DOM object observer module + Mutation_Handler__on_dxy_slowdown

1 files changed, 118 insertions, 0 deletions

diff --git a/scripts/rz_observer.js b/scripts/rz_observer.js
new file mode 100644
index 00000000..1e8eae6d
--- /dev/null
+++ b/scripts/rz_observer.js
@@ -0,0 +1,118 @@
+"use strict"
+
+/**
+ * DOM object observers
+ */
+define(
+        [],
+        function() {
+
+            var MutationObserver = window.MutationObserver;
+            // more portable version: var MutationObserver =
+            // window.MutationObserver ||
+            // window.WebKitMutationObserver;
+
+            /**
+             * observe SVG object's translate attribute (x,y values), measure
+             * change rate & invoke on_slowdown_threshold_reached() upon
+             * reaching change slowdown threshold.
+             *
+             * Caller is responsible to disconnect observer.
+             */
+            function Mutation_Handler__on_dxy_slowdown(
+                    on_slowdown_threshold_reached) {
+
+                var x_cur, y_cur, d, dx, dy, avg_d = 0;
+
+                this.on_slowdown_threshold_reached = on_slowdown_threshold_reached;
+
+                /**
+                 * handle observer mutation
+                 */
+                this.handle_mutation = function(m) {
+                    if ('transform' != m.attributeName || null == m.oldValue) {
+                        return;
+                    }
+
+                    /*
+                     * parsed txt example:
+                     * "translate(173.6007550157428,275.43228723527193)"
+                     */
+                    var rgx_m = m.oldValue.match(/\((\d+.\d+),(\d+.\d+)\)/);
+                    x_cur = rgx_m[1];
+                    y_cur = rgx_m[2];
+                    if (undefined == this.x_prv) {
+                        this.x_prv = x_cur;
+                        this.y_prv = y_cur;
+                        return;
+                    }
+                    dx = x_cur - this.x_prv;
+                    dy = y_cur - this.y_prv;
+
+                    var d = Math.sqrt(dx * dx + dy * dy);
+                    // average across last samples
+                    avg_d = (1.0 - this.most_recent_sample_weight) * avg_d
+                            + this.most_recent_sample_weight * d;
+
+                    // debug
+                    console.log({
+                        'dx' : dx,
+                        'dy' : dy,
+                        'd' : d,
+                        'avg_d' : avg_d,
+                    });
+
+                    if (avg_d < this.slowdown_threshold) {
+                        // slowdown threshold reached
+                        if (this.on_slowdown_threshold_reached) {
+                            this.on_slowdown_threshold_reached();
+                        }
+                    }
+
+                    this.x_prv = x_cur;
+                    this.y_prv = y_cur;
+                }
+            }
+
+            function new_Mutation_Handler__on_dxy_slowdown(
+                    on_slowdown_threshold_reached, slowdown_threshold,
+                    most_recent_sample_weight) {
+                if (undefined == slowdown_threshold) {
+                    slowdown_threshold = 0.07;
+                }
+                if (undefined == most_recent_sample_weight) {
+                    most_recent_sample_weight = 0.3;
+                }
+
+                var ret = new Mutation_Handler__on_dxy_slowdown(
+                        on_slowdown_threshold_reached);
+                ret.slowdown_threshold = slowdown_threshold;
+                ret.most_recent_sample_weight = most_recent_sample_weight;
+                return ret;
+            }
+
+            function new_MutationObserver(handler) {
+                /*
+                 * FIXME implemente with inheritence - currently triggers
+                 * 'illegal invocation', possibly due to some interaction with
+                 * requirejs
+                 */
+                // var o = new
+                // window.MutationObserver(Mutation_Observer.handler);
+                // var ret = Object.create(o);
+                // ret. = undefined;
+                // return ret;
+                var for_each_mutaion = function(m_set) {
+                    m_set.forEach(function(m) {
+                        handler.handle_mutation(m);
+                    })
+                };
+
+                return new MutationObserver(for_each_mutaion);
+            }
+
+            return {
+                new_MutationObserver : new_MutationObserver,
+                new_Mutation_Handler__on_dxy_slowdown : new_Mutation_Handler__on_dxy_slowdown,
+            };
+        });