Add thread-safety with locks to window manager and rendering code

Processes/TerminalProcess.cs

@@ -16,6 +16,7 @@ public class TerminalProcess : Process
     private readonly List<string> history = new();
     private string currentInput = "";
     private readonly List<Text> textLines = new();
+    private readonly object textLinesLock = new object();
     private const int LineHeight = 30;
     private Size lastSize = new Size(-1, -1);
 
@@ -26,11 +27,11 @@ public class TerminalProcess : Process
     internal override void Run()
     {
         window = WindowManager.CreateWindow(this, "Terminal", new Point(50, 50), new Size(400, 300));
-        window.AutoFlush = true;
 
         PrintLine("RemSox GUI Terminal v1.0");
         PrintLine("Type 'help' for commands.");
 
+        window.Flush();
         window.OnKeyEvent += HandleKey;
 
         while (!StopRequested)
@@ -40,7 +41,7 @@ public class TerminalProcess : Process
                 lastSize = window.Size;
                 UpdateDisplay();
             }
-            System.Threading.Thread.Sleep(50);
+            Thread.Sleep(50);
         }
 
         window.OnKeyEvent -= HandleKey;
@@ -106,6 +107,8 @@ public class TerminalProcess : Process
 
         if (maxLines < 1) maxLines = 1;
 
+        lock (textLinesLock)
+        {
             // Ensure we have enough Text elements for maxLines + 1 (input line)
             while (textLines.Count <= maxLines)
             {
@@ -143,5 +146,8 @@ public class TerminalProcess : Process
             {
                 textLines[i].Content = "";
             }
+
+            window.Flush();
+        }
     }
 }

UI/GUI/Rendering/CanvasRenderSource.cs

@@ -17,8 +17,11 @@ public sealed class CanvasRenderSource : IRenderSource
     private static Point lastPointerPosition = new Point(-1, -1);
     private static List<int> orderedWindowsCache = new();
     private static bool isZOrderDirty = true;
+    private static readonly object renderLock = new object();
 
     public void Render(IEnumerable<RenderCommand> commands)
+    {
+        lock (renderLock)
         {
             bool changed = false;
             foreach (RenderCommand command in commands)
@@ -112,8 +115,11 @@ public sealed class CanvasRenderSource : IRenderSource
                 isDirty = true;
             }
         }
+    }
 
     public static void CompositeAndDisplay(Canvas screenCanvas, Point pointerPosition)
+    {
+        lock (renderLock)
         {
             if (!isDirty && pointerPosition == lastPointerPosition)
             {
@@ -142,6 +148,7 @@ public sealed class CanvasRenderSource : IRenderSource
             lastPointerPosition = pointerPosition;
             isDirty = false;
         }
+    }
 
     private static void RenderWindow(Canvas canvas, RenderCommand command)
     {

UI/GUI/Windows/Window.cs

@@ -46,6 +46,7 @@ public sealed class Window(string title, int processId, int id, IRenderSource re
 
     public bool IsDragging => currentInteraction == InteractionMode.Drag;
 
+    private readonly object uiElementsLock = new object();
     private readonly Dictionary<int, UIElement> uiElements = [];
 
     private int nextUIElementId = 1;
@@ -87,7 +88,10 @@ public sealed class Window(string title, int processId, int id, IRenderSource re
             Flush();
         }
 
+        lock (uiElementsLock)
+        {
             uiElements.Add(uiElementId, uiElement);
+        }
 
         return uiElement;
     }
@@ -105,8 +109,16 @@ public sealed class Window(string title, int processId, int id, IRenderSource re
             return;
         }
 
+        bool anyChildChanged;
+        List<UIElement> elementsCopy;
+        
+        lock (uiElementsLock)
+        {
+            anyChildChanged = uiElements.Values.Any(e => e.AnyPropertyChanged);
+            elementsCopy = uiElements.Values.ToList();
+        }
+
         bool windowStateChanged = isFirstRender || Size != lastRenderedSize || IsFocused != lastRenderedIsFocused || Title != lastRenderedTitle;
-        bool anyChildChanged = uiElements.Values.Any(e => e.AnyPropertyChanged);
         bool positionChanged = Position != lastRenderedPosition;
         bool zIndexChanged = ZIndex != lastRenderedZIndex;
 
@@ -133,7 +145,7 @@ public sealed class Window(string title, int processId, int id, IRenderSource re
                 }
             });
 
-            foreach (UIElement element in uiElements.Values)
+            foreach (UIElement element in elementsCopy)
             {
                 commands.Add(new RenderCommand
                 {

UI/GUI/Windows/WindowManager.cs

@@ -13,8 +13,9 @@ namespace RemSox.UI.GUI.Windows;
 
 public static class WindowManager
 {
+    private static readonly object windowsLock = new object();
     // Process ID to list of windows
-    private static readonly ConcurrentDictionary<int, List<Window>> windows = new();
+    private static readonly Dictionary<int, List<Window>> windows = new();
 
     private static int nextWindowId = 1;
     private static int nextZIndex = 1;
@@ -76,39 +77,51 @@ public static class WindowManager
             ZIndex = nextZIndex++
         };
 
+        lock (windowsLock)
+        {
             if (!windows.ContainsKey(process.Id))
             {
                 windows[process.Id] = [];
             }
 
             windows[process.Id].Add(window);
+        }
 
         return window;
     }
 
     public static void CloseWindow(Window window)
+    {
+        lock (windowsLock)
         {
             if (windows.TryGetValue(window.ProcessId, out var processWindows))
             {
                 processWindows.Remove(window);
             }
+        }
         
         renderSource.Render(new[] { new RenderCommand { WindowId = window.Id, ElementId = window.Id, ElementType = "WindowClose", Position = window.Position, Properties = new Dictionary<string, object?>() } });
     }
 
     public static List<Window> GetWindowsForProcess(Process process)
+    {
+        lock (windowsLock)
         {
             if (windows.TryGetValue(process.Id, out var processWindows))
             {
-            return processWindows;
+                return processWindows.ToList();
             }
 
             return [];
         }
+    }
 
     public static void CloseWindowsForProcess(Process process)
     {
-        windows.TryRemove(process.Id, out _);
+        lock (windowsLock)
+        {
+            windows.Remove(process.Id);
+        }
     }
 
     public static void FocusWindow(Window? window)
@@ -137,7 +150,12 @@ public static class WindowManager
 
     public static Window? TryBeginInteract(Point pointerPosition)
     {
-        var allWindows = windows.Values.SelectMany(w => w).OrderByDescending(w => w.ZIndex);
+        List<Window> allWindows;
+        lock (windowsLock)
+        {
+            allWindows = windows.Values.SelectMany(w => w).OrderByDescending(w => w.ZIndex).ToList();
+        }
+
         foreach (var window in allWindows)
         {
             if (window.TryBeginInteract(pointerPosition))
@@ -150,14 +168,17 @@ public static class WindowManager
 
     public static void InvalidateAll()
     {
-        foreach (var processWindows in windows.Values)
+        List<Window> allWindows;
+        lock (windowsLock)
         {
-            foreach (var window in processWindows)
+            allWindows = windows.Values.SelectMany(w => w).ToList();
+        }
+
+        foreach (var window in allWindows)
         {
             window.Invalidate();
         }
     }
-    }
 
     private static int GetNextWindowId()
     {
@@ -166,13 +187,33 @@ public static class WindowManager
 
     sealed private class MuliRenderSource(List<IRenderSource> sources) : IRenderSource
     {
-        public void AddSource(IRenderSource source) => sources.Add(source);
+        private readonly object sourcesLock = new object();
 
-        public void RemoveSource(IRenderSource source) => sources.Remove(source);
+        public void AddSource(IRenderSource source)
+        {
+            lock (sourcesLock)
+            {
+                sources.Add(source);
+            }
+        }
+
+        public void RemoveSource(IRenderSource source)
+        {
+            lock (sourcesLock)
+            {
+                sources.Remove(source);
+            }
+        }
 
         public void Render(IEnumerable<RenderCommand> commands)
         {
-            foreach (IRenderSource source in sources)
+            List<IRenderSource> sourcesCopy;
+            lock (sourcesLock)
+            {
+                sourcesCopy = sources.ToList();
+            }
+
+            foreach (IRenderSource source in sourcesCopy)
             {
                 source.Render(commands);
             }