AxisLine and AxisArrowNode

Bamboo has no single AxisNode — instead, scenerystack/bamboo exports two interchangeable axis-drawing Nodes, both driven by a ChartTransform plus an Orientation (scenerystack/phet-core) saying which axis they represent:

• AxisLine extends scenerystack/scenery's Line — a plain stroked line, no arrowheads.
• AxisArrowNode extends scenerystack/scenery-phet's ArrowNode — the same idea, but double-headed by default, for charts that want to emphasize the axis extending indefinitely.

Both reposition themselves whenever the chart transform changes, and both auto-hide (setVisible( false )) when their position would fall outside the transform's current view bounds — so an axis pinned at, say, x = 0 disappears cleanly if the visible model range pans away from zero.

import { ChartTransform, AxisLine, AxisArrowNode, ChartRectangle } from 'scenerystack/bamboo';
import { Orientation } from 'scenerystack/phet-core';
import { Range } from 'scenerystack/dot';

A minimal example

const chartTransform = new ChartTransform( {
  viewWidth: 400,
  viewHeight: 200,
  modelXRange: new Range( -5, 5 ),
  modelYRange: new Range( -1, 1 )
} );

const chartRectangle = new ChartRectangle( chartTransform, { stroke: 'gray' } );

// A vertical AxisLine (the "y axis"), positioned at model x = 0.
const yAxis = new AxisLine( chartTransform, Orientation.VERTICAL, {
  value: 0
} );

// A horizontal AxisArrowNode (the "x axis"), positioned at model y = 0.
const xAxis = new AxisArrowNode( chartTransform, Orientation.HORIZONTAL, {
  value: 0
} );

Constructors

new AxisLine( chartTransform: ChartTransform, axisOrientation: Orientation, providedOptions?: AxisLineOptions )
new AxisArrowNode( chartTransform: ChartTransform, axisOrientation: Orientation, providedOptions?: AxisArrowNodeOptions )

Options

Option	AxisLine default	AxisArrowNode default	Effect
value	0	0	The position of the axis, in model coordinates on the opposite axis from axisOrientation (see tip below)
extension	0	20	How far past the ChartRectangle's edge (in view coordinates) the line/arrow is drawn
stroke / lineWidth (AxisLine, from LineOptions)	'black' / 2	—	Line styling
doubleHead / headHeight / headWidth / tailWidth (AxisArrowNode, from ArrowNodeOptions)	—	true / 10 / 10 / 2	Arrowhead styling

Methods

Both classes share the same shape: they recompute their geometry in a private update() (called on construction and on every chartTransform.changedEmitter firing), and expose only:

Member	Description
dispose()	Removes the chartTransform.changedEmitter listener before calling the superclass's dispose()

value is a coordinate on the opposite axis

For a VERTICAL AxisLine/AxisArrowNode (a vertical line representing the "y axis"), value is an x model coordinate — it's where that vertical line crosses the horizontal axis. Symmetrically, a HORIZONTAL axis's value is a y model coordinate. This is why the default value: 0 conventionally draws each axis through the origin, and why changing value moves the axis sideways/vertically rather than stretching it.