added keyboard navigation for selected images -> TOOD: allow visual keyboardnavigation when photo is not maximized

Photos/ViewModels/MainWindowViewModel.cs

@@ -91,10 +91,29 @@ public partial class MainWindowViewModel : ViewModelBase
         await SelectedPhoto.LoadFullImage();
     }
 
-    public void SelectedPhotoClicked()
+    public void ResetSelectedPhoto()
     {
         if (SelectedPhoto is null) return;
         SelectedPhoto.FullImage = null;
         SelectedPhoto = null;
     }
+
+    public async Task TryFocusImage(int index)
+    {
+        if (index < 0 || index >= Photos.Count ) return;
+        // if(SelectedPhoto != null) ResetSelectedPhoto();
+        SelectedPhoto = Photos[index];
+        await SelectedPhoto.LoadFullImage();
+    }
+
+    public void UnfocusPhoto() => ResetSelectedPhoto();
+
+    public bool IsPhotoFocused() => SelectedPhoto != null;
+
+    public int GetImageIndex(Image i)
+    {
+        var p = Photos.FirstOrDefault(x => x.PreviewImage == i.Source);
+        if (p is null) return -1;
+        return Photos.IndexOf(p);
+    }
 }

Photos/Views/MainWindow.axaml

@@ -20,7 +20,9 @@
         ExtendClientAreaChromeHints="NoChrome"
         TransparencyLevelHint="AcrylicBlur"
         Background="Transparent"
-        ExtendClientAreaToDecorationsHint="True">
+        ExtendClientAreaToDecorationsHint="True"
+        Focusable="True"
+        KeyDown="OnKeyDownHandler">
 
     <Design.DataContext>
         <vm:MainWindowViewModel/>
@@ -115,7 +117,8 @@
                     <ItemsRepeater ItemsSource="{Binding Photos}"
                                    HorizontalAlignment="Stretch"
                                    VerticalAlignment="Stretch"
-                                   ClipToBounds="False">
+                                   ClipToBounds="False"
+                                   IsTabStop="True">
                         <ItemsRepeater.Layout>
                             <UniformGridLayout MinItemWidth="220"
                                                MinItemHeight="290"
@@ -150,7 +153,9 @@
                                                 ClipToBounds="True"
                                                 Background="#14000000">
                                             <Image Source="{Binding PreviewImage}"
-                                                   Stretch="UniformToFill"/>
+                                                   Stretch="UniformToFill"
+                                                   PointerEntered="PointerEnteredPhotoHandler"
+                                                   />
                                         </Border>
 
                                         <TextBlock Text="{Binding DisplayName}"
@@ -184,14 +189,15 @@
             <TransitioningContentControl Grid.Row="0"
                                          Grid.RowSpan="2"
                                          Content="{Binding SelectedPhoto}"
-                                         ZIndex="50">
+                                         ZIndex="50"
+                                         >
                 <TransitioningContentControl.PageTransition>
                     <CrossFade Duration="0:0:0.18"/>
                 </TransitioningContentControl.PageTransition>
 
                 <i:Interaction.Behaviors>
                     <ic:EventTriggerBehavior EventName="PointerReleased">
-                        <ic:InvokeCommandAction Command="{Binding Path=DataContext.SelectedPhotoClicked, ElementName=Root}"/>
+                        <ic:InvokeCommandAction Command="{Binding Path=DataContext.ResetSelectedPhoto, ElementName=Root}"/>
                     </ic:EventTriggerBehavior>
                 </i:Interaction.Behaviors>
 
@@ -211,7 +217,7 @@
                                            Stretch="Uniform">
                                         <i:Interaction.Behaviors>
                                             <ic:EventTriggerBehavior EventName="PointerReleased">
-                                                <ic:InvokeCommandAction Command="{Binding Path=DataContext.SelectedPhotoClicked, ElementName=Root}"/>
+                                                <ic:InvokeCommandAction Command="{Binding Path=DataContext.ResetSelectedPhoto, ElementName=Root}"/>
                                             </ic:EventTriggerBehavior>
                                         </i:Interaction.Behaviors>
                                     </Image>

Photos/Views/MainWindow.axaml.cs

@@ -1,3 +1,4 @@
+using System.Threading.Tasks;
 using Avalonia.Controls;
 using Avalonia.Input;
 using Avalonia.Xaml.Interactions.DragAndDrop;
@@ -9,6 +10,7 @@ namespace Photos.Views;
 public partial class MainWindow : Window
 {
     private IFolderPickerService _folderPickerService;
+    private int _currentImageIndex = 0;
 
     public MainWindow()
     {
@@ -21,4 +23,60 @@ public partial class MainWindow : Window
     {
         (DataContext as MainWindowViewModel)?.WindowDropHandler(e);
     }
+
+    private void OnKeyDownHandler(object sender, KeyEventArgs e)
+    {
+        if (DataContext is not MainWindowViewModel vm) return;
+
+        async Task HandleEnter()
+        {
+            if (vm.IsPhotoFocused()) vm.UnfocusPhoto();
+            else await vm.TryFocusImage(_currentImageIndex);
+        }
+
+        void HandleEscape()
+        {
+            vm.UnfocusPhoto();
+        }
+
+        async Task HandleArrowKey()
+        {
+            if(vm.IsPhotoFocused()) await vm.TryFocusImage(_currentImageIndex);
+            // TODO: move basic selection
+        }
+
+        switch (e.Key)
+        {
+            case Key.Enter:
+                HandleEnter().GetAwaiter();
+                break;
+            case Key.Escape:
+                HandleEscape();
+                break;
+            case Key.Down:
+                break;
+            case Key.Left:
+                if (_currentImageIndex > 0)
+                {
+                    _currentImageIndex--;
+                    HandleArrowKey().GetAwaiter();
+                }
+                break;
+            case Key.Right:
+                if (_currentImageIndex < vm.Photos.Count - 1)
+                {
+                    _currentImageIndex++;
+                    HandleArrowKey().GetAwaiter();
+                }
+                break;
+        }
+    }
+
+    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;
+        _currentImageIndex = idx;
+    }
 }