Changed behavior to accept keyboard overrides, added keyboard mouse state validator and indirect rules to allow keyboard and mouse navigation

Photos/Views/MainWindow.axaml.cs

@@ -1,7 +1,11 @@
+using System;
+using System.Linq;
 using System.Threading.Tasks;
 using Avalonia.Controls;
 using Avalonia.Input;
+using Avalonia.VisualTree;
 using Avalonia.Xaml.Interactions.DragAndDrop;
+using Photos.Animations;
 using Photos.Models;
 using Photos.ViewModels;
 
@@ -9,8 +13,17 @@ namespace Photos.Views;
 
 public partial class MainWindow : Window
 {
+    private enum NavigationInputMode
+    {
+        Mouse,
+        Keyboard
+    }
+
+    private NavigationInputMode _navigationInputMode = NavigationInputMode.Mouse;
+
     private IFolderPickerService _folderPickerService;
     private int _currentImageIndex = 0;
+    private Control? _currentHoveredCard;
 
     public MainWindow()
     {
@@ -24,10 +37,25 @@ public partial class MainWindow : Window
         (DataContext as MainWindowViewModel)?.WindowDropHandler(e);
     }
 
-    private void OnKeyDownHandler(object sender, KeyEventArgs e)
+    private async void OnKeyDownHandler(object sender, KeyEventArgs e)
     {
         if (DataContext is not MainWindowViewModel vm) return;
 
+        // input state changer
+        switch (e.Key)
+        {
+            case Key.Enter:
+            case Key.Escape:
+            case Key.Left:
+            case Key.Right:
+            case Key.Up:
+            case Key.Down:
+                _navigationInputMode = NavigationInputMode.Keyboard;
+                UpdatePointerHoverSuppression();
+                UpdateKeyboardHover();
+                break;
+        }
+
         async Task HandleEnter()
         {
             if (vm.IsPhotoFocused()) vm.UnfocusPhoto();
@@ -45,28 +73,98 @@ public partial class MainWindow : Window
             // TODO: move basic selection
         }
 
+        int CalculateCurrentIndexHop()
+        {
+            // Values of UniformGridLayout
+            var minItemWidth = 220;
+            var minColumnSpacing = 18;
+
+            var repeaterWidth = Repeater.Bounds.Width;
+
+            var abstractedColumnCount = Math.Floor(repeaterWidth / (minItemWidth + minColumnSpacing));
+            return Math.Max(1, (int)abstractedColumnCount);
+        }
+
+        void HandleArrowKeyDown()
+        {
+            var nextIdx = CalculateCurrentIndexHop();
+            if (_currentImageIndex + nextIdx >= vm.Photos.Count) _currentImageIndex = vm.Photos.Count - 1;
+            else _currentImageIndex += nextIdx;
+        }
+
+        void HandleArrowKeyUp()
+        {
+            var nextIdx = CalculateCurrentIndexHop();
+            if (_currentImageIndex - nextIdx < 0) _currentImageIndex = 0;
+            else _currentImageIndex -= nextIdx;
+        }
+
+        Control? FindCardControlForCurrentIndex()
+        {
+            if (_currentImageIndex < 0 || _currentImageIndex >= vm.Photos.Count)
+                return null;
+
+            var currentPhoto = vm.Photos[_currentImageIndex];
+
+            return Repeater.GetVisualDescendants()
+                .OfType<Control>()
+                .FirstOrDefault(c =>
+                    ReferenceEquals(c.DataContext, currentPhoto) &&
+                    CardHoverEffectBehavior.GetIsEnabled(c));
+        }
+
+        void UpdateKeyboardHover()
+        {
+            if (DataContext is not MainWindowViewModel vm)
+                return;
+
+            if (_currentHoveredCard is not null)
+            {
+                CardHoverEffectBehavior.ResetHover(_currentHoveredCard);
+                _currentHoveredCard = null;
+            }
+
+            var newCard = FindCardControlForCurrentIndex();
+            if (newCard is null) return;
+
+            CardHoverEffectBehavior.ApplyHover(newCard);
+            _currentHoveredCard = newCard;
+            _currentHoveredCard.BringIntoView();
+        }
+
         switch (e.Key)
         {
-            case Key.Enter:
-                HandleEnter().GetAwaiter();
+            case Key.Enter: case Key.Space:
+                if (!vm.PhotosLoaded) await vm.OpenDirectory();
+                else await HandleEnter();
                 break;
             case Key.Escape:
                 HandleEscape();
                 break;
             case Key.Down:
+                HandleArrowKeyDown();
+                UpdateKeyboardHover();
+                await HandleArrowKey();
+                break;
+            case Key.Up:
+                HandleArrowKeyUp();
+                UpdateKeyboardHover();
+                await HandleArrowKey();
                 break;
             case Key.Left:
                 if (_currentImageIndex > 0)
                 {
                     _currentImageIndex--;
-                    HandleArrowKey().GetAwaiter();
+                    UpdateKeyboardHover();
+                    await HandleArrowKey();
                 }
                 break;
             case Key.Right:
                 if (_currentImageIndex < vm.Photos.Count - 1)
                 {
                     _currentImageIndex++;
-                    HandleArrowKey().GetAwaiter();
+                    UpdateKeyboardHover();
+                    await HandleArrowKey();
                 }
                 break;
         }
@@ -74,9 +172,34 @@ public partial class MainWindow : Window
 
     private void PointerEnteredPhotoHandler(object sender, PointerEventArgs e)
     {
-        if (sender is not Image i || DataContext is not MainWindowViewModel vm) return;
-        var idx = vm.GetImageIndex(i);
-        if (idx == -1) return;
+        if (sender is not Image image || DataContext is not MainWindowViewModel vm) return;
+
+        var photo = image.DataContext as Photo;
+        if (photo is null) return;
+
+        var idx = vm.Photos.IndexOf(photo);
+        if (idx < 0) return;
+
+        _navigationInputMode = NavigationInputMode.Mouse;
+        UpdatePointerHoverSuppression();
         _currentImageIndex = idx;
+
+        if (_currentHoveredCard is null) return;
+
+        CardHoverEffectBehavior.ResetHover(_currentHoveredCard);
+        _currentHoveredCard = null;
+    }
+
+    private void UpdatePointerHoverSuppression()
+    {
+        foreach (var control in Repeater.GetVisualDescendants().OfType<Control>())
+        {
+            if (CardHoverEffectBehavior.GetIsEnabled(control))
+            {
+                CardHoverEffectBehavior.SetSuppressPointerHover(
+                    control,
+                    _navigationInputMode == NavigationInputMode.Keyboard);
+            }
+        }
     }
 }