Culling API

include/core/SkCanvas.h

Index: include/core/SkCanvas.h
diff --git a/include/core/SkCanvas.h b/include/core/SkCanvas.h
index e639212e384b0f58dda00b3e8086cbe03a059688..bceedba3f3a9a59dbac1239a6bc0ac08494c139c 100644
--- a/include/core/SkCanvas.h
+++ b/include/core/SkCanvas.h
@@ -935,7 +935,26 @@ public:
         // do nothing. Subclasses may do something
     }
 
+    /**
+     *  This call asserts that subsequent draw operations (up to the matching popCull() call)
+     *  are fully contained within the given bounding box. The assertion is not enforced,
+     *  but the information might be used to quick-reject command blocks, so an incorrect
+     *  bounding box may result in incomplete rendering.
+     */
+    void pushCull(const SkRect& cullRect) {

[robertphillips, 2014/02/25 15:58:41]

++fCullCount?

+        fCullCount += 1;
+        this->onPushCull(cullRect);
+    }
 
+    /**
+     *  Terminates the current culling block, and restores the previous one (if any).
+     */
+    void popCull() {

[robertphillips, 2014/02/25 15:58:41]

Maybe and "SkASSERT(fCullCount > 0);" to assist debugging?

+        if (fCullCount > 0) {

[robertphillips, 2014/02/25 15:58:41]

--fCullCount?

+            fCullCount -= 1;
+            this->onPopCull();
+        }
+    }
     //////////////////////////////////////////////////////////////////////////
 
     /** Get the current bounder object.
@@ -1101,6 +1120,9 @@ protected:
     // can perform copy-on-write or invalidate any cached images
     void predrawNotify();
 
+    virtual void onPushCull(const SkRect& cullRect);
+    virtual void onPopCull();
+
 private:
     class MCRec;
 
@@ -1113,6 +1135,7 @@ private:
 
     SkBounder*  fBounder;
     int         fSaveLayerCount;    // number of successful saveLayer calls
+    int         fCullCount;         // number of active culls
 
     SkMetaData* fMetaData;