From 7277e9eeb4e8503407c4f86e7ea174870aae61d1 Mon Sep 17 00:00:00 2001
From: snewcomer <snewcomer24@gmail.com>
Date: Fri, 11 May 2018 14:01:54 -0500
Subject: [PATCH] ensure explicitly setting viewportUseIntersectionObserver is
 not allowed

---
 README.md                   | 5 ++---
 addon/mixins/in-viewport.js | 8 ++++++--
 2 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/README.md b/README.md
index bea69b7a..4bb29e0f 100644
--- a/README.md
+++ b/README.md
@@ -89,7 +89,6 @@ export default Component.extend(InViewportMixin, {
       viewportEnabled                 : true,
       viewportUseRAF                  : true,
       viewportSpy                     : false,
-      viewportUseIntersectionObserver : true,
       viewportScrollSensitivity       : 1,
       viewportRefreshRate             : 150,
       intersectionThreshold           : 0,
@@ -114,8 +113,9 @@ export default Component.extend(InViewportMixin, {
 - `viewportUseIntersectionObserver: boolean`
 
   Default: Depends on browser
+  Read-only
 
-  The Mixin by default will use the IntersectionObserver API. If IntersectionObserver is not supported in the target browser, ember-in-viewport will fallback to rAF.
+  The Mixin by default will use the IntersectionObserver API. If IntersectionObserver is not supported in the target browser, ember-in-viewport will fallback to rAF.  We prevent users from explicitly setting this to `true` as browsers lacking support for IntersectionObserver will throw an error.
 
   (https://developer.mozilla.org/en-US/docs/Web/API/Intersection_Observer_API)
   (https://developer.mozilla.org/en-US/docs/Web/API/IntersectionObserver/thresholds#Browser_compatibility)
@@ -191,7 +191,6 @@ module.exports = function(environment) {
       viewportEnabled                 : false,
       viewportUseRAF                  : true,
       viewportSpy                     : false,
-      viewportUseIntersectionObserver : true,
       viewportScrollSensitivity       : 1,
       viewportRefreshRate             : 100,
       viewportListeners               : [],
diff --git a/addon/mixins/in-viewport.js b/addon/mixins/in-viewport.js
index a172c9a7..0963d7a5 100644
--- a/addon/mixins/in-viewport.js
+++ b/addon/mixins/in-viewport.js
@@ -54,13 +54,17 @@ export default Mixin.create({
     // ensure this mixin runs first, then your component can override the options
     this._super(...arguments);
 
-    const options = assign({
+    let options = assign({
       viewportUseRAF: canUseRAF(),
-      viewportUseIntersectionObserver: canUseIntersectionObserver(),
       viewportEntered: false,
       viewportListeners: []
     }, this._buildOptions());
 
+    // set viewportUseIntersectionObserver after merging users config to avoid errors in browsers that lack support (https://github.com/DockYard/ember-in-viewport/issues/146)
+    options = assign(options, {
+      viewportUseIntersectionObserver: canUseIntersectionObserver(),
+    });
+
     setProperties(this, options);
     set(this, '_evtListenerClosures', []);
   },