Fix focusing the Terminal tab in the message window

Use more generic code to not fall into the same issue next time layout
changes, and to potentially support plugin tabs in the message window.

Fixes #1198.

src/keybindings.c

@@ -1738,14 +1738,43 @@ static void focus_sidebar(void)
 }
 
 
+static GtkWidget *find_focus_widget(GtkWidget *widget)
+{
+	GtkWidget *focus = NULL;
+
+	if (GTK_IS_BIN(widget)) /* optimized simple case */
+		focus = find_focus_widget(gtk_bin_get_child(GTK_BIN(widget)));
+	else if (GTK_IS_CONTAINER(widget))
+	{
+		GList *children = gtk_container_get_children(GTK_CONTAINER(widget));
+		GList *node;
+
+		for (node = children; node && ! focus; node = node->next)
+			focus = find_focus_widget(node->data);
+		g_list_free(children);
+	}
+
+	/* Some containers handled above might not have children and be what we want to focus
+	 * (e.g. GtkTreeView), so focus that if possible and we don't have anything better */
+	if (! focus && gtk_widget_get_can_focus(widget))
+		focus = widget;
+
+	return focus;
+}
+
+
 static void focus_msgwindow(void)
 {
 	if (ui_prefs.msgwindow_visible)
 	{
 		gint page_num = gtk_notebook_get_current_page(GTK_NOTEBOOK(msgwindow.notebook));
-		GtkWidget *page = gtk_notebook_get_nth_page(GTK_NOTEBOOK(msgwindow.notebook), page_num);
+		GtkWidget *widget = gtk_notebook_get_nth_page(GTK_NOTEBOOK(msgwindow.notebook), page_num);
 
-		gtk_widget_grab_focus(gtk_bin_get_child(GTK_BIN(page)));
+		widget = find_focus_widget(widget);
+		if (widget)
+			gtk_widget_grab_focus(widget);
+		else
+			utils_beep();
 	}
 }