounds, int maxWindowRectangles);
+    void addInteriorWindowRectangles(int maxWindowRectangles);
+    void addWindowRectangle(const SkRect& elementInteriorRect, bool elementIsAA);
     bool intersectIBounds(const SkIRect&);
 
-    SkIRect        fIBounds;
-    bool           fHasIBounds;
-    ElementList    fElements;
-    int32_t        fElementsGenID;
-    bool           fRequiresAA;
-    InitialState   fInitialState;
+    SkIRect              fIBounds;
+    bool                 fHasIBounds;
+    GrWindowRectangles   fWindowRects;
+    ElementList          fElements;
+    int32_t              fElementsGenID;
+    bool                 fRequiresAA;
+    InitialState         fInitialState;
 };
 
 #endif