The debug function takes an optional Boolean argument:
$text->debug( [ boolean ] );
If the value passed in is true, internal consistency checks will be turned on in the B-tree code associated with Text widgets. If false, the checks will be left off. Without any argument, the debug method will return the value "on" if it has been turned on and "off" if not. All text widgets in the application share the same debug flag.
scanDragto also takes (x, y) coordinates, which are compared to the scanMark (x, y) coordinates. The view within the Text widget is adjusted by 10 times the difference between the coordinates: