Allow window post-process in Avalonia

Author: Deadpikle

src/NetSparkle.UI.Avalonia/UIFactory.cs

@@ -101,6 +101,19 @@ public UIFactory(WindowIcon applicationIcon, string releaseNotesSeparatorTemplat
         /// </summary>
         public ReleaseNotesGrabber ReleaseNotesGrabberOverride { get; set; } = null;
 
+        /// <summary>
+        /// A delegate for handling windows that are created by a <see cref="UIFactory"/>
+        /// </summary>
+        /// <param name="window"><see cref="Window"/> that has been created and initialized (with view model, if applicable)</param>
+        /// <param name="factory"><see cref="UIFactory"/> that created the given <see cref="Window"/></param>
+        public delegate void WindowHandler(Window window, UIFactory factory);
+
+        /// <summary>
+        /// Set this property to manually do any other setup on a <see cref="Window"/> after it has been created by the <see cref="UIFactory"/>.
+        /// Can be used to tweak view models, change styles on the <see cref="Window"/>, etc.
+        /// </summary>
+        public WindowHandler ProcessWindowAfterInit { get; set; }
+
         /// <inheritdoc/>
         public virtual IUpdateAvailable CreateUpdateAvailableWindow(SparkleUpdater sparkle, List<AppCastItem> updates, bool isUpdateAlreadyDownloaded = false)
         {
@@ -130,6 +143,7 @@ public virtual IUpdateAvailable CreateUpdateAvailableWindow(SparkleUpdater spark
                 viewModel.ReleaseNotesGrabber = ReleaseNotesGrabberOverride;
             }
             viewModel.Initialize(sparkle, updates, isUpdateAlreadyDownloaded, ReleaseNotesHTMLTemplate, AdditionalReleaseNotesHeaderHTML, ReleaseNotesDateTimeFormat);
+            ProcessWindowAfterInit?.Invoke(window, this);
             return window;
         }
 
@@ -141,19 +155,23 @@ public virtual IDownloadProgress CreateProgressWindow(SparkleUpdater sparkle, Ap
                 ItemToDownload = item,
                 SoftwareWillRelaunchAfterUpdateInstalled = sparkle.RelaunchAfterUpdate
             };
-            return new DownloadProgressWindow(viewModel, _iconBitmap)
+            var window = new DownloadProgressWindow(viewModel, _iconBitmap)
             {
                 Icon = _applicationIcon
             };
+            ProcessWindowAfterInit?.Invoke(window, this);
+            return window;
         }
 
         /// <inheritdoc/>
         public virtual ICheckingForUpdates ShowCheckingForUpdates(SparkleUpdater sparkle)
         {
-            return new CheckingForUpdatesWindow(_iconBitmap)
+            var window = new CheckingForUpdatesWindow(_iconBitmap)
             { 
                 Icon = _applicationIcon
             };
+            ProcessWindowAfterInit?.Invoke(window, this);
+            return window;
         }
 
         /// <inheritdoc/>
@@ -211,6 +229,7 @@ private void ShowMessage(string title, string message)
                 Icon = _applicationIcon
             };
             messageWindow.WindowStartupLocation = WindowStartupLocation.CenterScreen;
+            ProcessWindowAfterInit?.Invoke(window, this);
             messageWindow.Show(); // TODO: This was ShowDialog; will this break anything?
         }