App

The App global variable is a static class which does not need to be instantiated with new. It allows you to access all the windows that are currently on screen, choose a frame rate for the frame and draw events, and control when the GUI event loop begins and terminates.

App Lifecycle	Runtime State	Individual Windows
launch()	running	windows
quit()	fps

Properties

.eventLoop

The eventLoop property has been deprecated and setting it no longer has an effect. Node’s event loop now continues to operate even while a GUI window is active and the OS is handling rendering and UI events. As a result, the launch() method now runs asynchronously and returns a Promise that resolves when the last window is closed. In the meantime, Node-based events like timers and intervals will fire normally.

Keep in mind though that you’ll still be better off using the frame or draw event for timing rather than setting up a timeout- or interval-based rendering callback.

.fps

By default, each window will attempt to re-render its content every time the display refreshes (typically 60 times per second). You can reduce this by setting App.fps to a smaller integer value. Raising it above the display’s native refresh rate will have no effect.

This setting is only relevant if you are listening for frame or draw events (or have a pending requestAnimationFrame) on your windows. Otherwise the canvas will only be updated when responding to UI interactions like keyboard and mouse events.

.running

A read-only boolean flagging whether any GUI windows are currently active. It is true while the Promise returned by launch() is still pending.

.windows

An array of references to all of the Window objects that have been created and not yet closed.

Methods

launch()

App.launch()

returns → Promise

Any Window you create will schedule the App to begin running as soon as the current function returns. You can make this happen sooner by calling App.launch() within your code. The launch() method is asynchronous and returns a Promise that resolves when the last window is closed so you may find it handy to place ‘clean up’ code in a .then() callback or after awaiting the launch() invocation.

quit()

App.quit()

By default your process will terminate once the final window has closed (and any timers or intervals you’ve set up have been cleared). If you wish to bring things to a swifter conclusion from code, call the App.quit() method from one of your event handlers instead.

Events

idle

Emitted when the final active window is closed via a user interface click on its close widget or by a programmatic call to the window’s close() method.