1 files changed, 85 insertions, 0 deletions
diff --git a/src/Godosa.Desktop/PadNavigator.cs b/src/Godosa.Desktop/PadNavigator.cs
new file mode 100644
index 0000000..b4b59d5
--- /dev/null
+++ b/src/Godosa.Desktop/PadNavigator.cs
@@ -0,0 +1,85 @@
+using System.Collections.Generic;
+using System.Linq;
+using Avalonia;
+using Avalonia.Controls;
+using Avalonia.Interactivity;
+using Avalonia.VisualTree;
+using Avalonia.Media;
+using Godosa.Core.Input;
+
+namespace Godosa.Desktop;
+
+/// <summary>Gamepad control of an open window: D-pad moves a highlight through its enabled
+/// buttons (wrapping), A presses (the game decides B/Start).</summary>
+public sealed class PadNavigator
+{
+    private static readonly Thickness HighlightThickness = new(2);
+    private readonly MenuCursor _cursor = new();
+    private readonly List<Button> _buttons = new();
+    private Control? _container;
+    private Button? _highlighted;
+    private readonly IBrush _highlight;
+
+    public PadNavigator(IBrush highlight) => _highlight = highlight;
+
+    /// <summary>The window pad input should drive now, or null (pad drives the character).</summary>
+    public Control? Active { get; private set; }
+
+    /// <summary>Highlight only while the gamepad is the device in use (keyboard/mouse users
+    /// get no stray gold border).</summary>
+    public bool ShowHighlight { get; set; }
+
+    public void Refresh(Control? active)
+    {
+        Active = active;
+        if (!ReferenceEquals(active, _container))
+        {
+            _container = active;
+            _cursor.Clamp(0);
+        }
+        Collect();
+        _cursor.Clamp(_buttons.Count);
+        Highlight();
+    }
+
+    public void Move(int delta)
+    {
+        Collect();
+        _cursor.Clamp(_buttons.Count);
+        _cursor.Move(delta, _buttons.Count);
+        Highlight();
+    }
+
+    public void Press()
+    {
+        Collect();
+        _cursor.Clamp(_buttons.Count);
+        if (_cursor.Index >= 0) Buttons.Press(_buttons[_cursor.Index]);
+    }
+
+    private void Collect()
+    {
+        _buttons.Clear();
+        if (_container is null) return;
+        _buttons.AddRange(_container.GetVisualDescendants().OfType<Button>()
+            .Where(b => b.IsEffectivelyVisible && b.IsEffectivelyEnabled));
+    }
+
+    private void Highlight()
+    {
+        var target = ShowHighlight && _cursor.Index >= 0 && _cursor.Index < _buttons.Count ? _buttons[_cursor.Index] : null;
+        if (ReferenceEquals(target, _highlighted)) return;
+        if (_highlighted is not null)
+        {
+            _highlighted.ClearValue(Button.BorderBrushProperty);
+            _highlighted.ClearValue(Button.BorderThicknessProperty);
+        }
+        _highlighted = target;
+        if (target is not null)
+        {
+            target.BorderBrush = _highlight;
+            target.BorderThickness = HighlightThickness;
+            target.BringIntoView(); // long option pages scroll
+        }
+    }
+}