From 255677d98ecc7e99bc9ebcec2ab1a866b39a00f6 Mon Sep 17 00:00:00 2001
From: 01zulfi <85733202+01zulfi@users.noreply.github.com>
Date: Mon, 29 Dec 2025 14:23:16 +0500
Subject: [PATCH] editor: improve headingUpdatePlugin performance
 Signed-off-by: 01zulfi <85733202+01zulfi@users.noreply.github.com>

---
 .../editor/src/extensions/heading/heading.ts  | 11 ++---
 .../table/prosemirror-tables/fixtables.ts     | 33 +--------------
 packages/editor/src/utils/prosemirror.ts      | 42 ++++++++++++++++++-
 3 files changed, 48 insertions(+), 38 deletions(-)

diff --git a/packages/editor/src/extensions/heading/heading.ts b/packages/editor/src/extensions/heading/heading.ts
index 5ac71eec6..a9e7ac4b7 100644
--- a/packages/editor/src/extensions/heading/heading.ts
+++ b/packages/editor/src/extensions/heading/heading.ts
@@ -26,6 +26,7 @@ import { Heading as TiptapHeading } from "@tiptap/extension-heading";
 import { Node } from "@tiptap/pm/model";
 import { Plugin, PluginKey, Selection, Transaction } from "@tiptap/pm/state";
 import { Callout } from "../callout/callout.js";
+import { changedDescendants } from "../../utils/prosemirror.js";
 
 const COLLAPSIBLE_BLOCK_TYPES = [
   "paragraph",
@@ -408,12 +409,10 @@ const headingUpdatePlugin = new Plugin({
     const newDoc = newState.doc;
     let modified = false;
 
-    newDoc.descendants((newNode, pos) => {
-      if (pos >= oldDoc.content.size) return;
+    function check(newNode: Node, pos: number, oldNode?: Node) {
+      if (!oldNode) return;
 
-      const oldNode = oldDoc.nodeAt(pos);
       if (
-        oldNode &&
         oldNode.type.name === "heading" &&
         oldNode.attrs.level !== newNode.attrs.level
       ) {
@@ -432,7 +431,9 @@ const headingUpdatePlugin = new Plugin({
           modified = true;
         }
       }
-    });
+    }
+
+    changedDescendants(oldDoc, newDoc, 0, check);
 
     return modified ? tr : null;
   }
diff --git a/packages/editor/src/extensions/table/prosemirror-tables/fixtables.ts b/packages/editor/src/extensions/table/prosemirror-tables/fixtables.ts
index 848be68ac..920ba1e5b 100644
--- a/packages/editor/src/extensions/table/prosemirror-tables/fixtables.ts
+++ b/packages/editor/src/extensions/table/prosemirror-tables/fixtables.ts
@@ -8,44 +8,13 @@ import { EditorState, PluginKey, Transaction } from "prosemirror-state";
 import { tableNodeTypes, TableRole } from "./schema.js";
 import { TableMap } from "./tablemap.js";
 import { CellAttrs, removeColSpan } from "./util.js";
+import { changedDescendants } from "../../../utils/prosemirror.js";
 
 /**
  * @public
  */
 export const fixTablesKey = new PluginKey<{ fixTables: boolean }>("fix-tables");
 
-/**
- * Helper for iterating through the nodes in a document that changed
- * compared to the given previous document. Useful for avoiding
- * duplicate work on each transaction.
- *
- * @public
- */
-function changedDescendants(
-  old: Node,
-  cur: Node,
-  offset: number,
-  f: (node: Node, pos: number) => void
-): void {
-  const oldSize = old.childCount,
-    curSize = cur.childCount;
-  outer: for (let i = 0, j = 0; i < curSize; i++) {
-    const child = cur.child(i);
-    for (let scan = j, e = Math.min(oldSize, i + 3); scan < e; scan++) {
-      if (old.child(scan) == child) {
-        j = scan + 1;
-        offset += child.nodeSize;
-        continue outer;
-      }
-    }
-    f(child, offset);
-    if (j < oldSize && old.child(j).sameMarkup(child))
-      changedDescendants(old.child(j), child, offset + 1, f);
-    else child.nodesBetween(0, child.content.size, f, offset + 1);
-    offset += child.nodeSize;
-  }
-}
-
 /**
  * Inspect all tables in the given state's document and return a
  * transaction that fixes them, if necessary. If `oldState` was
diff --git a/packages/editor/src/utils/prosemirror.ts b/packages/editor/src/utils/prosemirror.ts
index ff2068dd7..a10801f21 100644
--- a/packages/editor/src/utils/prosemirror.ts
+++ b/packages/editor/src/utils/prosemirror.ts
@@ -34,7 +34,8 @@ import {
   Slice,
   DOMParser,
   Schema,
-  Fragment
+  Fragment,
+  Node
 } from "prosemirror-model";
 import { EditorState, Selection, Transaction } from "prosemirror-state";
 import TextStyle from "@tiptap/extension-text-style";
@@ -410,3 +411,42 @@ export function ensureLeadingParagraph(node: Node, schema: Schema): Fragment {
 
   return fragment;
 }
+
+/**
+ * Helper for iterating through the nodes in a document that changed
+ * compared to the given previous document. Useful for avoiding
+ * duplicate work on each transaction.
+ *
+ * @public
+ */
+export function changedDescendants(
+  old: Node,
+  cur: Node,
+  offset: number,
+  f: (newNode: Node, pos: number, oldNode?: Node) => void
+): void {
+  const oldSize = old.childCount,
+    curSize = cur.childCount;
+  outer: for (let i = 0, j = 0; i < curSize; i++) {
+    const child = cur.child(i);
+    for (let scan = j, e = Math.min(oldSize, i + 3); scan < e; scan++) {
+      if (old.child(scan) == child) {
+        j = scan + 1;
+        offset += child.nodeSize;
+        continue outer;
+      }
+    }
+    f(child, offset, i < oldSize ? old.child(i) : undefined);
+    if (j < oldSize && old.child(j).sameMarkup(child)) {
+      changedDescendants(old.child(j), child, offset + 1, f);
+    } else {
+      child.nodesBetween(
+        0,
+        child.content.size,
+        f as (node: Node, pos: number) => void,
+        offset + 1
+      );
+    }
+    offset += child.nodeSize;
+  }
+}