Оформил: DeeCo
Автор: http://www.swissdelphicenter.ch

{ 
  Question/Abstract: 

  I often want to automatically run some code directly after the form has 
  shown. If this is done in the OnShow event it gets done while the form is 
  still invisible (not good if the code takes a little while to run.) 
  Currently, I use a Timer with its interval property set to about 200 and 
  enabled set to false. In the OnShow event I set Timer.Enabled := True and 
  the first statement in the OnTimer event is Timer.Enabled := False so the 
  event only runs once. 

  Answer: 

  Post a custom message to yourself. 
  The following code shows how to trigger a AfterShow, AfterCreate event. 

}

 const
   WM_AFTER_SHOW = WM_USER + 300; // custom message 
  WM_AFTER_CREATE = WM_USER + 301; // custom message 
type
   TForm1 = class(TForm)
     // OnShow event 
    procedure FormShow(Sender: TObject);
     // OnCreate event 
    procedure FormCreate(Sender: TObject);
   private
     procedure WmAfterShow(var Msg: TMessage); message WM_AFTER_SHOW;
     procedure WmAfterCreate(var Msg: TMessage); message WM_AFTER_CREATE;
   public
   end;

 var
   Form1: TForm1;

 implementation

 {$R *.DFM}

 procedure TForm1.WmAfterShow(var Msg: TMessage);
 begin
   ShowMessage('WM_AFTER_SHOW received!');
 end;

 procedure TForm1.WmAfterCreate(var Msg: TMessage);
 begin
   ShowMessage('WM_AFTER_CREATE received!');
 end;

 procedure TForm1.FormShow(Sender: TObject);
 begin
   // Post the custom message WM_AFTER_SHOW to our form 
  PostMessage(Self.Handle, WM_AFTER_SHOW, 0, 0);
 end;

 procedure TForm1.FormCreate(Sender: TObject);
 begin
   // Post the custom message WM_AFTER_CREATE to our form 
  PostMessage(Self.Handle, WM_AFTER_CREATE, 0, 0);
 end;