I am not familiar with fisicalab and may have not understood your question correctly, but are you certain that you need to use the -mouseMoved method? The following demo seems to work correctly on my system:
-(void)drawRect:(NSRect)rect { // ****** Background ***** // [[NSColor whiteColor] set]; [NSBezierPath fillRect:rect]; } // ----- Use this if you want 0,0 (origin) to be top, left ---- // // ----- Otherwise origin will be at bottom, left (Unflipped) ----- // -(BOOL)isFlipped { return YES; } @end //implementation