Ensure that the drag image during drag drop operations on Windows is of the correct scale.

ui/base/dragdrop/drag_utils_win.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/base/dragdrop/drag_utils.h"
 
 #include <objidl.h>
 #include <shlobj.h>
 #include <shobjidl.h>
 
 #include "base/win/scoped_comptr.h"
 #include "base/win/scoped_hdc.h"
 #include "third_party/skia/include/core/SkBitmap.h"
 #include "ui/base/dragdrop/os_exchange_data.h"
 #include "ui/base/dragdrop/os_exchange_data_provider_win.h"
 #include "ui/gfx/canvas.h"
 #include "ui/gfx/gdi_util.h"
 #include "ui/gfx/geometry/size.h"
 #include "ui/gfx/image/image_skia.h"
 #include "ui/gfx/skbitmap_operations.h"
+#include "ui/gfx/win/dpi.h"
 
 namespace drag_utils {
 
 static void SetDragImageOnDataObject(HBITMAP hbitmap,
                                      const gfx::Size& size_in_pixels,
                                      const gfx::Vector2d& cursor_offset,
                                      IDataObject* data_object) {
   base::win::ScopedComPtr<IDragSourceHelper> helper;
   HRESULT rv = CoCreateInstance(CLSID_DragDropHelper, 0, CLSCTX_INPROC_SERVER,
                                 IID_IDragSourceHelper, helper.ReceiveVoid());
@@ skipping 20 matching lines @@
   if (!bitmap || !bits)
     return NULL;
   DCHECK_EQ(sk_bitmap.rowBytes(), static_cast<size_t>(sk_bitmap.width() * 4));
   SkAutoLockPixels lock(sk_bitmap);
   memcpy(
       bits, sk_bitmap.getPixels(), sk_bitmap.height() * sk_bitmap.rowBytes());
   return bitmap;
 }
 
 void SetDragImageOnDataObject(const gfx::ImageSkia& image_skia,
                               const gfx::Vector2d& cursor_offset,

[sky, 2015/11/25 23:38:43]

I suspect you need to adjust cursor_offset too.

[ananta, 2015/12/01 02:42:28]

Done.

                               ui::OSExchangeData* data_object) {
   DCHECK(data_object && !image_skia.size().IsEmpty());
+
+  // Attempt to find a bitmap closely matching the current dpi scale.
+  gfx::ImageSkiaRep image_rep_for_scale = image_skia.GetRepresentation(
+      gfx::GetDPIScale());
+
   // InitializeFromBitmap() doesn't expect an alpha channel and is confused
   // by premultiplied colors, so unpremultiply the bitmap.
   // SetDragImageOnDataObject(HBITMAP) takes ownership of the bitmap.
-  HBITMAP bitmap = CreateHBITMAPFromSkBitmap(
-      SkBitmapOperations::UnPreMultiply(*image_skia.bitmap()));
+  HBITMAP bitmap = CreateHBITMAPFromSkBitmap(SkBitmapOperations::UnPreMultiply(
+      image_rep_for_scale.sk_bitmap()));
   if (bitmap) {
     // Attach 'bitmap' to the data_object.
     SetDragImageOnDataObject(
         bitmap,
         gfx::Size(image_skia.bitmap()->width(), image_skia.bitmap()->height()),
         cursor_offset,
         ui::OSExchangeDataProviderWin::GetIDataObject(*data_object));
   }
 
   // TODO: the above code is used in non-Ash, while below is used in Ash. If we
   // could figure this context out then we wouldn't do unnecessary work. However
   // as it stands getting this information in ui/base would be a layering
   // violation.
   data_object->provider().SetDragImage(image_skia, cursor_offset);
 }
 
 }  // namespace drag_utils