From 47ffaf9ca3c5f251661346d4ae6abae9d923aba5 Mon Sep 17 00:00:00 2001
From: Marijn Haverbeke <marijn@haverbeke.berlin>
Date: Fri, 22 Sep 2023 18:08:01 +0200
Subject: [PATCH] Fix an issue in the way the DOMReader treats positions in
 opaque nodes

FIX: Fix an issue in the way the DOM selection is being read that could break
backspacing of widgets on Android.

See https://discuss.codemirror.net/t/backspace-on-decoration-work-strangely-in-mobile-keyboard/7009
---
 src/domreader.ts | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/src/domreader.ts b/src/domreader.ts
index 15d296e..61de027 100644
--- a/src/domreader.ts
+++ b/src/domreader.ts
@@ -1,4 +1,5 @@
 import {ContentView} from "./contentview"
+import {domIndex, maxOffset} from "./dom"
 import {EditorState} from "@codemirror/state"
 
 export const LineBreakPlaceholder = "\uffff"
@@ -88,10 +89,19 @@ export class DOMReader {
         point.pos = this.text.length
   }
 
-  findPointInside(node: Node, maxLen: number) {
+  findPointInside(node: Node, length: number) {
     for (let point of this.points)
       if (node.nodeType == 3 ? point.node == node : node.contains(point.node))
-        point.pos = this.text.length + Math.min(maxLen, point.offset)
+        point.pos = this.text.length + (isAtEnd(node, point.node, point.offset) ? length : 0)
+  }
+}
+
+function isAtEnd(parent: Node, node: Node | null, offset: number) {
+  for (;;) {
+    if (!node || offset < maxOffset(node)) return false
+    if (node == parent) return true
+    offset = domIndex(node) + 1
+    node = node.parentNode
   }
 }