From 0d120fc115a1f22604d9ed6d298c516f38f27f13 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Fri, 29 May 2020 14:38:50 +0200
Subject: [PATCH] Hack selecting controls when switching tree.

---
 .../Diagnostics/ViewModels/MainViewModel.cs     | 17 ++++++++++++++++-
 .../Diagnostics/ViewModels/TreePageViewModel.cs |  2 +-
 2 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/src/Avalonia.Diagnostics/Diagnostics/ViewModels/MainViewModel.cs b/src/Avalonia.Diagnostics/Diagnostics/ViewModels/MainViewModel.cs
index 7addaba977..1d19e1a346 100644
--- a/src/Avalonia.Diagnostics/Diagnostics/ViewModels/MainViewModel.cs
+++ b/src/Avalonia.Diagnostics/Diagnostics/ViewModels/MainViewModel.cs
@@ -2,6 +2,7 @@
 using Avalonia.Controls;
 using Avalonia.Diagnostics.Models;
 using Avalonia.Input;
+using Avalonia.Threading;
 
 namespace Avalonia.Diagnostics.ViewModels
 {
@@ -49,7 +50,21 @@ namespace Avalonia.Diagnostics.ViewModels
                     value is TreePageViewModel newTree &&
                     oldTree?.SelectedNode?.Visual is IControl control)
                 {
-                    newTree.SelectControl(control);
+                    // HACK: We want to select the currently selected control in the new tree, but
+                    // to select nested nodes in TreeView, currently the TreeView has to be able to
+                    // expand the parent nodes. Because at this point the TreeView isn't visible,
+                    // this will fail unless we schedule the selection to run after layout.
+                    DispatcherTimer.RunOnce(
+                        () =>
+                        {
+                            try
+                            {
+                                newTree.SelectControl(control);
+                            }
+                            catch { }
+                        },
+                        TimeSpan.FromMilliseconds(0),
+                        DispatcherPriority.ApplicationIdle);
                 }
 
                 RaiseAndSetIfChanged(ref _content, value);
diff --git a/src/Avalonia.Diagnostics/Diagnostics/ViewModels/TreePageViewModel.cs b/src/Avalonia.Diagnostics/Diagnostics/ViewModels/TreePageViewModel.cs
index 4496cc0a1c..38ac88a83c 100644
--- a/src/Avalonia.Diagnostics/Diagnostics/ViewModels/TreePageViewModel.cs
+++ b/src/Avalonia.Diagnostics/Diagnostics/ViewModels/TreePageViewModel.cs
@@ -95,8 +95,8 @@ namespace Avalonia.Diagnostics.ViewModels
 
             if (node != null)
             {
-                Selection.SelectedIndex = node.Index;
                 ExpandNode(node.Parent);
+                Selection.SelectedIndex = node.Index;
             }
         }