detect when we can filter bitmaps/images directly, w/o a tmp layer

include/core/SkDevice.h

 /*
  * Copyright 2010 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkDevice_DEFINED
 #define SkDevice_DEFINED
 
@@ skipping 356 matching lines @@
     }
 
 private:
     friend class SkCanvas;
     friend struct DeviceCM; //for setMatrixClip
     friend class SkDraw;
     friend class SkDrawIter;
     friend class SkDeviceFilteredPaint;
     friend class SkImageFilter::DeviceProxy;
     friend class SkNoPixelsBitmapDevice;
+    friend class SkSurface_Raster;
 
-    friend class SkSurface_Raster;
+    /**
+     *  Will invoke the paint's imagefilter directly on the bitmap, and draw the result.
+     *  Assumes that the caller has previously called canCallFilterSprite().
+     */
+    void filterSprite(const SkDraw&, const SkBitmap&, int x, int y, const SkPaint&);

[Stephen White, 2015/12/04 19:22:51]

Since we're getting rid of drawSprite(), could we just call this filterBitmap(),
so it's not the lone Sprite-related thingy?

Come to think of it, this name is misleading wrt filterImage(), which actually
returns the filtered image (vs. this one, which draws it to the device).

Maybe drawBitmapAsSprite? drawBitmapFast()? fastDrawBitmap()?
drawFilteredBitmap()? (I think I like the last one best, but if there are other
possible optimizations here, maybe drawBitmapFast()?)

[reed1, 2015/12/04 19:33:29]

Agreed, the name is weird.

drawBitmapAsSprite sgtm.

 
     // used to change the backend's pixels (and possibly config/rowbytes)
     // but cannot change the width/height, so there should be no change to
     // any clip information.
     // TODO: move to SkBitmapDevice
     virtual void replaceBitmapBackendForRasterSurface(const SkBitmap&) {}
 
     virtual bool forceConservativeRasterClip() const { return false; }
 
     // just called by SkCanvas when built as a layer
@@ skipping 10 matching lines @@
     SkSurfaceProps fSurfaceProps;
 
 #ifdef SK_DEBUG
     bool        fAttachedToCanvas;
 #endif
 
     typedef SkRefCnt INHERITED;
 };
 
 #endif