create-menu-proxy

This signal is emitted when the toolbar needs information from the tool item about whether the item should appear in the toolbar overflow menu.

In response the tool item should either

The toolbar may cache the result of this signal. When the tool item changes how it will respond to this signal it must call rebuild_menu() to invalidate the cache and ensure that the toolbar rebuilds its overflow menu.

Callback function

bool callback(GtkToolItem toolitem);