brush.on()

brush.on(typenames, [listener])

If listener is specified, sets the event listener for the specified typenames and returns the brush. If an event listener was already registered for the same type and name, the existing listener is removed before the new listener is added. If listener is null, removes the current event listeners for the specified typenames, if any. If listener is not specified, returns the first currently-assigned listener matching the specified typenames, if any. When a specified event is dispatched, each listener will be invoked with the same context and arguments as selection.on listeners: the current datum d and index i, with the this context as the current DOM element.

The typenames is a string containing one or more typename separated by whitespace. Each typename is a type, optionally followed by a period (.) and a name, such as brush.foo and brush.bar; the name allows multiple listeners to be registered for the same type. The type must be one of the following:

• start - at the start of a brush gesture, such as on mousedown.
• brush - when the brush moves, such as on mousemove.
• end - at the end of a brush gesture, such as on mouseup.

See dispatch.on and Brush Events for more.