MDI приложения

Code:

            procedure TMainForm.ClientWndProc(var Message: TMessage);

            var

              Dc : hDC;

              Row : Integer;

              Col : Integer;

            begin

              with Message do

                case Msg of

                  WM_ERASEBKGND:

                  begin

                    Dc := TWMEraseBkGnd(Message).Dc;

                    for Row := 0 to ClientHeight div Image1.Picture.Height do

                      for Col := 0 to ClientWidth div Image1.Picture.Width do

                        BitBlt(Dc,

                           Col * Image1.Picture.Width,

                           Row * Image1.Picture.Height,

                           Image1.Picture.Width,

                           Image1.Picture.Height,

                           Image1.Picture.Bitmap.Canvas.Handle,

                           0,

                           0,

                           SRCCOPY);

                      Result := 1;

                  end;

                  else

                    Result := CallWindowProc(FPrevClientProc,

                                             ClientHandle,

                                             Msg,

                                             wParam,

                                             lParam);

              end;

            end;

Code:

               FClientInstance := MakeObjectInstance(ClientWndProc);

               FPrevClientProc := Pointer(GetWindowLong(ClientHandle,

                                          GWL_WNDPROC));

               SetWindowLong(ClientHandle,

                             GWL_WNDPROC, LongInt(FClientInstance));