Signal handling

connecting

To connect an object to a signal that it emits, call one of the object’s Connect... methods.

The connect methods all accept a handler argument that is a function with a specific signature. The first parameters is always the object that the signal is for. Some handlers have no additional parameters, others have more parameters that provide event-specific information.

button := gtk.ButtonNewWithLabel("a button")

// enable emitting of motion events
button.Widget().SetEvents(int32(gdk.GDK_POINTER_MOTION_MASK))

button.Widget().ConnectMotionNotifyEvent(
    func(widget *gtk.Widget, event *gdk.EventMotion) bool {
        fmt.Println(event.Y, event.Y)
        return false
    }
)

Remember that it may be necessary to upcast to access the desired connect method.

disconnecting

All of the Connect... methods return a handler id. The id may be used later to disconnect the handler.

    connectId := button.ConnectClicked(func(...) {
        ...
    })
    
    ...
    
    button.DisconnectClicked(connectId)

notify signal for a single property

ConnectNotifyProperty connects a callback to the notify signal for a specific property of an Object.

This is an example of connecting to the notify signal for a window’s title property.

    window := gtk.WindowNew(...)

    // connect to the "notify::title" signal
    window.Object().ConnectNotifyProperty(
        "title", func(object *gobject.Object, pspec *gobject.ParamSpec,
    ) {
        fmt.Println("title property changed")
    })

The returned value represents the connection, and may be passed to DisconnectNotify to remove it.

ConnectNotifyProperty is a special case, and has no direct equivalent in the GObject library.