Merge pull request #5 from nasa/open1202

[Plot] Improve plotting performance

platform/core/src/services/Throttle.js

@@ -0,0 +1,63 @@
+/*global define*/
+
+define(
+    [],
+    function () {
+        "use strict";
+
+        /**
+         * Throttler for function executions, registered as the `throttle`
+         * service.
+         *
+         * Usage:
+         *
+         *     throttle(fn, delay, [apply])
+         *
+         * Returns a function that, when invoked, will invoke `fn` after
+         * `delay` milliseconds, only if no other invocations are pending.
+         * The optional argument `apply` determines whether.
+         *
+         * The returned function will itself return a `Promise` which will
+         * resolve to the returned value of `fn` whenever that is invoked.
+         *
+         * @returns {Function}
+         */
+        function Throttle($timeout) {
+            /**
+             * Throttle this function.
+             * @param {Function} fn the function to throttle
+             * @param {number} [delay] the delay, in milliseconds, before
+             *        executing this function; defaults to 0.
+             * @param {boolean} apply true if a `$apply` call should be
+             *        invoked after this function executes; defaults to
+             *        `false`.
+             */
+            return function (fn, delay, apply) {
+                var activeTimeout;
+
+                // Clear active timeout, so that next invocation starts
+                // a new one.
+                function clearActiveTimeout() {
+                    activeTimeout = undefined;
+                }
+
+                // Defaults
+                delay = delay || 0;
+                apply = apply || false;
+
+                return function () {
+                    // Start a timeout if needed
+                    if (!activeTimeout) {
+                        activeTimeout = $timeout(fn, delay, apply);
+                        activeTimeout.then(clearActiveTimeout);
+                    }
+                    // Return whichever timeout is active (to get
+                    // a promise for the results of fn)
+                    return activeTimeout;
+                };
+            };
+        }
+
+        return Throttle;
+    }
+);