initial checkin for experimenting

src/core/SkCanvasDrawable.h

+/*
+ * Copyright 2014 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkCanvasDrawable_DEFINED
+#define SkCanvasDrawable_DEFINED
+
+#include "SkRefCnt.h"
+
+class SkCanvas;
+struct SkRect;
+
+/**
+ *  Base-class to capture a set of drawing commands (sent to SkCanvas). Instances of this class
+ *  need not be thread-safe, but they must be able to be used in a thread different from where
+ *  they were created.
+ */
+class SkCanvasDrawable : public SkRefCnt {
+public:
+    SkCanvasDrawable();
+
+    /**
+     *  Draws into the specified content. The drawing sequence will be balanced upon return
+     *  (i.e. the saveLevel() on the canvas will match what it was when draw() was called,
+     *  and the current matrix and clip settings will not be changed.
+     */
+    void draw(SkCanvas*);
+
+    /**
+     *  Return a unique value for this instance. If two calls to this return the same value,
+     *  it is presumed that calling the draw() method will render the same thing as well.
+     *
+     *  Subclasses that change their state should call notifyDrawingChanged() to ensure that
+     *  a new value will be returned the next time it is called.
+     */
+    uint32_t getGenerationID();
+
+    /**
+     *  If the drawable knows a bounds that will contains all of its drawing, return true and
+     *  set the parameter to that rectangle. If one is not known, ignore the parameter and
+     *  return false.
+     */
+    bool getBounds(SkRect*);
+
+    void notifyDrawingChanged();
+
+protected:
+    virtual void onDraw(SkCanvas*) = 0;
+
+    virtual bool onGetBounds(SkRect*) { return false; }
+
+private:
+    int32_t fGenerationID;
+};
+
+#endif