unit HookMain;

interface

uses
Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
StdCtrls, ExtCtrls;

type
THookForm = class(TForm)
SendBtn: TButton;
GroupBox1: TGroupBox;
LogList: TListBox;
DoLog: TCheckBox;
ExitBtn: TButton;
procedure SendBtnClick(Sender: TObject);
procedure FormCreate(Sender: TObject);
procedure FormDestroy(Sender: TObject);
procedure ExitBtnClick(Sender: TObject);
private
function AppWindowHook(var Message: TMessage): Boolean;
end;

var
HookForm: THookForm;

implementation

{$R *.DFM}

procedure THookForm.FormCreate(Sender: TObject);
begin
Application.HookMainWindow(AppWindowHook);
end;

procedure THookForm.FormDestroy(Sender: TObject);
begin
Application.UnhookMainWindow(AppWindowHook);
end;

function THookForm.AppWindowHook(var Message: TMessage): Boolean;
const
LogStr = 'Message ID: $%x, WParam: $%x, LParam: $%x';
begin
Result := True;
if DoLog.Checked then
with Message do
LogList.Items.Add(Format(LogStr, [Msg, WParam, LParam]));
end;

procedure THookForm.SendBtnClick(Sender: TObject);
begin
SendMessage(Application.Handle, WM_NULL, 0, 0);
end;

procedure THookForm.ExitBtnClick(Sender: TObject);
begin
Close;
end;

end.