The lower portion of the window contains buttons associated with states. By grabbing this subwindow's ``handle'' (the stippled area at the left) with the mouse, this subwindow can be ``torn off'' and displayed in a separate window. This feature is convenient when there are very many different states, as in the PETSc example in Section Interesting Examples .
The check-boxes selectively turn on and off the display of state rectangles and arrows. This feature can be important when the display gets complicated. The colored rectangles that are labeled with state names are themselves buttons, each of which brings up a histogram window for that particular state.