deactivate
The "deactivate" signal is emitted when either a GtkMenuItem within the current menu has been selected or the menu has been cancelled.
This signal initiates the menu's deactivate routine, which removes the key and pointer grabs from the menu and deselects any selected item before popping the menu down. It is largely used internally, and probably carries more overhead when called than the "selection-done" signal emitted under similar conditions.
Callback function
void callback(GtkWidget menu);
忘却曲線を使ってこの知識を確実に記憶に残す
