Top level graphic graphics statements are so called because they ignore layering, and always appear on top of all layered graphics. They can produce dynamic results on the screen. Top level graphics cannot be produced from the graphics toolbox, since they require care and planning in their use. They are primarily available for backward compatibility to previous versions of VTS.
As the parameters of a graphic statement change their values, the corresponding image changes on the screen accordingly. For example, the statement :
Bar(0, 0, XLoc(), YLoc(), 15, 1, 0);
will produce a solid white bar on the screen. One corner of the bar will be located at the top left corner (0,0). The other corner of the bar will be located at the coordinates (XLoc( ), YLoc( )). These are the coordinates of the mouse cursor. If the mouse moves, the corner of the bar will track the mouse position. Any of the parameters may be made dynamic in a similar manner. The parameters of the statement may be any expression, including ones that depend upon a variable which is read from the plant input devices. This is the technique used to animate the display.
The images produced by graphic statements are removed from the screen when the state containing those statements is stopped. In the previous example, the white bar would disappear from the screen as soon as the state containing the Bar statement was stopped.