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

include/core/SkCanvas.h

 /*
  * Copyright 2006 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 SkCanvas_DEFINED
 #define SkCanvas_DEFINED
 
@@ skipping 1410 matching lines @@
     // only for canvasutils
     const SkRegion& internal_private_getTotalClip() const;
 
     /*
      *  Returns true if drawing the specified rect (or all if it is null) with the specified
      *  paint (or default if null) would overwrite the entire root device of the canvas
      *  (i.e. the canvas' surface if it had one).
      */
     bool wouldOverwriteEntireSurface(const SkRect*, const SkPaint*, ShaderOverrideOpacity) const;
 
+    /**
+     *  Returns true if the paint's imagefilter can be invoked directly, without needed a temp
+     *  layer. This method calls through to the corresponding method on Device, but it also
+     *  checks the clip, as currently the filter can only be invoked directly if the result will
+     *  be clipped to the bounds of the bitmap (or smaller).
+     */
+    bool canCallFilterSprite(const SkRect& bounds, const SkPaint&);

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

I'm wondering why this is defined on SkCanvas. Are there (going to be) public
callers?

[Stephen White, 2015/12/04 19:23:35]

(Ignore this comment.. I see now it's private.)

 
     /*  These maintain a cache of the clip bounds in local coordinates,
         (converted to 2s-compliment if floats are slow).
      */
     mutable SkRect fCachedLocalClipBounds;
     mutable bool   fCachedLocalClipBoundsDirty;
     bool fAllowSoftClip;
     bool fAllowSimplifyClip;
     const bool fConservativeRasterClip;
 
@@ skipping 120 matching lines @@
 
 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