Add F11 fullscreen toggle support (#1879)

Author: Copilot

QuickLook/KeystrokeDispatcher.cs

@@ -46,7 +46,7 @@ protected KeystrokeDispatcher()
         _validKeys =
         [
             Keys.Up, Keys.Down, Keys.Left, Keys.Right,
-            Keys.Enter, Keys.Space, Keys.Escape
+            Keys.Enter, Keys.Space, Keys.Escape, Keys.F11
         ];
     }
 
@@ -135,6 +135,10 @@ private void InvokeRoutine(Keys key, bool isKeyDown)
                 case Keys.Space:
                     PipeServerManager.SendMessage(PipeMessages.Toggle);
                     break;
+
+                case Keys.F11:
+                    PipeServerManager.SendMessage(PipeMessages.Fullscreen);
+                    break;
             }
         }
         else

QuickLook/PipeServerManager.cs

@@ -36,6 +36,7 @@ public static class PipeMessages
     public const string Forget = "QuickLook.App.PipeMessages.Forget";
     public const string Close = "QuickLook.App.PipeMessages.Close";
     public const string Quit = "QuickLook.App.PipeMessages.Quit";
+    public const string Fullscreen = "QuickLook.App.PipeMessages.Fullscreen";
 }
 
 public class PipeServerManager : IDisposable
@@ -161,6 +162,12 @@ private bool MessageReceived(string msg)
                     DispatcherPriority.ApplicationIdle);
                 return false;
 
+            case PipeMessages.Fullscreen:
+                Application.Current.Dispatcher.BeginInvoke(
+                    new Action(() => ViewWindowManager.GetInstance().ToggleFullscreen()),
+                    DispatcherPriority.ApplicationIdle);
+                return false;
+
             case PipeMessages.Quit:
                 return true;
 

QuickLook/ViewWindowManager.cs

@@ -198,6 +198,14 @@ public void ReloadPreview()
         BeginShowNewWindow(_invokedPath, matchedPlugin);
     }
 
+    public void ToggleFullscreen()
+    {
+        if (!_viewerWindow.IsVisible)
+            return;
+
+        _viewerWindow.ToggleFullscreen();
+    }
+
     private void BeginShowNewWindow(string path, IViewer matchedPlugin)
     {
         _viewerWindow.UnloadPlugin();

QuickLook/ViewerWindow.Actions.cs

@@ -29,9 +29,11 @@
 using System.Windows;
 using System.Windows.Controls;
 using System.Windows.Input;
+using System.Windows.Interop;
 using System.Windows.Media;
 using System.Windows.Threading;
 using Wpf.Ui.Controls;
+using WinForms = System.Windows.Forms;
 using MenuItem = System.Windows.Controls.MenuItem;
 
 namespace QuickLook;
@@ -62,6 +64,70 @@ internal void RunAndClose()
         Close();
     }
 
+    internal void ToggleFullscreen()
+    {
+        if (_isFullscreen)
+        {
+            // Exit fullscreen
+            _isFullscreen = false;
+            
+            // Restore window properties
+            WindowStyle = _preFullscreenWindowStyle;
+            ResizeMode = _preFullscreenResizeMode;
+            
+            // Restore position and size
+            Left = _preFullscreenBounds.Left;
+            Top = _preFullscreenBounds.Top;
+            Width = _preFullscreenBounds.Width;
+            Height = _preFullscreenBounds.Height;
+            
+            // Restore window state last to avoid flicker
+            WindowState = _preFullscreenWindowState;
+        }
+        else
+        {
+            // Enter fullscreen
+            _isFullscreen = true;
+            
+            // Save current window properties before any changes
+            _preFullscreenWindowState = WindowState;
+            _preFullscreenWindowStyle = WindowStyle;
+            _preFullscreenResizeMode = ResizeMode;
+            
+            // Get current bounds (account for maximized state)
+            if (WindowState == WindowState.Maximized)
+            {
+                _preFullscreenBounds = RestoreBounds;
+            }
+            else
+            {
+                _preFullscreenBounds = new Rect(Left, Top, Width, Height);
+            }
+            
+            // Get the screen bounds where the window is currently located
+            var screen = WinForms.Screen.FromHandle(new WindowInteropHelper(this).Handle);
+            var screenBounds = screen.Bounds;
+            
+            // Get DPI scale factor for proper coordinate conversion
+            // scale.Horizontal and scale.Vertical contain the DPI scaling ratios (e.g., 1.5 for 150%)
+            var scale = DisplayDeviceHelper.GetScaleFactorFromWindow(this);
+            
+            // Set to normal state first to allow manual positioning
+            WindowState = WindowState.Normal;
+            
+            // Hide window chrome for true fullscreen
+            WindowStyle = WindowStyle.None;
+            ResizeMode = ResizeMode.NoResize;
+            
+            // Convert screen bounds from physical pixels to DIPs for WPF
+            var dipWidth = screenBounds.Width / scale.Horizontal;
+            var dipHeight = screenBounds.Height / scale.Vertical;
+            
+            // Use MoveWindow to set position and size with proper DPI handling
+            this.MoveWindow(screenBounds.Left, screenBounds.Top, dipWidth, dipHeight);
+        }
+    }
+
     private void PositionWindow(Size size)
     {
         // If the window is now maximized, do not move it

QuickLook/ViewerWindow.Properties.cs

@@ -37,6 +37,11 @@ public partial class ViewerWindow : INotifyPropertyChanged
 
     private bool _canOldPluginResize;
     private bool _pinned;
+    private bool _isFullscreen;
+    private WindowState _preFullscreenWindowState;
+    private WindowStyle _preFullscreenWindowStyle;
+    private ResizeMode _preFullscreenResizeMode;
+    private Rect _preFullscreenBounds;
 
     public bool Pinned
     {