Fires when actions of global interest to the client occur, such as when the focus shifts from one element to another, or when a child window closes. Some events do not necessarily mean that the state of the UI has changed. For example, if the user tabs to a text-entry field and then clicks a button to update the field, a TextChanged event fires even if the user did not actually change the text. When processing an event, it may be necessary for a client application to check whether anything has actually changed before taking action.