[gtkmm] Gtk docs: Avoid some warnings from gmmproc

[Kjell Ahlstedt <kjellahl src gnome org>]

commit dd3281e790f19777ad094bae7973cfeb6463d7eb
Author: Kjell Ahlstedt <kjellahlstedt gmail com>
Date:   Tue Dec 15 15:40:24 2020 +0100

    Gtk docs: Avoid some warnings from gmmproc
    
    * gtk/src/gtk_docs_override.xml: Add some substitute_enumerator_name.
    * gtk/src/widget.hg: Hand-code the description of activate().

 gtk/src/gtk_docs_override.xml |  2 ++
 gtk/src/widget.hg             | 15 +++++++++++++++
 2 files changed, 17 insertions(+)
---
diff --git a/gtk/src/gtk_docs_override.xml b/gtk/src/gtk_docs_override.xml
index 291ef54a..37198636 100644
--- a/gtk/src/gtk_docs_override.xml
+++ b/gtk/src/gtk_docs_override.xml
@@ -131,7 +131,9 @@
 <substitute_enumerator_name from_prefix="GTK_ORDERING_" to_prefix="Gtk::Ordering::" />
 <substitute_enumerator_name from_prefix="GTK_ACCESSIBLE_STATE_" to_prefix="Gtk::Accessible::State::" />
 <substitute_enumerator_name from_prefix="GTK_ACCESSIBLE_ROLE_" to_prefix="Gtk::Accessible::Role::" />
+<substitute_enumerator_name from_prefix="GTK_ACCESSIBLE_RELATION_" to_prefix="Gtk::Accessible::Relation::" />
 <substitute_enumerator_name from_prefix="GTK_FILTER_MATCH_" to_prefix="Gtk::Filter::Match::" />
+<substitute_enumerator_name from_prefix="GTK_FILTER_CHANGE_" to_prefix="Gtk::Filter::Change::" />
 <substitute_enumerator_name from_prefix="GTK_STRING_FILTER_MATCH_MODE_" 
to_prefix="Gtk::StringFilter::MatchMode::" />
 <!-- GdkWindowWindowClass is not wrapped in gtkmm. Don't substitute its enumerator names. -->
 <substitute_enumerator_name from="GDK_INPUT_ONLY" to="GDK_INPUT_ONLY" />
diff --git a/gtk/src/widget.hg b/gtk/src/widget.hg
index 529fbe5e..2187daa8 100644
--- a/gtk/src/widget.hg
+++ b/gtk/src/widget.hg
@@ -147,6 +147,21 @@ public:
 
   _WRAP_METHOD(bool mnemonic_activate(bool group_cycling), gtk_widget_mnemonic_activate)
 
+  /** For widgets that can be “activated” (buttons, menu items, etc.)
+   * this function activates them.
+   *
+   * The activation will emit the signal set using
+   * gtk_widget_class_set_activate_signal() during class initialization.
+   *
+   * Activation is what happens when you press Enter on a widget during
+   * key navigation.
+   *
+   * If you wish to handle the activation keybinding yourself, it is
+   * recommended to use gtk_widget_class_add_shortcut() with an action
+   * created with Gtk::SignalAction::create().
+   *
+   * @return <tt>true</tt> if the widget was activatable, else <tt>false</tt>.
+   */
   _WRAP_METHOD(bool activate(), gtk_widget_activate)
 
   _WRAP_METHOD(void set_can_focus(bool can_focus = true), gtk_widget_set_can_focus)