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Diffstat (limited to 'together/node_modules/asap/browser-raw.js')
| -rw-r--r-- | together/node_modules/asap/browser-raw.js | 223 |
1 files changed, 223 insertions, 0 deletions
diff --git a/together/node_modules/asap/browser-raw.js b/together/node_modules/asap/browser-raw.js new file mode 100644 index 0000000..9cee7e3 --- /dev/null +++ b/together/node_modules/asap/browser-raw.js @@ -0,0 +1,223 @@ +"use strict"; + +// Use the fastest means possible to execute a task in its own turn, with +// priority over other events including IO, animation, reflow, and redraw +// events in browsers. +// +// An exception thrown by a task will permanently interrupt the processing of +// subsequent tasks. The higher level `asap` function ensures that if an +// exception is thrown by a task, that the task queue will continue flushing as +// soon as possible, but if you use `rawAsap` directly, you are responsible to +// either ensure that no exceptions are thrown from your task, or to manually +// call `rawAsap.requestFlush` if an exception is thrown. +module.exports = rawAsap; +function rawAsap(task) { + if (!queue.length) { + requestFlush(); + flushing = true; + } + // Equivalent to push, but avoids a function call. + queue[queue.length] = task; +} + +var queue = []; +// Once a flush has been requested, no further calls to `requestFlush` are +// necessary until the next `flush` completes. +var flushing = false; +// `requestFlush` is an implementation-specific method that attempts to kick +// off a `flush` event as quickly as possible. `flush` will attempt to exhaust +// the event queue before yielding to the browser's own event loop. +var requestFlush; +// The position of the next task to execute in the task queue. This is +// preserved between calls to `flush` so that it can be resumed if +// a task throws an exception. +var index = 0; +// If a task schedules additional tasks recursively, the task queue can grow +// unbounded. To prevent memory exhaustion, the task queue will periodically +// truncate already-completed tasks. +var capacity = 1024; + +// The flush function processes all tasks that have been scheduled with +// `rawAsap` unless and until one of those tasks throws an exception. +// If a task throws an exception, `flush` ensures that its state will remain +// consistent and will resume where it left off when called again. +// However, `flush` does not make any arrangements to be called again if an +// exception is thrown. +function flush() { + while (index < queue.length) { + var currentIndex = index; + // Advance the index before calling the task. This ensures that we will + // begin flushing on the next task the task throws an error. + index = index + 1; + queue[currentIndex].call(); + // Prevent leaking memory for long chains of recursive calls to `asap`. + // If we call `asap` within tasks scheduled by `asap`, the queue will + // grow, but to avoid an O(n) walk for every task we execute, we don't + // shift tasks off the queue after they have been executed. + // Instead, we periodically shift 1024 tasks off the queue. + if (index > capacity) { + // Manually shift all values starting at the index back to the + // beginning of the queue. + for (var scan = 0, newLength = queue.length - index; scan < newLength; scan++) { + queue[scan] = queue[scan + index]; + } + queue.length -= index; + index = 0; + } + } + queue.length = 0; + index = 0; + flushing = false; +} + +// `requestFlush` is implemented using a strategy based on data collected from +// every available SauceLabs Selenium web driver worker at time of writing. +// https://docs.google.com/spreadsheets/d/1mG-5UYGup5qxGdEMWkhP6BWCz053NUb2E1QoUTU16uA/edit#gid=783724593 + +// Safari 6 and 6.1 for desktop, iPad, and iPhone are the only browsers that +// have WebKitMutationObserver but not un-prefixed MutationObserver. +// Must use `global` or `self` instead of `window` to work in both frames and web +// workers. `global` is a provision of Browserify, Mr, Mrs, or Mop. + +/* globals self */ +var scope = typeof global !== "undefined" ? global : self; +var BrowserMutationObserver = scope.MutationObserver || scope.WebKitMutationObserver; + +// MutationObservers are desirable because they have high priority and work +// reliably everywhere they are implemented. +// They are implemented in all modern browsers. +// +// - Android 4-4.3 +// - Chrome 26-34 +// - Firefox 14-29 +// - Internet Explorer 11 +// - iPad Safari 6-7.1 +// - iPhone Safari 7-7.1 +// - Safari 6-7 +if (typeof BrowserMutationObserver === "function") { + requestFlush = makeRequestCallFromMutationObserver(flush); + +// MessageChannels are desirable because they give direct access to the HTML +// task queue, are implemented in Internet Explorer 10, Safari 5.0-1, and Opera +// 11-12, and in web workers in many engines. +// Although message channels yield to any queued rendering and IO tasks, they +// would be better than imposing the 4ms delay of timers. +// However, they do not work reliably in Internet Explorer or Safari. + +// Internet Explorer 10 is the only browser that has setImmediate but does +// not have MutationObservers. +// Although setImmediate yields to the browser's renderer, it would be +// preferrable to falling back to setTimeout since it does not have +// the minimum 4ms penalty. +// Unfortunately there appears to be a bug in Internet Explorer 10 Mobile (and +// Desktop to a lesser extent) that renders both setImmediate and +// MessageChannel useless for the purposes of ASAP. +// https://github.com/kriskowal/q/issues/396 + +// Timers are implemented universally. +// We fall back to timers in workers in most engines, and in foreground +// contexts in the following browsers. +// However, note that even this simple case requires nuances to operate in a +// broad spectrum of browsers. +// +// - Firefox 3-13 +// - Internet Explorer 6-9 +// - iPad Safari 4.3 +// - Lynx 2.8.7 +} else { + requestFlush = makeRequestCallFromTimer(flush); +} + +// `requestFlush` requests that the high priority event queue be flushed as +// soon as possible. +// This is useful to prevent an error thrown in a task from stalling the event +// queue if the exception handled by Node.js’s +// `process.on("uncaughtException")` or by a domain. +rawAsap.requestFlush = requestFlush; + +// To request a high priority event, we induce a mutation observer by toggling +// the text of a text node between "1" and "-1". +function makeRequestCallFromMutationObserver(callback) { + var toggle = 1; + var observer = new BrowserMutationObserver(callback); + var node = document.createTextNode(""); + observer.observe(node, {characterData: true}); + return function requestCall() { + toggle = -toggle; + node.data = toggle; + }; +} + +// The message channel technique was discovered by Malte Ubl and was the +// original foundation for this library. +// http://www.nonblocking.io/2011/06/windownexttick.html + +// Safari 6.0.5 (at least) intermittently fails to create message ports on a +// page's first load. Thankfully, this version of Safari supports +// MutationObservers, so we don't need to fall back in that case. + +// function makeRequestCallFromMessageChannel(callback) { +// var channel = new MessageChannel(); +// channel.port1.onmessage = callback; +// return function requestCall() { +// channel.port2.postMessage(0); +// }; +// } + +// For reasons explained above, we are also unable to use `setImmediate` +// under any circumstances. +// Even if we were, there is another bug in Internet Explorer 10. +// It is not sufficient to assign `setImmediate` to `requestFlush` because +// `setImmediate` must be called *by name* and therefore must be wrapped in a +// closure. +// Never forget. + +// function makeRequestCallFromSetImmediate(callback) { +// return function requestCall() { +// setImmediate(callback); +// }; +// } + +// Safari 6.0 has a problem where timers will get lost while the user is +// scrolling. This problem does not impact ASAP because Safari 6.0 supports +// mutation observers, so that implementation is used instead. +// However, if we ever elect to use timers in Safari, the prevalent work-around +// is to add a scroll event listener that calls for a flush. + +// `setTimeout` does not call the passed callback if the delay is less than +// approximately 7 in web workers in Firefox 8 through 18, and sometimes not +// even then. + +function makeRequestCallFromTimer(callback) { + return function requestCall() { + // We dispatch a timeout with a specified delay of 0 for engines that + // can reliably accommodate that request. This will usually be snapped + // to a 4 milisecond delay, but once we're flushing, there's no delay + // between events. + var timeoutHandle = setTimeout(handleTimer, 0); + // However, since this timer gets frequently dropped in Firefox + // workers, we enlist an interval handle that will try to fire + // an event 20 times per second until it succeeds. + var intervalHandle = setInterval(handleTimer, 50); + + function handleTimer() { + // Whichever timer succeeds will cancel both timers and + // execute the callback. + clearTimeout(timeoutHandle); + clearInterval(intervalHandle); + callback(); + } + }; +} + +// This is for `asap.js` only. +// Its name will be periodically randomized to break any code that depends on +// its existence. +rawAsap.makeRequestCallFromTimer = makeRequestCallFromTimer; + +// ASAP was originally a nextTick shim included in Q. This was factored out +// into this ASAP package. It was later adapted to RSVP which made further +// amendments. These decisions, particularly to marginalize MessageChannel and +// to capture the MutationObserver implementation in a closure, were integrated +// back into ASAP proper. +// https://github.com/tildeio/rsvp.js/blob/cddf7232546a9cf858524b75cde6f9edf72620a7/lib/rsvp/asap.js |