问如何防止Windows会话解锁后表单位置大小的更改？

EN

unit Unit1;

interface

uses
  Winapi.Windows,
  Winapi.Messages,
  Vcl.Forms;

type
  TForm1 = class(TForm)
  private
    FSessionIsLocked: Boolean;
    FSessionWasUnlocked: Boolean;
    FRestoreNormalRect: Boolean;
    FLeft: Integer;
    FTop: Integer;
    FWidth: Integer;
    FHeight: Integer;

    procedure WMWTSSessionChange(var Msg: TMessage); message WM_WTSSESSION_CHANGE;

  protected

    procedure CreateWnd; override;
    procedure DestroyWnd; override;

    procedure WMExitSizeMove(var Msg: TMessage); message WM_EXITSIZEMOVE;
    procedure WMPosChanging(var Msg: TWmWindowPosChanging); message WM_WINDOWPOSCHANGING;
    procedure WMSize(var Msg: TWMSize); message WM_SIZE;
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

//--------------------------------------------------------------------------------------------------

procedure TForm1.CreateWnd;
begin
  inherited;

  WTSRegisterSessionNotification(WindowHandle, NOTIFY_FOR_THIS_SESSION);
end;

//--------------------------------------------------------------------------------------------------

procedure TForm1.DestroyWnd;
begin
  WTSUnRegisterSessionNotification(WindowHandle);

  inherited;
end;

//--------------------------------------------------------------------------------------------------

procedure TForm1.WMExitSizeMove(var Msg: TMessage);
var
  WP: TWindowPlacement;
  NormalRect: TRect;

begin
  WP.Length := SizeOf(TWindowPlacement);
  GetWindowPlacement(Self.Handle, @WP);
  NormalRect := WP.rcNormalPosition;

  FLeft := NormalRect.Left;
  FTop := NormalRect.Top;
  FWidth := NormalRect.Right - NormalRect.Left;
  FHeight := NormalRect.Bottom - NormalRect.Top;
end;

//--------------------------------------------------------------------------------------------------

procedure TForm1.WMPosChanging(var Msg: TWmWindowPosChanging);
begin
  { Sizepos changes might occur due to locks or unlocks. We need do prohibit both.
    While the session is locked we ignore all position changes.
    When the session has been unlocked we will ignore the next PosChanging message. }
  if FSessionIsLocked or FSessionWasUnlocked then
  begin
    { overwrite with the old settings }
    if FRestoreNormalRect then
    begin
      Msg.WindowPos.x := FLeft;
      Msg.WindowPos.y := FTop;
      Msg.WindowPos.cx := FWidth;
      Msg.WindowPos.cy := FHeight;

      Msg.Result := 0;
    end;

    { reset the variable, otherwise a manual resize would not be possible }
    if FSessionWasUnlocked then
      FSessionWasUnlocked := False;
  end;
end;

//--------------------------------------------------------------------------------------------------

procedure TiQForm.WMSize(var Msg: TWMSize);
begin
  inherited;

  { We need to restore our normal rect only if the form is not maximized. Because
    if it is maximized it only positioned on one monitor and will not be moved
    by windows. If we do not repsect this case we would be restoring the normal
    rect unintentionally in WMPosChanging for every maximized form. }
  FRestoreNormalRect := not (Msg.SizeType = SIZE_MAXIMIZED);
end;

//--------------------------------------------------------------------------------------------------

procedure TForm1.WMWTSSessionChange(var Msg: TMessage);
begin
  case Message.WParam of
    WTS_CONSOLE_DISCONNECT, WTS_REMOTE_DISCONNECT, WTS_SESSION_LOCK, WTS_SESSION_LOGOFF:
      begin
        FSessionIsLocked := True;
      end;
    WTS_CONSOLE_CONNECT, WTS_REMOTE_CONNECT, WTS_SESSION_UNLOCK, WTS_SESSION_LOGON:
      begin
        FSessionIsLocked := False;
        FSessionWasUnlocked := True;
      end;
  end;

  inherited;
end;

//--------------------------------------------------------------------------------------------------

end.