[gnome-control-center] media-keys: Handle 'Above_Tab' fake key

[Georges Basile Stavracas Neto <gbsneto src gnome org>]

commit eb3580ee9d3d51a89943fe290f78ef2feff75c51
Author: Florian Müllner <fmuellner gnome org>
Date:   Sat Jun 15 20:51:46 2019 +0200

    media-keys: Handle 'Above_Tab' fake key
    
    Mutter supports the 'Above_Tab' fake keysym that refers to the key
    that is physically located above the tab key. It is used in the default
    shortcut of the "Switch windows of an application" action.
    
    As gtk_accelerator_parse() doesn't recognize the keysym, we display
    the shortcut incorrectly as "disabled", and it is not taken into account
    for conflict resolution.
    
    Address this by translating binding that contains the 'Above_Tab' string
    to bindings where the string is replaced with each possible keysym that
    corresponds to the fixed keycode of KEY_GRAVE + 8.
    
    https://gitlab.gnome.org/GNOME/gnome-control-center/issues/581

 panels/keyboard/cc-keyboard-item.c | 120 ++++++++++++++++++++++++++++++++++++-
 1 file changed, 117 insertions(+), 3 deletions(-)
---
diff --git a/panels/keyboard/cc-keyboard-item.c b/panels/keyboard/cc-keyboard-item.c
index defddee2f..f046c6887 100644
--- a/panels/keyboard/cc-keyboard-item.c
+++ b/panels/keyboard/cc-keyboard-item.c
@@ -424,11 +424,119 @@ cc_keyboard_item_new (CcKeyboardItemType type)
   return CC_KEYBOARD_ITEM (object);
 }
 
+static guint *
+get_above_tab_keysyms (void)
+{
+  GdkKeymap *keymap = gdk_keymap_get_for_display (gdk_display_get_default ());
+  guint keycode = 0x29 /* KEY_GRAVE */ + 8;
+  g_autofree guint *keyvals = NULL;
+  GArray *keysyms;
+  int n_entries, i, j;
+
+  keysyms = g_array_new (TRUE, FALSE, sizeof (guint));
+
+  if (!gdk_keymap_get_entries_for_keycode (keymap, keycode, NULL, &keyvals, &n_entries))
+    goto out;
+
+  for (i = 0; i < n_entries; i++)
+    {
+      gboolean found = FALSE;
+
+      for (j = 0; j < keysyms->len; j++)
+        if (g_array_index (keysyms, guint, j) == keyvals[i])
+          {
+            found = TRUE;
+            break;
+          }
+
+      if (!found)
+        g_array_append_val (keysyms, keyvals[i]);
+    }
+
+out:
+  return (guint *)g_array_free (keysyms, FALSE);
+}
+
+/*
+ * translate_above_tab:
+ *
+ * @original_bindings: A list of accelerator strings
+ * @new_bindings: (out): Translated bindings if translation is needed
+ *
+ * Translate accelerator strings that contain the Above_Tab fake keysym
+ * used by mutter to strings that use the real keysyms that correspond
+ * to the key that is located physically above the tab key.
+ *
+ * Returns: %TRUE if strings were translated, %FALSE if @original_bindings
+ *   can be used unmodified
+ */
+static gboolean
+translate_above_tab (char **original_bindings,
+                     char ***new_bindings)
+{
+  GPtrArray *replaced_bindings;
+  g_autofree guint *above_tab_keysyms = NULL;
+  gboolean needs_translation = FALSE;
+  char **str;
+
+  for (str = original_bindings; *str && !needs_translation; str++)
+    needs_translation = strstr (*str, "Above_Tab") != NULL;
+
+  if (!needs_translation)
+    return FALSE;
+
+  above_tab_keysyms = get_above_tab_keysyms ();
+
+  replaced_bindings = g_ptr_array_new ();
+
+  for (str = original_bindings; *str; str++)
+    {
+      if (strstr (*str, "Above_Tab") == NULL)
+        {
+          g_ptr_array_add (replaced_bindings, g_strdup (*str));
+        }
+      else
+        {
+          g_auto (GStrv) split_str = g_strsplit (*str, "Above_Tab", -1);
+          int i;
+
+          for (i = 0; above_tab_keysyms[i]; i++)
+            {
+              g_autofree char *sym = NULL;
+
+              sym = gtk_accelerator_name (above_tab_keysyms[i], 0);
+              g_ptr_array_add (replaced_bindings, g_strjoinv (sym, split_str));
+            }
+        }
+      g_ptr_array_add (replaced_bindings, NULL);
+    }
+
+  *new_bindings = (char **)g_ptr_array_free (replaced_bindings, FALSE);
+  return TRUE;
+}
+
+static char *
+translate_binding_string (const char *str)
+{
+  g_autofree guint *above_tab_keysyms = NULL;
+  g_autofree char *symname = NULL;
+  g_auto (GStrv) split_str = NULL;
+
+  if (str == NULL || strstr (str, "Above_Tab") == NULL)
+    return g_strdup (str);
+
+  above_tab_keysyms = get_above_tab_keysyms ();
+  symname = gtk_accelerator_name (above_tab_keysyms[0], 0);
+
+  split_str = g_strsplit (str, "Above_Tab", -1);
+  return g_strjoinv (symname, split_str);
+}
+
 static GList *
 variant_get_key_combos (GVariant *variant)
 {
   GList *combos = NULL;
-  char **bindings = NULL, **str;
+  char **bindings = NULL, **translated_bindings, **str;
 
   if (g_variant_is_of_type (variant, G_VARIANT_TYPE_STRING))
     {
@@ -440,6 +548,12 @@ variant_get_key_combos (GVariant *variant)
       bindings = g_variant_dup_strv (variant, NULL);
     }
 
+  if (translate_above_tab (bindings, &translated_bindings))
+    {
+      g_strfreev (bindings);
+      bindings = translated_bindings;
+    }
+
   for (str = bindings; *str; str++)
     {
       CcKeyCombo *combo = g_new (CcKeyCombo, 1);
@@ -480,13 +594,13 @@ settings_get_binding (GSettings  *settings,
 
   variant = g_settings_get_value (settings, key);
   if (g_variant_is_of_type (variant, G_VARIANT_TYPE_STRING))
-    value = g_variant_dup_string (variant, NULL);
+    value = translate_binding_string (g_variant_get_string (variant, NULL));
   else if (g_variant_is_of_type (variant, G_VARIANT_TYPE_STRING_ARRAY))
     {
       const char **str_array;
 
       str_array = g_variant_get_strv (variant, NULL);
-      value = g_strdup (str_array[0]);
+      value = translate_binding_string (str_array[0]);
       g_free (str_array);
     }
   g_variant_unref (variant);