input-settings: detect trackball using udev ID_INPUT_TRACKBALL

Previously, trackballs were detected based on the presence of the
substring "trackball" in the device name. This had the downside of
missing devices, such as the Kensington Expert Mouse, which don't have
"trackball" in their names.

Rather than depending on the device name, use the ID_INPUT_TRACKBALL
property from udev to determine whether or not to treat a device as a
trackball.

This adds a new function, `is_trackball_device`, to MetaInputEvents, and
eliminates the `meta_input_device_is_trackball` function.

Fixes: https://gitlab.gnome.org/GNOME/mutter/issues/258

src/backends/meta-input-settings-private.h

@@ -115,6 +115,8 @@ struct _MetaInputSettingsClass
                                   GDesktopStylusButtonAction  tertiary);
   gboolean (* has_two_finger_scroll) (MetaInputSettings  *settings,
                                       ClutterInputDevice *device);
+  gboolean (* is_trackball_device) (MetaInputSettings  *settings,
+                                    ClutterInputDevice *device);
 };
 
 GSettings *           meta_input_settings_get_tablet_settings (MetaInputSettings  *settings,
@@ -141,6 +143,4 @@ WacomDevice * meta_input_settings_get_tablet_wacom_device (MetaInputSettings *se
                                                            ClutterInputDevice *device);
 #endif
 
-gboolean meta_input_device_is_trackball (ClutterInputDevice *device);
-
 #endif /* META_INPUT_SETTINGS_PRIVATE_H */

src/backends/meta-input-settings.c

@@ -709,22 +709,6 @@ update_touchpad_send_events (MetaInputSettings  *input_settings,
     }
 }
 
-gboolean
-meta_input_device_is_trackball (ClutterInputDevice *device)
-{
-  gboolean is_trackball;
-  char *name;
-
-  if (clutter_input_device_get_device_mode (device) == CLUTTER_INPUT_MODE_MASTER)
-    return FALSE;
-
-  name = g_ascii_strdown (clutter_input_device_get_device_name (device), -1);
-  is_trackball = strstr (name, "trackball") != NULL;
-  g_free (name);
-
-  return is_trackball;
-}
-
 static void
 update_trackball_scroll_button (MetaInputSettings  *input_settings,
                                 ClutterInputDevice *device)
@@ -733,11 +717,12 @@ update_trackball_scroll_button (MetaInputSettings  *input_settings,
   MetaInputSettingsPrivate *priv;
   guint button;
 
-  if (device && !meta_input_device_is_trackball (device))
-    return;
-
   priv = meta_input_settings_get_instance_private (input_settings);
   input_settings_class = META_INPUT_SETTINGS_GET_CLASS (input_settings);
+
+  if (device && !input_settings_class->is_trackball_device (input_settings, device))
+    return;
+
   /* This key is 'i' in the schema but it also specifies a minimum
    * range of 0 so the cast here is safe. */
   button = (guint) g_settings_get_int (priv->trackball_settings, "scroll-wheel-emulation-button");
@@ -756,7 +741,7 @@ update_trackball_scroll_button (MetaInputSettings  *input_settings,
         {
           device = devices->data;
 
-          if (meta_input_device_is_trackball (device))
+          if (input_settings_class->is_trackball_device (input_settings, device))
             input_settings_class->set_scroll_button (input_settings, device, button);
 
           devices = devices->next;

src/backends/native/meta-input-settings-native.c

@@ -398,9 +398,10 @@ is_mouse_device (ClutterInputDevice *device)
 }
 
 static gboolean
-is_trackball_device (ClutterInputDevice *device)
+meta_input_settings_native_is_trackball_device (MetaInputSettings  *settings,
+                                                ClutterInputDevice *device)
 {
-  return meta_input_device_is_trackball (device);
+  return has_udev_property (device, "ID_INPUT_TRACKBALL");
 }
 
 static void
@@ -419,7 +420,7 @@ meta_input_settings_native_set_trackball_accel_profile (MetaInputSettings
                                                         ClutterInputDevice         *device,
                                                         GDesktopPointerAccelProfile profile)
 {
-  if (!is_trackball_device (device))
+  if (!meta_input_settings_native_is_trackball_device (settings, device))
     return;
 
   set_device_accel_profile (device, profile);
@@ -588,6 +589,7 @@ meta_input_settings_native_class_init (MetaInputSettingsNativeClass *klass)
   input_settings_class->set_stylus_button_map = meta_input_settings_native_set_stylus_button_map;
 
   input_settings_class->has_two_finger_scroll = meta_input_settings_native_has_two_finger_scroll;
+  input_settings_class->is_trackball_device = meta_input_settings_native_is_trackball_device;
 }
 
 static void

src/backends/x11/meta-input-settings-x11.c

@@ -500,10 +500,10 @@ is_mouse (MetaInputSettings  *settings,
 }
 
 static gboolean
-is_trackball (MetaInputSettings  *settings,
+meta_input_settings_x11_is_trackball_device (MetaInputSettings  *settings,
                                              ClutterInputDevice *device)
 {
-  return meta_input_device_is_trackball (device);
+  return has_udev_property (settings, device, "ID_INPUT_TRACKBALL");
 }
 
 static void
@@ -566,7 +566,7 @@ meta_input_settings_x11_set_trackball_accel_profile (MetaInputSettings
                                                      ClutterInputDevice         *device,
                                                      GDesktopPointerAccelProfile profile)
 {
-  if (!is_trackball (settings, device))
+  if (!meta_input_settings_x11_is_trackball_device (settings, device))
     return;
 
   set_device_accel_profile (device, profile);
@@ -852,6 +852,7 @@ meta_input_settings_x11_class_init (MetaInputSettingsX11Class *klass)
   input_settings_class->set_stylus_button_map = meta_input_settings_x11_set_stylus_button_map;
 
   input_settings_class->has_two_finger_scroll = meta_input_settings_x11_has_two_finger_scroll;
+  input_settings_class->is_trackball_device = meta_input_settings_x11_is_trackball_device;
 }
 
 static void