Acts like a normal BButton: The value is B_CONTROL_ON while the object is being pressed and B_CONTROL_OFF otherwise. The images for these two states should be different; by convention, the "on" image is a highlighted version of the "off" image. If the button can be disabled, it needs an additional "disabled" image.

Acts like a checkbox: Its value switches between B_CONTROL_ON and B_CONTROL_OFF every time the user presses (and releases) the button. If the button can be disabled, it needs two additional "disabled" images: One for disabled-while-on and the other for disabled-while-off.