utils/fullscreen.js

let wake_lock

function request_wake_lock() {
    navigator.wakeLock?.request('screen').then(lock => wake_lock = lock).catch(e => console.warn(e.message))
}

function visibility_change_handler() {
    if (wake_lock && document.visibilityState == 'visible')
        request_wake_lock()
}

export default function toggle_fullscreen(event_or_elem, landscape=true, target_screen, elem) {
    if (event_or_elem.preventDefault)
        event_or_elem.preventDefault()
    elem ??= event_or_elem?.currentTarget || event_or_elem
    const was_not_fullscreen_before = !document.fullscreenElement
    if (was_not_fullscreen_before) {
        if (!elem.dataset.has_fullscreen_handler) {
            elem.dataset.has_fullscreen_handler = true
            elem.addEventListener('fullscreenchange', () => {
                if (elem.classList.toggle('fullscreen')) {
                    if (landscape)
                        screen.orientation.lock('landscape').catch(e => console.warn(e.message))  // Works only in Chrome Android. See: https://bugzilla.mozilla.org/show_bug.cgi?id=1744125
                    request_wake_lock()
                    document.addEventListener('visibilitychange', visibility_change_handler)
                } else
                    wake_lock?.release().then(() => wake_lock = null)
            })
        }
        elem.requestFullscreen({navigationUI: 'hide', screen: target_screen}).catch(e => console.warn(e.message))
    } else
        document.exitFullscreen()
    return was_not_fullscreen_before
}