title: Delphi how to implement OnAfterMonitorDpiChanged
body: <p>I am using a subclass <code>TMyForm = class( tForm )</code> for all my forms.
  I do not want to add the same code in all my forms and would like to override the <code>OnAfterMonitorDpiChanged</code> and add the common code into TMyForm.</p>
  
  <p>How I can do that?
  Or do I have to use
  <code>procedure WMDpiChanged(var Message: TWMDpi); message WM_DPICHANGED;</code> ?</p>
  
  <p>Delphi 10.3.3</p>