Type ActivateEvent

object --+        
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    Object --+    
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         Event --+
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                ActivateEvent

An activate event is sent when a top-level window or the entire application is being activated or deactivated.

A top-level window (a dialog or frame) receives an activate event when is being activated or deactivated. This is indicated visually by the title bar changing colour, and a subwindow gaining the keyboard focus. An application is activated or deactivated when one of its frames becomes activated, or a frame becomes inactivate resulting in all application frames being inactive.

Please note that usually you should call event.Skip() in your handlers for these events so the default handlers will still be called, as not doing so can result in strange effects.