System Menu: How to hide/move standard menuitems

Question

In the system menu (topleft of titlebar), I can add my own menu items. I can also delete e.g.DeleteMenu(SysMenu, SC_MINIMIZE, MF_BYCOMMAND) ;

However if I delete the standard ones [restore,minimize,maximize,size,close] their functionality is lost (i.e. maximize button no longer works)

Is there a way to hide these menuitems or move them off the first rank of the system menu? a) make them not visible b) move to a submenu c) delete but still get button messages

Answer 1

a) make them not visible

The API has no concept of a hidden/invisible menu item.

b) move to a submenu

You can move (or rather delete and add) items to a submenu without effecting functionality.

E.g. move "minimize" to a submenu:

var
  SysMenu, SubMenu: HMENU;
  StrMin: string;
  StrMinLen: Integer;
begin
  SysMenu := GetSystemMenu(Handle, False);
  StrMinLen := GetMenuString(SysMenu, SC_MINIMIZE, nil, 0, MF_BYCOMMAND);
  if StrMinLen > 0 then begin
    Inc(StrMinLen);
    SetLength(StrMin, StrMinLen);
    GetMenuString(SysMenu, SC_MINIMIZE, PChar(StrMin), StrMinLen, MF_BYCOMMAND);
    SubMenu := CreateMenu;
    if SubMenu <> 0 then begin
      DeleteMenu(SysMenu, SC_MINIMIZE, MF_BYCOMMAND);
      AppendMenu(SubMenu, MF_STRING, SC_MINIMIZE, PChar(StrMin));
      InsertMenu(SysMenu, 0, MF_BYPOSITION or MF_POPUP, SubMenu, 'Minimize->');
      InsertMenu(SysMenu, 1, MF_BYPOSITION or MF_SEPARATOR, 0, nil);
    end;
  end;

Destroy the submenu before restoring the system menu:

var
  Info: TMenuItemInfo;
begin
  Info.cbSize := SizeOf(Info);
  Info.fMask := MIIM_SUBMENU;
  if GetMenuItemInfo(GetSystemMenu(Handle, False), 0, True, Info) then
    DestroyMenu(Info.hSubMenu);
  GetSystemMenu(Handle, True);

c) delete but still get button messages

If you delete, f.i., the "minimize" item, the system does not send WM_SYSCOMMAND messages for the minimize command to the window. So there won't be any command to respond to.

You can still listen for button messages, f.i. a left button down. But a button down/up message is not actually the same thing with a button click. A button click consists of three actions, mouse down, capture and up again on the button. If you want to do it anyway an example can be:

procedure TForm1.WMNCLButtonDown(var Message: TWMNCLButtonDown);
begin
  inherited;
  if (Message.HitTest = HTMINBUTTON) and not IsIconic(Handle) then
    ShowWindow(Handle, SW_MINIMIZE);
end;