Fix arbitrary game ordering when sorting by Favorites (#7170)

* Fix arbitrary sorting by "Favorite" in the UI by making it the same as sorting alphabetically while giving favorites priority.

* Use a more engineered solution rather than string hacks.

* Address code style warnings. Add null checking. Make title name comparison case insensitive.

* one more style fix

---------

Co-authored-by: Logan Stromberg <lostromb@microsoft.com>

src/Ryujinx/UI/ViewModels/AppListFavoriteComparable.cs

@@ -0,0 +1,43 @@
+using Ryujinx.UI.App.Common;
+using System;
+
+namespace Ryujinx.Ava.UI.ViewModels
+{
+    /// <summary>
+    /// Implements a custom comparer which is used for sorting titles by favorite on a UI.
+    /// Returns a sorted list of favorites in alphabetical order, followed by all non-favorites sorted alphabetical.
+    /// </summary>
+    public readonly struct AppListFavoriteComparable : IComparable
+    {
+        /// <summary>
+        /// The application data being compared.
+        /// </summary>
+        private readonly ApplicationData app;
+
+        /// <summary>
+        /// Constructs a new <see cref="AppListFavoriteComparable"/> with the specified application data.
+        /// </summary>
+        /// <param name="app">The app data being compared.</param>
+        public AppListFavoriteComparable(ApplicationData app)
+        {
+            ArgumentNullException.ThrowIfNull(app, nameof(app));
+            this.app = app;
+        }
+
+        /// <inheritdoc/>
+        public readonly int CompareTo(object o)
+        {
+            if (o is AppListFavoriteComparable other)
+            {
+                if (app.Favorite == other.app.Favorite)
+                {
+                    return string.Compare(app.Name, other.app.Name, StringComparison.OrdinalIgnoreCase);
+                }
+
+                return app.Favorite ? -1 : 1;
+            }
+
+            throw new InvalidCastException($"Cannot cast {o.GetType()} to {nameof(AppListFavoriteComparable)}");
+        }
+    }
+}

src/Ryujinx/UI/ViewModels/MainWindowViewModel.cs

@@ -965,8 +965,8 @@ namespace Ryujinx.Ava.UI.ViewModels
                                                                : SortExpressionComparer<ApplicationData>.Descending(app => app.FileSize),
                 ApplicationSort.Path            => IsAscending ? SortExpressionComparer<ApplicationData>.Ascending(app => app.Path)
                                                                : SortExpressionComparer<ApplicationData>.Descending(app => app.Path),
-                ApplicationSort.Favorite        => !IsAscending ? SortExpressionComparer<ApplicationData>.Ascending(app => app.Favorite)
+                ApplicationSort.Favorite        => IsAscending ? SortExpressionComparer<ApplicationData>.Ascending(app => new AppListFavoriteComparable(app))
-                                                                : SortExpressionComparer<ApplicationData>.Descending(app => app.Favorite),
+                                                                : SortExpressionComparer<ApplicationData>.Descending(app => new AppListFavoriteComparable(app)),
                 _ => null,
 #pragma warning restore IDE0055
             };