unit MainFormUnt;

 

interface

 

uses

  Winapi.Windows,

  Winapi.Messages,

  System.SysUtils,

  System.Classes,

  Vcl.Controls,

  Vcl.Forms,

  Vcl.StdCtrls;

 

const

   WM_AFTER_SHOW = WM_USER + 331 ;

 

type

 

  TFormX = class(TForm)

  private

    FOnAfterShow: TNotifyEvent;

    FOnShowBackUp: TNotifyEvent;

    procedure DoFormShow(Sender: TObject);

    procedure DoAfterShow( var aMessage : TMessage ); message WM_AFTER_SHOW;

  public

    constructor Create(AOwner: TComponent); override;

    property OnAfterShow: TNotifyEvent read FOnAfterShow write FOnAfterShow;

  end;

  TForm = class(TFormX);

 

 

  TMainForm = class(TForm)

    Memo1: TMemo;

    procedure FormCreate(Sender: TObject);

    procedure FormShow(Sender: TObject);

    procedure FormAfterShow(Sender: TObject);

  private

    { Private declarations }

  public

    { Public declarations }

  end;

 

var

  MainForm: TMainForm;

 

implementation

 

{$R *.dfm}

 

{$REGION ' TFormX '}

procedure TFormX.DoAfterShow( var aMessage : TMessage );

begin

  if Assigned(FOnAfterShow) then FOnAfterShow(Self);

end;

 

procedure TFormX.DoFormShow(Sender: TObject);

begin

  Inherited;

  if Assigned(FOnShowBackUp) then FOnShowBackUp(self);

  OnShow := FOnShowBackUp;

  PostMessage( Handle, WM_AFTER_SHOW, 0 , 0 ); // This will post a message to itself

end;

 

constructor TFormX.Create(AOwner: TComponent);

begin

  inherited Create(AOwner);

 

  FOnShowBackUp := OnShow;

  OnShow := DoFormShow;

end;

 

{$ENDREGION}

 

procedure TMainForm.FormShow(Sender: TObject);

begin

   Memo1.Lines.Add('on show' );

end;

 

procedure TMainForm.FormAfterShow(Sender: TObject);

begin

 

  Memo1.Lines.Add('on after show' );

end;

 

procedure TMainForm.FormCreate(Sender: TObject);

begin

   OnAfterShow := FormAfterShow;

end;

 

end.