Author: Jonas Bilinkevicius

Is there a way of hiding a TMainMenu?

Answer:

Yes, do not hide it. What you do is leave it visible (as well as caption bar and 
border) and then just size the whole window so that only the client area is 
visible, all the nonclient area, including the menu bar, simply lies outside the 
visible screen. The alternative is to use a toolbar menu instead of a standard menu 
bar.

1   { ... }
2   private {in form declaration}
3   
4   procedure WMGetMinMaxInfo(var msg: TWMGetMinMaxInfo); message WM_GETMINMAXINFO;
5   { ... }
6   
7   procedure TForm1.WMGetMinMaxInfo(var msg: TWMGetMinMaxInfo);
8   begin
9     inherited;
10    with msg.MinMaxInfo^.ptMaxTrackSize do
11    begin
12      X := GetDeviceCaps(Canvas.handle, HORZRES) + (Width - ClientWidth);
13      Y := GetDeviceCaps(Canvas.handle, VERTRES) + (Height - ClientHeight);
14    end;
15  end;
16  
17  procedure TForm1.Button2Click(Sender: TObject);
18  const
19    Rect: TRect = (Left: 0; Top: 0; Right: 0; Bottom: 0);
20    FullScreen: Boolean = False;
21  begin
22    FullScreen := not FullScreen;
23    if FullScreen then
24    begin
25      Rect := BoundsRect;
26      SetBounds(Left - ClientOrigin.X, Top - ClientOrigin.Y,
27        GetDeviceCaps(Canvas.handle, HORZRES) + (Width - ClientWidth),
28        GetDeviceCaps(Canvas.handle, VERTRES) + (Height - ClientHeight));
29      { Label2.caption := IntToStr(GetDeviceCaps(Canvas.handle, VERTRES)); }
30    end
31    else
32      BoundsRect := Rect;
33  end;