TrayIcon.cs

using System.Runtime.InteropServices;
using Microsoft.UI.Xaml;
using WinRT.Interop;

namespace NoteUI;

internal sealed class TrayIcon : IDisposable
{
    private const int GWL_WNDPROC = -4;
    private const int WM_APP = 0x8000;
    private const int WM_TRAYICON = WM_APP + 1;
    private const int WM_LBUTTONDBLCLK = 0x0203;
    private const int WM_RBUTTONUP = 0x0205;

    private const int NIM_ADD = 0x00;
    private const int NIM_DELETE = 0x02;
    private const int NIF_MESSAGE = 0x01;
    private const int NIF_ICON = 0x02;
    private const int NIF_TIP = 0x04;

    private const uint TPM_RETURNCMD = 0x0100;
    private const uint TPM_NONOTIFY = 0x0080;
    private const uint MF_STRING = 0x0000;
    private const uint MF_SEPARATOR = 0x0800;

    private readonly IntPtr _hwnd;
    private readonly IntPtr _icon;
    private readonly WndProcDelegate _wndProcDelegate;
    private readonly IntPtr _prevWndProc;
    private bool _disposed;

    public event Action? ShowRequested;
    public event Action? ExitRequested;

    private delegate IntPtr WndProcDelegate(IntPtr hWnd, uint msg, IntPtr wParam, IntPtr lParam);

    public TrayIcon(Window window, string tooltip)
    {
        _hwnd = WindowNative.GetWindowHandle(window);

        // Load icon from exe resource (embedded via ApplicationIcon)
        var exePath = Environment.ProcessPath ?? "";
        _icon = ExtractIcon(IntPtr.Zero, exePath, 0);

        // Subclass window to receive tray messages
        _wndProcDelegate = WndProc;
        _prevWndProc = SetWindowLongPtr(_hwnd, GWL_WNDPROC,
            Marshal.GetFunctionPointerForDelegate(_wndProcDelegate));

        var nid = new NOTIFYICONDATA
        {
            cbSize = Marshal.SizeOf<NOTIFYICONDATA>(),
            hWnd = _hwnd,
            uID = 1,
            uFlags = NIF_MESSAGE | NIF_ICON | NIF_TIP,
            uCallbackMessage = WM_TRAYICON,
            hIcon = _icon,
            szTip = tooltip,
            szInfo = "",
            szInfoTitle = ""
        };
        Shell_NotifyIcon(NIM_ADD, ref nid);
    }

    private IntPtr WndProc(IntPtr hWnd, uint msg, IntPtr wParam, IntPtr lParam)
    {
        if (msg == WM_TRAYICON)
        {
            var mouseMsg = (int)lParam;
            if (mouseMsg == WM_LBUTTONDBLCLK)
                ShowRequested?.Invoke();
            else if (mouseMsg == WM_RBUTTONUP)
                ShowContextMenu();
            return IntPtr.Zero;
        }
        return CallWindowProc(_prevWndProc, hWnd, msg, wParam, lParam);
    }

    private void ShowContextMenu()
    {
        var menu = CreatePopupMenu();
        AppendMenu(menu, MF_STRING, 1, "Notes");
        AppendMenu(menu, MF_SEPARATOR, 0, null);
        AppendMenu(menu, MF_STRING, 2, "Quitter");

        GetCursorPos(out var pt);
        SetForegroundWindow(_hwnd);
        var cmd = TrackPopupMenuEx(menu, TPM_RETURNCMD | TPM_NONOTIFY,
            pt.X, pt.Y, _hwnd, IntPtr.Zero);
        DestroyMenu(menu);

        if (cmd == 1) ShowRequested?.Invoke();
        else if (cmd == 2) ExitRequested?.Invoke();
    }

    public void Dispose()
    {
        if (_disposed) return;
        _disposed = true;

        var nid = new NOTIFYICONDATA
        {
            cbSize = Marshal.SizeOf<NOTIFYICONDATA>(),
            hWnd = _hwnd,
            uID = 1,
            szTip = "",
            szInfo = "",
            szInfoTitle = ""
        };
        Shell_NotifyIcon(NIM_DELETE, ref nid);

        if (_icon != IntPtr.Zero)
            DestroyIcon(_icon);

        if (_prevWndProc != IntPtr.Zero)
            SetWindowLongPtr(_hwnd, GWL_WNDPROC, _prevWndProc);
    }

    // ── Structures ──────────────────────────────────────────────

    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
    private struct NOTIFYICONDATA
    {
        public int cbSize;
        public IntPtr hWnd;
        public int uID;
        public int uFlags;
        public int uCallbackMessage;
        public IntPtr hIcon;
        [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 128)]
        public string szTip;
        public int dwState;
        public int dwStateMask;
        [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 256)]
        public string szInfo;
        public int uTimeoutOrVersion;
        [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 64)]
        public string szInfoTitle;
        public int dwInfoFlags;
    }

    [StructLayout(LayoutKind.Sequential)]
    private struct POINT { public int X, Y; }

    // ── P/Invoke ────────────────────────────────────────────────

    [DllImport("shell32.dll", CharSet = CharSet.Unicode)]
    private static extern bool Shell_NotifyIcon(int dwMessage, ref NOTIFYICONDATA lpData);

    [DllImport("shell32.dll", CharSet = CharSet.Unicode)]
    private static extern IntPtr ExtractIcon(IntPtr hInst, string lpszExeFileName, int nIconIndex);

    [DllImport("user32.dll")]
    private static extern bool DestroyIcon(IntPtr hIcon);

    [DllImport("user32.dll", SetLastError = true)]
    private static extern IntPtr SetWindowLongPtr(IntPtr hWnd, int nIndex, IntPtr dwNewLong);

    [DllImport("user32.dll")]
    private static extern IntPtr CallWindowProc(IntPtr lpPrevWndFunc, IntPtr hWnd, uint msg, IntPtr wParam, IntPtr lParam);

    [DllImport("user32.dll")]
    private static extern IntPtr CreatePopupMenu();

    [DllImport("user32.dll", CharSet = CharSet.Unicode)]
    private static extern bool AppendMenu(IntPtr hMenu, uint uFlags, nuint uIDNewItem, string? lpNewItem);

    [DllImport("user32.dll")]
    private static extern int TrackPopupMenuEx(IntPtr hMenu, uint fuFlags, int x, int y, IntPtr hwnd, IntPtr lptpm);

    [DllImport("user32.dll")]
    private static extern bool DestroyMenu(IntPtr hMenu);

    [DllImport("user32.dll")]
    private static extern bool SetForegroundWindow(IntPtr hWnd);

    [DllImport("user32.dll")]
    private static extern bool GetCursorPos(out POINT lpPoint);
}