This appears to be because Cocoa locks any drawing to the confines of your canvas until your return from your event - as such, although you may perform actions on other gadgets, they will not be redrawn at all (as they are outside the clipping region of the screen). Short of redrawing all other windows when returning from EVENT_GADGETPAINT, there isn't much MaxGUI can do about this as this is by Cocoa's design.
As such, it should probably be written in the docs that EVENT_GADGETPAINT should only be used to paint the concerned canvas and actions on other gadgets shouldn't be performed when repsonding to this event using hooks.
As such, it should probably be written in the docs that EVENT_GADGETPAINT should only be used to paint the concerned canvas and actions on other gadgets shouldn't be performed when repsonding to this event using hooks.