scrollwheel support in GtkOptionMenu.

[Alex Larsson <alexl redhat com>]

Here is a short patch that allows you to change the active GtkOptionMenu 
item by using the mouse scroll-wheel.

Ok to commit this?

/ Alex

Index: gtkoptionmenu.c
===================================================================
RCS file: /cvs/gnome/gtk+/gtk/gtkoptionmenu.c,v
retrieving revision 1.51
diff -u -p -r1.51 gtkoptionmenu.c
--- gtkoptionmenu.c	2001/08/17 16:33:04	1.51
+++ gtkoptionmenu.c	2001/09/16 21:44:05
@@ -80,6 +80,8 @@ static void gtk_option_menu_position    
 static void gtk_option_menu_show_all        (GtkWidget          *widget);
 static void gtk_option_menu_hide_all        (GtkWidget          *widget);
 static GtkType gtk_option_menu_child_type   (GtkContainer       *container);
+static gint gtk_option_menu_scroll_event    (GtkWidget          *widget,
+					     GdkEventScroll     *event);
 
 enum
 {
@@ -147,6 +149,7 @@ gtk_option_menu_class_init (GtkOptionMen
   widget_class->expose_event = gtk_option_menu_expose;
   widget_class->button_press_event = gtk_option_menu_button_press;
   widget_class->key_press_event = gtk_option_menu_key_press;
+  widget_class->scroll_event = gtk_option_menu_scroll_event;
   widget_class->show_all = gtk_option_menu_show_all;
   widget_class->hide_all = gtk_option_menu_hide_all;
 
@@ -881,5 +884,33 @@ gtk_option_menu_hide_all (GtkWidget *wid
 
   gtk_widget_hide (widget);
   gtk_container_foreach (container, (GtkCallback) gtk_widget_hide_all, NULL);
+}
+
+static gint
+gtk_option_menu_scroll_event (GtkWidget          *widget,
+			      GdkEventScroll     *event)
+{
+  GtkOptionMenu *option_menu = GTK_OPTION_MENU (widget);
+  gint index;
+  gint n_children;
+    
+  index = gtk_option_menu_get_history (option_menu);
+
+  if (index != -1)
+    {
+      n_children = g_list_length (GTK_MENU_SHELL (option_menu->menu)->children);
+      
+      if (event->direction == GDK_SCROLL_UP)
+	index--;
+      else
+	index++;
+
+      index = MAX (index, 0);
+      index = MIN (index, n_children - 1);
+
+      gtk_option_menu_set_history (option_menu, index);
+    }
+
+  return TRUE;
 }