From 83bc7037441ec61e2dec60e8ad8040913937beb2 Mon Sep 17 00:00:00 2001
From: Rui Matos <tiagomatos@gmail.com>
Date: Fri, 8 May 2015 17:31:48 +0200
Subject: [PATCH] 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.
---
 src/backends/x11/meta-input-settings-x11.c | 49 +++++++++++++++++-----
 1 file 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 d0a344024..6ef219ff6 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