Returns the icon used to represent the window. The window's icon may be shown in the title bar, the task bar, or a task manager. An icon can be set by calling set_icon() or set_icon_list() .
If a list of icons was set using set_icon_list() , this method will return the first icon in the list.
By default a window does not have an icon. If no icon was set, this method will return null.
See also: set_icon() , set_icon_list() , get_icon_list()