NavigationBar

NavigationBar is the strip shown at the bottom of every running Sim: the sim's title on the left, a row of per-Screen buttons and a home button for multi-screen sims, and the PhET/accessibility menu buttons on the right. Sim constructs exactly one NavigationBar internally — you never build one yourself, and its constructor even takes the owning Sim instance as an argument. Documented here because you'll see it referenced when reading Sim/Screen internals or customizing sim chrome via LookAndFeel, and because its static size constants are occasionally useful for layout math.

import { NavigationBar } from 'scenerystack/sim';

NavigationBar.NAVIGATION_BAR_SIZE; // Dimension2 - the bar's un-scaled design size (width matches HomeScreenView's layout bounds; height 40)

You configure the navigation bar through Screen and Sim, not NavigationBar itself

As a sim author, everything you'd want to change about the navigation bar is exposed elsewhere: a screen's button icon and label come from Screen's navigationBarIcon/name options (built with ScreenIcon), and the bar's fill/text colors come from Sim.lookAndFeel (a LookAndFeel instance, exported from scenerystack/joist). There's no supported way to construct or restyle a NavigationBar directly.

Constructor

new NavigationBar( sim: Sim, tandem: Tandem )

Constructed once by Sim during startup; not intended to be called from simulation code.

Behavior worth knowing

Aspect	Detail
Single-screen sims	Shows only the sim title (left) and PhET/a11y buttons (right) — no home button or per-screen buttons, since there's nothing to switch between
Multi-screen sims	Adds a home button and one button per entry in sim.simScreens, laid out and centered via ManualConstraint, with each screen's width driven by its navigationBarIcon's label
Fill when on the home screen	The bar's background matches HomeScreen.BACKGROUND_COLOR (black) while the home screen is selected, so it visually blends into the HomeScreen rather than showing as a separate bar
layout( scale, width, height )	Called by Sim on window resize to rescale/reposition the bar's contents; not meant to be called directly by simulation code

Related

• Sim — owns the single NavigationBar instance and its lookAndFeel.
• Screen — supplies the name/navigationBarIcon each screen button displays.
• ScreenIcon — builds the icon navigationBarIcon expects.
• HomeScreen — the screen the home button switches to, and whose background color the bar matches when selected.