The author appears to credit the X Window System or Microsoft Windows with repaint-on-expose. To my knowledge that was first implemented (along with regions) by

The author appears to credit the X Window System or Microsoft Windows with repaint-on-expose. To my knowledge that was first implemented (along with regions) by Bill Atkinson for the Apple Lisa, because he misremembered what he saw on the visit to PARC; overlapped windows in the PARC systems at the time didn't automatically and efficiently repaint only the affected area.