Buttons on Windows

• A window may contain a button bar.
• buttons may have a controller, call a function or evaluate a string in response to the onclick event.

    var a_buttons = new Array();
    a_buttons[0] = new Button (45, 15, "Help", help_button);
    a_buttons[1] = new Button (45, 15, "Button2", controller);
    a_buttons[2] = new Button (45, 15, "Hello", "Button3('Hello')");
    a_buttons[3] = new Button (0, 0, "Square", addSquare);