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/* Copyright (c) 2006-2013 by OpenLayers Contributors (see authors.txt for
* full list of contributors). Published under the 2-clause BSD license.
* See license.txt in the OpenLayers distribution or repository for the
* full text of the license. */
/**
* @requires OpenLayers/SingleFile.js
* @requires OpenLayers/Util/vendorPrefix.js
*/
/**
* Namespace: OpenLayers.Animation
* A collection of utility functions for executing methods that repaint a
* portion of the browser window. These methods take advantage of the
* browser's scheduled repaints where requestAnimationFrame is available.
*/
OpenLayers.Animation = (function(window) {
/**
* Property: isNative
* {Boolean} true if a native requestAnimationFrame function is available
*/
var requestAnimationFrame = OpenLayers.Util.vendorPrefix.js(window, "requestAnimationFrame");
var isNative = !!(requestAnimationFrame);
/**
* Function: requestFrame
* Schedule a function to be called at the next available animation frame.
* Uses the native method where available. Where requestAnimationFrame is
* not available, setTimeout will be called with a 16ms delay.
*
* Parameters:
* callback - {Function} The function to be called at the next animation frame.
* element - {DOMElement} Optional element that visually bounds the animation.
*/
var requestFrame = (function() {
var request = window[requestAnimationFrame] ||
function(callback, element) {
window.setTimeout(callback, 16);
};
// bind to window to avoid illegal invocation of native function
return function(callback, element) {
request.apply(window, [callback, element]);
};
})();
// private variables for animation loops
var counter = 0;
var loops = {};
/**
* Function: start
* Executes a method with <requestFrame> in series for some
* duration.
*
* Parameters:
* callback - {Function} The function to be called at the next animation frame.
* duration - {Number} Optional duration for the loop. If not provided, the
* animation loop will execute indefinitely.
* element - {DOMElement} Optional element that visually bounds the animation.
*
* Returns:
* {Number} Identifier for the animation loop. Used to stop animations with
* <stop>.
*/
function start(callback, duration, element) {
duration = duration > 0 ? duration : Number.POSITIVE_INFINITY;
var id = ++counter;
var start = +new Date;
loops[id] = function() {
if (loops[id] && +new Date - start <= duration) {
callback();
if (loops[id]) {
requestFrame(loops[id], element);
}
} else {
delete loops[id];
}
};
requestFrame(loops[id], element);
return id;
}
/**
* Function: stop
* Terminates an animation loop started with <start>.
*
* Parameters:
* id - {Number} Identifier returned from <start>.
*/
function stop(id) {
delete loops[id];
}
return {
isNative: isNative,
requestFrame: requestFrame,
start: start,
stop: stop
};
})(window);
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