{ MDI的背景代码 }
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;
// 在DC上平铺图象
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 // 传递其他消息
Result := CallWindowProc FPrevClientProc,
ClientHandle,
Msg,
wParam,
lParam);
end;
end;

- 在你的主窗体的OnShow事件中加入以下代码:

// MDI背景平铺代码，与WndProc链接
FClientInstance := MakeObjectInstance ClientWndProc);
FPrevClientProc := Pointer GetWindowLong ClientHandle,GWL_WNDPROC));
SetWindowLong ClientHandle,GWL_WNDPROC,LongInt FClientInstance));

- 现在你有一个背景了!