[Settings] Fix flyout position when ComboBox is aligned to the right

Natsurainko.FluentLauncher/Behaviors/SetComboBoxWidthFromItemsBehavior.cs

@@ -0,0 +1,115 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using System.Windows.Threading;
+using Microsoft.UI.Dispatching;
+using Microsoft.UI.Xaml;
+using Microsoft.UI.Xaml.Automation.Peers;
+using Microsoft.UI.Xaml.Automation.Provider;
+using Microsoft.UI.Xaml.Controls;
+using Microsoft.UI.Xaml.Controls.Primitives;
+using Microsoft.Xaml.Interactivity;
+using Windows.Foundation;
+
+namespace Natsurainko.FluentLauncher.Behaviors
+{
+    class SetComboBoxWidthFromItemsBehavior : Behavior<ComboBox>
+    {
+        public static readonly DependencyProperty SetComboBoxWidthFromItemsProperty =
+        DependencyProperty.RegisterAttached
+        (
+            "SetComboBoxWidthFromItems",
+            typeof(bool),
+            typeof(SetComboBoxWidthFromItemsBehavior),
+            new PropertyMetadata(false, OnSetComboBoxWidthFromItemsPropertyChanged)
+        );
+
+        public bool SetComboBoxWidthFromItems 
+        { 
+            get => (bool)GetValue(SetComboBoxWidthFromItemsProperty); 
+            set => SetValue(SetComboBoxWidthFromItemsProperty, value);
+        }
+
+        protected override void OnAttached()
+        {
+            AssociatedObject.Loaded += OnComboBoxLoaded;
+        }
+
+        private static void OnSetComboBoxWidthFromItemsPropertyChanged(
+            DependencyObject dpo, 
+            DependencyPropertyChangedEventArgs e)
+        {
+            ComboBox comboBox = ((SetComboBoxWidthFromItemsBehavior)dpo).AssociatedObject;
+            bool newValue = (bool)e.NewValue;
+            bool oldValue = (bool)e.OldValue;
+
+            if (comboBox != null && newValue != oldValue)
+            {
+                if (newValue == true)
+                {
+                    comboBox.Loaded += OnComboBoxLoaded;
+                }
+                else
+                {
+                    comboBox.Loaded -= OnComboBoxLoaded;
+                }
+            }
+        }
+
+        private static void OnComboBoxLoaded(object sender, RoutedEventArgs e)
+        {
+            ComboBox comboBox = (ComboBox) sender;
+
+            comboBox.DispatcherQueue.TryEnqueue(() => { comboBox.SetWidthFromItems(); });
+        }
+    }
+
+    public static class ComboBoxExtensionMethods
+    {
+        public static void SetWidthFromItems(this ComboBox comboBox)
+        {
+            double comboBoxWidth = 60; // size of combobox without content
+
+            // Create the peer and provider to expand the comboBox in code behind. 
+            ComboBoxAutomationPeer peer = new ComboBoxAutomationPeer(comboBox);
+            IExpandCollapseProvider provider = (IExpandCollapseProvider)peer.GetPattern(PatternInterface.ExpandCollapse);
+
+            EventHandler<object> eventHandler = null;
+            eventHandler = new EventHandler<object>((_, _) =>
+            {
+                if (comboBox.IsDropDownOpen //&&
+                    /*comboBox.ItemContainerGenerator.Status == GeneratorStatus.ContainersGenerated*/)
+                {
+                    double width = 0;
+
+                    // Get the container of the item
+                    foreach (var item in comboBox.Items)
+                    {
+                        //TODO: combobox.items are not necessarily ComboBoxItems
+                        // var cont = comboBox.ContainerFromIndex(0);
+                        // var a = comboBox.ItemContainerGenerator.ContainerFromItem(item);
+                        TextBlock comboBoxItem = new TextBlock { Text = item.ToString() };
+                        comboBoxItem.Measure(new Size(double.PositiveInfinity, double.PositiveInfinity));
+                        if (comboBoxItem.DesiredSize.Width > width)
+                        {
+                            width = comboBoxItem.DesiredSize.Width;
+                        }
+                    }
+                    comboBox.Width = comboBoxWidth + width;
+                    // Remove the event handler. 
+                    // comboBox.ItemContainerGenerator.StatusChanged -= eventHandler;
+                    comboBox.DropDownOpened -= eventHandler;
+                    provider.Collapse();
+                }
+            });
+
+            // comboBox.ItemContainerGenerator.StatusChanged += eventHandler;
+            comboBox.DropDownOpened += eventHandler;
+
+            // Expand the comboBox to generate all its ComboBoxItem's. 
+            provider.Expand();
+        }
+    }
+}

Natsurainko.FluentLauncher/Views/Pages/Settings/Launch.xaml

@@ -8,7 +8,9 @@
     xmlns:local="using:Natsurainko.FluentLauncher.Views.Pages.Settings"
     xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
     xmlns:vm="using:Natsurainko.FluentLauncher.ViewModels.Pages.Settings"
+    xmlns:behaviors ="using:Natsurainko.FluentLauncher.Behaviors"
     Background="Transparent"
+    xmlns:i="using:Microsoft.Xaml.Interactivity"
     mc:Ignorable="d">
     <Page.DataContext>
         <vm:Launch />
@@ -55,6 +57,9 @@
                                     VerticalAlignment="Center"
                                     ItemsSource="{Binding GameFolders}"
                                     SelectedItem="{Binding CurrentGameFolder, Mode=TwoWay}">
+                                    <i:Interaction.Behaviors>
+                                        <behaviors:SetComboBoxWidthFromItemsBehavior SetComboBoxWidthFromItems="True"/>
+                                    </i:Interaction.Behaviors>
                                     <ComboBox.ItemTemplate>
                                         <DataTemplate x:DataType="x:String">
                                             <TextBlock Text="{Binding}" TextTrimming="CharacterEllipsis" />