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.