83 lines
2.8 KiB
JavaScript
83 lines
2.8 KiB
JavaScript
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define([
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'./defined',
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'./getTimestamp'
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], function(
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defined,
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getTimestamp) {
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'use strict';
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if (typeof window === 'undefined') {
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return;
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}
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var implementation = window.requestAnimationFrame;
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(function() {
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// look for vendor prefixed function
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if (!defined(implementation)) {
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var vendors = ['webkit', 'moz', 'ms', 'o'];
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var i = 0;
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var len = vendors.length;
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while (i < len && !defined(implementation)) {
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implementation = window[vendors[i] + 'RequestAnimationFrame'];
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++i;
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}
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}
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// build an implementation based on setTimeout
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if (!defined(implementation)) {
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var msPerFrame = 1000.0 / 60.0;
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var lastFrameTime = 0;
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implementation = function(callback) {
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var currentTime = getTimestamp();
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// schedule the callback to target 60fps, 16.7ms per frame,
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// accounting for the time taken by the callback
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var delay = Math.max(msPerFrame - (currentTime - lastFrameTime), 0);
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lastFrameTime = currentTime + delay;
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return setTimeout(function() {
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callback(lastFrameTime);
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}, delay);
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};
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}
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})();
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/**
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* A browser-independent function to request a new animation frame. This is used to create
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* an application's draw loop as shown in the example below.
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*
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* @exports requestAnimationFrame
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*
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* @param {requestAnimationFrame~Callback} callback The function to call when the next frame should be drawn.
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* @returns {Number} An ID that can be passed to {@link cancelAnimationFrame} to cancel the request.
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*
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*
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* @example
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* // Create a draw loop using requestAnimationFrame. The
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* // tick callback function is called for every animation frame.
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* function tick() {
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* scene.render();
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* Cesium.requestAnimationFrame(tick);
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* }
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* tick();
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*
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* @see {@link https://www.w3.org/TR/html51/webappapis.html#animation-frames|The Web API Animation Frames interface}
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*/
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function requestAnimationFrame(callback) {
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// we need this extra wrapper function because the native requestAnimationFrame
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// functions must be invoked on the global scope (window), which is not the case
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// if invoked as Cesium.requestAnimationFrame(callback)
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return implementation(callback);
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}
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/**
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* A function that will be called when the next frame should be drawn.
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* @callback requestAnimationFrame~Callback
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*
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* @param {Number} timestamp A timestamp for the frame, in milliseconds.
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*/
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return requestAnimationFrame;
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});
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