From 6a0a0f92ac41bdec87c76bcbe2c0856bdafe6ffa Mon Sep 17 00:00:00 2001
From: BobLd <38405645+BobLd@users.noreply.github.com>
Date: Sat, 9 Nov 2024 13:03:57 +0000
Subject: [PATCH] Ensure VirtualizingStackPanel correct element size estimate
 and fix #17460

---
 src/Avalonia.Controls/VirtualizingStackPanel.cs | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/Avalonia.Controls/VirtualizingStackPanel.cs b/src/Avalonia.Controls/VirtualizingStackPanel.cs
index b3d61a9b643..f84582ce6bd 100644
--- a/src/Avalonia.Controls/VirtualizingStackPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingStackPanel.cs
@@ -2,7 +2,6 @@
 using System.Collections.Generic;
 using System.Collections.Specialized;
 using System.Diagnostics;
-using System.Drawing;
 using System.Linq;
 using Avalonia.Controls.Primitives;
 using Avalonia.Controls.Utils;
@@ -164,6 +163,9 @@ protected override Size MeasureOverride(Size availableSize)
                 _realizedElements ??= new();
                 _measureElements ??= new();
 
+                // We need to set the lastEstimatedElementSizeU before calling CalculateDesiredSize()
+                _ = EstimateElementSizeU();
+
                 // We handle horizontal and vertical layouts here so X and Y are abstracted to:
                 // - Horizontal layouts: U = horizontal, V = vertical
                 // - Vertical layouts: U = vertical, V = horizontal