Interactivity mode is a new feature of the Teigha graphics system . It allows for automatic interruption of the drawing process if the process is taking a long time. Of course in this case the drawing will not be drawn completely, but this feature can be useful for multiple consecutive redraws when the result of the intermediate redraw is not so important.
Complex graphic scenes with a large number of elements are sometimes drawn slowly. In this case, dynamic graphic elements (such as cursors, grip/snap points, selection rectangles, user interface elements, and so on) are drawn slowly too because to correctly combine graphic scenes and dynamic graphic elements, the renderer must redraw all underlying scene elements.