[mutter] backends: Add envvar to disable wacom configuration

[Carlos Garnacho <carlosg src gnome org>]

commit 9000eef49dba1462fc67c89a4b731985cf3eda7f
Author: Carlos Garnacho <carlosg gnome org>
Date:   Wed Oct 4 00:42:39 2017 +0200

    backends: Add envvar to disable wacom configuration
    
    People that relied on xsetwacom to configure their tablets used to get
    away with this by disabling the wacom g-s-d plugin prior to running
    their scripts. This is not possible anymore with mutter managing device
    configuration.
    
    Given that X11 shall not go away soon and there's a core of stubbornly
    accustomed users, provide a MUTTER_DISABLE_WACOM_CONFIGURATION envvar
    to provide *some* way to do this.

 src/backends/meta-input-settings.c |   16 +++++++++++++---
 1 files changed, 13 insertions(+), 3 deletions(-)
---
diff --git a/src/backends/meta-input-settings.c b/src/backends/meta-input-settings.c
index 8130bf5..d6c7b57 100644
--- a/src/backends/meta-input-settings.c
+++ b/src/backends/meta-input-settings.c
@@ -1308,8 +1308,18 @@ check_add_mappable_device (MetaInputSettings  *input_settings,
 {
   MetaInputSettingsPrivate *priv;
   DeviceMappingInfo *info;
+  ClutterInputDeviceType device_type;
   GSettings *settings;
 
+  device_type = clutter_input_device_get_device_type (device);
+
+  if ((device_type == CLUTTER_TABLET_DEVICE ||
+       device_type == CLUTTER_PEN_DEVICE ||
+       device_type == CLUTTER_ERASER_DEVICE ||
+       device_type == CLUTTER_PAD_DEVICE) &&
+      g_getenv ("MUTTER_DISABLE_WACOM_CONFIGURATION") != NULL)
+    return FALSE;
+
   settings = lookup_device_settings (device);
 
   if (!settings)
@@ -1323,8 +1333,8 @@ check_add_mappable_device (MetaInputSettings  *input_settings,
   info->settings = settings;
 
 #ifdef HAVE_LIBWACOM
-  if (clutter_input_device_get_device_type (device) == CLUTTER_TABLET_DEVICE ||
-      clutter_input_device_get_device_type (device) == CLUTTER_PAD_DEVICE)
+  if (device_type == CLUTTER_TABLET_DEVICE ||
+      device_type == CLUTTER_PAD_DEVICE)
     {
       WacomError *error = libwacom_error_new ();
 
@@ -1342,7 +1352,7 @@ check_add_mappable_device (MetaInputSettings  *input_settings,
     }
 #endif
 
-  if (clutter_input_device_get_device_type (device) == CLUTTER_PAD_DEVICE)
+  if (device_type == CLUTTER_PAD_DEVICE)
     {
       info->group_modes =
         g_new0 (guint, clutter_input_device_get_n_mode_groups (device));