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 {
 
+// The DragDropHelper object on Windows supports images with width upto 300 px.
+// Images with widths more than that are clipped.
+const int kMaxDragImageWidth = 300;
+
 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());
   if (SUCCEEDED(rv)) {
     SHDRAGIMAGE sdi;
     sdi.sizeDragImage = size_in_pixels.ToSIZE();
+    sdi.sizeDragImage.cx =
+        std::min<int>(kMaxDragImageWidth, sdi.sizeDragImage.cx);

[ananta, 2015/12/01 02:47:07]

If the width is more than 300 the bitmap is displayed clipped but is still
better than what we see today. Once the blink fix lands it should be better.

     sdi.crColorKey = 0xFFFFFFFF;
     sdi.hbmpDragImage = hbitmap;
-    sdi.ptOffset = gfx::PointAtOffsetFromOrigin(cursor_offset).ToPOINT();
+    gfx::Point point_at_offset_in_pixels = gfx::win::DIPToScreenPoint(
+        gfx::PointAtOffsetFromOrigin(cursor_offset));
+    sdi.ptOffset = point_at_offset_in_pixels.ToPOINT();
     helper->InitializeFromBitmap(&sdi, data_object);
   }
 }
 
 // Blit the contents of the canvas to a new HBITMAP. It is the caller's
 // responsibility to release the |bits| buffer.
 static HBITMAP CreateHBITMAPFromSkBitmap(const SkBitmap& sk_bitmap) {
   base::win::ScopedGetDC screen_dc(NULL);
   BITMAPINFOHEADER header;
   gfx::CreateBitmapHeader(sk_bitmap.width(), sk_bitmap.height(), &header);
@@ skipping 29 matching lines @@
   }
 
   // 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