add browser support

src/Avalonia.Base/Input/Platform/PlatformHotkeyConfiguration.cs

@@ -81,6 +81,10 @@ namespace Avalonia.Input.Platform
             {
                 new KeyGesture(Key.Apps)
             };
+            Back = new List<KeyGesture>
+            {
+                new KeyGesture(Key.Left, KeyModifiers.Alt)
+            };
         }
 
         public KeyModifiers CommandModifiers { get; set; }
@@ -101,5 +105,6 @@ namespace Avalonia.Input.Platform
         public List<KeyGesture> MoveCursorToTheStartOfDocumentWithSelection { get; set; }
         public List<KeyGesture> MoveCursorToTheEndOfDocumentWithSelection { get; set; }
         public List<KeyGesture> OpenContextMenu { get; set; }
+        public List<KeyGesture> Back { get; set; }
     }
 }

src/Avalonia.Controls/TopLevel.cs

@@ -18,6 +18,8 @@ using Avalonia.Rendering;
 using Avalonia.Styling;
 using Avalonia.Utilities;
 using Avalonia.VisualTree;
+using Avalonia.Input.Platform;
+using System.Linq;
 
 namespace Avalonia.Controls
 {
@@ -223,20 +225,24 @@ namespace Avalonia.Controls
                 };
             }
 
-            var backKeyGesture = new KeyGesture(Key.Left, KeyModifiers.Alt);
-            _backGestureSubscription = _inputManager?.PreProcess.OfType<RawInputEventArgs>().Subscribe(e =>
+            _backGestureSubscription = _inputManager?.PreProcess.Subscribe(e =>
             {
                 bool backRequested = false;
 
                 if (e is RawKeyEventArgs rawKeyEventArgs && rawKeyEventArgs.Type == RawKeyEventType.KeyDown)
                 {
-                    var keyEvent = new KeyEventArgs()
+                    var keymap = AvaloniaLocator.Current.GetService<PlatformHotkeyConfiguration>()?.Back;
+
+                    if (keymap != null)
                     {
-                        KeyModifiers = (KeyModifiers)rawKeyEventArgs.Modifiers,
-                        Key = rawKeyEventArgs.Key
-                    };
+                        var keyEvent = new KeyEventArgs()
+                        {
+                            KeyModifiers = (KeyModifiers)rawKeyEventArgs.Modifiers,
+                            Key = rawKeyEventArgs.Key
+                        };
 
-                    backRequested = backKeyGesture.Matches(keyEvent);
+                        backRequested = keymap.Any( key => key.Matches(keyEvent));
+                    }
                 }
                 else if(e is RawPointerEventArgs pointerEventArgs)
                 {

src/Browser/Avalonia.Browser/BrowserSystemNavigationManager.cs

@@ -0,0 +1,24 @@
+using System;
+using Avalonia.Browser.Interop;
+using Avalonia.Interactivity;
+using Avalonia.Platform;
+
+namespace Avalonia.Browser
+{
+    internal class BrowserSystemNavigationManager : ISystemNavigationManager
+    {
+        public event EventHandler<RoutedEventArgs>? BackRequested;
+
+        public BrowserSystemNavigationManager()
+        {
+            NavigationHelper.AddBackHandler(() =>
+            {
+                var routedEventArgs = new RoutedEventArgs();
+
+                BackRequested?.Invoke(this, routedEventArgs);
+
+                return routedEventArgs.Handled;
+            });
+        }
+    }
+}

src/Browser/Avalonia.Browser/BrowserTopLevelImpl.cs

@@ -19,7 +19,8 @@ using Avalonia.Rendering.Composition;
 
 namespace Avalonia.Browser
 {
-    internal class BrowserTopLevelImpl : ITopLevelImplWithTextInputMethod, ITopLevelImplWithNativeControlHost, ITopLevelImplWithStorageProvider
+    internal class BrowserTopLevelImpl : ITopLevelImplWithTextInputMethod, ITopLevelImplWithNativeControlHost, ITopLevelImplWithStorageProvider,
+        ITopLevelWithSystemNavigationManager
     {
         private Size _clientSize;
         private IInputRoot? _inputRoot;
@@ -234,5 +235,7 @@ namespace Avalonia.Browser
 
         public INativeControlHostImpl? NativeControlHost { get; }
         public IStorageProvider StorageProvider { get; } = new BrowserStorageProvider();
+
+        public ISystemNavigationManager SystemNavigationManager { get; } = new BrowserSystemNavigationManager();
     }
 }

src/Browser/Avalonia.Browser/Interop/NavigationHelper.cs

@@ -0,0 +1,10 @@
+using System;
+using System.Runtime.InteropServices.JavaScript;
+
+namespace Avalonia.Browser.Interop;
+
+internal static partial class NavigationHelper
+{
+    [JSImport("NavigationHelper.addBackHandler", AvaloniaModule.MainModuleName)]
+    public static partial void AddBackHandler([JSMarshalAs<JSType.Function<JSType.Boolean>>] Func<bool> backHandlerCallback);
+}

src/Browser/Avalonia.Browser/webapp/modules/avalonia.ts

@@ -5,6 +5,7 @@ import { AvaloniaDOM } from "./avalonia/dom";
 import { Caniuse } from "./avalonia/caniuse";
 import { StreamHelper } from "./avalonia/stream";
 import { NativeControlHost } from "./avalonia/nativeControlHost";
+import { NavigationHelper } from "./avalonia/navigationHelper";
 
 async function registerAvaloniaModule(api: RuntimeAPI): Promise<void> {
     api.setModuleImports("avalonia", {
@@ -15,7 +16,8 @@ async function registerAvaloniaModule(api: RuntimeAPI): Promise<void> {
         DpiWatcher,
         AvaloniaDOM,
         StreamHelper,
-        NativeControlHost
+        NativeControlHost,
+        NavigationHelper
     });
 }
 export {
@@ -27,6 +29,7 @@ export {
     AvaloniaDOM,
     StreamHelper,
     NativeControlHost,
+    NavigationHelper,
 
     registerAvaloniaModule
 };

src/Browser/Avalonia.Browser/webapp/modules/avalonia/navigationHelper.ts

@@ -0,0 +1,14 @@
+export class NavigationHelper {
+    public static addBackHandler(backHandlerCallback: () => Boolean) {
+        history.pushState(null, "", window.location.href);
+        window.onpopstate = () => {
+            const handled = backHandlerCallback();
+
+            if (!handled) {
+                history.back();
+            } else {
+                history.forward();
+            }
+        };
+    }
+}