From 7ce311834fc69c889d9ba0722fae5e1dd690af4b Mon Sep 17 00:00:00 2001
From: Mike Chen <mhchen@gmail.com>
Date: Wed, 28 Nov 2018 11:57:21 -0800
Subject: [PATCH] Fix errant scroll behavior on /new when using keyboard
 scrolling (#1203)

Disable textarea resize and window scroll method when doing anything
that does not actually modify the textarea contents (e.g. arrow keys,
pgup/pgdn).

Fixes #1109
---
 .../initializers/initEditorResize.js          | 21 ++++++++++++++++---
 1 file changed, 18 insertions(+), 3 deletions(-)

diff --git a/app/assets/javascripts/initializers/initEditorResize.js b/app/assets/javascripts/initializers/initEditorResize.js
index ac4fb1126..56c05f381 100644
--- a/app/assets/javascripts/initializers/initEditorResize.js
+++ b/app/assets/javascripts/initializers/initEditorResize.js
@@ -3,8 +3,12 @@
  * It is a slightly modified version of the solution found here.
  * stackoverflow.com/questions/18262729/ how-to-stop-window-jumping-when-typing-in-autoresizing-textarea
  */
+// eslint-disable-next-line no-unused-vars
 function initEditorResize() {
-  var observe, scrollLeft, scrollTop;
+  var observe;
+  var scrollLeft;
+  var scrollTop;
+  var lastText;
   var textarea = document.getElementById('article_body_markdown');
   var oldEditor = document.getElementById('markdown-editor-main');
 
@@ -39,15 +43,26 @@ function initEditorResize() {
   }
 
   function resize() {
+    var len;
+    var newText = textarea.value;
+    // Don't resize or scroll if not modifying the text
+    if (newText === lastText) {
+      return;
+    }
+    lastText = newText;
     textarea.style.height = 'auto';
     textarea.style.height = textarea.scrollHeight - 29 + 'px';
     window.scrollTo(scrollLeft, scrollTop);
     if (oldEditor) {
       return;
     }
-    var len = textarea.value.length;
+    len = textarea.value.length;
     // If character entered is at the end of the textarea (therefore cursor)
-    if((textarea.selectionEnd > (len - 15)) && len > 400 && document.activeElement === textarea ) {
+    if (
+      textarea.selectionEnd > len - 15 &&
+      len > 400 &&
+      document.activeElement === textarea
+    ) {
       window.scrollTo(scrollLeft, 10000);
     } else {
       window.scrollTo(scrollLeft, scrollTop);