SkClipStack::Element tweaks.

(
This is intended to facilitate efficient kMatrix_SaveFlags emulation
on restore():

  * collect all clip stack elements for the current save count into a
    side clip stack
  * canvas.restore(everything)
  * replay the collected clip ops to restore the initial clip state
  => we restored the matrix but the clip state is unchanged
)

Two main changes:

  * expose the save count for SkClipStack::Element
  * expose a replay method for the same (logic relocated from
    SkCanvas::replayClips)

The SkCanvas::ClipVisitor shuffling is to enable forward decl
in SkClipStack.h (cannot fwdecl a nested class).

R=reed@google.com, robertphillips@google.com
TBR=reed@google.com

Author: fmalita@chromium.org

Review URL: https://codereview.chromium.org/269693003

2 files changed, 18 insertions, 8 deletions

diff --git a/include/core/SkCanvas.h b/include/core/SkCanvas.h
index ee8ad250d2..b92b1460fd 100644
--- a/include/core/SkCanvas.h
+++ b/include/core/SkCanvas.h
@@ -24,6 +24,7 @@
     #define SK_LEGACY_DRAWTEXT_VIRTUAL
 #endif
 
+class SkCanvasClipVisitor;
 class SkBaseDevice;
 class SkDraw;
 class SkDrawFilter;
@@ -1134,14 +1135,7 @@ public:
         return &fClipStack;
     }
 
-    class ClipVisitor {
-    public:
-        virtual ~ClipVisitor();
-        virtual void clipRect(const SkRect&, SkRegion::Op, bool antialias) = 0;
-        virtual void clipRRect(const SkRRect&, SkRegion::Op, bool antialias) = 0;
-        virtual void clipPath(const SkPath&, SkRegion::Op, bool antialias) = 0;
-    };
-
+    typedef SkCanvasClipVisitor ClipVisitor;
     /**
      *  Replays the clip operations, back to front, that have been applied to
      *  the canvas, calling the appropriate method on the visitor for each
@@ -1504,5 +1498,12 @@ static inline SkCanvas::SaveFlags& operator|=(SkCanvas::SaveFlags& lhs,
     return lhs;
 }
 
+class SkCanvasClipVisitor {
+public:
+    virtual ~SkCanvasClipVisitor();
+    virtual void clipRect(const SkRect&, SkRegion::Op, bool antialias) = 0;
+    virtual void clipRRect(const SkRRect&, SkRegion::Op, bool antialias) = 0;
+    virtual void clipPath(const SkPath&, SkRegion::Op, bool antialias) = 0;
+};
 
 #endif
diff --git a/include/core/SkClipStack.h b/include/core/SkClipStack.h
index 028d551560..4243cee7b0 100644
--- a/include/core/SkClipStack.h
+++ b/include/core/SkClipStack.h
@@ -16,6 +16,7 @@
 #include "SkTDArray.h"
 #include "SkTLazy.h"
 
+class SkCanvasClipVisitor;
 
 // Because a single save/restore state can have multiple clips, this class
 // stores the stack depth (fSaveCount) and clips (fDeque) separately.
@@ -74,6 +75,9 @@ public:
         //!< Call to get the type of the clip element.
         Type getType() const { return fType; }
 
+        //!< Call to get the save count associated with this clip element.
+        int getSaveCount() const { return fSaveCount; }
+
         //!< Call if getType() is kPath to get the path.
         const SkPath& getPath() const { SkASSERT(kPath_Type == fType); return *fPath.get(); }
 
@@ -156,6 +160,11 @@ public:
             return kPath_Type == fType && fPath.get()->isInverseFillType();
         }
 
+        /**
+        * Replay this clip into the visitor.
+        */
+        void replay(SkCanvasClipVisitor*) const;
+
     private:
         friend class SkClipStack;