A control defines the way mouse and keyboard act on a window or an object. It can also be associated to a toolbox (regions of interest drawing for example). According to the type of objects contained in the window, some action modes can be disabled. For example, the selection mode has no effect on a volume because there are no areas to select on a volume. But you can select areas in a ROI graph (graph nodes).

Note : some controls are available only on selected objects. You can select objects in a window via the right click menu view / select objects.