Notification fired when this canvas becomes visible or hidden to the user. Note - this method is fired when the Canvas.isVisible state of this component changes. It may be fired in
response an explicit call to Canvas.show or Canvas.hide or Canvas.setVisibility, or in response to a parent component being shown or hidden when this widgets visibility is set to "inherit". Note that a call to Canvas.show or Canvas.hide will
not always fire this notification. If this widget has a hidden parent, show or hide would change this components
visibility property, and may update the CSS visibility
attribute of the drawn handle in the DOM, but would not actually hide or reveal the component to the user and as such
the notification would not fire.
Note also that this notification will only be fired for components which have been
drawn.
- Parameters:
event - the event