[mutter] device-manager-x11: Ignore events if no source device is set

[Marco Trevisan <marcotrevi src gnome org>]

commit 427670cc638d02f84897ae7fa174de4ac995e7dc
Author: Marco Trevisan (Treviño) <mail 3v1n0 net>
Date:   Wed Oct 2 22:19:34 2019 +0200

    device-manager-x11: Ignore events if no source device is set
    
    There might be some inconsistent event for which we don't have a known
    source device.
    
    In the current state we don't handle them and we could crash when getting
    the current device tool.
    
    So, add an utility function that retrieves the source device for an event
    that warns if no device is found, and use this for Motion, Key and Button
    events.
    
    In case we don't have a valid source in such case, just return early instead
    of trying to generate invalid clutter events.
    
    https://gitlab.gnome.org/GNOME/mutter/merge_requests/823

 src/backends/x11/meta-device-manager-x11.c | 38 +++++++++++++++++++++++-------
 1 file changed, 30 insertions(+), 8 deletions(-)
---
diff --git a/src/backends/x11/meta-device-manager-x11.c b/src/backends/x11/meta-device-manager-x11.c
index c2a0ec112..c6ddb7d6f 100644
--- a/src/backends/x11/meta-device-manager-x11.c
+++ b/src/backends/x11/meta-device-manager-x11.c
@@ -1291,6 +1291,22 @@ handle_raw_event (MetaDeviceManagerX11 *manager_xi2,
     }
 }
 
+static ClutterInputDevice *
+get_source_device_checked (MetaDeviceManagerX11 *manager_xi2,
+                           XIDeviceEvent        *xev)
+{
+  ClutterInputDevice *source_device;
+
+  source_device = g_hash_table_lookup (manager_xi2->devices_by_id,
+                                       GINT_TO_POINTER (xev->sourceid));
+
+  if (!source_device)
+    g_warning ("Impossible to get the source device with id %d for event of "
+               "type %d", xev->sourceid, xev->evtype);
+
+  return source_device;
+}
+
 gboolean
 meta_device_manager_x11_translate_event (MetaDeviceManagerX11 *manager_xi2,
                                          XEvent               *xevent,
@@ -1379,6 +1395,10 @@ meta_device_manager_x11_translate_event (MetaDeviceManagerX11 *manager_xi2,
         char buffer[7] = { 0, };
         gunichar n;
 
+        source_device = get_source_device_checked (manager_xi2, xev);
+        if (!source_device)
+          return FALSE;
+
         event->key.type = event->type = (xev->evtype == XI_KeyPress)
                                       ? CLUTTER_KEY_PRESS
                                       : CLUTTER_KEY_RELEASE;
@@ -1413,8 +1433,6 @@ meta_device_manager_x11_translate_event (MetaDeviceManagerX11 *manager_xi2,
         event_x11->caps_lock_set =
           clutter_keymap_get_caps_lock_state (CLUTTER_KEYMAP (keymap_x11));
 
-        source_device = g_hash_table_lookup (manager_xi2->devices_by_id,
-                                             GINT_TO_POINTER (xev->sourceid));
         clutter_event_set_source_device (event, source_device);
 
         device = g_hash_table_lookup (manager_xi2->devices_by_id,
@@ -1458,8 +1476,10 @@ meta_device_manager_x11_translate_event (MetaDeviceManagerX11 *manager_xi2,
       {
         XIDeviceEvent *xev = (XIDeviceEvent *) xi_event;
 
-        source_device = g_hash_table_lookup (manager_xi2->devices_by_id,
-                                             GINT_TO_POINTER (xev->sourceid));
+        source_device = get_source_device_checked (manager_xi2, xev);
+        if (!source_device)
+          return FALSE;
+
         device = g_hash_table_lookup (manager_xi2->devices_by_id,
                                       GINT_TO_POINTER (xev->deviceid));
 
@@ -1626,7 +1646,7 @@ meta_device_manager_x11_translate_event (MetaDeviceManagerX11 *manager_xi2,
             break;
           }
 
-        if (source_device != NULL && device->stage != NULL)
+        if (device->stage != NULL)
           _clutter_input_device_set_stage (source_device, device->stage);
 
         if (xev->flags & XIPointerEmulated)
@@ -1644,8 +1664,10 @@ meta_device_manager_x11_translate_event (MetaDeviceManagerX11 *manager_xi2,
         XIDeviceEvent *xev = (XIDeviceEvent *) xi_event;
         double delta_x, delta_y;
 
-        source_device = g_hash_table_lookup (manager_xi2->devices_by_id,
-                                             GINT_TO_POINTER (xev->sourceid));
+        source_device = get_source_device_checked (manager_xi2, xev);
+        if (!source_device)
+          return FALSE;
+
         device = g_hash_table_lookup (manager_xi2->devices_by_id,
                                       GINT_TO_POINTER (xev->deviceid));
 
@@ -1716,7 +1738,7 @@ meta_device_manager_x11_translate_event (MetaDeviceManagerX11 *manager_xi2,
                                              event->motion.y,
                                              &xev->valuators);
 
-        if (source_device != NULL && device->stage != NULL)
+        if (device->stage != NULL)
           _clutter_input_device_set_stage (source_device, device->stage);
 
         if (xev->flags & XIPointerEmulated)