add SkImage::newSurface

src/image/SkImage_Base.h

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkImage_Base_DEFINED
 #define SkImage_Base_DEFINED
 
 #include "SkImage.h"
+#include "SkSurface.h"
+
+static SkSurfaceProps copy_or_safe_defaults(const SkSurfaceProps* props) {
+    return props ? *props : SkSurfaceProps(0, kUnknown_SkPixelGeometry);
+}
 
 class SkImage_Base : public SkImage {
 public:
-    SkImage_Base(int width, int height) : INHERITED(width, height) {}
+    SkImage_Base(int width, int height, const SkSurfaceProps* props)
+        : INHERITED(width, height)
+        , fProps(copy_or_safe_defaults(props))
+    {}
+
+    /**
+     *  If the props weren't know at constructor time, call this but only before the image is
+     *  ever released into the wild (since the props field must appear to be immutable).
+     */
+    void initWithProps(const SkSurfaceProps& props) {
+        SkASSERT(this->unique());   // only viewed by one thread
+        SkSurfaceProps* mutableProps = const_cast<SkSurfaceProps*>(&fProps);
+        SkASSERT(mutableProps != &props);   // check for self-assignment
+        mutableProps->~SkSurfaceProps();
+        new (mutableProps) SkSurfaceProps(props);
+    }
+
+    const SkSurfaceProps& props() const { return fProps; }
 
     virtual void onDraw(SkCanvas*, SkScalar x, SkScalar y, const SkPaint*) const = 0;
     virtual void onDrawRect(SkCanvas*, const SkRect* src,
                                   const SkRect& dst, const SkPaint*) const = 0;
+    virtual SkSurface* onNewSurface(const SkImageInfo&, const SkSurfaceProps&) const = 0;
 
     // Default impl calls onDraw
     virtual bool onReadPixels(SkBitmap*, const SkIRect& subset) const;
 
     virtual const void* onPeekPixels(SkImageInfo*, size_t* /*rowBytes*/) const {
         return NULL;
     }
 
     virtual GrTexture* onGetTexture() const { return NULL; }
 
     // return a read-only copy of the pixels. We promise to not modify them,
     // but only inspect them (or encode them).
     virtual bool getROPixels(SkBitmap*) const { return false; }
 
     virtual SkShader* onNewShader(SkShader::TileMode,
                                   SkShader::TileMode,
                                   const SkMatrix* localMatrix) const { return NULL; };
+
 private:
+    const SkSurfaceProps fProps;
+
     typedef SkImage INHERITED;
 };
 
+static inline SkImage_Base* as_IB(SkImage* image) {
+    return static_cast<SkImage_Base*>(image);
+}
+
+static inline const SkImage_Base* as_IB(const SkImage* image) {
+    return static_cast<const SkImage_Base*>(image);
+}
+
 #endif