Delphi里面的MDI Form是一个比较特殊的Form, 他在Form的Client区域内加了一个
ClientWindow, 而这个Window不是一个TWinControl, 是通过WinApi函数建立的.
由于该Window的WndProc功能较弱, 不支持你所要的功能.
解决方法是把按钮和label放到ToolBar或者Panel中, 但是Toolbar/panel必须
Align到四个边中的一个. 要想画背景, 可以通过重写它的ClientWndProc过程, 让
他能够画图.
下面式从Delphi 32深度历险中下载过来的 MDI_BKGRD.ZIP 里面的文字说明文件:
HereI are the steps to add a wallpaper to the client area of of a
MDI parent form:
1) Create a new project
2) Set the form's FormStyle to fsMDIForm
3) Drop an image on the form and select a bitmap into it.
4) Find the { Private Declarations } comment in the form's
definition and add these lines right after it:
FClientInstance,
FPrevClientProc : TFarProc;
PROCEDURE ClientWndProc(VAR Message: TMessage);
5) Find the "implementation" line and the {$R *.DFM} line that
follows it. After that line, enter this code:
PROCEDURE TForm1.ClientWndProc(VAR Message: TMessage);
VAR
MyDC : hDC;
Ro, Co : Word;
begin
with Message do
case Msg of
WM_ERASEBKGND:
begin
MyDC := TWMEraseBkGnd(Message).DC;
FOR Ro := 0 TO ClientHeight DIV Image1.Picture.Height DO
FOR Co := 0 TO ClientWIDTH DIV Image1.Picture.Width DO
BitBlt(MyDC, Co*Image1.Picture.Width, Ro*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;
6) Start an OnCreate method for the form and put these lines in it:
FClientInstance := MakeObjectInstance(ClientWndProc);
FPrevClientProc := Pointer(GetWindowLong(ClientHandle, GWL_WNDPROC));
SetWindowLong(ClientHandle, GWL_WNDPROC, LongInt(FClientInstance));
7) Add a new form to your project and set its FormStyle to
fsMDIChild.
Now you have a working MDI project with "wallpaper". The image
component is not visible, but its bitmap is replicated to cover
the MDI form's client area.
There is still one problem
when you minimize the child window its
icon will be drawn against a gray rectangle.
要提供完整的如同普通TWinControl的功能, 几乎的重写TCustom, 太麻烦了.
