[libdazzle] gtk: add helper to proxy GActionGroups from one widget to another

[Christian Hergert <chergert src gnome org>]

commit 25ec560f592260135f1158817e313916d7a1c713
Author: Christian Hergert <chergert redhat com>
Date:   Thu Jun 22 16:58:15 2017 -0700

    gtk: add helper to proxy GActionGroups from one widget to another
    
    This can be useful when you have a situation with a HeaderBar and the
    Content Area. You want the header bar to activate actions in the content
    area, but they are not in a direct parent/child relationship. Therefore
    the action muxer in Gtk cannot activate those actions.
    
    This gets around that issue by looking at all the action groups associated
    with the `from_widget` and ensuring them that they are copied to `widget`.
    
    You can clear the old entry with a NULL `from_widget`.
    
    Use a muxer key so that you can override previously muxed groups.

 src/util/dzl-gtk.c |   68 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 src/util/dzl-gtk.h |    3 ++
 2 files changed, 71 insertions(+), 0 deletions(-)
---
diff --git a/src/util/dzl-gtk.c b/src/util/dzl-gtk.c
index 1386714..aa34228 100644
--- a/src/util/dzl-gtk.c
+++ b/src/util/dzl-gtk.c
@@ -367,3 +367,71 @@ dzl_gtk_widget_action_set (GtkWidget   *widget,
   g_object_set_valist (G_OBJECT (action), first_property, args);
   va_end (args);
 }
+
+/**
+ * dzl_gtk_widget_mux_action_groups:
+ * @widget: a #GtkWidget
+ * @from_widget: A #GtkWidget containing the groups to copy
+ * @mux_key: a unique key to represent the muxing
+ *
+ * This function will find all of the actions on @from_widget in various
+ * groups and add them to @widget. As this just copies the action groups
+ * over, note that it does not allow for muxing items within the same
+ * group.
+ *
+ * You should specify a key for @mux_key so that if the same mux key is
+ * seen again, the previous muxings will be removed.
+ */
+void
+dzl_gtk_widget_mux_action_groups (GtkWidget   *widget,
+                                  GtkWidget   *from_widget,
+                                  const gchar *mux_key)
+{
+  const gchar * const *old_prefixes = NULL;
+  const gchar **prefixes = NULL;
+
+  g_return_if_fail (GTK_IS_WIDGET (widget));
+  g_return_if_fail (!from_widget || GTK_IS_WIDGET (from_widget));
+  g_return_if_fail (mux_key != NULL);
+
+  /*
+   * First check to see if there are any old action groups that
+   * were muxed for which we need to unmux.
+   */
+
+  old_prefixes = g_object_get_data (G_OBJECT (widget), mux_key);
+
+  if (old_prefixes != NULL)
+    {
+      for (guint i = 0; old_prefixes [i]; i++)
+        gtk_widget_insert_action_group (widget, old_prefixes [i], NULL);
+    }
+
+  /*
+   * Now, if there is a from_widget to mux, get all of their action
+   * groups and mux them across to our target widget.
+   */
+
+  if (from_widget != NULL)
+    {
+      prefixes = gtk_widget_list_action_prefixes (from_widget);
+      if (prefixes == NULL)
+        return;
+
+      for (guint i = 0; prefixes [i]; i++)
+        {
+          GActionGroup *group = gtk_widget_get_action_group (from_widget, prefixes [i]);
+
+          if G_UNLIKELY (group == NULL)
+            continue;
+
+          gtk_widget_insert_action_group (widget, prefixes [i], group);
+        }
+    }
+
+  /* Store the set of muxed prefixes so that we can unmux them later. */
+
+  g_object_set_data_full (G_OBJECT (widget), mux_key,
+                          g_strdupv ((gchar **)prefixes),
+                          (GDestroyNotify) g_strfreev);
+}
diff --git a/src/util/dzl-gtk.h b/src/util/dzl-gtk.h
index e507e10..62df399 100644
--- a/src/util/dzl-gtk.h
+++ b/src/util/dzl-gtk.h
@@ -36,6 +36,9 @@ gboolean      dzl_gtk_widget_action_with_string  (GtkWidget               *widge
                                                   const gchar             *group,
                                                   const gchar             *name,
                                                   const gchar             *param);
+void          dzl_gtk_widget_mux_action_groups   (GtkWidget               *widget,
+                                                  GtkWidget               *from_widget,
+                                                  const gchar             *mux_key);
 void          dzl_gtk_widget_hide_with_fade      (GtkWidget               *widget);
 void          dzl_gtk_widget_show_with_fade      (GtkWidget               *widget);
 void          dzl_gtk_widget_add_style_class     (GtkWidget               *widget,