如何在mdi主窗口内平铺一张图纸？？？？？？

Question

thanks

Answer 1

...
    ImgMain: TImage;
  private
    FClientInstance : TFarProc;
    FPrevClientProc : TFarProc;
    procedure ClientWndProc(var message:TMessage);
...procedure TForm1.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 ImgMain.Picture.Height do
          for Col := 0 to ClientWidth div ImgMain.Picture.Width do
            BitBlt(Dc,
               Col * ImgMain.Picture.Width,
               Row * ImgMain.Picture.Height,
               ImgMain.Picture.Width,
               ImgMain.Picture.Height,
               ImgMain.Picture.Bitmap.Canvas.Handle,
               0,
               0,
               SRCCOPY);
          Result := 1;
      end;
      else
        Result := CallWindowProc(FPrevClientProc,
                                 ClientHandle,
                                 Msg,
                                 wParam,
                                 lParam);
  end;
end;procedure TForm1.FormCreate(Sender: TObject);
begin   FClientInstance := MakeObjectInstance(ClientWndProc);
   FPrevClientProc := Pointer(GetWindowLong(ClientHandle,GWL_WNDPROC));
   SetWindowLong(ClientHandle,GWL_WNDPROC, LongInt(FClientInstance));end;

Answer 2

为什么运行的时候会出现这样的错误
Exception EDivByZero in module Project2.ext at 00062953.
Division by zero.

Answer 3

FClientInstance := MakeObjectInstance(ClientWndProc);
   FPrevClientProc := Pointer(GetWindowLong(ClientHandle,GWL_WNDPROC));
   SetWindowLong(ClientHandle,GWL_WNDPROC, LongInt(FClientInstance));我只要把setwindowlong屏蔽就能通过？为什么