Make markers accessible

async function init() {
    // Import the needed libraries.
    const [{ Marker3DInteractiveElement, PopoverElement }, { PinElement }] =
        await Promise.all([
            google.maps.importLibrary('maps3d'),
            google.maps.importLibrary('marker'),
        ]);

    const map3DElement = document.querySelector('gmp-map-3d');

    // Set LatLng and title text for the markers. The first marker (Boynton Pass)
    // receives the initial focus when tab is pressed. Use arrow keys to move
    // between markers; press tab again to cycle through the map controls.
    const tourStops = [
        {
            position: { lat: 34.8791806, lng: -111.8265049 },
            title: 'Boynton Pass',
        },
        {
            position: { lat: 34.8559195, lng: -111.7988186 },
            title: 'Airport Mesa',
        },
        {
            position: { lat: 34.832149, lng: -111.7695277 },
            title: 'Chapel of the Holy Cross',
        },
        {
            position: { lat: 34.823736, lng: -111.8001857 },
            title: 'Red Rock Crossing',
        },
        {
            position: { lat: 34.800326, lng: -111.7665047 },
            title: 'Bell Rock',
        },
    ];

    tourStops.forEach(({ position, title }, i) => {
        const pin = new PinElement({
            glyphText: String(i + 1),
            scale: 1.5,
            glyphColor: '#FFFFFF',
        });
        const popover = new PopoverElement();

        const content = `${String(i + 1)}. ${title}`;
        const header = document.createElement('span');
        // Include the label for screen readers.
        header.ariaLabel = `This is marker ${String(i + 1)}. ${title}`;
        header.slot = 'header';

        popover.append(header);
        popover.append(content);

        const interactiveMarker = new Marker3DInteractiveElement({
            // Include a title, used for accessibility text for use by screen readers.
            title,
            position,
            gmpPopoverTargetElement: popover,
        });

        interactiveMarker.append(pin);

        map3DElement.append(interactiveMarker);
        map3DElement.append(popover);
    });

    document.body.append(map3DElement);
}

void init();
index.js

/* 
 * Always set the map height explicitly to define the size of the div element
 * that contains the map. 
 */
html,
map {
    height: 100%;
}
body {
    height: 100%;
    margin: 0;
    padding: 0;
}
style.css

<html>
    <head>
        <title>Map</title>

        <link rel="stylesheet" type="text/css" href="./style.css" />
        <script type="module" src="./index.js"></script>
        <script>
            // prettier-ignore
            (g=>{var h,a,k,p="The Google Maps JavaScript API",c="google",l="importLibrary",q="__ib__",m=document,b=window;b=b[c]||(b[c]={});var d=b.maps||(b.maps={}),r=new Set,e=new URLSearchParams,u=()=>h||(h=new Promise(async(f,n)=>{await (a=m.createElement("script"));e.set("libraries",[...r]+"");for(k in g)e.set(k.replace(/[A-Z]/g,t=>"_"+t[0].toLowerCase()),g[k]);e.set("callback",c+".maps."+q);a.src=`https://maps.${c}apis.com/maps/api/js?`+e;d[q]=f;a.onerror=()=>h=n(Error(p+" could not load."));a.nonce=m.querySelector("script[nonce]")?.nonce||"";m.head.append(a)}));d[l]?console.warn(p+" only loads once. Ignoring:",g):d[l]=(f,...n)=>r.add(f)&&u().then(()=>d[l](f,...n))})({
                key: "GOOGLE_MAPS_API_KEY"
            });
        </script>
    </head>
    <body>
        <gmp-map-3d
            center="34.8405,-111.7909,1322.7"
            range="13279.5"
            tilt="67.44"
            heading="0.01"
            mode="satellite"
            gesture-handling="cooperative"></gmp-map-3d>
    </body>
</html>
index.html