[mutter] MetaIdleMonitor: fire immediately watches that are already expired

[Giovanni Campagna <gcampagna src gnome org>]

commit 2fc9e1af58cd344d0c12c3a05365f52894e18b03
Author: Giovanni Campagna <gcampagn redhat com>
Date:   Mon Sep 16 14:27:08 2013 +0200

    MetaIdleMonitor: fire immediately watches that are already expired
    
    The XSync semantics mandate that alarms already expired will not
    fire until the counter is reset and the alarm triggered again, so
    clients traditionally called get_idle_time() first to see if they
    should install the alarm.
    This is inherently racy, as by the time the call is handled by
    mutter and the reply received the idle time could be different.
    Instead, if we see that the watch would have fired in the past,
    fire it immediately.
    
    This is a behavior change, but it's a compatible one, as all legacy
    clients are calling get_idle_time() first, and it was perfectly
    possible for the idle time counter to trigger the alarm right
    after the get_idle_time() call.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=707302

 src/core/meta-idle-monitor.c |   29 ++++++++++++++++++++++++++++-
 1 files changed, 28 insertions(+), 1 deletions(-)
---
diff --git a/src/core/meta-idle-monitor.c b/src/core/meta-idle-monitor.c
index 00b6ddb..d351e65 100644
--- a/src/core/meta-idle-monitor.c
+++ b/src/core/meta-idle-monitor.c
@@ -74,7 +74,8 @@ typedef struct
   guint64                   timeout_msec;
 
   /* x11 */
-  XSyncAlarm               xalarm;
+  XSyncAlarm                xalarm;
+  int                       idle_source_id;
 } MetaIdleMonitorWatch;
 
 enum
@@ -110,6 +111,12 @@ fire_watch (MetaIdleMonitorWatch *watch)
   monitor = watch->monitor;
   g_object_ref (monitor);
 
+  if (watch->idle_source_id)
+    {
+      g_source_remove (watch->idle_source_id);
+      watch->idle_source_id = 0;
+    }
+
   id = watch->id;
   is_user_active_watch = (watch->timeout_msec == 0);
 
@@ -281,6 +288,12 @@ idle_monitor_watch_free (MetaIdleMonitorWatch *watch)
 
   monitor = watch->monitor;
 
+  if (watch->idle_source_id)
+    {
+      g_source_remove (watch->idle_source_id);
+      watch->idle_source_id = 0;
+    }
+
   if (watch->notify != NULL)
     watch->notify (watch->user_data);
 
@@ -449,6 +462,17 @@ meta_idle_monitor_get_for_device (int device_id)
   return device_monitors[device_id];
 }
 
+static gboolean
+fire_watch_idle (gpointer data)
+{
+  MetaIdleMonitorWatch *watch = data;
+
+  watch->idle_source_id = 0;
+  fire_watch (watch);
+
+  return FALSE;
+}
+
 static MetaIdleMonitorWatch *
 make_watch (MetaIdleMonitor           *monitor,
             guint64                    timeout_msec,
@@ -471,6 +495,9 @@ make_watch (MetaIdleMonitor           *monitor,
       watch->xalarm = _xsync_alarm_set (monitor, XSyncPositiveTransition, timeout_msec, TRUE);
 
       g_hash_table_add (monitor->alarms, (gpointer) watch->xalarm);
+
+      if (meta_idle_monitor_get_idletime (monitor) > (gint64)timeout_msec)
+        watch->idle_source_id = g_idle_add (fire_watch_idle, watch);
     }
   else
     {