SPMediaKeyTap breaks OmniPlan.

[tbunch]

OmniPlan relies on being receiving events matching mask:

NSLeftMouseDraggedMask | NSLeftMouseUpMask | NSOtherMouseDown | NSOtherMouseUp | NSFlagsChangedMask | NSPeriodicMask | NSSystemDefinedMask

with type NSSystemDefined and subtype 7

From user reports, it sounds as if Spotify is intercepting these events. I'll look at your source and see if I can't figure out why this is happening, since it sounds as though these are not events you're trying to intercept and block.

[tbunch]

I think I have to transfer blame to Apple for this. If I install a trivial event tap whose even callback always just returns the input, suddenly I'm other apps are getting NSSystemDefined events with subtype 7, data1=1, data2=1 that weren't there before.

Just for edification purposes, if you write your own tracking loop and expect to exit on mouseUp, you'll find that when Exposé is triggered you won't ever get your mouseUp and you'll be stuck in the loop. The only way I know of to get this is too look for NSSystemDefined events of subtype 7 and exit the loop. So suddenly when Spotify is installed everyone's mouse tracking loops immediately exit.

So really the bug is against Apple and Exposé I think.