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Emoji: Optimize emoji loader with sessionStorage, willReadFrequently, and OffscreenCanvas.

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* Use `sessionStorage` to remember the previous results of calls to `browserSupportsEmoji()` for 1 week.
* Optimize reading from canvas by supplying the `willReadFrequently` option for the 2D context.
* When `OffscreenCanvas` is available, offload `browserSupportsEmoji()` to a web worker to prevent blocking the main thread. This is of primary benefit to Safari which does not yet support `willReadFrequently`.
* Remove obsolete support for IE11 since promises are now utilized. Nevertheless, ES3 syntax is maintained and IE11 will simply short-circuit.

Props westonruter, dmsnell, peterwilsoncc, valterlorran, flixos90, spacedmonkey, joemcgill.
Fixes #58472.


git-svn-id: https://develop.svn.wordpress.org/trunk@56074 602fd350-edb4-49c9-b593-d223f7449a82
This commit is contained in:
Weston Ruter 2023-06-27 17:22:59 +00:00
parent a13f8969de
commit f9eaba01e1
2 changed files with 292 additions and 78 deletions
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6
.jshintrc
View File

@ -24,6 +24,10 @@
"wp": false,
"export": false,
"module": false,
"require": false
"require": false,
"WorkerGlobalScope": false,
"self": false,
"OffscreenCanvas": false,
"Promise": false
}
}

322
src/js/_enqueues/lib/emoji-loader.js
View File

@ -2,65 +2,189 @@
* @output wp-includes/js/wp-emoji-loader.js
*/
( function( window, document, settings ) {
var src, ready, ii, tests;
/**
* Emoji Settings as exported in PHP via _print_emoji_detection_script().
* @typedef WPEmojiSettings
* @type {object}
* @property {?object} source
* @property {?string} source.concatemoji
* @property {?string} source.twemoji
* @property {?string} source.wpemoji
* @property {?boolean} DOMReady
* @property {?Function} readyCallback
*/
// Create a canvas element for testing native browser support of emoji.
var canvas = document.createElement( 'canvas' );
var context = canvas.getContext && canvas.getContext( '2d' );
/**
* Support tests.
* @typedef SupportTests
* @type {object}
* @property {?boolean} flag
* @property {?boolean} emoji
*/
/**
* IIFE to detect emoji support and load Twemoji if needed.
*
* @param {Window} window
* @param {Document} document
* @param {WPEmojiSettings} settings
*/
( function wpEmojiLoader( window, document, settings ) {
if ( typeof Promise === 'undefined' ) {
return;
}
var sessionStorageKey = 'wpEmojiSettingsSupports';
var tests = [ 'flag', 'emoji' ];
/**
* Checks whether the browser supports offloading to a Worker.
*
* @since 6.3.0
*
* @private
*
* @returns {boolean}
*/
function supportsWorkerOffloading() {
return (
typeof Worker !== 'undefined' &&
typeof OffscreenCanvas !== 'undefined' &&
typeof URL !== 'undefined' &&
URL.createObjectURL &&
typeof Blob !== 'undefined'
);
}
/**
* @typedef SessionSupportTests
* @type {object}
* @property {number} timestamp
* @property {SupportTests} supportTests
*/
/**
* Get support tests from session.
*
* @since 6.3.0
*
* @private
*
* @returns {?SupportTests} Support tests, or null if not set or older than 1 week.
*/
function getSessionSupportTests() {
if (
typeof sessionStorage !== 'undefined' &&
sessionStorageKey in sessionStorage
) {
try {
/** @type {SessionSupportTests} */
var item = JSON.parse(
sessionStorage.getItem( sessionStorageKey )
);
if (
typeof item === 'object' &&
typeof item.timestamp === 'number' &&
new Date().valueOf() < item.timestamp + 604800 && // Note: Number is a week in seconds.
typeof item.supportTests === 'object'
) {
return item.supportTests;
}
} catch ( e ) {}
}
return null;
}
/**
* Persist the supports in session storage.
*
* @since 6.3.0
*
* @private
*
* @param {SupportTests} supportTests Support tests.
*/
function setSessionSupportTests( supportTests ) {
if ( typeof sessionStorage !== 'undefined' ) {
try {
/** @type {SessionSupportTests} */
var item = {
supportTests: supportTests,
timestamp: new Date().valueOf()
};
sessionStorage.setItem(
sessionStorageKey,
JSON.stringify( item )
);
} catch ( e ) {}
}
}
/**
* Checks if two sets of Emoji characters render the same visually.
*
* This function may be serialized to run in a Worker. Therefore, it cannot refer to variables from the containing
* scope. Everything must be passed by parameters.
*
* @since 4.9.0
*
* @private
*
* @param {CanvasRenderingContext2D} context 2D Context.
* @param {string} set1 Set of Emoji to test.
* @param {string} set2 Set of Emoji to test.
*
* @return {boolean} True if the two sets render the same.
*/
function emojiSetsRenderIdentically( set1, set2 ) {
function emojiSetsRenderIdentically( context, set1, set2 ) {
// Cleanup from previous test.
context.clearRect( 0, 0, canvas.width, canvas.height );
context.clearRect( 0, 0, context.canvas.width, context.canvas.height );
context.fillText( set1, 0, 0 );
var rendered1 = canvas.toDataURL();
var rendered1 = new Uint32Array(
context.getImageData(
0,
0,
context.canvas.width,
context.canvas.height
).data
);
// Cleanup from previous test.
context.clearRect( 0, 0, canvas.width, canvas.height );
context.clearRect( 0, 0, context.canvas.width, context.canvas.height );
context.fillText( set2, 0, 0 );
var rendered2 = canvas.toDataURL();
var rendered2 = new Uint32Array(
context.getImageData(
0,
0,
context.canvas.width,
context.canvas.height
).data
);
return rendered1 === rendered2;
return rendered1.every( function ( rendered2Data, index ) {
return rendered2Data === rendered2[ index ];
} );
}
/**
* Determines if the browser properly renders Emoji that Twemoji can supplement.
*
* This function may be serialized to run in a Worker. Therefore, it cannot refer to variables from the containing
* scope. Everything must be passed by parameters.
*
* @since 4.2.0
*
* @private
*
* @param {CanvasRenderingContext2D} context 2D Context.
* @param {string} type Whether to test for support of "flag" or "emoji".
*
* @return {boolean} True if the browser can render emoji, false if it cannot.
*/
function browserSupportsEmoji( type ) {
function browserSupportsEmoji( context, type ) {
var isIdentical;
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';
switch ( type ) {
case 'flag':
/*
@ -70,6 +194,7 @@
* the browser doesn't render it correctly (white flag emoji + transgender symbol).
*/
isIdentical = emojiSetsRenderIdentically(
context,
'\uD83C\uDFF3\uFE0F\u200D\u26A7\uFE0F', // as a zero-width joiner sequence
'\uD83C\uDFF3\uFE0F\u200B\u26A7\uFE0F' // separated by a zero-width space
);
@ -86,6 +211,7 @@
* the browser doesn't render it correctly ([U] + [N]).
*/
isIdentical = emojiSetsRenderIdentically(
context,
'\uD83C\uDDFA\uD83C\uDDF3', // as the sequence of two code points
'\uD83C\uDDFA\u200B\uD83C\uDDF3' // as the two code points separated by a zero-width space
);
@ -102,6 +228,7 @@
* the browser doesn't render it correctly (black flag emoji + [G] + [B] + [E] + [N] + [G]).
*/
isIdentical = emojiSetsRenderIdentically(
context,
// as the flag sequence
'\uD83C\uDFF4\uDB40\uDC67\uDB40\uDC62\uDB40\uDC65\uDB40\uDC6E\uDB40\uDC67\uDB40\uDC7F',
// with each code point separated by a zero-width space
@ -129,6 +256,7 @@
* sequence come from older emoji standards.
*/
isIdentical = emojiSetsRenderIdentically(
context,
'\uD83E\uDEF1\uD83C\uDFFB\u200D\uD83E\uDEF2\uD83C\uDFFF', // as the zero-width joiner sequence
'\uD83E\uDEF1\uD83C\uDFFB\u200B\uD83E\uDEF2\uD83C\uDFFF' // separated by a zero-width space
);
@ -139,6 +267,48 @@
return false;
}
/**
* Checks emoji support tests.
*
* This function may be serialized to run in a Worker. Therefore, it cannot refer to variables from the containing
* scope. Everything must be passed by parameters.
*
* @since 6.3.0
*
* @private
*
* @param {string[]} tests Tests.
*
* @return {SupportTests} Support tests.
*/
function testEmojiSupports( tests ) {
var canvas;
if (
typeof WorkerGlobalScope !== 'undefined' &&
self instanceof WorkerGlobalScope
) {
canvas = new OffscreenCanvas( 300, 150 ); // Dimensions are default for HTMLCanvasElement.
} else {
canvas = document.createElement( 'canvas' );
}
var context = canvas.getContext( '2d', { willReadFrequently: true } );
/*
* 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';
var supports = {};
tests.forEach( function ( test ) {
supports[ test ] = browserSupportsEmoji( context, test );
} );
return supports;
}
/**
* Adds a script to the head of the document.
*
@ -146,68 +316,108 @@
*
* @since 4.2.0
*
* @param {Object} src The url where the script is located.
* @param {string} src The url where the script is located.
*
* @return {void}
*/
function addScript( src ) {
var script = document.createElement( 'script' );
script.src = src;
script.defer = script.type = 'text/javascript';
document.getElementsByTagName( 'head' )[0].appendChild( script );
script.defer = true;
document.head.appendChild( script );
}
tests = Array( 'flag', 'emoji' );
settings.supports = {
everything: true,
everythingExceptFlag: true
};
// Create a promise for DOMContentLoaded since the worker logic may finish after the event has fired.
var domReadyPromise = new Promise( function ( resolve ) {
document.addEventListener( 'DOMContentLoaded', resolve, {
once: true
} );
} );
// Obtain the emoji support from the browser, asynchronously when possible.
new Promise( function ( resolve ) {
var supportTests = getSessionSupportTests();
if ( supportTests ) {
resolve( supportTests );
return;
}
if ( supportsWorkerOffloading() ) {
try {
/*
* Note that this string contains the real source code for the
* copied functions, _not_ a string representation of them. This
* is because it's not possible to transfer a Function across
* threads. The lack of quotes is intentional. The function names
* are copied to variable names since minification will munge the
* function names, thus breaking the ability for the functions to
* refer to each other.
*/
var workerScript =
'var emojiSetsRenderIdentically = ' + emojiSetsRenderIdentically + ';' +
'var browserSupportsEmoji = ' + browserSupportsEmoji + ';' +
'var testEmojiSupports = ' + testEmojiSupports + ';' +
'postMessage(testEmojiSupports(' + JSON.stringify(tests) + '));';
var blob = new Blob( [ workerScript ], {
type: 'text/javascript'
} );
var worker = new Worker( URL.createObjectURL( blob ) );
worker.onmessage = function ( event ) {
supportTests = event.data;
setSessionSupportTests( supportTests );
resolve( supportTests );
};
return;
} catch ( e ) {}
}
supportTests = testEmojiSupports( tests );
setSessionSupportTests( supportTests );
resolve( supportTests );
} )
// Once the browser emoji support has been obtained from the session, finalize the settings.
.then( function ( supportTests ) {
/*
* Tests the browser support for flag emojis and other emojis, and adjusts the
* support settings accordingly.
*/
for( ii = 0; ii < tests.length; ii++ ) {
settings.supports[ tests[ ii ] ] = browserSupportsEmoji( tests[ ii ] );
for ( var test in supportTests ) {
settings.supports[ test ] = supportTests[ test ];
settings.supports.everything = settings.supports.everything && settings.supports[ tests[ ii ] ];
settings.supports.everything =
settings.supports.everything && settings.supports[ test ];
if ( 'flag' !== tests[ ii ] ) {
settings.supports.everythingExceptFlag = settings.supports.everythingExceptFlag && settings.supports[ tests[ ii ] ];
if ( 'flag' !== test ) {
settings.supports.everythingExceptFlag =
settings.supports.everythingExceptFlag &&
settings.supports[ test ];
}
}
settings.supports.everythingExceptFlag = settings.supports.everythingExceptFlag && ! settings.supports.flag;
settings.supports.everythingExceptFlag =
settings.supports.everythingExceptFlag &&
! settings.supports.flag;
// Sets DOMReady to false and assigns a ready function to settings.
settings.DOMReady = false;
settings.readyCallback = function () {
settings.DOMReady = true;
};
} )
.then( function () {
return domReadyPromise;
} )
.then( function () {
// When the browser can not render everything we need to load a polyfill.
if ( ! settings.supports.everything ) {
ready = function() {
settings.readyCallback();
};
/*
* Cross-browser version of adding a dom ready event.
*/
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 || {};
var src = settings.source || {};
if ( src.concatemoji ) {
addScript( src.concatemoji );
@ -216,5 +426,5 @@
addScript( src.wpemoji );
}
}
} );
} )( window, document, window._wpemojiSettings );