Retrieves a `GdkCursor` pointer for the device currently set on the specified `GdkSurface`.
If the return value is null then there is no custom cursor set on the specified surface, and it is using the cursor for its parent surface.
Use [method@Gdk.Surface.set_cursor] to unset the cursor of the surface.
| this |
a `GdkSurface` |
| device |
a pointer `GdkDevice` |
|
a `GdkCursor` |