I've found the solution to a long-standing problem, which for example
afflicted users of Sawfish WM. Under certain conditions (in fact during a long
enough sync key/board grab), some keys were repeated:
Explanation:
============
1/ XKB-enabled Xfree86 implements key-repeating in software (w/ timers). When a
hardware Key Release arrives, the software timer is canceled.
2/
Xfree86 implements key(board) grabs in GrabModeSync by switching a pointer
dev->public.processInputProc
to either
dev->public.enqueueInputProc ... events are put in a queue for later processing
or
dev->public.realInputProc
The problem is, that the public.enqueueInputProc (which is EnqueueEvent() in
xc/programs/Xserver/dix/events.c) does not invoke function
AccessXCancelRepeatKey(), which cancels the timer.
So, if during Sync grab, key Release is signalled/read from kernel(hardware), the
timer is not cancelled. Therefore it is run (later), and generates a pair of
Release/Press events, and reschedules itself (so it can result in many incorrect key
events).
Fix:
====
I've made a _quick_ fix, basically adding into the EnqueueEvent():
if (xE->u.u.type==KeyRelease)
AccessXCancelRepeatKey(xkbi,key);
I will continue reviewing the related code, but i'm very new to xfree86 sources,
so others' opinion would help.
Michal Maruska
--
http://maruska.dyndns.org
http://maruska.dyndns.org/comp/
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