+ * Returns the context's pixel ratio, which is the ratio between the device
+ * pixel ratio and the backing store ratio. Typically this is 1 for conventional
+ * displays, and > 1 for HiDPI displays (such as the Retina MBP).
+ * See http://www.html5rocks.com/en/tutorials/canvas/hidpi/ for more details.
+ *
+ * @param {!CanvasRenderingContext2D} context The canvas's 2d context.
+ * @return {number} The ratio of the device pixel ratio and the backing store
+ * ratio for the specified context.
+ */
+Dygraph.getContextPixelRatio = function(context) {
+ try {
+ var devicePixelRatio = window.devicePixelRatio;
+ var backingStoreRatio = context.webkitBackingStorePixelRatio ||
+ context.mozBackingStorePixelRatio ||
+ context.msBackingStorePixelRatio ||
+ context.oBackingStorePixelRatio ||
+ context.backingStorePixelRatio || 1;
+ if (devicePixelRatio !== undefined) {
+ return devicePixelRatio / backingStoreRatio;
+ } else {
+ // At least devicePixelRatio must be defined for this ratio to make sense.
+ // We default backingStoreRatio to 1: this does not exist on some browsers
+ // (i.e. desktop Chrome).
+ return 1;
+ }
+ } catch (e) {
+ return 1;
+ }
+};
+
+/**
+ * Checks whether the user is on an Android browser.
+ * Android does not fully support the <canvas> tag, e.g. w/r/t/ clipping.
+ * @return {boolean}
+ * @private
+ */
+Dygraph.isAndroid = function() {
+ return (/Android/).test(navigator.userAgent);
+};
+
+
+/**
+ * TODO(danvk): use @template here when it's better supported for classes.
+ * @param {!Array} array
+ * @param {number} start
+ * @param {number} length
+ * @param {function(!Array,?):boolean=} predicate
+ * @constructor
+ */
+Dygraph.Iterator = function(array, start, length, predicate) {
+ start = start || 0;
+ length = length || array.length;
+ this.hasNext = true; // Use to identify if there's another element.
+ this.peek = null; // Use for look-ahead
+ this.start_ = start;
+ this.array_ = array;
+ this.predicate_ = predicate;
+ this.end_ = Math.min(array.length, start + length);
+ this.nextIdx_ = start - 1; // use -1 so initial advance works.
+ this.next(); // ignoring result.
+};
+
+/**
+ * @return {Object}
+ */
+Dygraph.Iterator.prototype.next = function() {
+ if (!this.hasNext) {
+ return null;
+ }
+ var obj = this.peek;
+
+ var nextIdx = this.nextIdx_ + 1;
+ var found = false;
+ while (nextIdx < this.end_) {
+ if (!this.predicate_ || this.predicate_(this.array_, nextIdx)) {
+ this.peek = this.array_[nextIdx];
+ found = true;
+ break;
+ }
+ nextIdx++;
+ }
+ this.nextIdx_ = nextIdx;
+ if (!found) {
+ this.hasNext = false;
+ this.peek = null;
+ }
+ return obj;
+};
+
+/**
+ * Returns a new iterator over array, between indexes start and
+ * start + length, and only returns entries that pass the accept function
+ *
+ * @param {!Array} array the array to iterate over.
+ * @param {number} start the first index to iterate over, 0 if absent.
+ * @param {number} length the number of elements in the array to iterate over.
+ * This, along with start, defines a slice of the array, and so length
+ * doesn't imply the number of elements in the iterator when accept doesn't
+ * always accept all values. array.length when absent.
+ * @param {function(?):boolean=} opt_predicate a function that takes
+ * parameters array and idx, which returns true when the element should be
+ * returned. If omitted, all elements are accepted.
+ * @private
+ */
+Dygraph.createIterator = function(array, start, length, opt_predicate) {
+ return new Dygraph.Iterator(array, start, length, opt_predicate);
+};
+
+// Shim layer with setTimeout fallback.
+// From: http://paulirish.com/2011/requestanimationframe-for-smart-animating/
+// Should be called with the window context:
+// Dygraph.requestAnimFrame.call(window, function() {})
+Dygraph.requestAnimFrame = (function() {
+ return window.requestAnimationFrame ||
+ window.webkitRequestAnimationFrame ||
+ window.mozRequestAnimationFrame ||
+ window.oRequestAnimationFrame ||
+ window.msRequestAnimationFrame ||
+ function (callback) {
+ window.setTimeout(callback, 1000 / 60);
+ };
+})();
+
+/**
+ * Call a function at most maxFrames times at an attempted interval of
+ * framePeriodInMillis, then call a cleanup function once. repeatFn is called
+ * once immediately, then at most (maxFrames - 1) times asynchronously. If
+ * maxFrames==1, then cleanup_fn() is also called synchronously. This function
+ * is used to sequence animation.
+ * @param {function(number)} repeatFn Called repeatedly -- takes the frame
+ * number (from 0 to maxFrames-1) as an argument.
+ * @param {number} maxFrames The max number of times to call repeatFn
+ * @param {number} framePeriodInMillis Max requested time between frames.
+ * @param {function()} cleanupFn A function to call after all repeatFn calls.