gsm: Fix race condition in idle monitor

In _xsync_alarm_set(), the positive and negative transition intervals
are set to the same value. However, the SYNC extension defines the
positive transition as set when the counter goes from strictly below the
threshold to greater than or equal to the threshold and similarly a
negative transition is triggered when the counter goes form strictly
greater than the threshold to less than or equal to the threshold.

Thus in the current set up there's a chance that the positive transition
can trigger, marking the session as idle, and some user input occur on
the same click so the IDLETIME count will hit the threshold but not go
above so the negative transition will not trigger. Thus the session will
not be marked as active.

The negative transition threshold should be set to 1ms less than the
positive transition to ensure that it always fires.

Based on gnome-session commit: 861313503a741f0129611ca005cf6d7c27124b54
From: Christopher Halse Rogers <[email protected]>
Gnome bug: https://bugzilla.gnome.org/show_bug.cgi?id=627903

1 files changed, 1 insertions, 0 deletions

diff --git a/mate-session/gs-idle-monitor.c b/mate-session/gs-idle-monitor.c
index e2d51f0..7d56ac0 100644
--- a/mate-session/gs-idle-monitor.c
+++ b/mate-session/gs-idle-monitor.c
@@ -448,6 +448,7 @@ _xsync_alarm_set (GSIdleMonitor      *monitor,
         attr.delta = delta;
         attr.events = TRUE;
 
+        attr.trigger.wait_value = _int64_to_xsyncvalue (_xsyncvalue_to_int64 (watch->interval) - 1);
         attr.trigger.test_type = XSyncPositiveTransition;
         if (watch->xalarm_positive != None) {
                 g_debug ("GSIdleMonitor: updating alarm for positive transition wait=%ld",