perf(portals): replace brute-force repaint with targeted delta restoration

Remove EnsureWindowsFreshUnderPortals which forced full desktop fill and
all-window invalidation every frame while any portal was open. Replace
with delta-based region restoration that only repaints screen areas where
portal control bounds actually changed.

- Add PreviousControlBounds tracking on DesktopPortal
- Add RestoreScreenRegion for selective desktop/window/portal re-blit
- Add RestorePortalDelta for submenu open/close transitions
- Add RestorePortalRegions called on portal removal
- Remove NeedsCleanupFrame mechanism (restoration is now immediate)
- Fix orphaned project GUID in solution file
- Add tests for delta tracking, immediate restoration, no force-invalidation

Author: Nikolaos Protopapas

Examples/DemoApp/Program.cs

@@ -1,4 +1,5 @@
 using SharpConsoleUI;
+using SharpConsoleUI.Configuration;
 using SharpConsoleUI.Core;
 using SharpConsoleUI.Drivers;
 using SharpConsoleUI.Helpers;
@@ -14,7 +15,10 @@ static async Task<int> Main(string[] args)
 
         try
         {
-            var windowSystem = new ConsoleWindowSystem(new NetConsoleDriver(RenderMode.Buffer));
+            var options = new ConsoleWindowSystemOptions(
+                StatusBarOptions: new StatusBarOptions(ShowStartButton: true)
+            );
+            var windowSystem = new ConsoleWindowSystem(new NetConsoleDriver(RenderMode.Buffer), options: options);
             using var disposables = new DisposableManager();
 
             windowSystem.StatusBarStateService.TopStatus = "SharpConsoleUI Demo | Ctrl+T: Theme Selector";

SharpConsoleUI.Tests/Rendering/DesktopPortalTests.cs

@@ -202,6 +202,80 @@ public void RenderDesktopPortals_CollectsControlBoundsAfterRender()
 		Assert.True(firstBound.Height > 0, $"Control bound height should be > 0, got {firstBound.Height}");
 	}
 
+	[Fact]
+	public void RenderDesktopPortals_TracksPreviousControlBounds()
+	{
+		var system = TestWindowSystemBuilder.CreateTestSystem(80, 24);
+		var content = new MarkupControl(new List<string> { "Hello" });
+
+		var portal = system.DesktopPortalService.CreatePortal(new DesktopPortalOptions(
+			Content: content,
+			Bounds: new Rectangle(0, 0, 40, 10)));
+
+		// First render — PreviousControlBounds starts empty
+		Assert.Empty(portal.PreviousControlBounds);
+
+		system.Render.UpdateDisplay();
+
+		// After first render, ControlBounds should be populated
+		Assert.NotEmpty(portal.ControlBounds);
+
+		// Force a second render by marking dirty
+		portal.IsDirty = true;
+		system.Render.UpdateDisplay();
+
+		// PreviousControlBounds should now contain the bounds from the first render
+		Assert.NotEmpty(portal.PreviousControlBounds);
+	}
+
+	[Fact]
+	public void RemovePortal_RestoresScreenWithoutCleanupFrame()
+	{
+		var system = TestWindowSystemBuilder.CreateTestSystem(80, 24);
+		var content = new MarkupControl(new List<string> { "Hello" });
+
+		var portal = system.DesktopPortalService.CreatePortal(new DesktopPortalOptions(
+			Content: content,
+			Bounds: new Rectangle(5, 5, 30, 10)));
+
+		// Render so portal has a buffer and control bounds
+		system.Render.UpdateDisplay();
+		Assert.NotNull(portal.Buffer);
+		Assert.NotEmpty(portal.ControlBounds);
+
+		// Remove portal — should restore regions immediately
+		system.DesktopPortalService.RemovePortal(portal);
+
+		Assert.False(system.DesktopPortalService.HasPortals);
+		// DesktopNeedsRender should be set for the next frame
+		Assert.True(system.Render.DesktopNeedsRender);
+	}
+
+	[Fact]
+	public void RenderWithPortalOpen_DoesNotForceAllWindowsDirty()
+	{
+		var system = TestWindowSystemBuilder.CreateTestSystem(80, 24);
+
+		// Create a window and render it
+		var window = new Window(system) { Left = 0, Top = 0, Width = 40, Height = 12 };
+		window.AddControl(new MarkupControl(new List<string> { "Window content" }));
+		system.WindowStateService.AddWindow(window);
+
+		system.Render.UpdateDisplay();
+		Assert.False(window.IsDirty); // Window should be clean after render
+
+		// Open a portal
+		system.DesktopPortalService.CreatePortal(new DesktopPortalOptions(
+			Content: new MarkupControl(new List<string> { "Portal" }),
+			Bounds: new Rectangle(50, 5, 20, 5)));
+
+		// Render — portal is dirty, but window should NOT be force-dirtied
+		system.Render.UpdateDisplay();
+
+		// Window should still be clean (not force-invalidated)
+		Assert.False(window.IsDirty);
+	}
+
 	#endregion
 
 	#region Hit Testing

SharpConsoleUI.sln

@@ -77,18 +77,7 @@ Global
 		{BC01AF69-9657-4CAA-819E-979B7E1FC831}.Release|x64.Build.0 = Release|Any CPU
 		{BC01AF69-9657-4CAA-819E-979B7E1FC831}.Release|x86.ActiveCfg = Release|Any CPU
 		{BC01AF69-9657-4CAA-819E-979B7E1FC831}.Release|x86.Build.0 = Release|Any CPU
-		{877F0629-B17F-46DE-975E-7D9486B89D9D}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
-		{877F0629-B17F-46DE-975E-7D9486B89D9D}.Debug|Any CPU.Build.0 = Debug|Any CPU
-		{877F0629-B17F-46DE-975E-7D9486B89D9D}.Debug|x64.ActiveCfg = Debug|Any CPU
-		{877F0629-B17F-46DE-975E-7D9486B89D9D}.Debug|x64.Build.0 = Debug|Any CPU
-		{877F0629-B17F-46DE-975E-7D9486B89D9D}.Debug|x86.ActiveCfg = Debug|Any CPU
-		{877F0629-B17F-46DE-975E-7D9486B89D9D}.Debug|x86.Build.0 = Debug|Any CPU
-		{877F0629-B17F-46DE-975E-7D9486B89D9D}.Release|Any CPU.ActiveCfg = Release|Any CPU
-		{877F0629-B17F-46DE-975E-7D9486B89D9D}.Release|Any CPU.Build.0 = Release|Any CPU
-		{877F0629-B17F-46DE-975E-7D9486B89D9D}.Release|x64.ActiveCfg = Release|Any CPU
-		{877F0629-B17F-46DE-975E-7D9486B89D9D}.Release|x64.Build.0 = Release|Any CPU
-		{877F0629-B17F-46DE-975E-7D9486B89D9D}.Release|x86.ActiveCfg = Release|Any CPU
-		{877F0629-B17F-46DE-975E-7D9486B89D9D}.Release|x86.Build.0 = Release|Any CPU
+
 		{FCAB68F0-B3B4-43BB-9506-145FE0D02736}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
 		{FCAB68F0-B3B4-43BB-9506-145FE0D02736}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{FCAB68F0-B3B4-43BB-9506-145FE0D02736}.Debug|x64.ActiveCfg = Debug|Any CPU
@@ -299,7 +288,7 @@ Global
 	EndGlobalSection
 	GlobalSection(NestedProjects) = preSolution
 		{BC01AF69-9657-4CAA-819E-979B7E1FC831} = {B36A84DF-456D-A817-6EDD-3EC3E7F6E11F}
-		{877F0629-B17F-46DE-975E-7D9486B89D9D} = {B36A84DF-456D-A817-6EDD-3EC3E7F6E11F}
+
 		{FCAB68F0-B3B4-43BB-9506-145FE0D02736} = {B36A84DF-456D-A817-6EDD-3EC3E7F6E11F}
 		{5A0FDF41-ECDA-45C3-B738-AE2822F8FE0B} = {B36A84DF-456D-A817-6EDD-3EC3E7F6E11F}
 		{9272729B-62ED-417E-910B-1BA3B1366A9A} = {B36A84DF-456D-A817-6EDD-3EC3E7F6E11F}

SharpConsoleUI/ConsoleWindowSystem.cs

@@ -612,7 +612,7 @@ public int Run()
 					}
 
 					// Frame pacing: render if windows are dirty OR metrics need update OR desktop needs render OR animations active
-					bool shouldRender = AnyWindowDirty() || metricsNeedUpdate || Render.DesktopNeedsRender || Animations.HasActiveAnimations || Render.IsStatusBarDirty() || _desktopPortalService.AnyPortalDirty() || _desktopPortalService.NeedsCleanupFrame;
+					bool shouldRender = AnyWindowDirty() || metricsNeedUpdate || Render.DesktopNeedsRender || Animations.HasActiveAnimations || Render.IsStatusBarDirty() || _desktopPortalService.AnyPortalDirty();
 
 					// Calculate recommended sleep duration once (used in both branches)
 					var recommendedSleep = _inputStateService.GetRecommendedSleepDuration(

SharpConsoleUI/Core/DesktopPortal.cs

@@ -90,6 +90,9 @@ public class DesktopPortal
 		/// <summary>Cached control bounds from last render (used for selective rendering and hit testing).</summary>
 		internal List<LayoutRect> ControlBounds { get; set; } = new();
 
+		/// <summary>Control bounds from the previous render — used to compute delta regions for restoration.</summary>
+		internal List<LayoutRect> PreviousControlBounds { get; set; } = new();
+
 		/// <summary>The container implementation that connects Content to this portal.</summary>
 		internal DesktopPortalContainer Container { get; }
 

SharpConsoleUI/Core/DesktopPortalService.cs

@@ -23,7 +23,6 @@ public class DesktopPortalService
 		private readonly List<DesktopPortal> _portals = new();
 		private readonly Stack<Window?> _savedActiveWindows = new();
 		private int _nextZOrder;
-		private bool _needsCleanupFrame;
 
 		/// <summary>
 		/// Initializes a new instance of the DesktopPortalService class.
@@ -43,16 +42,6 @@ public DesktopPortalService(ILogService logService, ConsoleWindowSystem windowSy
 		/// </summary>
 		public bool HasPortals => _portals.Count > 0;
 
-		/// <summary>
-		/// Gets whether a cleanup frame is needed (portals were just removed).
-		/// Cleared after the cleanup frame runs.
-		/// </summary>
-		public bool NeedsCleanupFrame
-		{
-			get => _needsCleanupFrame;
-			internal set => _needsCleanupFrame = value;
-		}
-
 		/// <summary>
 		/// Gets the topmost portal (highest ZOrder), or null if none.
 		/// </summary>
@@ -103,11 +92,8 @@ public void RemovePortal(DesktopPortal portal)
 			// Disconnect content from invalidation chain
 			portal.Content.Container = null;
 
-			// Invalidate all windows — next frame repaints everything fresh
-			foreach (var window in _windowSystem.Windows.Values)
-			{
-				window.IsDirty = true;
-			}
+			// Restore screen regions that were covered by this portal
+			_windowSystem.Render.RestorePortalRegions(portal);
 
 			// Restore focus
 			if (_savedActiveWindows.Count > 0)
@@ -121,7 +107,6 @@ public void RemovePortal(DesktopPortal portal)
 				}
 			}
 
-			_needsCleanupFrame = true;
 			_windowSystem.Render.DesktopNeedsRender = true;
 		}
 
@@ -142,20 +127,16 @@ public void DismissAllPortals()
 				originalWindow = _savedActiveWindows.Pop();
 			}
 
-			// Remove all portals
+			// Capture portals before clearing
 			var portalsCopy = _portals.ToList();
 			_portals.Clear();
 
+			// Restore screen regions and clean up each portal
 			foreach (var portal in portalsCopy)
 			{
 				portal.OnDismiss?.Invoke();
 				portal.Content.Container = null;
-			}
-
-			// Invalidate all windows — next frame repaints everything fresh
-			foreach (var window in _windowSystem.Windows.Values)
-			{
-				window.IsDirty = true;
+				_windowSystem.Render.RestorePortalRegions(portal);
 			}
 
 			// Restore original active window
@@ -164,7 +145,6 @@ public void DismissAllPortals()
 				_windowSystem.SetActiveWindow(originalWindow);
 			}
 
-			_needsCleanupFrame = true;
 			_windowSystem.Render.DesktopNeedsRender = true;
 		}