Better UI , better performance and added split screen feature by anirudhqwerty · Pull Request #34 · awaescher/StageManager

anirudhqwerty · 2026-03-11T15:26:40Z

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Copilot

Pull request overview

This PR overhauls the StageManager Windows app with UI improvements, performance optimizations, and a new split-screen feature. It replaces the previous window show/hide strategy pattern with direct BringToTop()/Focus() calls, introduces thread-safe concurrency primitives (SemaphoreSlim, ConcurrentDictionary, locks), modernizes the UI with Mica backdrop and animations, and adds Ctrl+Click split-screen support via a new WindowLayoutManager.

Changes:

Added split-screen layout feature (ToggleSplit, WindowLayoutManager.SplitScreen) allowing multiple scenes to be tiled side-by-side via Ctrl+Click
Replaced Dictionary with ConcurrentDictionary, added SemaphoreSlim transition locks and _stateLock for thread safety across SceneManager and WindowsManager
Modernized UI with Mica backdrop, animated scene cards, rounded thumbnails, and replaced the overlap-check timer with a simpler mouse-position-based sidebar flyover

Reviewed changes

Copilot reviewed 40 out of 51 changed files in this pull request and generated 9 comments.

Show a summary per file

File	Description
StageManager/SceneManager.cs	Core rewrite: thread-safe scene management, split-screen support, changed grouping key from process name to window handle
StageManager/MainWindow.xaml.cs	Sidebar flyover logic, Mica backdrop, Ctrl+Click split, replaced timer with mouse-based visibility
StageManager/MainWindow.xaml	Complete UI redesign with animated cards, shadows, rounded corners, ScrollViewer
StageManager/Native/WindowLayoutManager.cs	New file: DPI-aware split-screen layout computation and atomic window positioning
StageManager/Native/WindowsManager.cs	Switched to ConcurrentDictionary, proper hook cleanup, removed mouse hook thread
StageManager/Native/WindowsWindow.cs	Icon caching, UWP process resolution, expanded ignore lists, nullable annotations
StageManager/Strategies/ScreenOffsetWindowStrategy.cs	Partial implementation: Show works, Hide is empty
StageManager/Strategies/NormalizeAndMinimizeWindowStrategy.cs	Show changed to BringToTop, Hide emptied
StageManager/DwmThumbnail.xaml.cs	Thumbnail cleanup on Unload, handle re-registration, DPI rounding fixes
StageManager/Desktop.cs	Registry key caching, icon visibility cache
StageManager/Native/Interop/NativeMethods.cs	Added MonitorFromWindow, DwmSetWindowAttribute, Win32Size struct
StageManager/AutoStart.cs	Fixed registry key disposal with `using`
StageManager/StageManager.csproj	Added CA1416 suppression, Microsoft.Xaml.Behaviors.Wpf package
ReadMe.md	Documented split-screen, marked multi-monitor as complete
.github/workflows/dotnet-desktop.yml	Updated to .NET 8, actions v4, conditional release steps
.dotnet_home/**	Accidentally committed .NET telemetry/cache files
Other files	Minor cleanups: nullable annotations, comment removal, formatting

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Copilot · 2026-03-12T07:16:51Z

 		public void Hide(IWindow window)
 		{
-			throw new System.NotImplementedException();
 		}


Both ScreenOffsetWindowStrategy.Hide and NormalizeAndMinimizeWindowStrategy.Hide have empty bodies — the implementation was removed but no replacement was added. The Hide method previously called Win32.ShowWindow(window.Handle, Win32.SW.SW_MINIMIZE) for the normalize strategy and should have stored the position and moved the window off-screen for the offset strategy (using the declared OFF_SCREEN_OFFSET constant and _originalPositions dictionary). With empty Hide methods, the WindowStrategy pattern is effectively broken — Show does something but Hide is a no-op. While it appears that WindowStrategy is no longer called from SceneManager, this makes both strategy classes dead/incomplete code.

Copilot · 2026-03-12T07:16:51Z

+		public event EventHandler<SceneChangedEventArgs>? SceneChanged;
+		public event EventHandler<CurrentSceneSelectionChangedEventArgs>? CurrentSceneSelectionChanged;
+
+		private IWindowStrategy WindowStrategy { get; } = new NormalizeAndMinimizeWindowStrategy();


WindowStrategy is declared and initialized but never used anywhere in the new SceneManager code. The old code called WindowStrategy.Show(w) and WindowStrategy.Hide(o) during scene switching, but those calls have been removed and replaced with direct BringToTop()/Focus() calls. This makes the WindowStrategy property and the entire IWindowStrategy abstraction dead code. Either remove the unused property or restore the strategy-based show/hide pattern if window hiding is still desired.

Copilot · 2026-03-12T07:16:51Z

 		{
-			var existentScene = FindSceneForProcess(GetWindowGroupKey(window));
-			var scene = existentScene ?? new Scene(window.ProcessName, window);
+			if (object.Equals(scene, _current)) return;


SwitchTo reads _current (line 179) outside of any lock before acquiring _transitionLock. This creates a race condition: another thread could change _current between the check on line 179 and the lock acquisition on line 181, causing the method to either skip a needed transition or proceed with stale data. The equality check should be moved inside the locked region.

Copilot · 2026-03-12T07:16:51Z

+
+			// Cache physical screen dimensions once at startup
+			var primaryScreen = System.Windows.Forms.Screen.PrimaryScreen;
+			_cachedPhysicalScreenHeight = primaryScreen.Bounds.Height;


System.Windows.Forms.Screen.PrimaryScreen can return null (it's annotated as nullable in .NET 6+). Accessing .Bounds.Height directly will throw a NullReferenceException if no primary screen is detected. Add a null check or use a fallback value.

Suggested change

_cachedPhysicalScreenHeight = primaryScreen.Bounds.Height;

_cachedPhysicalScreenHeight = primaryScreen?.Bounds.Height ?? (int)SystemParameters.PrimaryScreenHeight;

Copilot · 2026-03-12T07:16:52Z

 |**Product stage**||
 |virtual desktop support (pin window)|⬜|
-|multi-monitor support|⬜|
+|multi-monitor support|✅|


The ReadMe claims "multi-monitor support" is now complete (✅), but the implementation has some single-monitor assumptions. In MainWindow.xaml.cs, _cachedPhysicalScreenHeight is cached from PrimaryScreen at startup and never updated, meaning the flyover trigger zone (lines 349-350) will use the wrong height on non-primary monitors. The WindowLayoutManager.SplitScreen does correctly use MonitorFromWindow per window, but the sidebar activation logic is primary-monitor-only.

Copilot · 2026-03-12T07:16:52Z

@@ -0,0 +1 @@
+61e865d1-0113-41a6-8217-422fb0204ee1


The .dotnet_home/ directory containing .NET telemetry data, machine IDs, and sentinel files has been committed to the repository. These files contain local build environment artifacts (telemetry payloads, machine identifiers) that should not be tracked in version control. They should be removed from the PR and added to .gitignore.

Suggested change

61e865d1-0113-41a6-8217-422fb0204ee1

# MachineId cache intentionally cleared; do not commit user-level cache data.

Copilot · 2026-03-12T07:16:52Z

+		private void WindowsManager_WindowCreated(IWindow window, bool firstCreate)
 		{
-			var scene = FindSceneForWindow(window);
-			if (scene is null)
+			Scene scene;
+			lock (_stateLock)
 			{
 				scene = new Scene(GetWindowGroupKey(window), window);
 				_scenes.Add(scene);
-				SceneChanged?.Invoke(this, new SceneChangedEventArgs(scene, window, ChangeType.Created));
 			}

-			await SwitchTo(scene);
+			RaiseOnCapturedContext(() =>
+				SceneChanged?.Invoke(this, new SceneChangedEventArgs(scene, window, ChangeType.Created)));
+
+			SwitchTo(scene).SafeFireAndForget();


The WindowsManager_WindowCreated handler always creates a new Scene for every window, using window.Handle.ToString() as the group key (line 391). This means every window gets its own scene, and new windows from an already-tracked process are never added to an existing scene. The previous code used FindSceneForProcess(GetWindowGroupKey(window)) to group windows of the same process into the same scene. This is a significant behavioral change — all windows will now appear as separate scenes in the sidebar, which seems inconsistent with the purpose of a "stage manager" that groups related windows.

Copilot · 2026-03-12T07:16:52Z

+using System.Windows.Forms;

 namespace StageManager.Strategies
 {
 	internal class ScreenOffsetWindowStrategy : IWindowStrategy
 	{
+		private const int OFF_SCREEN_OFFSET = 32000;


The System.Windows.Forms namespace is imported but unused in this file. Only Win32 and ConcurrentDictionary types are actually used. Additionally, the constant OFF_SCREEN_OFFSET is declared but never referenced.

Copilot · 2026-03-12T07:16:53Z

+				Dispatcher.BeginInvoke(() => Mode = WindowMode.OffScreen);
 			}
+
+


There is an extra blank line here (two consecutive blank lines). Minor formatting inconsistency.

Suggested change

anirudhqwerty added 15 commits March 10, 2026 23:09

Fix issues and improvements

9840449

Cleanup: remove temporary new files directory

012b374

fixed many bugs

a6e198d

some performance fixes and ui bugs

5f297b8

added ctrl for split option

50def52

fixed phantom window

e976425

performance improvements and fixed memory leak issues

d4ee54b

added to do list and notes

80cb168

added a single panel for todo and notes

12f77ac

removed to do list and notes

b0dc2b7

fixed switching bugs

8cf71b7

fixed split screen bugs

f2bb614

updated readme

4f1b129

Fix GitHub Actions target framework and workflow triggers

71459c0

Update deprecated GitHub Actions to v4

c2cf4f1

awaescher requested a review from Copilot March 12, 2026 07:13

Copilot started reviewing on behalf of awaescher March 12, 2026 07:13 View session

Copilot AI reviewed Mar 12, 2026

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Better UI , better performance and added split screen feature#34

Better UI , better performance and added split screen feature#34
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	_cachedPhysicalScreenHeight = primaryScreen.Bounds.Height;
	_cachedPhysicalScreenHeight = primaryScreen?.Bounds.Height ?? (int)SystemParameters.PrimaryScreenHeight;

		@@ -0,0 +1 @@
		61e865d1-0113-41a6-8217-422fb0204ee1 No newline at end of file

	61e865d1-0113-41a6-8217-422fb0204ee1
	# MachineId cache intentionally cleared; do not commit user-level cache data.

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