xi2: ignore extraneous events for smooth scroll

Since the event will be ignored anyway after it's translated (slave
devices are disabled), don't let it run in the smooth scroll code path,
as it will burn our caches for the actual event we're interested in.

https://bugzilla.gnome.org/show_bug.cgi?id=673644

diff --git a/gdk/x11/gdkdevicemanager-xi2.c b/gdk/x11/gdkdevicemanager-xi2.c
index a34bd0952d1c36bcd62307192c2b1e2d7f72dfdc..15f095b1ef4ea823d2a8cda19e58e55684497db6 100644 (file)
--- a/gdk/x11/gdkdevicemanager-xi2.c
+++ b/gdk/x11/gdkdevicemanager-xi2.c
@@ -1305,13 +1305,24 @@ gdk_x11_device_manager_xi2_translate_event (GdkEventTranslator *translator,
     case XI_Motion:
       {
         XIDeviceEvent *xev = (XIDeviceEvent *) ev;
-        GdkDevice *source_device;
+        GdkDevice *source_device, *device;
         gdouble delta_x, delta_y;
 
         source_device = g_hash_table_lookup (device_manager->id_table,
                                              GUINT_TO_POINTER (xev->sourceid));
+        device = g_hash_table_lookup (device_manager->id_table,
+                                      GUINT_TO_POINTER (xev->deviceid));
 
-        if (scroll_valuators_changed (GDK_X11_DEVICE_XI2 (source_device),
+        /* When scrolling, X might send events twice here; once with both the
+         * device and the source device set to the physical device, and once
+         * with the device set to the master device.
+         * Since we are only interested in the latter, and
+         * scroll_valuators_changed() updates the valuator cache for the
+         * source device, we need to explicitly ignore the first event in
+         * order to get the correct delta for the second.
+         */
+        if (gdk_device_get_device_type (device) != GDK_DEVICE_TYPE_SLAVE &&
+            scroll_valuators_changed (GDK_X11_DEVICE_XI2 (source_device),
                                       &xev->valuators, &delta_x, &delta_y))
           {
             event->scroll.type = GDK_SCROLL;
@@ -1333,9 +1344,7 @@ gdk_x11_device_manager_xi2_translate_event (GdkEventTranslator *translator,
             event->scroll.delta_x = delta_x;
             event->scroll.delta_y = delta_y;
 
-            event->scroll.device = g_hash_table_lookup (device_manager->id_table,
-                                                        GUINT_TO_POINTER (xev->deviceid));
-
+            event->scroll.device = device;
             gdk_event_set_source_device (event, source_device);
 
             event->scroll.state = _gdk_x11_device_xi2_translate_state (&xev->mods, &xev->buttons, &xev->group);
@@ -1350,9 +1359,7 @@ gdk_x11_device_manager_xi2_translate_event (GdkEventTranslator *translator,
         event->motion.x_root = (gdouble) xev->root_x;
         event->motion.y_root = (gdouble) xev->root_y;
 
-        event->motion.device = g_hash_table_lookup (device_manager->id_table,
-                                                    GINT_TO_POINTER (xev->deviceid));
-
+        event->motion.device = device;
         gdk_event_set_source_device (event, source_device);
 
         event->motion.state = _gdk_x11_device_xi2_translate_state (&xev->mods, &xev->buttons, &xev->group);