Centralize decision about whether to do bicubic filtering, and fallbacks to mip, bilerp, or nearest

src/gpu/effects/GrBicubicEffect.h

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrBicubicTextureEffect_DEFINED
 #define GrBicubicTextureEffect_DEFINED
 
@@ skipping 60 matching lines @@
 
     /**
      * Create a Mitchell filter effect with a texture matrix and a domain.
      */
     static GrEffectRef* Create(GrTexture* tex, const SkMatrix& matrix, const SkRect& domain) {
         AutoEffectUnref effect(SkNEW_ARGS(GrBicubicEffect, (tex, gMitchellCoefficients, matrix,
                                                             domain)));
         return CreateEffectRef(effect);
     }
 
+    /**
+     * Determines whether the bicubic effect should be used based on the transformation from the
+     * local coords to the device. Returns true if the bicubic effect should be used. filterMode
+     * is set to appropriate filtering mode to use regardless of the return result (e.g. when this
+     * returns false it may indicate that the best fallback is to use kMipMap, kBilerp, or
+     * kNearest).
+     */
+    static bool ShouldUseBicubic(const SkMatrix& localCoordsToDevice,
+                                 GrTextureParams::FilterMode* filterMode);
+
 private:
     GrBicubicEffect(GrTexture*, const SkScalar coefficients[16],
                     const SkMatrix &matrix, const SkShader::TileMode tileModes[2]);
     GrBicubicEffect(GrTexture*, const SkScalar coefficients[16],
                     const SkMatrix &matrix, const SkRect& domain);
     virtual bool onIsEqual(const GrEffect&) const SK_OVERRIDE;
 
     float           fCoefficients[16];
     GrTextureDomain fDomain;
 
     GR_DECLARE_EFFECT_TEST;
 
     static const SkScalar gMitchellCoefficients[16];
 
     typedef GrSingleTextureEffect INHERITED;
 };
 
 #endif