From 9e6deb238645cbf93b15adf619a90d19c1cdbf54 Mon Sep 17 00:00:00 2001
From: Tim <tim.uniewski@gmail.com>
Date: Wed, 13 Jul 2022 09:22:34 +0200
Subject: [PATCH] fix for ProgressBar not listening to size changes of parent

If the track for the progressbar changes its size the indicator needs to update as well.
---
 src/Avalonia.Controls/ProgressBar.cs | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/src/Avalonia.Controls/ProgressBar.cs b/src/Avalonia.Controls/ProgressBar.cs
index d0e8e8f1a0..56b9caf085 100644
--- a/src/Avalonia.Controls/ProgressBar.cs
+++ b/src/Avalonia.Controls/ProgressBar.cs
@@ -100,6 +100,7 @@ namespace Avalonia.Controls
         private double _indeterminateStartingOffset;
         private double _indeterminateEndingOffset;
         private Border? _indicator;
+        private IDisposable? _trackSizeChangedListener;
 
         public static readonly StyledProperty<bool> IsIndeterminateProperty =
             AvaloniaProperty.Register<ProgressBar, bool>(nameof(IsIndeterminate));
@@ -195,8 +196,9 @@ namespace Avalonia.Controls
         /// <inheritdoc/>
         protected override Size ArrangeOverride(Size finalSize)
         {
+            var result = base.ArrangeOverride(finalSize);
             UpdateIndicator();
-            return base.ArrangeOverride(finalSize);
+            return result;
         }
 
         protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs change)
@@ -216,8 +218,15 @@ namespace Avalonia.Controls
         /// <inheritdoc/>
         protected override void OnApplyTemplate(TemplateAppliedEventArgs e)
         {
+            // dispose any previous track size listener
+            _trackSizeChangedListener?.Dispose();
+            
             _indicator = e.NameScope.Get<Border>("PART_Indicator");
 
+            // listen to size changes of the indicators track (parent) and update the indicator there. 
+            _trackSizeChangedListener = _indicator.Parent?.GetPropertyChangedObservable(BoundsProperty)
+                .Subscribe(_ => UpdateIndicator());
+            
             UpdateIndicator();
         }