XGrabKey questions

[Peter Hutterer]

Wang Baisheng wrote:
>>
>>> 	First, for params keyboard_mode, the man page says "If the keyboard_mode
>>> argument is GrabModeAsync, keyboard event processing continues as usual",
>>> but when I write some code like, "   XGrabKey(display,
>>> XKeysymToKeycode(display, XK_d), 0, rootWindow, True, GrabModeAsync,
>>> GrabModeAsync);", the focus application can not receive any key d press
>>> event.
>> this is correct. you told the x server to deliver any d press that
>> happens on the root window (== every press) to you. No matter who has
>> the focus.
>>
>> grabs work top down (checking the root window first for grabs). event
>> delivery works bottom up (checking focus window first for delivery).
>> This is an important distinction.
> 
> You mean that if I use the parameter GrabModeAsync, the x server only deliver 
> the d press to the root window and then do not deliver it to the focus 
> window. 
> And if I want to let the focus window receive the d press event I have to send 
> the d press event manually when the root window receive the d press event.

yep. if you use GrabModeSync, the server stores the event in the device, 
  and replays it on the next window down when you call 
XAllowEvent(ReplayKeyboard).

>>>  And the man page says "Actual keyboard changes are not lost while the
>>> keyboard is frozen; they are simply queued in the server for later
>>> processing", but after I receive the key press event, I call
>>> XAllowEvents, but I can not receive any KeyRelease event, why ?
>> you can't XAllowEvents if you don't freeze the device. so it's either
>> GrabModeAsync or XAllowEvents.
> 
> Yes. I passed GrabModeSync to the XGrabKey. After I receive the key press 
> event, I call XAllowEvents but I can not receive any KeyRelease event.

Well, here's the problem. When you call XAllowEvent(ReplayKeyboard), you 
also release the grab. So the release event is sent to the focus window, 
not to your grabbing client.

Cheers,
   Peter