Expression.watch

Watch the given expression for changes.

The notify function will be called 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_the this argument to watch
notifycallback to invoke when the expression changes

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 [gtk.expression_watch.ExpressionWatch.unwatch]. You should call [gtk.expression_watch.ExpressionWatch.ref_] if you want to keep the watch around.