在 form 中放一个 TEdit 就可以进行验证，以下是调试成功的代码：
//进出标题栏的捕捉
unit Unit1;
interface
uses
Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
StdCtrls;
type
TForm1 = class(TForm)
Edit1: TEdit;
procedure FormCreate(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
procedure AppMessage(var Msg:TMsg;var Handled:Boolean);
end;
var
Form1: TForm1;
implementation
{$R *.DFM}
{ TForm1 }
var
InCaption:Boolean=false;
procedure TForm1.AppMessage(var Msg: TMsg; var Handled: Boolean);
var
Statechange:Boolean;
begin
Statechange:=false;
if Msg.message=WM_NCMOUSEMOVE then
begin
if DefWindowProc(handle,WM_NCHitTest,0,
GetMessagePos)=HTCAPTION then
begin
if not(InCaption) then Statechange:=true;
end
else
if InCaption then Statechange:=true;
//到标题栏上面的边框，也是出标题栏
end;
if Msg.message=WM_MOUSEMOVE then
if InCaption then Statechange:=true;
if statechange then
begin
InCaption:=not(InCaption);
if InCaption then Edit1.Text:='In Caption' //进入标题栏
else Edit1.Text:='Out Caption'; //从标题出来
end;
end;
procedure TForm1.FormCreate(Sender: TObject);
begin
Application.OnMessage:=AppMessage;
end;
end.
