Add Ctrl+Z undo for completed drawing actions with permanent eraser semantics

CHANGELOG.md

@@ -6,6 +6,26 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 
+## v1.0.13
+
+### Added
+- **Undo (Ctrl+Z) with Permanent Eraser Semantics**
+  - Press `Ctrl+Z` while drawing mode is active to undo the most recent **completed** action (pen stroke, line, rectangle, circle)
+  - Erased items are permanently deleted and are never restored by undo
+  - New `DrawingHistory` service tracks completed actions using stable element IDs
+  - Added unit tests covering undo behavior and eraser permanence
+
+### Changed
+- **Tool Completion Events**
+  - Tools report completed actions (pen on mouse-up; shapes on second click) so undo is per-action instead of per-mouse-move
+  - Eraser reports erased elements so history entries are marked removed
+- **Keyboard Hook Handling for Ctrl+Z**
+  - Detects `Ctrl+Z` only when drawing mode is active
+  - Suppresses `Ctrl+Z` during drawing mode to prevent pass-through to underlying apps
+- **History Reset Behavior**
+  - Undo history is cleared when clearing the canvas and when exiting drawing mode
+
+
 ## v1.0.12
 
 ### Added

Installer/GhostDraw.Installer.wixproj

@@ -1,6 +1,6 @@
 <Project Sdk="WixToolset.Sdk/4.0.5">
   <PropertyGroup>
-    <Version Condition="'$(Version)' == ''">1.0.12</Version>
+    <Version Condition="'$(Version)' == ''">1.0.13</Version>
     <OutputName>GhostDrawSetup-$(Version)</OutputName>
     <OutputType>Package</OutputType>
     <Platform>x64</Platform>

Src/GhostDraw/App.xaml.cs

@@ -81,6 +81,7 @@ protected override void OnStartup(StartupEventArgs e)
             _keyboardHook.CircleToolPressed += OnCircleToolPressed;
             _keyboardHook.HelpPressed += OnHelpPressed;
             _keyboardHook.ScreenshotFullPressed += OnScreenshotFullPressed;
+            _keyboardHook.UndoPressed += OnUndoPressed;
             _keyboardHook.Start();
 
             // Setup system tray icon
@@ -367,7 +368,7 @@ private void OnScreenshotFullPressed(object? sender, EventArgs e)
             _logger?.LogInformation("====== OnScreenshotFullPressed CALLED ======");
             _logger?.LogInformation("DrawingManager null: {IsNull}", _drawingManager == null);
             _logger?.LogInformation("DrawingManager.IsDrawingMode: {IsDrawingMode}", _drawingManager?.IsDrawingMode);
-            
+
             // Capture full screenshot if drawing mode is active
             if (_drawingManager?.IsDrawingMode == true)
             {
@@ -388,6 +389,29 @@ private void OnScreenshotFullPressed(object? sender, EventArgs e)
         }
     }
 
+    private void OnUndoPressed(object? sender, EventArgs e)
+    {
+        try
+        {
+            _logger?.LogInformation("Ctrl+Z pressed - undoing last action");
+
+            // Undo last action if drawing mode is active
+            if (_drawingManager?.IsDrawingMode == true)
+            {
+                _drawingManager?.UndoLastAction();
+            }
+            else
+            {
+                _logger?.LogDebug("Undo ignored - drawing mode is NOT active");
+            }
+        }
+        catch (Exception ex)
+        {
+            _logger?.LogError(ex, "Exception in OnUndoPressed");
+            _exceptionHandler?.HandleException(ex, "Undo pressed handler");
+        }
+    }
+
     protected override void OnExit(ExitEventArgs e)
     {
         _logger?.LogInformation("Application exiting");

Src/GhostDraw/Core/AppSettings.cs

@@ -86,7 +86,7 @@ public class AppSettings
     /// </summary>
     [JsonPropertyName("screenshotSavePath")]
     public string ScreenshotSavePath { get; set; } = System.IO.Path.Combine(
-        Environment.GetFolderPath(Environment.SpecialFolder.MyPictures), 
+        Environment.GetFolderPath(Environment.SpecialFolder.MyPictures),
         "GhostDraw");
 
     /// <summary>

Src/GhostDraw/Core/DrawTool.cs

@@ -12,22 +12,22 @@ public enum DrawTool
     /// Freehand drawing tool (default)
     /// </summary>
     Pen,
-    
+
     /// <summary>
     /// Straight line tool - click two points to draw a line
     /// </summary>
     Line,
-    
+
     /// <summary>
     /// Eraser tool - removes drawing objects underneath the cursor
     /// </summary>
     Eraser,
-    
+
     /// <summary>
     /// Rectangle tool - click two points to draw a rectangle
     /// </summary>
     Rectangle,
-    
+
     /// <summary>
     /// Circle tool - click two points to draw a circle/ellipse
     /// </summary>

Src/GhostDraw/Core/GlobalKeyboardHook.cs

@@ -20,6 +20,7 @@ public class GlobalKeyboardHook : IDisposable
     private const int VK_C = 0x43;         // 67 - 'C' key for circle tool
     private const int VK_F1 = 0x70;        // 112 - 'F1' key for help
     private const int VK_S = 0x53;         // 83 - 'S' key for screenshot (Ctrl+S only)
+    private const int VK_Z = 0x5A;         // 90 - 'Z' key for undo (Ctrl+Z only)
     private const int VK_LCONTROL = 0xA2;  // 162 - Left Control key
     private const int VK_RCONTROL = 0xA3;  // 163 - Right Control key
 
@@ -41,6 +42,7 @@ public class GlobalKeyboardHook : IDisposable
     public event EventHandler? CircleToolPressed;
     public event EventHandler? HelpPressed;
     public event EventHandler? ScreenshotFullPressed;
+    public event EventHandler? UndoPressed;
 
     // NEW: Raw key events for recorder
     public event EventHandler<KeyEventArgs>? KeyPressed;
@@ -51,7 +53,7 @@ public class GlobalKeyboardHook : IDisposable
     private Dictionary<int, bool> _keyStates = new();
     private bool _wasHotkeyActive = false;
     private volatile bool _isControlPressed = false;
-    
+
     // Drawing mode state - used to determine if we should suppress keys
     private volatile bool _isDrawingModeActive = false;
 
@@ -65,7 +67,7 @@ public GlobalKeyboardHook(ILogger<GlobalKeyboardHook> logger)
         foreach (var vk in _hotkeyVKs)
             _keyStates[vk] = false;
     }
-    
+
     /// <summary>
     /// Configures the hotkey combination
     /// </summary>
@@ -184,7 +186,7 @@ private nint SetHook(LowLevelKeyboardProc proc)
     private nint HookCallback(int nCode, nint wParam, nint lParam)
     {
         bool shouldSuppressKey = false;
-        
+
         try
         {
             if (nCode >= 0)
@@ -202,8 +204,8 @@ private nint HookCallback(int nCode, nint wParam, nint lParam)
                 if (vkCode == VK_LCONTROL || vkCode == VK_RCONTROL)
                 {
                     _isControlPressed = isKeyDown;
-                    _logger.LogDebug("Control key ({Type}) {State}", 
-                        vkCode == VK_LCONTROL ? "Left" : "Right", 
+                    _logger.LogDebug("Control key ({Type}) {State}",
+                        vkCode == VK_LCONTROL ? "Left" : "Right",
                         isKeyDown ? "PRESSED" : "RELEASED");
                 }
 
@@ -269,12 +271,12 @@ private nint HookCallback(int nCode, nint wParam, nint lParam)
                     _logger.LogInformation("====== CTRL+S DETECTED ======");
                     _logger.LogInformation("Control key state: {IsControlPressed}", _isControlPressed);
                     _logger.LogInformation("Drawing mode active: {IsDrawingModeActive}", _isDrawingModeActive);
-                    
+
                     _logger.LogInformation("Ctrl+S pressed - firing ScreenshotFullPressed event");
                     ScreenshotFullPressed?.Invoke(this, EventArgs.Empty);
-                    _logger.LogInformation("ScreenshotFullPressed event fired, subscribers: {Count}", 
+                    _logger.LogInformation("ScreenshotFullPressed event fired, subscribers: {Count}",
                         ScreenshotFullPressed?.GetInvocationList().Length ?? 0);
-                    
+
                     // Suppress Ctrl+S when drawing mode is active to prevent Windows Snipping Tool
                     if (_isDrawingModeActive)
                     {
@@ -285,10 +287,21 @@ private nint HookCallback(int nCode, nint wParam, nint lParam)
                     {
                         _logger.LogInformation("KEY WILL NOT BE SUPPRESSED - Drawing mode is inactive");
                     }
-                    
+
                     _logger.LogInformation("====== END CTRL+S HANDLING ======");
                 }
 
+                // Check for Ctrl+Z key press (undo - only when drawing mode is active)
+                if (vkCode == VK_Z && isKeyDown && _isControlPressed && _isDrawingModeActive)
+                {
+                    _logger.LogInformation("Ctrl+Z pressed - firing UndoPressed event");
+                    UndoPressed?.Invoke(this, EventArgs.Empty);
+
+                    // Suppress Ctrl+Z when drawing mode is active to prevent underlying apps from receiving it
+                    shouldSuppressKey = true;
+                    _logger.LogDebug("Ctrl+Z suppressed - drawing mode is active");
+                }
+
                 // Track hotkey state
                 if (_hotkeyVKs.Contains(vkCode))
                 {
@@ -328,7 +341,7 @@ private nint HookCallback(int nCode, nint wParam, nint lParam)
             _logger.LogTrace("Key suppressed - not calling CallNextHookEx");
             return (nint)1;
         }
-        
+
         // MUST call CallNextHookEx for non-suppressed keys to allow other applications to process them
         return CallNextHookEx(_hookID, nCode, wParam, lParam);
     }
@@ -359,7 +372,7 @@ public void SetDrawingModeActive(bool isActive)
     {
         var previousState = _isDrawingModeActive;
         _isDrawingModeActive = isActive;
-        
+
         if (previousState != isActive)
         {
             _logger.LogInformation("====== DRAWING MODE STATE CHANGED ======");

Src/GhostDraw/Core/ServiceConfiguration.cs

@@ -58,6 +58,7 @@ public static ServiceProvider ConfigureServices()
         services.AddSingleton<AppSettingsService>();
         services.AddSingleton<CursorHelper>();
         services.AddSingleton<ScreenshotService>();
+        services.AddSingleton<DrawingHistory>();
 
         // Register drawing tools
         services.AddSingleton<GhostDraw.Tools.PenTool>();

Src/GhostDraw/GhostDraw.csproj

@@ -8,7 +8,7 @@
     <UseWPF>true</UseWPF>
     <UseWindowsForms>true</UseWindowsForms>
     <ApplicationIcon>Assets\favicon.ico</ApplicationIcon>
-    <Version>1.0.12</Version>
+    <Version>1.0.13</Version>
     <EnableWindowsTargeting>true</EnableWindowsTargeting>
   </PropertyGroup>
 

Src/GhostDraw/Helpers/CursorHelper.cs

@@ -216,8 +216,8 @@ public WpfCursor CreateEraserCursor()
                         for (int i = 0; i < 3; i++)
                         {
                             int offset = i * 5;
-                            g.DrawLine(texturePen, 
-                                eraserLeft + offset, eraserTop, 
+                            g.DrawLine(texturePen,
+                                eraserLeft + offset, eraserTop,
                                 eraserLeft + offset + 6, eraserTop + eraserHeight);
                         }
                     }
@@ -410,7 +410,7 @@ public WpfCursor CreateLineCursor(string colorHex)
                     // Left circle is at the hotspot (where the mouse clicks)
                     int circleRadius = 4;
                     int circleSpacing = 20; // Increased spacing for better visibility
-                    
+
                     // Position left circle at the hotspot (6 pixels from left edge for visual balance)
                     Point leftCircleCenter = new Point(6, size / 2);
                     Point rightCircleCenter = new Point(6 + circleSpacing, size / 2);
@@ -424,36 +424,36 @@ public WpfCursor CreateLineCursor(string colorHex)
                     // Draw left circle (outline) - this is where the line starts
                     using (Pen circlePen = new Pen(Color.White, 2))
                     {
-                        g.DrawEllipse(circlePen, 
-                            leftCircleCenter.X - circleRadius, 
-                            leftCircleCenter.Y - circleRadius, 
-                            circleRadius * 2, 
+                        g.DrawEllipse(circlePen,
+                            leftCircleCenter.X - circleRadius,
+                            leftCircleCenter.Y - circleRadius,
+                            circleRadius * 2,
                             circleRadius * 2);
                     }
                     using (Pen circleOutline = new Pen(Color.Black, 1))
                     {
-                        g.DrawEllipse(circleOutline, 
-                            leftCircleCenter.X - circleRadius - 1, 
-                            leftCircleCenter.Y - circleRadius - 1, 
-                            circleRadius * 2 + 2, 
+                        g.DrawEllipse(circleOutline,
+                            leftCircleCenter.X - circleRadius - 1,
+                            leftCircleCenter.Y - circleRadius - 1,
+                            circleRadius * 2 + 2,
                             circleRadius * 2 + 2);
                     }
 
                     // Draw right circle (outline)
                     using (Pen circlePen = new Pen(Color.White, 2))
                     {
-                        g.DrawEllipse(circlePen, 
-                            rightCircleCenter.X - circleRadius, 
-                            rightCircleCenter.Y - circleRadius, 
-                            circleRadius * 2, 
+                        g.DrawEllipse(circlePen,
+                            rightCircleCenter.X - circleRadius,
+                            rightCircleCenter.Y - circleRadius,
+                            circleRadius * 2,
                             circleRadius * 2);
                     }
                     using (Pen circleOutline = new Pen(Color.Black, 1))
                     {
-                        g.DrawEllipse(circleOutline, 
-                            rightCircleCenter.X - circleRadius - 1, 
-                            rightCircleCenter.Y - circleRadius - 1, 
-                            circleRadius * 2 + 2, 
+                        g.DrawEllipse(circleOutline,
+                            rightCircleCenter.X - circleRadius - 1,
+                            rightCircleCenter.Y - circleRadius - 1,
+                            circleRadius * 2 + 2,
                             circleRadius * 2 + 2);
                     }
 

Src/GhostDraw/Managers/DrawingManager.cs

@@ -447,4 +447,28 @@ public void CaptureFullScreenshot()
             // Don't re-throw - not critical
         }
     }
+
+    /// <summary>
+    /// Undoes the last drawing action (called via Ctrl+Z)
+    /// </summary>
+    public void UndoLastAction()
+    {
+        try
+        {
+            if (_overlayWindow.IsVisible)
+            {
+                _logger.LogInformation("Undo last action (Ctrl+Z)");
+                _overlayWindow.UndoLastAction();
+            }
+            else
+            {
+                _logger.LogDebug("UndoLastAction ignored - overlay not visible");
+            }
+        }
+        catch (Exception ex)
+        {
+            _logger.LogError(ex, "Failed to undo last action");
+            // Don't re-throw - not critical
+        }
+    }
 }

Src/GhostDraw/Services/AppSettingsService.cs

@@ -48,7 +48,7 @@ private AppSettings LoadSettings()
             if (settings != null)
             {
                 _logger.LogInformation("Settings loaded successfully");
-                
+
                 // Save to ensure latest format
                 _settingsStore.Save(settings);
                 return settings;
@@ -280,8 +280,8 @@ public void SetActiveTool(DrawTool tool)
     /// </summary>
     public DrawTool ToggleTool()
     {
-        var newTool = _currentSettings.ActiveTool == DrawTool.Pen 
-            ? DrawTool.Line 
+        var newTool = _currentSettings.ActiveTool == DrawTool.Pen
+            ? DrawTool.Line
             : DrawTool.Pen;
         SetActiveTool(newTool);
         return newTool;