[mutter] backends/x11: Preserve XI1 XDevice throughout ClutterInputDevice lifetime

[Carlos Garnacho <carlosg src gnome org>]

commit 57f55d486d291d517475f46d52144d9734c53b17
Author: Carlos Garnacho <carlosg gnome org>
Date:   Tue Jan 30 13:07:32 2018 +0100

    backends/x11: Preserve XI1 XDevice throughout ClutterInputDevice lifetime
    
    Opening and closing the device may result into XI2 grabs being cut short,
    resulting into pad buttons being rendered ineffective, and other possible
    misbehaviors. This is an XInput flaw that fell in the gap between XI1 and
    XI2, and has no easy fix. It pays us for mixing both versions, I guess...
    
    Work this around by keeping the XI1 XDevice attached to the
    ClutterInputDevice, this way it will live long enough that this is not
    a concern.
    
    Investigation of this bug was mostly carried by Peter Hutterer, I'm just
    the executing hand.
    
    https://gitlab.gnome.org/GNOME/mutter/issues/7
    
    Closes: #7

 src/backends/x11/meta-input-settings-x11.c | 48 ++++++++++++++++++++++++++----
 1 file changed, 42 insertions(+), 6 deletions(-)
---
diff --git a/src/backends/x11/meta-input-settings-x11.c b/src/backends/x11/meta-input-settings-x11.c
index 01b02a379..7d1d360a3 100644
--- a/src/backends/x11/meta-input-settings-x11.c
+++ b/src/backends/x11/meta-input-settings-x11.c
@@ -55,6 +55,46 @@ enum {
   SCROLL_METHOD_NUM_FIELDS
 };
 
+static void
+device_free_xdevice (gpointer user_data)
+{
+  MetaDisplay *display = meta_get_display ();
+  MetaBackend *backend = meta_get_backend ();
+  Display *xdisplay = meta_backend_x11_get_xdisplay (META_BACKEND_X11 (backend));
+  XDevice *xdev = user_data;
+
+  meta_error_trap_push (display);
+  XCloseDevice (xdisplay, xdev);
+  meta_error_trap_pop (display);
+}
+
+static XDevice *
+device_ensure_xdevice (ClutterInputDevice *device)
+{
+  MetaDisplay *display = meta_get_display ();
+  MetaBackend *backend = meta_get_backend ();
+  Display *xdisplay = meta_backend_x11_get_xdisplay (META_BACKEND_X11 (backend));
+  int device_id = clutter_input_device_get_device_id (device);
+  XDevice *xdev = NULL;
+
+  xdev = g_object_get_data (G_OBJECT (device), "meta-input-settings-xdevice");
+  if (xdev)
+    return xdev;
+
+  meta_error_trap_push (display);
+  xdev = XOpenDevice (xdisplay, device_id);
+  meta_error_trap_pop (display);
+
+  if (xdev)
+    {
+      g_object_set_data_full (G_OBJECT (device),
+                              "meta-input-settings-xdevice",
+                              xdev, device_free_xdevice);
+    }
+
+  return xdev;
+}
+
 static void *
 get_property (ClutterInputDevice *device,
               const gchar        *property,
@@ -540,7 +580,6 @@ meta_input_settings_x11_set_tablet_mapping (MetaInputSettings     *settings,
   MetaDisplay *display = meta_get_display ();
   MetaBackend *backend = meta_get_backend ();
   Display *xdisplay = meta_backend_x11_get_xdisplay (META_BACKEND_X11 (backend));
-  int device_id = clutter_input_device_get_device_id (device);
   XDevice *xdev;
 
   if (!display)
@@ -548,13 +587,12 @@ meta_input_settings_x11_set_tablet_mapping (MetaInputSettings     *settings,
 
   /* Grab the puke bucket! */
   meta_error_trap_push (display);
-  xdev = XOpenDevice (xdisplay, device_id);
+  xdev = device_ensure_xdevice (device);
   if (xdev)
     {
       XSetDeviceMode (xdisplay, xdev,
                       mapping == G_DESKTOP_TABLET_MAPPING_ABSOLUTE ?
                       Absolute : Relative);
-      XCloseDevice (xdisplay, xdev);
     }
 
   if (meta_error_trap_pop_with_return (display))
@@ -738,7 +776,6 @@ meta_input_settings_x11_set_stylus_button_map (MetaInputSettings          *setti
   MetaDisplay *display = meta_get_display ();
   MetaBackend *backend = meta_get_backend ();
   Display *xdisplay = meta_backend_x11_get_xdisplay (META_BACKEND_X11 (backend));
-  int device_id = clutter_input_device_get_device_id (device);
   XDevice *xdev;
 
   if (!display)
@@ -746,7 +783,7 @@ meta_input_settings_x11_set_stylus_button_map (MetaInputSettings          *setti
 
   /* Grab the puke bucket! */
   meta_error_trap_push (display);
-  xdev = XOpenDevice (xdisplay, device_id);
+  xdev = device_ensure_xdevice (device);
   if (xdev)
     {
       guchar map[8] = {
@@ -761,7 +798,6 @@ meta_input_settings_x11_set_stylus_button_map (MetaInputSettings          *setti
       };
 
       XSetDeviceButtonMapping (xdisplay, xdev, map, G_N_ELEMENTS (map));
-      XCloseDevice (xdisplay, xdev);
     }
 
   if (meta_error_trap_pop_with_return (display))