[mutter/wip/carlosg/drop-external-keyboard-detection] backends/native: Drop external keyboard detection for ::touch-mode

[Carlos Garnacho <carlosg src gnome org>]

commit aa1de53f940d956d3f726a1633156c1fc239111b
Author: Carlos Garnacho <carlosg gnome org>
Date:   Fri May 29 13:28:11 2020 +0200

    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

 src/backends/native/meta-seat-native.c | 48 +++-------------------------------
 src/backends/native/meta-seat-native.h |  1 -
 2 files changed, 4 insertions(+), 45 deletions(-)
---
diff --git a/src/backends/native/meta-seat-native.c b/src/backends/native/meta-seat-native.c
index 9c25d4abf7..ecff929bd8 100644
--- a/src/backends/native/meta-seat-native.c
+++ b/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);
 
diff --git a/src/backends/native/meta-seat-native.h b/src/backends/native/meta-seat-native.h
index 2d780618f6..61e6ffd30b 100644
--- a/src/backends/native/meta-seat-native.h
+++ b/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;