Add WDA_EXCLUDEFROMCAPTURE support to hide edge light from screen capture (#22)

Copilot · shanselman · web-flow · commit 606a9325ca86 · 2025-12-07T20:06:03.000-08:00
* Initial plan

* Implement WDA_EXCLUDEFROMCAPTURE feature with settings persistence

- Add AppSettings class for persistent configuration storage
- Add P/Invoke declarations for SetWindowDisplayAffinity Windows API
- Implement exclude from capture functionality for main and additional monitor windows
- Add tray menu option with checkmark for the feature
- Add control toolbar button (🎥) for quick toggle
- Persist setting across application restarts using JSON configuration
- Update README with comprehensive documentation about screen sharing mode
- Update help dialog to mention the new feature

Co-authored-by: shanselman &lt;2892+shanselman@users.noreply.github.com&gt;

* Add error handling and improve accessibility for exclude from capture feature

- Add error handling to SetWindowDisplayAffinity calls with debug logging
- Improve JSON deserialization with validation and error recovery
- Update button tooltip to clearly indicate current state for better accessibility
- Add SetLastError to P/Invoke declaration for proper error reporting

Co-authored-by: shanselman &lt;2892+shanselman@users.noreply.github.com&gt;

* Fix error handling to capture Win32 error codes immediately

- Store error code immediately after API call to ensure accuracy
- Add missing System namespace import in AppSettings.cs

Co-authored-by: shanselman &lt;2892+shanselman@users.noreply.github.com&gt;

* Simplify exclude-from-capture: default ON, remove button from UI

---------

Co-authored-by: copilot-swe-agent[bot] &lt;198982749+Copilot@users.noreply.github.com&gt;
Co-authored-by: shanselman &lt;2892+shanselman@users.noreply.github.com&gt;
Co-authored-by: Scott Hanselman &lt;scott@hanselman.com&gt;
diff --git a/README.md b/README.md
@@ -14,6 +14,7 @@ A lightweight WPF application that adds a customizable glowing edge light effect
 - **Toggle On/Off**: Quickly enable or disable the edge light effect
 - **Hideable Controls**: Hide the control toolbar for a cleaner look, restore via tray menu
 - **Always On Top**: Stays visible above all other windows
+- **Exclude from Screen Capture**: Optional setting to hide the edge light from screen sharing (Teams, Zoom) and screenshots
 - **Keyboard Shortcuts**: 
   - `Ctrl+Shift+L` - Toggle light on/off
   - `Ctrl+Shift+Up` - Increase brightness
@@ -85,9 +86,19 @@ The executable will be in `bin\Release\net10.0-windows\win-x64\publish\WindowsEd
    - 🔥 **Warmer Color** - Shifts the glow towards a warmer, amber tone
    - 💡 **Toggle Light** - Turn the effect on/off
    - 🖥️ **Switch Monitor** - Move to next monitor (if multiple monitors)
+   - 🖥️🖥️ **All Monitors** - Show on all monitors (if multiple monitors)
+   - 🎥 **Exclude from Capture** - Hide from screen sharing and screenshots
    - ✖ **Exit** - Close the application
 4. Hide the control toolbar for a cleaner look using the tray menu (right-click tray icon → "Hide Controls")
 
+### Screen Sharing Mode
+
+When sharing your screen on video conferencing apps (Teams, Zoom, etc.), you may want the edge light to be visible to you but invisible to viewers. Enable **"Exclude from Screen Capture"** via:
+- Click the 🎥 button in the control toolbar, or
+- Right-click the tray icon → "Exclude from Screen Capture"
+
+**Note**: When this setting is enabled, the edge light will also be excluded from screenshots taken with Windows Snipping Tool, PrintScreen, or other capture tools.
+
 ### Keyboard Shortcuts
 
 - **Ctrl+Shift+L**: Toggle the edge light on/off
diff --git a/WindowsEdgeLight/AppSettings.cs b/WindowsEdgeLight/AppSettings.cs
@@ -0,0 +1,92 @@
+using System;
+using System.IO;
+using System.Text.Json;
+
+namespace WindowsEdgeLight;
+
+/// <summary>
+/// Application settings that persist across sessions
+/// </summary>
+public class AppSettings
+{
+    private static readonly string SettingsFilePath = Path.Combine(
+        Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData),
+        "WindowsEdgeLight",
+        "settings.json");
+
+    /// <summary>
+    /// When enabled, excludes the edge light from screen capture (Teams, screenshots, etc.)
+    /// Note: When enabled, screenshots won't capture the edge light effect
+    /// </summary>
+    public bool ExcludeFromCapture { get; set; } = true;
+
+    /// <summary>
+    /// Load settings from disk
+    /// </summary>
+    public static AppSettings Load()
+    {
+        try
+        {
+            if (File.Exists(SettingsFilePath))
+            {
+                var json = File.ReadAllText(SettingsFilePath);
+                var options = new JsonSerializerOptions
+                {
+                    AllowTrailingCommas = true,
+                    ReadCommentHandling = JsonCommentHandling.Skip
+                };
+                var settings = JsonSerializer.Deserialize<AppSettings>(json, options);
+                
+                // Validate deserialized settings
+                if (settings != null)
+                {
+                    return settings;
+                }
+            }
+        }
+        catch (JsonException ex)
+        {
+            System.Diagnostics.Debug.WriteLine($"Failed to parse settings file: {ex.Message}");
+            // Delete corrupted settings file
+            try
+            {
+                if (File.Exists(SettingsFilePath))
+                {
+                    File.Delete(SettingsFilePath);
+                }
+            }
+            catch { /* Ignore deletion errors */ }
+        }
+        catch (Exception ex)
+        {
+            System.Diagnostics.Debug.WriteLine($"Failed to load settings: {ex.Message}");
+        }
+
+        return new AppSettings();
+    }
+
+    /// <summary>
+    /// Save settings to disk
+    /// </summary>
+    public void Save()
+    {
+        try
+        {
+            var directory = Path.GetDirectoryName(SettingsFilePath);
+            if (directory != null && !Directory.Exists(directory))
+            {
+                Directory.CreateDirectory(directory);
+            }
+
+            var json = JsonSerializer.Serialize(this, new JsonSerializerOptions 
+            { 
+                WriteIndented = true 
+            });
+            File.WriteAllText(SettingsFilePath, json);
+        }
+        catch (Exception ex)
+        {
+            System.Diagnostics.Debug.WriteLine($"Failed to save settings: {ex.Message}");
+        }
+    }
+}
diff --git a/WindowsEdgeLight/ControlWindow.xaml b/WindowsEdgeLight/ControlWindow.xaml
@@ -3,7 +3,7 @@
     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
     Title="Controls"
-    Width="370"
+    Width="366"
     Height="48"
     AllowsTransparency="True"
     Background="Transparent"
diff --git a/WindowsEdgeLight/MainWindow.xaml.cs b/WindowsEdgeLight/MainWindow.xaml.cs
@@ -36,6 +36,10 @@ public partial class MainWindow : Window
     // Tracks whether the control window should be visible (controls initial visibility and toggle state)
     private bool isControlWindowVisible = true;
     private ToolStripMenuItem? toggleControlsMenuItem;
+    private ToolStripMenuItem? excludeFromCaptureMenuItem;
+    
+    // Application settings
+    private AppSettings settings = new AppSettings();
 
     private class MonitorWindowContext
     {
@@ -74,6 +78,12 @@ private class MonitorWindowContext
     [DllImport("user32.dll")]
     private static extern bool UnregisterHotKey(IntPtr hWnd, int id);
 
+    [DllImport("user32.dll", SetLastError = true)]
+    private static extern bool SetWindowDisplayAffinity(IntPtr hWnd, uint dwAffinity);
+    
+    private const uint WDA_NONE = 0x00000000;
+    private const uint WDA_EXCLUDEFROMCAPTURE = 0x00000011;
+
     [DllImport("user32.dll")]
     private static extern IntPtr MonitorFromPoint(POINT pt, uint dwFlags);
     
@@ -141,6 +151,10 @@ public MainWindow()
     {
         InitializeComponent();
         hoverCursorRing = FindName("HoverCursorRing") as Ellipse;
+        
+        // Load settings
+        settings = AppSettings.Load();
+        
         SetupNotifyIcon();
     }
 
@@ -190,6 +204,12 @@ private void SetupNotifyIcon()
     toggleControlsMenuItem = new ToolStripMenuItem("🎛️ Hide Controls", null, (s, e) => ToggleControlsVisibility());
     contextMenu.Items.Add(toggleControlsMenuItem);
     
+    // Add exclude from capture menu item with checkmark
+    excludeFromCaptureMenuItem = new ToolStripMenuItem("🎥 Exclude from Screen Capture", null, (s, e) => ToggleExcludeFromCapture());
+    excludeFromCaptureMenuItem.CheckOnClick = true;
+    excludeFromCaptureMenuItem.Checked = settings.ExcludeFromCapture;
+    contextMenu.Items.Add(excludeFromCaptureMenuItem);
+    
     contextMenu.Items.Add(new ToolStripSeparator());
     contextMenu.Items.Add("✖ Exit", null, (s, e) => System.Windows.Application.Current.Shutdown());
         
@@ -218,6 +238,7 @@ private void ShowHelp()
 • Control toolbar with brightness, color temp, and monitor options
 • Color temperature controls (🔥 warmer, ❄️ cooler)
 • Switch between monitors or show on all monitors
+• Exclude from screen capture (🎥) - invisible in Teams/Zoom sharing
 
 Created by Scott Hanselman
 Version {version}";
@@ -297,6 +318,9 @@ private void Window_Loaded(object sender, RoutedEventArgs e)
         this.SizeChanged += Window_SizeChanged;
         this.LocationChanged += Window_LocationChanged;
 
+        // Apply exclude from capture setting
+        ApplyExcludeFromCapture();
+
         InstallMouseHook();
     }
 
@@ -693,6 +717,65 @@ private void UpdateTrayMenuToggleControlsText()
         }
     }
 
+    public void ToggleExcludeFromCapture()
+    {
+        settings.ExcludeFromCapture = !settings.ExcludeFromCapture;
+        settings.Save();
+        
+        // Update menu checkmark
+        if (excludeFromCaptureMenuItem != null)
+        {
+            excludeFromCaptureMenuItem.Checked = settings.ExcludeFromCapture;
+        }
+        
+        // Apply the setting to all windows
+        ApplyExcludeFromCapture();
+    }
+
+    private void ApplyExcludeFromCapture()
+    {
+        var hwnd = new WindowInteropHelper(this).Handle;
+        if (hwnd != IntPtr.Zero)
+        {
+            var result = SetWindowDisplayAffinity(hwnd, settings.ExcludeFromCapture ? WDA_EXCLUDEFROMCAPTURE : WDA_NONE);
+            if (!result)
+            {
+                var error = Marshal.GetLastWin32Error();
+                System.Diagnostics.Debug.WriteLine($"Failed to set display affinity for main window. Error: {error}");
+            }
+        }
+        
+        // Apply to control window
+        if (controlWindow != null)
+        {
+            var controlHwnd = new WindowInteropHelper(controlWindow).Handle;
+            if (controlHwnd != IntPtr.Zero)
+            {
+                var result = SetWindowDisplayAffinity(controlHwnd, settings.ExcludeFromCapture ? WDA_EXCLUDEFROMCAPTURE : WDA_NONE);
+                if (!result)
+                {
+                    var error = Marshal.GetLastWin32Error();
+                    System.Diagnostics.Debug.WriteLine($"Failed to set display affinity for control window. Error: {error}");
+                }
+            }
+        }
+        
+        // Apply to all additional monitor windows
+        foreach (var ctx in additionalMonitorWindows)
+        {
+            var monitorHwnd = new WindowInteropHelper(ctx.Window).Handle;
+            if (monitorHwnd != IntPtr.Zero)
+            {
+                var result = SetWindowDisplayAffinity(monitorHwnd, settings.ExcludeFromCapture ? WDA_EXCLUDEFROMCAPTURE : WDA_NONE);
+                if (!result)
+                {
+                    var error = Marshal.GetLastWin32Error();
+                    System.Diagnostics.Debug.WriteLine($"Failed to set display affinity for monitor window. Error: {error}");
+                }
+            }
+        }
+    }
+
     public void IncreaseBrightness()
     {
         currentOpacity = Math.Min(MaxOpacity, currentOpacity + OpacityStep);
@@ -1030,6 +1113,14 @@ private MonitorWindowContext CreateMonitorWindow(Screen screen)
             int extendedStyle = GetWindowLong(hwnd, GWL_EXSTYLE);
             SetWindowLong(hwnd, GWL_EXSTYLE, extendedStyle | WS_EX_TRANSPARENT | WS_EX_LAYERED);
 
+            // Apply exclude from capture setting
+            var result = SetWindowDisplayAffinity(hwnd, settings.ExcludeFromCapture ? WDA_EXCLUDEFROMCAPTURE : WDA_NONE);
+            if (!result)
+            {
+                var error = Marshal.GetLastWin32Error();
+                System.Diagnostics.Debug.WriteLine($"Failed to set display affinity for monitor window during creation. Error: {error}");
+            }
+
             // Verify and update DPI if WPF reports a different value after window is loaded
             var source = PresentationSource.FromVisual(window);
             if (source != null)
@@ -1109,6 +1200,11 @@ public bool HasMultipleMonitors()
         return availableMonitors.Length > 1;
     }
 
+    public bool IsExcludeFromCaptureEnabled()
+    {
+        return settings.ExcludeFromCapture;
+    }
+
     private void Window_SizeChanged(object sender, SizeChangedEventArgs e)
     {
         // Recreate geometry when window size changes (e.g., different monitor resolution)
diff --git a/docs/SESSION_LOG.md b/docs/SESSION_LOG.md
