info-mac@uw-beaver (12/15/84)
From: apope@bbn-labs-b.arpa Kato.SV had some questions about InvalRect. Here's what Inside Mac tells us about it: InvalRect is a Window Manager procedure that marks a rectangular portion of a window as requiring redrawing. A call to InvalRect has no immediate effect on the screen--it simply precipitates a subsequent update event for the window. In response to that update event, your code should redraw the invalid portion of the window. (For simplicity, you might just redraw the entire window; your QuickDraw calls will be clipped to the region you previously marked as invalid by InvalRect and InvalRgn calls. Make sure you use BeginUpdate and EndUpdate.) The Window Manager has a hook--a global variable called paintWhite--that controls whether or not it paints the invalid portion of the window white just before generating the update event. In the normal case, this painting is done. ...Art Pope, BBN Labs Inc.