program.pas

program Test;
{$mode objfpc}{$H+}
//{$linklib c}

uses iup, sysutils, classes;

function btn_test(self : pihandle) : integer;
begin
    IupMessage('', 'Hello!');
    result := IUP_CLOSE;
end;

var res : integer;
    dlg, btn : pihandle;
begin
    try
    res := IupOpen(@argc, @argv);
    writeln(res);
    writeln(IupVersion);

    btn := IupButton('Salut !', nil);
    dlg := IupDialog(btn);

    IupSetAttribute(dlg, 'TITLE', 'Title window');
    IupSetCallback(btn, 'ACTION', ICallBack(@btn_test));

    IupShowXY(dlg, IUP_CENTER, IUP_CENTER);

    IupMainLoop;

    IupClose;
    except on e : Exception do
        begin
            writeln(e.helpcontext);
            writeln(e.tostring);
        end;
    end;
end.