Réduire une Form avec un click droit sur la barre de titre

type
TForm1 = class(TForm)
private
{ Private-Deklarationen }
FOldHeight : Integer;
procedure WMNCRButtonDown( var Msg : TWMNCRButtonDown); message WM_NCRBUTTONDOWN;
public
{ Public-Deklarationen }
end;

var
Form1: TForm1;

implementation

{$R *.DFM}

procedure TForm1.WMNCRButtonDown( var Msg : TWMNCRButtonDown);
begin
if (Msg.HitTest = HTCAPTION) then
if (ClientHeight = 0) then
begin
ClientHeight := FOldHeight;
Application.ProcessMessages;
end
else
begin
FOldHeight := ClientHeight;
ClientHeight := 0;
Application.ProcessMessages;
end
end;