You may have noticed that the drag feedback is rather sad-looking.
Just a box, maybe with a plus sign or an arrow; you don't
even know what it is you're dragging.
Let's fix that. We'll drag the icon of the file around.
We'll need to add the drag image to the data object.
void OnLButtonDown(HWND hwnd, BOOL fDoubleClick, int x, int y, UINT...