/*

Important:

This is sample code demonstrating API, technology or techniques in development.

Although this sample code has been reviewed for technical accuracy, it is not 

final. Apple is supplying this information to help you plan for the adoption of 

the technologies and programming interfaces described herein. This information 

is subject to change, and software implemented based on this sample code should 

be tested with final operating system software and final documentation. Newer 

versions of this sample code may be provided with future seeds of the API or 

technology. For information about updates to this and other developer 

documentation, view the New & Updated sidebars in subsequent documentation seeds.

*/

/*

File: PosterCircle.js

Abstract: Defines JavaScript functionality for the PosterCircle sample.

          Implements each ring of the cylinder. Creates and appends 12 posters

          to each ring. Adds numbers to each poster. Translates and rotates 

          each of them.

Version: 1.0

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*/

/* Each ring of the cylinder contains 12 posters */

const POSTERS_PER_RING = 12;

/*

   Implements each ring of the cylinder that. Applies translation

   and rotation transformations to each poster.  

*/

function setup_posters(ring)

{

    /* We create a ring by creating and dividing a 360 degrees circle into 12 equal parts

       that each contains a poster */

    /* posterAngle has a value of 30 degrees */   

    var posterAngle = 360 / POSTERS_PER_RING;

    for (var index = 0; index < POSTERS_PER_RING; index ++) 

    {

        /* Each poster is a div element */

        var poster = document.createElement('div');

        /* Applies the CSS "poster" class to the poster */

        poster.className = 'poster';

        /* Compute and assign a transform to the poster */

        var transform = ['rotate3d(0,1,0,', (posterAngle * index), 'deg) translateZ(200px)'].join('');

        poster.style.webkitTransform = transform;

        /* Create a placeholder for the number on each number */

        var content = poster.appendChild(document.createElement('p'));

        /* Add a number to the poster */

        content.textContent = index;

        /* Add the poster to this ring */

        ring.appendChild(poster);

    }

}

/*

    Called when the "Poster Circle" page loads. Calls the setup_posters

    function to implement all three rings of the cylinder.

*/

function init()

{

    setup_posters(document.getElementById('ring-1'));

    setup_posters(document.getElementById('ring-2'));

    setup_posters(document.getElementById('ring-3'));

}

/* Call the init function when the "Poster Circle" page is fully loaded */

window.addEventListener('load', init, false);