Use a GCD-queue

[rastersize]

Possibly use a serial GCD-queue instead of the current callback function.

[tonyxiao]

What would be the benefit of using GCD queue?

[rastersize]

The thinking when I created this issue was primarily to not worry about blocking whoever is calling the current callback function. I.e. allowing it (CDEventsCallback(…)) to return almost instantaneously instead of as now, where it loops through the possibly large list of events, after quite some time.