From 1f939c00d31a499b3619f2b0d534ffa42cf2e3fc Mon Sep 17 00:00:00 2001
From: Marijn Haverbeke <marijn@haverbeke.berlin>
Date: Wed, 3 Jul 2024 16:17:53 +0200
Subject: [PATCH] Fix bug in viewport tracking for edit contexts

FIX: Fix a bug where EditContext-based editing could corrupt the document
in some situations.

Issue https://github.com/codemirror/dev/issues/1396
---
 src/domobserver.ts | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/domobserver.ts b/src/domobserver.ts
index baa98ad..fc0341f 100644
--- a/src/domobserver.ts
+++ b/src/domobserver.ts
@@ -549,7 +549,7 @@ class EditContextManager {
       if (change.from == this.from && anchor < this.from) change.from = anchor
       else if (change.to == this.to && anchor > this.to) change.to = anchor
 
-      // Edit context sometimes fire empty changes
+      // Edit contexts sometimes fire empty changes
       if (change.from == change.to && !change.insert.length) return
 
       this.pendingContextChange = change
@@ -612,6 +612,7 @@ class EditContextManager {
         if (pending.from == fromA && pending.to == toA && pending.insert.eq(insert)) {
           pending = this.pendingContextChange = null // Match
           off += dLen
+          this.to += dLen
           return
         } else { // Mismatch, revert
           pending = null