allow imagefilter to manage CTM decomposition

include/core/SkImageFilter.h

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkImageFilter_DEFINED
 #define SkImageFilter_DEFINED
 
@@ skipping 198 matching lines @@
      */
     sk_sp<SkImageFilter> makeWithLocalMatrix(const SkMatrix&) const;
 
 #ifdef SK_SUPPORT_LEGACY_IMAGEFILTER_PTR
     SkImageFilter* newWithLocalMatrix(const SkMatrix& matrix) const {
         return this->makeWithLocalMatrix(matrix).release();
     }
 #endif
 
     /**
+     *  ImageFilters can natively handle scaling and translate components in the CTM. Only some of
+     *  them can handle affine (or more complex) matrices. This call returns true iff the filter
+     *  and all of its (non-null) inputs can handle these more complex matrices.
+     */
+    bool canHandleAffine() const { return this->onCanHandleAffine(); }

[Stephen White, 2016/04/25 14:09:34]

<bikeshed> Could we add a noun to that? canHandleAffineMatrix() or
canHandleAffineTransforms()? </bikeshed>

+
+    /**
      * Return an imagefilter which transforms its input by the given matrix.
      */
     static sk_sp<SkImageFilter> MakeMatrixFilter(const SkMatrix& matrix,
                                                  SkFilterQuality quality,
                                                  sk_sp<SkImageFilter> input);
 
 #ifdef SK_SUPPORT_LEGACY_IMAGEFILTER_PTR
     static SkImageFilter* CreateMatrixFilter(const SkMatrix& matrix,
                                              SkFilterQuality filterQuality,
                                              SkImageFilter* input = nullptr) {
@@ skipping 106 matching lines @@
                                       SkIPoint* offset) const;
 
     /**
      *  Return true (and return a ref'd colorfilter) if this node in the DAG is just a
      *  colorfilter w/o CropRect constraints.
      */
     virtual bool onIsColorFilterNode(SkColorFilter** /*filterPtr*/) const {
         return false;
     }
 
+    virtual bool onCanHandleAffine() const;
+
     /** Given a "srcBounds" rect, computes destination bounds for this filter.
      *  "dstBounds" are computed by transforming the crop rect by the context's
      *  CTM, applying it to the initial bounds, and intersecting the result with
      *  the context's clip bounds.  "srcBounds" (if non-null) are computed by
      *  intersecting the initial bounds with "dstBounds", to ensure that we never
      *  sample outside of the crop rect (this restriction may be relaxed in the
      *  future).
      */
     bool applyCropRect(const Context&, const SkIRect& srcBounds, SkIRect* dstBounds) const;
 
@@ skipping 41 matching lines @@
  */
 #define SK_IMAGEFILTER_UNFLATTEN_COMMON(localVar, expectedCount)    \
     Common localVar;                                                \
     do {                                                            \
         if (!localVar.unflatten(buffer, expectedCount)) {           \
             return NULL;                                            \
         }                                                           \
     } while (0)
 
 #endif