I've encountered some code that's new to me...

I've never really seen a type declaration of a procedure of object, and I just don't see the point. Why couldn't the developer simply keep a field of type Boolean?

interface

    type
      TFinishedCaptureEvent = procedure(AFinished: Boolean) of object;

      TFrameCard = class(TFrame)
      ...
      private
        FOnFinishedCapture: TFinishedCaptureEvent;
      public
        property OnFinishedCapture: TFinishedCaptureEvent read FOnFinishedCapture write FOnFinishedCapture;
      end;    

implementation

  ...

  if Assigned(FOnFinishedCapture) then
        FOnFinishedCapture(False);