x11: Allow XTest and core events to reset idletime

Now that we've removed the X11 specific backend of the idle monitor,
add back a cut-down version of it for the explicit purpose of being
told about idle time resets when XTest events are used.

XTest events are usually used by test suites and remote display software
to inject events into an X11 session. We should consider somebody moving
the mouse remotely to be just as "active" as somebody moving it locally.

https://bugzilla.gnome.org/show_bug.cgi?id=705942

src/backends/x11/meta-backend-x11.c

@@ -46,6 +46,7 @@
 #include "display-private.h"
 #include "compositor/compositor-private.h"
 #include "backends/meta-dnd-private.h"
+#include "backends/meta-idle-monitor-private.h"
 
 struct _MetaBackendX11Private
 {
@@ -56,6 +57,8 @@ struct _MetaBackendX11Private
 
   int xsync_event_base;
   int xsync_error_base;
+  XSyncAlarm user_active_alarm;
+  XSyncCounter counter;
 
   int xinput_opcode;
   int xinput_event_base;
@@ -82,6 +85,79 @@ G_DEFINE_TYPE_WITH_CODE (MetaBackendX11, meta_backend_x11, META_TYPE_BACKEND,
                          G_IMPLEMENT_INTERFACE (G_TYPE_INITABLE,
                                                 initable_iface_init));
 
+
+static void
+uint64_to_xsync_value (uint64_t    value,
+                       XSyncValue *xsync_value)
+{
+  XSyncIntsToValue (xsync_value, value & 0xffffffff, value >> 32);
+}
+
+static XSyncAlarm
+xsync_user_active_alarm_set (MetaBackendX11Private *priv)
+{
+  XSyncAlarmAttributes attr;
+  XSyncValue delta;
+  unsigned long flags;
+
+  flags = (XSyncCACounter | XSyncCAValueType | XSyncCATestType |
+           XSyncCAValue | XSyncCADelta | XSyncCAEvents);
+
+  XSyncIntToValue (&delta, 0);
+  attr.trigger.counter = priv->counter;
+  attr.trigger.value_type = XSyncAbsolute;
+  attr.delta = delta;
+  attr.events = TRUE;
+
+  uint64_to_xsync_value (1, &attr.trigger.wait_value);
+
+  attr.trigger.test_type = XSyncNegativeTransition;
+  return XSyncCreateAlarm (priv->xdisplay, flags, &attr);
+}
+
+static XSyncCounter
+find_idletime_counter (MetaBackendX11Private *priv)
+{
+  int i;
+  int n_counters;
+  XSyncSystemCounter *counters;
+  XSyncCounter counter = None;
+
+  counters = XSyncListSystemCounters (priv->xdisplay, &n_counters);
+  for (i = 0; i < n_counters; i++)
+    {
+      if (g_strcmp0 (counters[i].name, "IDLETIME") == 0)
+        {
+          counter = counters[i].counter;
+          break;
+        }
+    }
+  XSyncFreeSystemCounterList (counters);
+
+  return counter;
+}
+
+static void
+handle_alarm_notify (MetaBackend           *backend,
+                     XSyncAlarmNotifyEvent *alarm_event)
+{
+  MetaBackendX11 *x11 = META_BACKEND_X11 (backend);
+  MetaBackendX11Private *priv = meta_backend_x11_get_instance_private (x11);
+  MetaIdleMonitor *idle_monitor;
+  XSyncAlarmAttributes attr;
+
+  if (alarm_event->state != XSyncAlarmActive ||
+      alarm_event->alarm != priv->user_active_alarm)
+    return;
+
+  attr.events = TRUE;
+  XSyncChangeAlarm (priv->xdisplay, priv->user_active_alarm,
+                    XSyncCAEvents, &attr);
+
+  idle_monitor = meta_backend_get_idle_monitor (backend, 0);
+  meta_idle_monitor_reset_idletime (idle_monitor);
+}
+
 static void
 meta_backend_x11_translate_device_event (MetaBackendX11 *x11,
                                          XIDeviceEvent  *device_event)
@@ -264,6 +340,9 @@ handle_host_xevent (MetaBackend *backend,
   bypass_clutter = (meta_backend_x11_handle_host_xevent (x11, event) ||
                     bypass_clutter);
 
+  if (event->type == (priv->xsync_event_base + XSyncAlarmNotify))
+    handle_alarm_notify (backend, (XSyncAlarmNotifyEvent *) event);
+
   if (event->type == priv->xkb_event_base)
     {
       XkbEvent *xkb_ev = (XkbEvent *) event;
@@ -410,6 +489,12 @@ meta_backend_x11_post_init (MetaBackend *backend)
       !XSyncInitialize (priv->xdisplay, &major, &minor))
     meta_fatal ("Could not initialize XSync");
 
+  priv->counter = find_idletime_counter (priv);
+  if (priv->counter == None)
+    meta_fatal ("Could not initialize XSync counter");
+
+  priv->user_active_alarm = xsync_user_active_alarm_set (priv);
+
   if (XQueryExtension (priv->xdisplay,
                        "XInputExtension",
                        &priv->xinput_opcode,
@@ -657,11 +742,28 @@ initable_iface_init (GInitableIface *initable_iface)
   initable_iface->init = meta_backend_x11_initable_init;
 }
 
+static void
+meta_backend_x11_finalize (GObject *object)
+{
+  MetaBackendX11 *x11 = META_BACKEND_X11 (object);
+  MetaBackendX11Private *priv = meta_backend_x11_get_instance_private (x11);
+
+  if (priv->user_active_alarm != None)
+    {
+      XSyncDestroyAlarm (priv->xdisplay, priv->user_active_alarm);
+      priv->user_active_alarm = None;
+    }
+
+  G_OBJECT_CLASS (meta_backend_x11_parent_class)->finalize (object);
+}
+
 static void
 meta_backend_x11_class_init (MetaBackendX11Class *klass)
 {
   MetaBackendClass *backend_class = META_BACKEND_CLASS (klass);
+  GObjectClass *object_class = G_OBJECT_CLASS (klass);
 
+  object_class->finalize = meta_backend_x11_finalize;
   backend_class->create_clutter_backend = meta_backend_x11_create_clutter_backend;
   backend_class->post_init = meta_backend_x11_post_init;
   backend_class->grab_device = meta_backend_x11_grab_device;