Sets the default mouse pointer for a `GdkSurface`.
Passing null for the cursor argument means that this
will use the cursor of its parent surface. Most surfaces should use this default. Note that cursor must be for the same
display as this.
Use [ctor@Gdk.Cursor.new_from_name] or [ctor@Gdk.Cursor.new_from_texture] to create the cursor. To make the cursor invisible, use gdk_blank_cursor.
| this |
a `GdkSurface` |
| cursor |
a `GdkCursor` |