The barry Object

The barry object

Barry Launcher hands your app's root item a barry object as the app starts. Declare it to get it:

Rectangle {
    id: app
    required property var barry
    ...
}

required makes it arrive before your bindings and Component.onCompleted run, so you can use it anywhere, even in a Settings location. (A root without the property works too; it just gets no barry.)

Properties

barry.scale	real	1 on the Thor's bottom screen (1240 × 1080). Smaller or larger on other screens. Multiply your sizes by it.
barry.dataDirUrl	url	Your app's own folder for saving things, as a file:// URL ending in /. Kept across updates, deleted when the app is removed.
barry.dataDir	string	The same folder, as a plain path.
barry.appDirUrl	url	Where your app's files are installed (read-only in spirit: an update replaces it).
barry.appDir	string	The same, as a plain path.
barry.appId	string	Your id from barry-app.json.
barry.appName	string	Your name.

Functions

barry.close()	Quit the app. The bottom screen goes back to what it showed before (the home screen, usually).
barry.request(method, path, body, done)	Call your app's service. body (an object, or null) goes as JSON; done(status, reply) gets the HTTP status (0: no answer) and the reply's JSON (null if it isn't JSON).

Your service

These are only for apps with a service ("service" in barry-app.json):

barry.serviceUrl	string	"http://127.0.0.1:PORT/", or "" without a service, or on a Barry Launcher too old for services
barry.serviceToken	string	For an Image whose source is the service: add ?token= and this. barry.request sends it by itself.

Image { source: app.barry.serviceUrl + "map.png?token=" + app.barry.serviceToken }

You don't need a close button: users can go home by swiping up from the bottom edge or holding the AYN button, and close your app with the ✕ on its tile. A close button is still friendly in an app people use briefly.

Saving things

Settings (simplest)

import QtCore

Settings {
    id: saved
    location: app.barry.dataDirUrl + "settings.ini"
    property int highScore: 0
    property string playerName: ""
}

Assign to a property (saved.highScore = 120) and it's saved; it's read back on the next start. Good for numbers, text, true/false.

Lists and records

QML can read files but not write them, so keep lists and records in a Settings string, as JSON:

Settings { id: saved; location: app.barry.dataDirUrl + "notes.ini"; property string notes: "[]" }

function addNote(text) {
    const list = JSON.parse(saved.notes)
    list.unshift({ text: text, at: Date.now() })
    saved.notes = JSON.stringify(list)
}

Keep it to a few hundred kilobytes. For more, QtQuick.LocalStorage (a SQLite database) works too: Barry Launcher points Qt's data folder into your app's data folder, so the database is yours and goes when the app is removed.

Screen and input

• Size: your root item fills the screen. On the Thor that's 1240 × 1080 (landscape). Use anchors and barry.scale rather than fixed positions so other screens work.
• Touch is the input. Use TapHandler, DragHandler, PinchHandler or MultiPointTouchArea. The Thor's sticks and buttons stay with Steam and the game on the top screen.
• The bottom edge belongs to Barry Launcher: a swipe up from the bottom 45 pixels goes home. Keep swipes away from it.
• Typing: Barry Launcher's on-screen keyboard follows text focus over the accessibility bus, as it does for Firefox and Signal. Qt Quick's text fields report their focus there, but check it with your own app on the device.
• Going home doesn't close your app: it keeps running behind the home screen until its tile's ✕, or barry.close(). Stop timers and animations that don't need to run, so a background app costs nothing.

What you can import

Everything that Qt 6.8 on SteamOS has; the most useful:

Module	For
QtQuick	items, text, images, animation, touch handlers
QtQuick.Controls	buttons, sliders, lists, text fields (styles: Basic, Fusion, Material, Universal)
QtQuick.Layouts	rows, columns and grids that share space
QtQuick.Shapes	lines and curves, SVG paths
QtQuick.Particles, QtQuick.Effects	particles, blur, shadow, colour effects
QtCore	Settings, standard paths
QtMultimedia	sound and video
QtQuick3D	3D scenes
QtWebSockets, XMLHttpRequest	the network
QtTextToSpeech, QtSensors, QtPositioning	speech, sensors, location (if the device has them)

These come with SteamOS (its KDE desktop needs them). Other distributions running the portable Barry Launcher may have fewer: say in your README what your app needs.

Not supported: native (C++) QML plugins, other programs, and other languages. An app is QML and JavaScript, plus its images, sounds and fonts, and, when it really needs one, a Python service.