Question

I need to handle when the user restores the form by double clicking the title bar. I tried handling the WM_SYSCOMMAND window message however this only works if the user restores the form via clicking the restore button in the system menu.

I am using DevExpress ribbon form components if this matters.

Thanks.

Answer 1

I think you mean double-clicking on the title bar because double clicking on the system menu closes the form.
WM_SYSCOMMAND should work since the sequence of messages when double-clicking on the title bar to restore the form is:

Message posted: hwnd=$004E0820 WM_NCLBUTTONDBLCLK wParam $00000002 lParam $000705D4 Process Project1.exe (2380)
=> Message sent: hwnd=$004E0820 WM_SYSCOMMAND restore cmd requested (-44,-44) Process Project1.exe (2380)
Message sent: hwnd=$004E0820 WM_WINDOWPOSCHANGING wParam $00000000 lParam $0012F4CC Process Project1.exe (2380)
Message sent: hwnd=$004E0820 WM_GETMINMAXINFO wParam $00000000 lParam $0012EF6C Process Project1.exe (2380)
Message sent: hwnd=$004E0820 WM_NCCALCSIZE wParam $00000001 lParam $0012F4A0 Process Project1.exe (2380)
Message sent: hwnd=$004E0820 WM_NCPAINT update region  40040F4B Process Project1.exe (2380)
Message sent: hwnd=$004E0820 WM_ERASEBKGND wParam $31011DCA lParam $00000000 Process Project1.exe (2380)
Message sent: hwnd=$004E0820 WM_WINDOWPOSCHANGED wParam $00000000 lParam $0012F4CC Process Project1.exe (2380)

The problem is that the CmdType const SC_RESTORE2 = 61730 //0xF122 is missing in Windows.pas.

See the working code below:

type
  TForm7 = class(TForm)
  private
    procedure WMSysCommand(var Message: TWMSysCommand); message WM_SYSCOMMAND;
  end;

var
  Form7: TForm7;

implementation

{$R *.dfm}

{ TForm7 }

const
  SC_RESTORE2 = 61730; //0xF122

procedure TForm7.WMSysCommand(var Message: TWMSysCommand);
begin
  case Message.CmdType of
    SC_RESTORE2 : beep;
  end;
  inherited;
end;

Update: reference to SC_RESTORE2 from WM_SYSCOMMAND Notification on MSDN (see the “values in C#” part)