clutter/x11: Implement keycode remap to keysyms on virtual key devices

Keycode lookup can fail for serveral reasons, e.g. if there is no combination of
modifiers and keycodes that can produce the target keysym with the current
keyboard layout.

In case the keycode lookup fails, remap temporarily the keysym to an unused
keycodes.

Fixes: https://gitlab.gnome.org/GNOME/gnome-shell/issues/109

clutter/clutter/x11/clutter-keymap-x11.c

@@ -76,6 +76,9 @@ struct _ClutterKeymapX11
   DirectionCacheEntry group_direction_cache[4];
   int current_group;
 
+  GHashTable *reserved_keycodes;
+  GQueue *available_keycodes;
+
   guint caps_lock_state : 1;
   guint num_lock_state  : 1;
   guint has_direction   : 1;
@@ -422,15 +425,97 @@ clutter_keymap_x11_set_property (GObject      *gobject,
     }
 }
 
+static void
+clutter_keymap_x11_refresh_reserved_keycodes (ClutterKeymapX11 *keymap_x11)
+{
+  Display *dpy = clutter_x11_get_default_display ();
+  GHashTableIter iter;
+  gpointer key, value;
+
+  g_hash_table_iter_init (&iter, keymap_x11->reserved_keycodes);
+  while (g_hash_table_iter_next (&iter, &key, &value))
+    {
+      guint reserved_keycode = GPOINTER_TO_UINT (key);
+      guint reserved_keysym = GPOINTER_TO_UINT (value);
+      guint actual_keysym = XkbKeycodeToKeysym (dpy, reserved_keycode, 0, 0);
+
+      /* If an available keycode is no longer mapped to the stored keysym, then
+       * the keycode should not be considered available anymore and should be
+       * removed both from the list of available and reserved keycodes.
+       */
+      if (reserved_keysym != actual_keysym)
+        {
+          g_hash_table_iter_remove (&iter);
+          g_queue_remove (keymap_x11->available_keycodes, key);
+        }
+    }
+}
+
+static gboolean
+clutter_keymap_x11_replace_keycode (ClutterKeymapX11 *keymap_x11,
+                                    KeyCode           keycode,
+                                    KeySym            keysym)
+{
+  if (CLUTTER_BACKEND_X11 (keymap_x11->backend)->use_xkb)
+    {
+      Display *dpy = clutter_x11_get_default_display ();
+      XkbDescPtr xkb = get_xkb (keymap_x11);
+      XkbMapChangesRec changes;
+
+      XFlush (dpy);
+
+      xkb->device_spec = XkbUseCoreKbd;
+      memset (&changes, 0, sizeof(changes));
+
+      if (keysym != NoSymbol)
+        {
+          int types[XkbNumKbdGroups] = { XkbOneLevelIndex };
+          XkbChangeTypesOfKey (xkb, keycode, 1, XkbGroup1Mask, types, &changes);
+          XkbKeySymEntry (xkb, keycode, 0, 0) = keysym;
+        }
+      else
+        {
+          /* Reset to NoSymbol */
+          XkbChangeTypesOfKey (xkb, keycode, 0, XkbGroup1Mask, NULL, &changes);
+        }
+
+      changes.changed = XkbKeySymsMask | XkbKeyTypesMask;
+      changes.first_key_sym = keycode;
+      changes.num_key_syms = 1;
+      changes.first_type = 0;
+      changes.num_types = xkb->map->num_types;
+      XkbChangeMap (dpy, xkb, &changes);
+
+      XFlush (dpy);
+
+      return TRUE;
+    }
+
+  return FALSE;
+}
+
 static void
 clutter_keymap_x11_finalize (GObject *gobject)
 {
   ClutterKeymapX11 *keymap;
   ClutterEventTranslator *translator;
+  GHashTableIter iter;
+  gpointer key, value;
 
   keymap = CLUTTER_KEYMAP_X11 (gobject);
   translator = CLUTTER_EVENT_TRANSLATOR (keymap);
 
+  clutter_keymap_x11_refresh_reserved_keycodes (keymap);
+  g_hash_table_iter_init (&iter, keymap->reserved_keycodes);
+  while (g_hash_table_iter_next (&iter, &key, &value))
+    {
+      guint keycode = GPOINTER_TO_UINT (key);
+      clutter_keymap_x11_replace_keycode (keymap, keycode, NoSymbol);
+    }
+
+  g_hash_table_destroy (keymap->reserved_keycodes);
+  g_queue_free (keymap->available_keycodes);
+
   _clutter_backend_remove_event_translator (keymap->backend, translator);
 
   if (keymap->xkb_desc != NULL)
@@ -462,6 +547,8 @@ clutter_keymap_x11_init (ClutterKeymapX11 *keymap)
 {
   keymap->current_direction = PANGO_DIRECTION_NEUTRAL;
   keymap->current_group = -1;
+  keymap->reserved_keycodes = g_hash_table_new (NULL, NULL);
+  keymap->available_keycodes = g_queue_new ();
 }
 
 static ClutterTranslateReturn
@@ -731,6 +818,72 @@ clutter_keymap_x11_get_entries_for_keyval (ClutterKeymapX11  *keymap_x11,
     }
 }
 
+static guint
+clutter_keymap_x11_get_available_keycode (ClutterKeymapX11 *keymap_x11)
+{
+  if (CLUTTER_BACKEND_X11 (keymap_x11->backend)->use_xkb)
+    {
+      clutter_keymap_x11_refresh_reserved_keycodes (keymap_x11);
+
+      if (g_hash_table_size (keymap_x11->reserved_keycodes) < 5)
+        {
+          Display *dpy = clutter_x11_get_default_display ();
+          XkbDescPtr xkb = get_xkb (keymap_x11);
+          guint i;
+
+          for (i = xkb->max_key_code; i >= xkb->min_key_code; --i)
+            {
+              if (XkbKeycodeToKeysym (dpy, i, 0, 0) == NoSymbol)
+                return i;
+            }
+        }
+
+      return GPOINTER_TO_UINT (g_queue_pop_head (keymap_x11->available_keycodes));
+    }
+
+  return 0;
+}
+
+gboolean clutter_keymap_x11_reserve_keycode (ClutterKeymapX11 *keymap_x11,
+                                             guint             keyval,
+                                             guint            *keycode_out)
+{
+  g_return_val_if_fail (CLUTTER_IS_KEYMAP_X11 (keymap_x11), FALSE);
+  g_return_val_if_fail (keyval != 0, FALSE);
+  g_return_val_if_fail (keycode_out != NULL, FALSE);
+
+  *keycode_out = clutter_keymap_x11_get_available_keycode (keymap_x11);
+
+  if (*keycode_out == NoSymbol)
+    {
+      g_warning ("Cannot reserve a keycode for keyval %d: no available keycode", keyval);
+      return FALSE;
+    }
+
+  if (!clutter_keymap_x11_replace_keycode (keymap_x11, *keycode_out, keyval))
+    {
+      g_warning ("Failed to remap keycode %d to keyval %d", *keycode_out, keyval);
+      return FALSE;
+    }
+
+  g_hash_table_insert (keymap_x11->reserved_keycodes, GUINT_TO_POINTER (*keycode_out), GUINT_TO_POINTER (keyval));
+  g_queue_remove (keymap_x11->available_keycodes, GUINT_TO_POINTER (*keycode_out));
+
+  return TRUE;
+}
+
+void clutter_keymap_x11_release_keycode_if_needed (ClutterKeymapX11 *keymap_x11,
+                                                   guint             keycode)
+{
+  g_return_if_fail (CLUTTER_IS_KEYMAP_X11 (keymap_x11));
+
+  if (!g_hash_table_contains (keymap_x11->reserved_keycodes, GUINT_TO_POINTER (keycode)) ||
+      g_queue_index (keymap_x11->available_keycodes, GUINT_TO_POINTER (keycode)) != -1)
+    return;
+
+  g_queue_push_tail (keymap_x11->available_keycodes, GUINT_TO_POINTER (keycode));
+}
+
 void
 clutter_keymap_x11_latch_modifiers (ClutterKeymapX11 *keymap_x11,
                                     uint32_t          level,

clutter/clutter/x11/clutter-keymap-x11.h

@@ -58,7 +58,11 @@ gboolean clutter_keymap_x11_keycode_for_keyval (ClutterKeymapX11 *keymap_x11,
 void     clutter_keymap_x11_latch_modifiers (ClutterKeymapX11 *keymap_x11,
                                              uint32_t          level,
                                              gboolean          enable);
-
+gboolean clutter_keymap_x11_reserve_keycode (ClutterKeymapX11 *keymap_x11,
+                                             guint             keyval,
+                                             guint            *keycode_out);
+void     clutter_keymap_x11_release_keycode_if_needed (ClutterKeymapX11 *keymap_x11,
+                                                       guint             keycode);
 G_END_DECLS
 
 #endif /* __CLUTTER_KEYMAP_X11_H__ */

clutter/clutter/x11/clutter-virtual-input-device-x11.c

@@ -140,10 +140,15 @@ clutter_virtual_input_device_x11_notify_keyval (ClutterVirtualInputDevice *virtu
   uint32_t keycode, level;
 
   if (!clutter_keymap_x11_keycode_for_keyval (keymap, keyval, &keycode, &level))
+    {
+      level = 0;
+
+      if (!clutter_keymap_x11_reserve_keycode (keymap, keyval, &keycode))
         {
           g_warning ("No keycode found for keyval %x in current group", keyval);
           return;
         }
+    }
 
   if (!_clutter_keymap_x11_get_is_modifier (keymap, keycode) &&
       key_state == CLUTTER_KEY_STATE_PRESSED)
@@ -153,9 +158,13 @@ clutter_virtual_input_device_x11_notify_keyval (ClutterVirtualInputDevice *virtu
                      (KeyCode) keycode,
                      key_state == CLUTTER_KEY_STATE_PRESSED, 0);
 
-  if (!_clutter_keymap_x11_get_is_modifier (keymap, keycode) &&
+
-      key_state == CLUTTER_KEY_STATE_RELEASED)
+  if (key_state == CLUTTER_KEY_STATE_RELEASED)
+    {
+      if (!_clutter_keymap_x11_get_is_modifier (keymap, keycode))
         clutter_keymap_x11_latch_modifiers (keymap, level, FALSE);
+      clutter_keymap_x11_release_keycode_if_needed (keymap, keycode);
+    }
 }
 
 static void