input-settings-x11: Factor out a get_property() helper

We'll need to get the value of some properties. Fail if the number of
items returned is less than we expect and warn if it exceeds it so
that we can easily find out if items are added to a property later and
fix it.

1 files changed, 39 insertions, 10 deletions

diff --git a/src/backends/x11/meta-input-settings-x11.c b/src/backends/x11/meta-input-settings-x11.c
index d0a34402..6ef219ff 100644
--- a/src/backends/x11/meta-input-settings-x11.c
+++ b/src/backends/x11/meta-input-settings-x11.c
@@ -35,6 +35,38 @@
 
 G_DEFINE_TYPE (MetaInputSettingsX11, meta_input_settings_x11, META_TYPE_INPUT_SETTINGS)
 
+static void *
+get_property (ClutterInputDevice *device,
+              const gchar        *property,
+              Atom                type,
+              int                 format,
+              gulong              nitems)
+{
+  MetaBackend *backend = meta_get_backend ();
+  Display *xdisplay = meta_backend_x11_get_xdisplay (META_BACKEND_X11 (backend));
+  gulong nitems_ret, bytes_after_ret;
+  int rc, device_id, format_ret;
+  Atom property_atom, type_ret;
+  guchar *data_ret = NULL;
+
+  property_atom = XInternAtom (xdisplay, property, False);
+  device_id = clutter_input_device_get_device_id (device);
+
+  rc = XIGetProperty (xdisplay, device_id, property_atom,
+                      0, 10, False, type, &type_ret, &format_ret,
+                      &nitems_ret, &bytes_after_ret, &data_ret);
+  if (rc == Success && type_ret == type && format_ret == format && nitems_ret >= nitems)
+    {
+      if (nitems_ret > nitems)
+        g_warning ("Property '%s' for device '%s' returned %lu items, expected %lu",
+                   property, clutter_input_device_get_device_name (device), nitems_ret, nitems);
+      return data_ret;
+    }
+
+  meta_XFree (data_ret);
+  return NULL;
+}
+
 static void
 change_property (ClutterInputDevice *device,
                  const gchar        *property,
@@ -45,23 +77,20 @@ change_property (ClutterInputDevice *device,
 {
   MetaBackend *backend = meta_get_backend ();
   Display *xdisplay = meta_backend_x11_get_xdisplay (META_BACKEND_X11 (backend));
-  gulong nitems_ret, bytes_after_ret;
-  int rc, device_id, format_ret;
-  Atom property_atom, type_ret;
+  int device_id;
+  Atom property_atom;
   guchar *data_ret;
 
   property_atom = XInternAtom (xdisplay, property, False);
   device_id = clutter_input_device_get_device_id (device);
 
-  rc = XIGetProperty (xdisplay, device_id, property_atom,
-                      0, 0, False, type, &type_ret, &format_ret,
-                      &nitems_ret, &bytes_after_ret, &data_ret);
+  data_ret = get_property (device, property, type, format, nitems);
+  if (!data_ret)
+    return;
 
+  XIChangeProperty (xdisplay, device_id, property_atom, type,
+                    format, XIPropModeReplace, data, nitems);
   meta_XFree (data_ret);
-
-  if (rc == Success && type_ret == type && format_ret == format)
-    XIChangeProperty (xdisplay, device_id, property_atom, type,
-                      format, XIPropModeReplace, data, nitems);
 }
 
 static void