images with offset bitmap don't share genid

src/image/SkImage_Raster.cpp

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkImage_Base.h"
 #include "SkBitmap.h"
 #include "SkCanvas.h"
 #include "SkColorTable.h"
 #include "SkData.h"
 #include "SkImagePriv.h"
 #include "SkPixelRef.h"
 #include "SkSurface.h"
 
 #if SK_SUPPORT_GPU
 #include "GrContext.h"
 #include "SkGr.h"
 #include "SkGrPriv.h"
 #endif
 
+// fixes https://bug.skia.org/5096
+static bool is_not_subset(const SkBitmap& bm) {
+    SkASSERT(bm.pixelRef());
+    SkISize dim = bm.pixelRef()->info().dimensions();
+    SkASSERT(dim != bm.dimensions() || bm.pixelRefOrigin().isZero());
+    return dim == bm.dimensions();
+}
+
 class SkImage_Raster : public SkImage_Base {
 public:
     static bool ValidArgs(const Info& info, size_t rowBytes, bool hasColorTable,
                           size_t* minSize) {
         const int maxDimension = SK_MaxS32 >> 2;
 
         if (info.width() <= 0 || info.height() <= 0) {
             return false;
         }
         if (info.width() > maxDimension || info.height() > maxDimension) {
@@ skipping 42 matching lines @@
 
     // exposed for SkSurface_Raster via SkNewImageFromPixelRef
     SkImage_Raster(const SkImageInfo&, SkPixelRef*, const SkIPoint& origin, size_t rowBytes);
 
     SkPixelRef* getPixelRef() const { return fBitmap.pixelRef(); }
 
     bool isOpaque() const override;
     bool onAsLegacyBitmap(SkBitmap*, LegacyBitmapMode) const override;
 
     SkImage_Raster(const SkBitmap& bm)
-        : INHERITED(bm.width(), bm.height(), bm.getGenerationID())
+        : INHERITED(bm.width(), bm.height(),
+                    is_not_subset(bm) ? bm.getGenerationID()
+                                      : (uint32_t)kNeedNewImageUniqueID)
         , fBitmap(bm)
     {
         if (bm.pixelRef()->isPreLocked()) {
             // we only preemptively lock if there is no chance of triggering something expensive
             // like a lazy decode or imagegenerator. PreLocked means it is flat pixels already.
             fBitmap.lockPixels();
         }
         SkASSERT(fBitmap.isImmutable());
     }
 
@@ skipping 182 matching lines @@
         // pixelref since the caller might call setImmutable() themselves
         // (thus changing our state).
         if (fBitmap.isImmutable()) {
             bitmap->setInfo(fBitmap.info(), fBitmap.rowBytes());
             bitmap->setPixelRef(fBitmap.pixelRef(), fBitmap.pixelRefOrigin());
             return true;
         }
     }
     return this->INHERITED::onAsLegacyBitmap(bitmap, mode);
 }