[mutter] seat-native: Check for tablet-switch devices from meta_seat_native_constructed

[Carlos Garnacho <carlosg src gnome org>]

commit 88cabf8039b4561520128ddb108341c75904aca8
Author: Hans de Goede <hdegoede redhat com>
Date:   Wed Oct 14 21:23:04 2020 +0200

    seat-native: Check for tablet-switch devices from meta_seat_native_constructed
    
    Detect if a tablet-mode-switch device is already present when mutter
    starts by checking for this from meta_seat_native_constructed. This
    mirrors how we also set has_touchscreen from meta_seat_native_constructed.
    
    This fixes tablet-mode-switches only being recognized when they are added
    at runtime.
    
    https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1506

 src/backends/native/meta-seat-native.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)
---
diff --git a/src/backends/native/meta-seat-native.c b/src/backends/native/meta-seat-native.c
index 8f8f13a099..b96ae3a250 100644
--- a/src/backends/native/meta-seat-native.c
+++ b/src/backends/native/meta-seat-native.c
@@ -1367,6 +1367,25 @@ has_touchscreen (MetaSeatNative *seat)
   return FALSE;
 }
 
+static gboolean
+has_tablet_switch (MetaSeatNative *seat)
+{
+  GSList *l;
+
+  for (l = seat->devices; l; l = l->next)
+    {
+      MetaInputDeviceNative *device_native = META_INPUT_DEVICE_NATIVE (l->data);
+
+      if (libinput_device_has_capability (device_native->libinput_device,
+                                          LIBINPUT_DEVICE_CAP_SWITCH) &&
+          libinput_device_switch_has_switch (device_native->libinput_device,
+                                             LIBINPUT_SWITCH_TABLET_MODE))
+        return TRUE;
+    }
+
+  return FALSE;
+}
+
 static void
 update_touch_mode (MetaSeatNative *seat)
 {
@@ -2519,6 +2538,7 @@ meta_seat_native_constructed (GObject *object)
     }
 
   seat->has_touchscreen = has_touchscreen (seat);
+  seat->has_tablet_switch = has_tablet_switch (seat);
   update_touch_mode (seat);
 
   if (G_OBJECT_CLASS (meta_seat_native_parent_class)->constructed)