From 4cf3dd0b79667dd81142ebac9e58216e18ff08b3 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@users.noreply.github.com>
Date: Tue, 31 Oct 2023 14:00:49 +0100
Subject: [PATCH] Inserting items makes the StartU unstable.

Fixes layout problems in a kinda complex scenario where items are inserted before doing a `BringIntoView`. Couldn't manage to write a test, but all other updates of `_firstIndex` make `_startUUnstable`: this was one missing that was an oversight.
---
 .../Primitives/RealizedStackElements.cs                          | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/Avalonia.Controls.TreeDataGrid/Primitives/RealizedStackElements.cs b/src/Avalonia.Controls.TreeDataGrid/Primitives/RealizedStackElements.cs
index 47f24cc4..b03623cc 100644
--- a/src/Avalonia.Controls.TreeDataGrid/Primitives/RealizedStackElements.cs
+++ b/src/Avalonia.Controls.TreeDataGrid/Primitives/RealizedStackElements.cs
@@ -294,6 +294,7 @@ public void ItemsInserted(int index, int count, Action<Control, int, int> update
                 {
                     // The insertion point was before the first element, update the first index.
                     _firstIndex += count;
+                    _startUUnstable = true;
                 }
                 else
                 {