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

(cherry-picked from commit e3e933c47a69bd137bb83b3692d105d1261d16ff)

3 files changed, 186 insertions, 6 deletions

diff --git a/clutter/clutter/x11/clutter-keymap-x11.c b/clutter/clutter/x11/clutter-keymap-x11.c
index 32cb5a279..f1bdf16a2 100644
--- a/clutter/clutter/x11/clutter-keymap-x11.c
+++ b/clutter/clutter/x11/clutter-keymap-x11.c
@@ -79,6 +79,9 @@ struct _ClutterKeymapX11
   guint current_cache_serial;
   DirectionCacheEntry group_direction_cache[4];
   int current_group;
+
+  GHashTable *reserved_keycodes;
+  GQueue *available_keycodes;
 #endif
 
   guint caps_lock_state : 1;
@@ -441,16 +444,100 @@ clutter_keymap_x11_set_property (GObject      *gobject,
     }
 }
 
+#ifdef HAVE_XKB
+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;
+}
+#endif
+
 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);
 
 #ifdef HAVE_XKB
+  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)
@@ -460,6 +547,7 @@ clutter_keymap_x11_finalize (GObject *gobject)
   G_OBJECT_CLASS (clutter_keymap_x11_parent_class)->finalize (gobject);
 }
 
+
 static void
 clutter_keymap_x11_class_init (ClutterKeymapX11Class *klass)
 {
@@ -483,6 +571,11 @@ clutter_keymap_x11_init (ClutterKeymapX11 *keymap)
 {
   keymap->current_direction = PANGO_DIRECTION_NEUTRAL;
   keymap->current_group = -1;
+
+#ifdef HAVE_XKB
+  keymap->reserved_keycodes = g_hash_table_new (NULL, NULL);
+  keymap->available_keycodes = g_queue_new ();
+#endif
 }
 
 static ClutterTranslateReturn
@@ -766,6 +859,80 @@ clutter_keymap_x11_get_entries_for_keyval (ClutterKeymapX11  *keymap_x11,
     }
 }
 
+#ifdef HAVE_XKB
+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;
+}
+#endif
+
+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);
+
+#ifdef HAVE_XKB
+  *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;
+#else
+  return FALSE;
+#endif
+}
+
+void clutter_keymap_x11_release_keycode_if_needed (ClutterKeymapX11 *keymap_x11,
+                                                   guint             keycode)
+{
+  g_return_if_fail (CLUTTER_IS_KEYMAP_X11 (keymap_x11));
+
+#ifdef HAVE_XKB
+  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));
+#endif
+}
+
 void
 clutter_keymap_x11_latch_modifiers (ClutterKeymapX11 *keymap_x11,
                                     uint32_t          level,
diff --git a/clutter/clutter/x11/clutter-keymap-x11.h b/clutter/clutter/x11/clutter-keymap-x11.h
index 4b5b403c8..4decb44ee 100644
--- a/clutter/clutter/x11/clutter-keymap-x11.h
+++ b/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__ */
diff --git a/clutter/clutter/x11/clutter-virtual-input-device-x11.c b/clutter/clutter/x11/clutter-virtual-input-device-x11.c
index e16ba3fd0..cab26c38c 100644
--- a/clutter/clutter/x11/clutter-virtual-input-device-x11.c
+++ b/clutter/clutter/x11/clutter-virtual-input-device-x11.c
@@ -143,8 +143,13 @@ clutter_virtual_input_device_x11_notify_keyval (ClutterVirtualInputDevice *virtu
 
   if (!clutter_keymap_x11_keycode_for_keyval (keymap, keyval, &keycode, &level))
     {
-      g_warning ("No keycode found for keyval %x in current group", keyval);
-      return;
+      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) &&
@@ -155,9 +160,13 @@ 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)
-    clutter_keymap_x11_latch_modifiers (keymap, level, FALSE);
+
+  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