Fixed in r21160.

DisplayableManagers can not observe events directly on the Interactor instead of the InteractorStyle. The InteractorStyle was swallowing the LeftButtonPressEvent which the Crosshair navigation mode needed.

Added priorities to events in DisplayableManagers.

Added Abort flag to events on the Interactor for the DisplayableManagers.

Tested with r21181, both issues appear to be unresolved, or maybe I am missing something, see screencast here: http://www.screencast.com/t/yYxDSKuhtHw

r21165 breaks the fix in r21160.

r21165 was introduced to fix a crash in the 3D Viewer introduced in r21160.

r21165 look harmless. Not sure why it breaks r21160.

Fixed (again) in r21186.

Moved the fix in r21165 down a couple of lines. For some reason, this makes a difference. In both configurations, the events registered by AdditionalInitializeStep() are cached until later in the setup. So it shouldn't make a difference. But somehow, having the interactor cached early, causes the events registered in AdditionalInitializeStep() to be lost.

"git bisect" ROCKS!

Jim, I tested this, and it looks like it depends on how fast I move
the mouse whether I will see the crosshair in the other slices or not.
Looks like the most reliable is to use navigation mode, in which case
it syncs everything pretty well.

Also, at least for my main use case of crosshairs, all slice viewers
are showing the same slice location, so there is no need to change
slice and crosshair will work as expected, so as far as I am
concerned, the issue is resolved. Thank you!