watch


Description:

public unowned ExpressionWatch watch (Object? this_, owned ExpressionNotify notify)

Installs a watch for the given `expression` that calls the `notify` function whenever the evaluation of `self` may have changed.

GTK cannot guarantee that the evaluation did indeed change when the notify gets invoked, but it guarantees the opposite: When it did in fact change, the `notify` will be invoked.

Parameters:

this

a `GtkExpression`

this_

the `this` argument to watch

notify

callback to invoke when the expression changes

user_data

user data to pass to the `notify` callback

user_destroy

destroy notify for `user_data`

Returns:

The newly installed watch. Note that the only reference held to the watch will be released when the watch is unwatched which can happen automatically, and not just via [method@Gtk.ExpressionWatch.unwatch]. You should call [method@Gtk.ExpressionWatch.ref] if you want to keep the watch around.