backends/native: Drop external keyboard detection for ::touch-mode

This cannot be made to work reliably. Some factoids:

- Internal devices may be connected via USB.
- The ACPI spec provides the _PLD (Physical location of device) hook to
  determine how is an USB device connected, with an anecdotal success
  rate. Internal devices may be seen as external and vice-versa, there is
  also an "unknown" value that is widely used.
- There may be non-USB keyboards, the old "AT Translated Set 2 Keyboard"
  interface does not change on hotplugging.
- Libinput has an internal series of quirks to classify keyboards as
  internal of external, also with an "unknown" value.

These heuristics are kinda hopeless to get right by our own hand. Drop
this external keyboard detection in the hope that there will be something
more deterministic to rely on in the future (e.g. the libinput quirks
made available to us directly or indirectly).

Fixes: https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/2378
Related: https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/2353

https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1277

clutter/clutter/clutter-seat.c

@@ -682,7 +682,6 @@ clutter_seat_warp_pointer (ClutterSeat *seat,
  * requirements are fulfilled:
  *
  *  - A touchscreen is available
- *  - No external keyboard is attached to the device
  *  - A tablet mode switch, if present, is enabled
  *
  * Returns: %TRUE if the device is a tablet that doesn't have an external

src/backends/native/meta-seat-native.c

@@ -1380,35 +1380,6 @@ has_touchscreen (MetaSeatNative *seat)
   return FALSE;
 }
 
-static gboolean
-has_external_keyboard (MetaSeatNative *seat)
-{
-  GList *devices, *l;
-  gboolean has_external = FALSE;
-
-  devices = g_udev_client_query_by_subsystem (seat->udev_client, "input");
-
-  for (l = devices; l; l = l->next)
-    {
-      if (!g_udev_device_has_property (l->data, "ID_INPUT_KEYBOARD"))
-        continue;
-
-      /* May be "hid" or something else, we don't care. This property
-       * will not be present in virtual "AT Translated Set 2 keyboard"
-       * devices.
-       */
-      if (!g_udev_device_has_property (l->data, "ID_TYPE"))
-        break;
-
-      has_external = TRUE;
-      break;
-    }
-
-  g_list_free_full (devices, g_object_unref);
-
-  return has_external;
-}
-
 static void
 update_touch_mode (MetaSeatNative *seat)
 {
@@ -1421,10 +1392,10 @@ update_touch_mode (MetaSeatNative *seat)
   else if (seat->has_tablet_switch && !seat->tablet_mode_switch_state)
     touch_mode = FALSE;
   /* If tablet mode is enabled, or if there is no tablet mode switch
-   * (eg. kiosk machines), check availability of external keyboards.
+   * (eg. kiosk machines), assume touch-mode.
    */
   else
-    touch_mode = !seat->has_external_keyboard;
+    touch_mode = TRUE;
 
   if (seat->touch_mode != touch_mode)
     {
@@ -1465,12 +1436,7 @@ evdev_add_device (MetaSeatNative         *seat,
 
   g_signal_emit_by_name (seat, "device-added", device);
 
-  if (type == CLUTTER_KEYBOARD_DEVICE)
-    {
-      seat->has_external_keyboard = has_external_keyboard (seat);
-      check_touch_mode = TRUE;
-    }
-  else if (type == CLUTTER_TOUCHSCREEN_DEVICE)
+  if (type == CLUTTER_TOUCHSCREEN_DEVICE)
     {
       seat->has_touchscreen = TRUE;
       check_touch_mode = TRUE;
@@ -1503,12 +1469,7 @@ evdev_remove_device (MetaSeatNative        *seat,
 
   device_type = clutter_input_device_get_device_type (device);
 
-  if (device_type == CLUTTER_KEYBOARD_DEVICE)
-    {
-      seat->has_external_keyboard = has_external_keyboard (seat);
-      update_touch_mode (seat);
-    }
-  else if (device_type == CLUTTER_TOUCHSCREEN_DEVICE)
+  if (device_type == CLUTTER_TOUCHSCREEN_DEVICE)
     {
       seat->has_touchscreen = has_touchscreen (seat);
       update_touch_mode (seat);
@@ -2553,7 +2514,6 @@ meta_seat_native_constructed (GObject *object)
         xkb_keymap_led_get_index (xkb_keymap, XKB_LED_NAME_SCROLL);
     }
 
-  seat->has_external_keyboard = has_external_keyboard (seat);
   seat->has_touchscreen = has_touchscreen (seat);
   update_touch_mode (seat);
 

src/backends/native/meta-seat-native.h

@@ -120,7 +120,6 @@ struct _MetaSeatNative
 
   GUdevClient *udev_client;
   guint tablet_mode_switch_state : 1;
-  guint has_external_keyboard    : 1;
   guint has_touchscreen          : 1;
   guint has_tablet_switch        : 1;
   guint touch_mode               : 1;