The source file SimpleViewerImpl.mesa demonstrates a simple but expandable use of the viewers software. Of note are calls on ViewerOps.RegisterViewerClass to create a new class of viewer, ViewerClasses.NotifyProc to handle mouse input, and ViewerClasses.PaintProc to repaint the viewer.

SimpleViewer provides interactive movement of a rectangle in a viewer in response to a mouse action within the viewer. The rectangle moves only if the left mouse is down; the rectangle will jump to the current mouse position if Control-J is typed. The current time will be printed in the message window if Control-T is typed.

This program requires the name of a tip table as sole argument. It creates a viewer within which mouse actions are reported by printing at the current mouse location the list of atoms produced by the TIP mechanism for the given .tip file.