So after a few weeks, I came to the following results:
A) Proxy window:
Make use of a non layer-backed proxy window, which is placed on top of the target window as a child window. The proxy window has the same shape, as the target window, and since it is not layer-backed, it will properly receive and ignore events. The proxy window delegates all events to the target window by overwriting sendEvent:
. The target window is set to ignore all mouse events.
B) Global Mouse Pointer observation:
Install both a global and local event monitor for NSMouseMovedMask|NSLeftMouseDraggedMask
events using addGlobalMonitorForEventsMatchingMask
and addLocalMonitorForEventsMatchingMask
. The event monitors disable and enable ignoring mouse events on all registered target windows based on the current global mouse position. In the case of circular windows, the distance between the mouse pointer and every target window must be calculated.
Both approaches work well in generally, but I've been experiencing some unpredictable misbehaviors of the child window approach (where the child window is 'out-of-sync' of its parent's position).
UPDATE: Both approaches have some significant disadvantages: In A), the proxy window sometimes may be out of sync and may be placed slightly off the actual window.
In B), the event monitor has a big impact on battery life while moving the mouse, even if the app is not the front-most application.