Hi, Petr.
On 23.12.2013 16:54, Petr Pchelko wrote:
The problem:
nativeSyncQueue synchronizes the native event queue. However, there are several
situations when a dummy event posted to the native queue is not dispatched.
These are our own nested loop in doAWTRunLoop and Cocoa's internal nested loop
in NSView:dragImage.
As I remember doAWTRunLoop process events and selectors in case of
drags/DnD otherwise how we got mouse events? Or I have missed something?
Solution:
1. The interruptNativeSyncQueue was introduced. In case we are waiting for the
native event queue this method interrupts waiting, otherwise it's a no-op. This
is needed for the following reason: suppose the nativeSyncQueue is called on
EDT. While the queue is flushed some event was processed which caused us to
call doAWTRunLoop. As EDT is blocked we would have got a deadlock. Interrupting
the wait lets EDT flush it's events and lets AppKit exit a nested loop. When
the nativeSyncQueue is interrupted we do not immediately exit realSync, but
flush EDT and try to sync native queue again. Most likely in this case we would
not be in a nested loop and will successfully sync a native queue.
2. A lightweight version of nativeSyncQueue was introduced. This one does not
flush the event queue, it only flushes a selector queue. This is needed to not
deadlock when realSync was called during DnD. Suppose nativeSyncQueue is called
while the app is in the native nested dragging loop. Until dragging operation
finishes only dragging-related events will be processed. So we have no
opportunity to flush the queue as our dummy event will be blocked by a dragging
nested loop.
I've tested it by running almost all awt and swing tests. No new failures, some
tests start to pass after the fix.
With best regards. Petr.
--
Best regards, Sergey.
