While preparing the stripped down application I figured out that this
has nothing to do with event handling but is indeed a drawing problem.
The stripped down version (subclass of NSView) worked perfectly also
under GNUstep. My ObjectBrowserView was actually a subclass or
NSImageView since I wanted to have a background image. :-) Now this
NSImageView was setup with [_platformObject
setImageScaling:NSScaleToFit]. This turned out to be the problem. After
adding
#ifndef __APPLE__
- (void)setImageScaling:(NSImageScaling)image
{
[super setImageScaling:NSScaleNone];
}
#endif
to my NSImageView subclass the performance problem was gone. Now I have
a rather ugly blue frame around the image but I can at least reasonably
select objects now which is much more important.
On MacOSX (10.2.8) I see no performance problem even with NSScaleToFit.
However, I can live with this solution.