From a2328cd7f0037f402c346cda4b690e07ab9ba818 Mon Sep 17 00:00:00 2001
From: webzwo0i <webzwo0i@c3d2.de>
Date: Sat, 10 Oct 2020 17:57:22 +0200
Subject: [PATCH] timeslider: bugfix: follow pad contents - only goToLineNumber
 if it exists (#4390)

---
 src/static/js/broadcast.js | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/src/static/js/broadcast.js b/src/static/js/broadcast.js
index 0ae71d86..f14bea49 100644
--- a/src/static/js/broadcast.js
+++ b/src/static/js/broadcast.js
@@ -255,9 +255,15 @@ function loadBroadcastJS(socket, sendSocketMsg, fireWhenAllScriptsAreLoaded, Bro
       debugLog(e);
     }
 
-    var lineNumber = Changeset.opIterator(Changeset.unpack(changeset).ops).next().lines;
+    // we want to scroll to the area that is changed before the lines are mutated and we can't go
+    // to a line that is not there yet
+    let lineNumber = Changeset.opIterator(Changeset.unpack(changeset).ops).next().lines;
     if($('#options-followContents').is(":checked") || $('#options-followContents').prop("checked")){
-      goToLineNumber(lineNumber);
+      if(padContents.currentLines.length <= lineNumber){
+        goToLineNumber(padContents.currentLines.length-1)
+      } else {
+        goToLineNumber(lineNumber);
+      }
     }
 
     Changeset.mutateTextLines(changeset, padContents);