Make SkImageGenerator::getPixels() return an enum.

include/core/SkImageGenerator.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 SkImageGenerator_DEFINED
 #define SkImageGenerator_DEFINED
 
 #include "SkColor.h"
 #include "SkImageInfo.h"
 
 class SkBitmap;
 class SkData;
 class SkImageGenerator;
 
+//#define SK_SUPPORT_LEGACY_IMAGE_GENERATOR_RETURN
+
 /**
  *  Takes ownership of SkImageGenerator.  If this method fails for
  *  whatever reason, it will return false and immediatetely delete
  *  the generator.  If it succeeds, it will modify destination
  *  bitmap.
  *
  *  If generator is NULL, will safely return false.
  *
  *  If this fails or when the SkDiscardablePixelRef that is
  *  installed into destination is destroyed, it will call
@@ skipping 10 matching lines @@
 /**
  *  On success, installs a discardable pixelref into destination, based on encoded data.
  *  Regardless of success or failure, the caller must still balance their ownership of encoded.
  */
 SK_API bool SkInstallDiscardablePixelRef(SkData* encoded, SkBitmap* destination);
 
 /**
  *  An interface that allows a purgeable PixelRef (such as a
  *  SkDiscardablePixelRef) to decode and re-decode an image as needed.
  */
-class SK_API SkImageGenerator {
+class SK_API SkImageGenerator : public SkNoncopyable {
 public:
     /**
      *  The PixelRef which takes ownership of this SkImageGenerator
      *  will call the image generator's destructor.
      */
     virtual ~SkImageGenerator() { }
 
     /**
      *  Return a ref to the encoded (i.e. compressed) representation,
      *  of this data.
      *
      *  If non-NULL is returned, the caller is responsible for calling
      *  unref() on the data when it is finished.
      */
     SkData* refEncodedData() { return this->onRefEncodedData(); }
 
     /**
      *  Return some information about the image, allowing the owner of
      *  this object to allocate pixels.
      *
      *  Repeated calls to this function should give the same results,
      *  allowing the PixelRef to be immutable.
      *
      *  @return false if anything goes wrong.
      */
     bool getInfo(SkImageInfo* info);
 
     /**
+     *  Used to describe the result of a call to getPixels().
+     *
+     *  Result is the union of possible results from subclasses.
+     */
+    enum Result {
+        /**
+         *  General return value for success.
+         */
+        kSuccess,
+        /**
+         *  The input is incomplete. A partial image was generated.
+         */
+        kIncompleteInput,
+        /**
+         *  The generator cannot convert to match the request, ignoring
+         *  dimensions.
+         */
+        kInvalidConversion,
+        /**
+         *  The generator cannot scale to requested size.
+         */
+        kInvalidScale,
+        /**
+         *  Parameters (besides info) are invalid. e.g. NULL pixels, rowBytes
+         *  too small, etc.
+         */
+        kInvalidParameters,
+        /**
+         *  The input did not contain a valid image.
+         */
+        kInvalidInput,
+        /**
+         *  Fulfilling this request requires rewinding the input, which is not
+         *  supported for this input.
+         */
+        kCouldNotRewind,
+        /**
+         *  This method is not implemented by this generator.
+         */
+        kUnimplemented,
+    };
+
+    /**
      *  Decode into the given pixels, a block of memory of size at
      *  least (info.fHeight - 1) * rowBytes + (info.fWidth *
      *  bytesPerPixel)
      *
      *  Repeated calls to this function should give the same results,
      *  allowing the PixelRef to be immutable.
      *
      *  @param info A description of the format (config, size)
      *         expected by the caller.  This can simply be identical
      *         to the info returned by getInfo().
      *
      *         This contract also allows the caller to specify
      *         different output-configs, which the implementation can
      *         decide to support or not.
      *
+     *         A size that does not match getInfo() implies a request
+     *         to scale. If the generator cannot perform this scale,
+     *         it will return kInvalidScale.
+     *
      *  If info is kIndex8_SkColorType, then the caller must provide storage for up to 256
      *  SkPMColor values in ctable. On success the generator must copy N colors into that storage,
      *  (where N is the logical number of table entries) and set ctableCount to N.
      *
      *  If info is not kIndex8_SkColorType, then the last two parameters may be NULL. If ctableCount
      *  is not null, it will be set to 0.
      *
-     *  @return false if anything goes wrong or if the image info is
-     *          unsupported.
+     *  @return Result kSuccess, or another value explaining the type of failure.
      */
-    bool getPixels(const SkImageInfo& info, void* pixels, size_t rowBytes,
-                   SkPMColor ctable[], int* ctableCount);
+    Result getPixels(const SkImageInfo& info, void* pixels, size_t rowBytes,
+                     SkPMColor ctable[], int* ctableCount);
 
     /**
      *  Simplified version of getPixels() that asserts that info is NOT kIndex8_SkColorType.
      */
-    bool getPixels(const SkImageInfo& info, void* pixels, size_t rowBytes);
+    Result getPixels(const SkImageInfo& info, void* pixels, size_t rowBytes);
 
     /**
      *  If planes or rowBytes is NULL or if any entry in planes is NULL or if any entry in rowBytes
      *  is 0, this imagegenerator should output the sizes and return true if it can efficiently
      *  return YUV planar data. If it cannot, it should return false. Note that either planes and
      *  rowBytes are both fully defined and non NULL/non 0 or they are both NULL or have NULL or 0
      *  entries only. Having only partial planes/rowBytes information is not supported.
      *
      *  If all planes and rowBytes entries are non NULL or non 0, then it should copy the
      *  associated YUV data into those planes of memory supplied by the caller. It should validate
      *  that the sizes match what it expected. If the sizes do not match, it should return false.
      */
     bool getYUV8Planes(SkISize sizes[3], void* planes[3], size_t rowBytes[3],
                        SkYUVColorSpace* colorSpace);
 
     /**
      *  If the default image decoder system can interpret the specified (encoded) data, then
      *  this returns a new ImageGenerator for it. Otherwise this returns NULL. Either way
      *  the caller is still responsible for managing their ownership of the data.
      */
     static SkImageGenerator* NewFromData(SkData*);
 
 protected:
     virtual SkData* onRefEncodedData();
     virtual bool onGetInfo(SkImageInfo* info);
+#ifdef SK_SUPPORT_LEGACY_IMAGE_GENERATOR_RETURN
     virtual bool onGetPixels(const SkImageInfo& info,
                              void* pixels, size_t rowBytes,
                              SkPMColor ctable[], int* ctableCount);
+#endif
+    // TODO (scroggo): rename to onGetPixels.
+    virtual Result onGetPixelsEnum(const SkImageInfo& info,
+                                   void* pixels, size_t rowBytes,
+                                   SkPMColor ctable[], int* ctableCount);
     virtual bool onGetYUV8Planes(SkISize sizes[3], void* planes[3], size_t rowBytes[3]);
     virtual bool onGetYUV8Planes(SkISize sizes[3], void* planes[3], size_t rowBytes[3],
                                  SkYUVColorSpace* colorSpace);
 };
 
 #endif  // SkImageGenerator_DEFINED