From 4cdf51ccb39d2cccb8d321d9871f7f9d2bef5041 Mon Sep 17 00:00:00 2001
From: Matt McCormick <matt.mccormick@kitware.com>
Date: Sat, 28 Jul 2018 23:52:03 -0400
Subject: [PATCH] feat(createViewer): Add interpolation enabled observer method

---
 src/createViewer.js | 29 ++++++++++++++++++++++++-----
 1 file changed, 24 insertions(+), 5 deletions(-)

diff --git a/src/createViewer.js b/src/createViewer.js
index 6e3969ff..c48a5bd0 100644
--- a/src/createViewer.js
+++ b/src/createViewer.js
@@ -223,15 +223,34 @@ const createViewer = (
   }
 
 
-  let interpolationEnabled = true;
-  publicAPI.setInterpolationEnabled = (interpolation) => {
-    const toggleInterpolationButton = document.getElementById(`${viewerDOMId}-toggleInterpolationButton`);
-    if (interpolation && !interpolationEnabled || !interpolation && interpolationEnabled) {
-      interpolationEnabled = !interpolationEnabled;
+  const toggleInterpolationButton = document.getElementById(`${viewerDOMId}-toggleInterpolationButton`);
+
+  const toggleInterpolationHandlers = [];
+  const toggleInterpolationButtonListener = (event) => {
+    const enabled = toggleInterpolationButton.checked;
+    toggleInterpolationHandlers.forEach((handler) => {
+      handler.call(null, enabled);
+    })
+  }
+  toggleInterpolationButton.addEventListener('click', toggleInterpolationButtonListener)
+
+  publicAPI.subscribeToggleInterpolation = (handler) => {
+    const index = toggleInterpolationHandlers.length;
+    toggleInterpolationHandlers.push(handler);
+    function unsubscribe() {
+      toggleInterpolationHandlers[index] = null;
+    }
+    return Object.freeze({ unsubscribe });
+  }
+
+  publicAPI.setInterpolationEnabled = (enabled) => {
+    const interpolation = toggleInterpolationButton.checked;
+    if (enabled && !interpolation || !enabled && interpolation) {
       toggleInterpolationButton.click();
     }
   }
 
+
   publicAPI.setViewMode = (mode) => {
     switch(mode) {
     case 'XPlane':