Main thread checks

PSPDFRuntime.mm

PSPDF_EXTERN BOOL PSPDFIsMainThread(void) {
    // dispatch_get_current_queue is deprecated because most of the time it's not a good idea to call it.
    // NSThread.isMainThread simply calls pthread_main_np so we can save a bit if we call it directly.
    PSPDF_DEPRECATED_NOWARN(return pthread_main_np() || dispatch_get_current_queue() == dispatch_get_main_queue();)

It is my impression this check does no more good than NSThread.isMainThread.

If pthread_main_np returns false, then the second will always be false as well because that queue only runs in the main thread.
on the other hand, If pthread_main_np returns false, the second condition will never run.

And what do you think about this kind of condition:

dispatch_queue_get_label(dispatch_get_main_queue()) == dispatch_queue_get_label(DISPATCH_CURRENT_QUEUE_LABEL)