( function( window, document, settings ) {

	var src, ready;

	/**

	 * Detect if the browser supports rendering emoji or flag emoji. Flag emoji are a single glyph

	 * made of two characters, so some browsers (notably, Firefox OS X) don't support them.

	 *

	 * @since 4.2.0

	 *

	 * @param type {String} Whether to test for support of "simple" or "flag" emoji.

	 * @return {Boolean} True if the browser can render emoji, false if it cannot.

	 */

	function browserSupportsEmoji( type ) {

		var canvas = document.createElement( 'canvas' ),

			context = canvas.getContext && canvas.getContext( '2d' );

		if ( ! context || ! context.fillText ) {

			return false;

		}

		/*

		 * Chrome on OS X added native emoji rendering in M41. Unfortunately,

		 * it doesn't work when the font is bolder than 500 weight. So, we

		 * check for bold rendering support to avoid invisible emoji in Chrome.

		 */

		context.textBaseline = 'top';

		context.font = '600 32px Arial';

		if ( type === 'flag' ) {

			/*

			 * This works because the image will be one of three things:

			 * - Two empty squares, if the browser doesn't render emoji

			 * - Two squares with 'G' and 'B' in them, if the browser doesn't render flag emoji

			 * - The British flag

			 *

			 * The first two will encode to small images (1-2KB data URLs), the third will encode

			 * to a larger image (4-5KB data URL).

			 */

			context.fillText( String.fromCharCode( 55356, 56812, 55356, 56807 ), 0, 0 );

			return canvas.toDataURL().length > 3000;

		} else {

			/*

			 * This creates a smiling emoji, and checks to see if there is any image data in the

			 * center pixel. In browsers that don't support emoji, the character will be rendered

			 * as an empty square, so the center pixel will be blank.

			 */

			context.fillText( String.fromCharCode( 55357, 56835 ), 0, 0 );

			return context.getImageData( 16, 16, 1, 1 ).data[0] !== 0;

		}

	}

	function addScript( src ) {

		var script = document.createElement( 'script' );

		script.src = src;

		script.type = 'text/javascript';

		document.getElementsByTagName( 'head' )[0].appendChild( script );

	}

	settings.supports = {

		simple: browserSupportsEmoji( 'simple' ),

		flag:   browserSupportsEmoji( 'flag' )

	};

	settings.DOMReady = false;

	settings.readyCallback = function() {

		settings.DOMReady = true;

	};

	if ( ! settings.supports.simple || ! settings.supports.flag ) {

		ready = function() {

			settings.readyCallback();

		};

		if ( document.addEventListener ) {

			document.addEventListener( 'DOMContentLoaded', ready, false );

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

		} else {

			window.attachEvent( 'onload', ready );

			document.attachEvent( 'onreadystatechange', function() {

				if ( 'complete' === document.readyState ) {

					settings.readyCallback();

				}

			} );

		}

		src = settings.source || {};

		if ( src.concatemoji ) {

			addScript( src.concatemoji );

		} else if ( src.wpemoji && src.twemoji ) {

			addScript( src.twemoji );

			addScript( src.wpemoji );

		}

	}

} )( window, document, window._wpemojiSettings );