This method is only useful to OpenAlias plug-ins. You should call it whenever a change has been made to a model or a window. However, it could be expensive to use, so you might use it only after completing all necessary changes. For example, a plug-in might project several curves on to a surface and then trim the surface. You could call AlUniverse::redrawScreen() after each projection and after the trim: that would create an interesting visual effect as each curve appears on the surface. Alternatively, if you prefer speed over the visual effects, you might call AlUniverse::redrawScreen() only after trimming is complete.

If you do not use AlUniverse::redrawScreen(), the display shows out-of-date images of the data.

You can improve performance by postponing screen updates until all objects have been updated. The developer can implement this speed-up by using AlUniverse::doUpdates().