Implement difference clip rects with window rectangles

include/gpu/GrClip.h

 /*
  * Copyright 2010 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrClip_DEFINED
 #define GrClip_DEFINED
 
 #include "GrFragmentProcessor.h"
 #include "GrTypesPriv.h"
+#include "GrWindowRectangles.h"
 
 class GrDrawContext;
 
 /**
  * Produced by GrClip. It provides a set of modifications to the drawing state that are used to
  * create the final GrPipeline for a GrBatch.
  */
 class GrAppliedClip : public SkNoncopyable {
 public:
     GrAppliedClip(const SkRect& drawBounds)
         : fHasStencilClip(false)
         , fClippedDrawBounds(drawBounds) {
     }
 
     const GrScissorState& scissorState() const { return fScissorState; }
+    const GrWindowRectangles& windows() const { return fWindows; }
     GrFragmentProcessor* clipCoverageFragmentProcessor() const { return fClipCoverageFP.get(); }
     bool hasStencilClip() const { return fHasStencilClip; }
 
     /**
      * Intersects the applied clip with the provided rect. Returns false if the draw became empty.
      */
     bool addScissor(const SkIRect& irect) {
         return fScissorState.intersect(irect) && fClippedDrawBounds.intersect(SkRect::Make(irect));
     }
 
+    /**
+     * Adds an exclusive window rectangle to the clip. It is not currently supported to switch the
+     * windows to inclusive mode.
+     */
+    void addWindowRectangle(const SkIRect& window, const GrCaps& caps) {
+        fWindows.addWindow(window, caps);
+    }
+
     void addCoverageFP(sk_sp<GrFragmentProcessor> fp) {
         SkASSERT(!fClipCoverageFP);
         fClipCoverageFP = fp;
     }
 
     void addStencilClip() {
         SkASSERT(!fHasStencilClip);
         fHasStencilClip = true;
     }
 
     /**
      * Returns the device bounds of the draw after clip has been applied. TODO: Ideally this would
      * consider the combined effect of all clipping techniques in play (scissor, stencil, fp, etc.).
      */
     const SkRect& clippedDrawBounds() const { return fClippedDrawBounds; }
 
 private:
     GrScissorState             fScissorState;
+    GrWindowRectangles         fWindows;
     sk_sp<GrFragmentProcessor> fClipCoverageFP;
     bool                       fHasStencilClip;
     SkRect                     fClippedDrawBounds;
     typedef SkNoncopyable INHERITED;
 };
 
 /**
  * GrClip is an abstract base class for applying a clip. It constructs a clip mask if necessary, and
  * fills out a GrAppliedClip instructing the caller on how to set up the draw state.
  */
@@ skipping 123 matching lines @@
 
 private:
     bool apply(GrContext*, GrDrawContext*, bool useHWAA, bool hasUserStencilSettings,
                GrAppliedClip* out) const final;
 
     GrScissorState   fScissorState;
     bool             fHasStencilClip;
 };
 
 #endif