The 'onPaint' callback

Event number: 9
Generated for: Any visible object
Synonym: onDraw

Normally, APL takes care of all drawing and updating of an object on the screen. However, the onPaint callback can be used to supplement (or even to replace) the default drawing method for given object. It is invoked whenever the object needs to be redrawn for any reason (for example, if a property has been changed, or if the window was previously obscured and now has been uncovered).