Layers/shell/windows/LayersShell/MainWindow.xaml.cs

using System;
using System.IO;
using System.Runtime.InteropServices;
using Microsoft.UI;
using Microsoft.UI.Windowing;
using Microsoft.UI.Xaml;
using Microsoft.UI.Xaml.Controls;
using Microsoft.UI.Xaml.Input;
using Microsoft.UI.Xaml.Media;
using Windows.Graphics;
using WinRT.Interop;

namespace LayersShell;

public sealed partial class MainWindow : Window
{
    private IntPtr _handle = IntPtr.Zero;
    private IntPtr _hwnd = IntPtr.Zero;

    private const double DefaultLogicalWidth = 480;
    private const double DefaultLogicalHeight = 640;

    private bool _isFocused = true;
    private bool _isHovered = false;

    public MainWindow()
    {
        InitializeComponent();
        Title = "Layers";
        _hwnd = WindowNative.GetWindowHandle(this);

        var appWindow = AppWindow.GetFromWindowId(Win32Interop.GetWindowIdFromWindow(_hwnd));
        if (appWindow is not null)
        {
            appWindow.SetPresenter(AppWindowPresenterKind.Overlapped);
            if (appWindow.Presenter is OverlappedPresenter op)
            {
                op.IsAlwaysOnTop = true;
                op.IsResizable = true;
                op.IsMaximizable = false;
                op.IsMinimizable = true;
                op.SetBorderAndTitleBar(hasBorder: false, hasTitleBar: false);
            }
            appWindow.ResizeClient(new SizeInt32((int)DefaultLogicalWidth, (int)DefaultLogicalHeight));
        }

        // Windows App SDK 1.3+: assign a backdrop directly, no MicaController wiring needed.
        SystemBackdrop = new MicaBackdrop { Kind = Microsoft.UI.Composition.SystemBackdrops.MicaKind.Base };

        Activated += OnActivated;
        Closed += OnClosed;

        DispatcherQueue.TryEnqueue(() =>
        {
            PointToRust();
            LayersNative.StartupIfNeeded();
            CreateNativeHandle();
            StartRenderLoop();
        });
    }

    private void OnActivated(object sender, WindowActivatedEventArgs e)
    {
        _isFocused = e.WindowActivationState != WindowActivationState.Deactivated;
        ApplyFade();
    }

    private void OnClosed(object sender, WindowEventArgs args)
    {
        _renderTimer?.Stop();
        _renderTimer = null;
        if (_handle != IntPtr.Zero)
        {
            LayersNative.layers_destroy(_handle);
            _handle = IntPtr.Zero;
        }
    }

    private void PointToRust()
    {
        var exe = System.Reflection.Assembly.GetEntryAssembly()?.Location;
        if (string.IsNullOrEmpty(exe)) return;
        var binDir = Path.GetDirectoryName(exe) ?? string.Empty;
        var pluginRoot = Path.GetDirectoryName(binDir) ?? string.Empty;
        if (string.IsNullOrEmpty(pluginRoot)) return;
        LayersNative.layers_set_plugin_root(pluginRoot);
    }

    private void CreateNativeHandle()
    {
        if (_handle != IntPtr.Zero) return;
        var scale = (float)RenderSurface.CompositionScaleX;
        var width = (float)RenderSurface.ActualWidth;
        var height = (float)RenderSurface.ActualHeight;
        if (width <= 0 || height <= 0 || scale <= 0) return;

        // wgpu's dx12 backend wants an ISwapChainPanelNative*. Query it off the XAML element's
        // IUnknown rather than passing the raw WinRT object pointer.
        var iid = typeof(ISwapChainPanelNative).GUID;
        var unknown = Marshal.GetIUnknownForObject(RenderSurface);
        IntPtr native = IntPtr.Zero;
        try
        {
            int hr = Marshal.QueryInterface(unknown, in iid, out native);
            if (hr < 0 || native == IntPtr.Zero) return;
            _handle = LayersNative.layers_create_from_swap_chain_panel(native, width, height, scale);
        }
        finally
        {
            if (native != IntPtr.Zero) Marshal.Release(native);
            Marshal.Release(unknown);
        }
    }

    private DispatcherTimer? _renderTimer;
    private void StartRenderLoop()
    {
        _renderTimer = new DispatcherTimer
        {
            Interval = TimeSpan.FromMilliseconds(1000.0 / 60.0),
        };
        _renderTimer.Tick += (_, __) =>
        {
            if (_handle != IntPtr.Zero)
            {
                LayersNative.layers_render(_handle);
            }
        };
        _renderTimer.Start();
    }

    private void ApplyFade()
    {
        double target = (_isFocused && _isHovered) ? 1.0
            : (_isFocused || _isHovered) ? 0.5
            : 0.1;
        if (Content is FrameworkElement root)
        {
            root.Opacity = target;
        }
    }

    // --- Input routing ---

    private void RenderSurface_SizeChanged(object sender, SizeChangedEventArgs e)
    {
        if (_handle == IntPtr.Zero)
        {
            CreateNativeHandle();
            return;
        }
        var scale = (float)RenderSurface.CompositionScaleX;
        LayersNative.layers_resize(_handle, (float)e.NewSize.Width, (float)e.NewSize.Height, scale);
    }

    private void RenderSurface_PointerMoved(object sender, PointerRoutedEventArgs e)
    {
        if (_handle == IntPtr.Zero) return;
        var p = e.GetCurrentPoint(RenderSurface).Position;
        LayersNative.layers_mouse_move(_handle, (float)p.X, (float)p.Y);
    }

    private void RenderSurface_PointerPressed(object sender, PointerRoutedEventArgs e)
    {
        RenderSurface.Focus(FocusState.Programmatic);
        PushMouseButton(e, pressed: true);
    }

    private void RenderSurface_PointerReleased(object sender, PointerRoutedEventArgs e)
    {
        PushMouseButton(e, pressed: false);
    }

    private void PushMouseButton(PointerRoutedEventArgs e, bool pressed)
    {
        if (_handle == IntPtr.Zero) return;
        var p = e.GetCurrentPoint(RenderSurface);
        uint btn;
        var props = p.Properties;
        if (props.IsLeftButtonPressed || (!pressed && !props.IsRightButtonPressed && !props.IsMiddleButtonPressed)) btn = 0;
        else if (props.IsRightButtonPressed) btn = 1;
        else if (props.IsMiddleButtonPressed) btn = 2;
        else btn = 0;
        LayersNative.layers_mouse_button(_handle, (float)p.Position.X, (float)p.Position.Y, btn, pressed);
    }

    private void RenderSurface_PointerWheel(object sender, PointerRoutedEventArgs e)
    {
        if (_handle == IntPtr.Zero) return;
        var p = e.GetCurrentPoint(RenderSurface);
        var dy = (float)p.Properties.MouseWheelDelta / 3.0f;
        LayersNative.layers_mouse_scroll(_handle, (float)p.Position.X, (float)p.Position.Y, 0.0f, dy);
    }

    private void RenderSurface_PointerEntered(object sender, PointerRoutedEventArgs e)
    {
        _isHovered = true;
        ApplyFade();
    }

    private void RenderSurface_PointerExited(object sender, PointerRoutedEventArgs e)
    {
        _isHovered = false;
        if (_handle != IntPtr.Zero)
        {
            LayersNative.layers_mouse_left(_handle);
        }
        ApplyFade();
    }

    private void RenderSurface_KeyDown(object sender, KeyRoutedEventArgs e) => DispatchKey(e, pressed: true);
    private void RenderSurface_KeyUp(object sender, KeyRoutedEventArgs e)   => DispatchKey(e, pressed: false);

    private void DispatchKey(KeyRoutedEventArgs e, bool pressed)
    {
        if (_handle == IntPtr.Zero) return;
        uint named = WinKeyMap.MapVirtualKey(e.Key);
        string? text = named == 0 ? WinKeyMap.TextForKey(e.Key) : null;
        uint mods = WinKeyMap.CurrentModifiers();
        LayersNative.layers_key_event(_handle, named, text, mods, (ushort)e.Key, pressed);
    }
}