lightweight variant (#1)

Reviewed-on: #1 Co-authored-by: Aleksandr Neychev <alexnejchev73@gmail.com>
2026-08-12 13:37:30 +00:00
parent a0d3098fe4
commit 55ac8e6556
147 changed files with 4055 additions and 2349 deletions
@@ -0,0 +1,161 @@
+using System.Drawing;
+using System.Runtime.InteropServices;
+using CursorLang.Core.Interop;
+
+namespace CursorLang.Agent.Interop;
+
+/// <summary>
+/// Plain GDI: a font, text, and an off-screen bitmap to draw them into.
+/// </summary>
+/// <remarks>
+/// GDI rather than GDI+ on purpose. <c>System.Drawing.Common</c> would make the drawing
+/// code shorter, but it is a separate assembly with a native GDI+ library behind it, and
+/// how little this process weighs is the entire reason it exists apart from the window.
+/// Everything the popup needs — one rounded rectangle and one line of text — GDI can do
+/// on its own, and it draws the text with ClearType, exactly as Windows does everywhere else.
+/// </remarks>
+internal static class GdiNative
+{
+    internal const int TRANSPARENT = 1;
+
+    internal const uint DT_SINGLELINE = 0x00000020;
+    internal const uint DT_CENTER = 0x00000001;
+    internal const uint DT_VCENTER = 0x00000004;
+    internal const uint DT_CALCRECT = 0x00000400;
+    internal const uint DT_NOPREFIX = 0x00000800;
+    internal const uint DT_NOCLIP = 0x00000100;
+
+    private const int DEFAULT_CHARSET = 1;
+    private const int OUT_TT_PRECIS = 4;
+    private const int CLIP_DEFAULT_PRECIS = 0;
+    private const int CLEARTYPE_QUALITY = 5;
+    private const int DEFAULT_PITCH = 0;
+
+    /// <summary>
+    /// The face the popup is written in.
+    /// </summary>
+    /// <remarks>
+    /// WPF is asked for "Segoe UI" at FontWeight SemiBold and resolves that to the
+    /// seguisb.ttf face. To GDI that face is a family of its own — "Segoe UI Semibold" —
+    /// and asking for the "Segoe UI" family at weight 600 lands on Bold instead, which
+    /// is visibly heavier. So the family is named outright and the weight is left to the
+    /// mapper: the family has one member and no synthetic emboldening happens.
+    /// </remarks>
+    private const string SemiBoldFace = "Segoe UI Semibold";
+
+    private const int FW_DONTCARE = 0;
+
+    /// <summary>
+    /// A font of the given size in physical pixels.
+    /// </summary>
+    /// <remarks>
+    /// The size in the settings is in WPF units, that is 1/96 inch, while GDI counts
+    /// pixels — hence the multiplication by the monitor scale. The height is negative:
+    /// that asks for the em size rather than the cell height, which is what a font size
+    /// means everywhere else.
+    /// </remarks>
+    internal static IntPtr CreateFont(double wpfFontSize, double scale)
+    {
+        var height = (int)Math.Round(wpfFontSize * scale);
+
+        return CreateFontW(
+            -height, 0, 0, 0, FW_DONTCARE,
+            false, false, false,
+            DEFAULT_CHARSET, OUT_TT_PRECIS, CLIP_DEFAULT_PRECIS, CLEARTYPE_QUALITY, DEFAULT_PITCH,
+            SemiBoldFace);
+    }
+
+    /// <summary>The size of a single line of text with the font selected into the context.</summary>
+    internal static Size MeasureText(IntPtr deviceContext, string text)
+    {
+        var bounds = default(PopupWindowNative.Rect);
+        DrawText(deviceContext, text, text.Length, ref bounds,
+            DT_CALCRECT | DT_SINGLELINE | DT_NOPREFIX);
+
+        return new Size(bounds.Right - bounds.Left, bounds.Bottom - bounds.Top);
+    }
+
+    /// <summary>A colour as GDI wants it: 0x00BBGGRR, the alpha carried elsewhere.</summary>
+    internal static uint ToColorRef(Color color) =>
+        (uint)(color.R | (color.G << 8) | (color.B << 16));
+
+    [DllImport("gdi32.dll", CharSet = CharSet.Unicode, EntryPoint = "CreateFontW")]
+    private static extern IntPtr CreateFontW(int cHeight, int cWidth, int cEscapement, int cOrientation,
+        int cWeight, bool bItalic, bool bUnderline, bool bStrikeOut,
+        int iCharSet, int iOutPrecision, int iClipPrecision, int iQuality, int iPitchAndFamily,
+        string pszFaceName);
+
+    /// <summary>
+    /// A 32-bit surface to draw the popup into before anyone can see it.
+    /// </summary>
+    /// <remarks>
+    /// Top-down — a negative height — so that the first row of <paramref name="bits"/>
+    /// is the top row of the picture and the alpha fixing up afterwards can walk the
+    /// memory straight through.
+    /// </remarks>
+    internal static IntPtr CreateSurface(IntPtr deviceContext, int width, int height, out IntPtr bits)
+    {
+        var header = new BitmapInfoHeader
+        {
+            biSize = Marshal.SizeOf<BitmapInfoHeader>(),
+            biWidth = width,
+            biHeight = -height,
+            biPlanes = 1,
+            biBitCount = 32,
+            biCompression = BI_RGB,
+        };
+
+        return CreateDIBSection(deviceContext, ref header, DIB_RGB_COLORS, out bits, IntPtr.Zero, 0);
+    }
+
+    private const uint BI_RGB = 0;
+    private const uint DIB_RGB_COLORS = 0;
+
+    [DllImport("gdi32.dll")]
+    internal static extern IntPtr CreateCompatibleDC(IntPtr hdc);
+
+    [DllImport("gdi32.dll")]
+    internal static extern bool DeleteDC(IntPtr hdc);
+
+    [DllImport("gdi32.dll")]
+    private static extern IntPtr CreateDIBSection(IntPtr hdc, ref BitmapInfoHeader header, uint usage,
+        out IntPtr bits, IntPtr section, uint offset);
+
+    [DllImport("gdi32.dll")]
+    internal static extern IntPtr SelectObject(IntPtr hdc, IntPtr h);
+
+    [DllImport("gdi32.dll")]
+    internal static extern bool DeleteObject(IntPtr ho);
+
+    [DllImport("gdi32.dll")]
+    internal static extern int SetBkMode(IntPtr hdc, int mode);
+
+    [DllImport("gdi32.dll")]
+    internal static extern uint SetTextColor(IntPtr hdc, uint color);
+
+    [DllImport("user32.dll", CharSet = CharSet.Unicode, EntryPoint = "DrawTextW")]
+    internal static extern int DrawText(IntPtr hdc, string lpchText, int cchText,
+        ref PopupWindowNative.Rect lprc, uint format);
+
+    [DllImport("user32.dll")]
+    internal static extern IntPtr GetDC(IntPtr hWnd);
+
+    [DllImport("user32.dll")]
+    internal static extern int ReleaseDC(IntPtr hWnd, IntPtr hDC);
+
+    [StructLayout(LayoutKind.Sequential)]
+    private struct BitmapInfoHeader
+    {
+        public int biSize;
+        public int biWidth;
+        public int biHeight;
+        public short biPlanes;
+        public short biBitCount;
+        public uint biCompression;
+        public uint biSizeImage;
+        public int biXPelsPerMeter;
+        public int biYPelsPerMeter;
+        public uint biClrUsed;
+        public uint biClrImportant;
+    }
+}
@@ -0,0 +1,98 @@
+using System.Runtime.InteropServices;
+using CursorLang.Core.Interop;
+
+namespace CursorLang.Agent.Interop;
+
+/// <summary>
+/// The system context menu — the one the tray icon raises.
+/// </summary>
+/// <remarks>
+/// A menu built this way is drawn by Windows, so the theme and the language chosen in
+/// the application no longer reach it. That is the accepted price of leaving WPF: a WPF
+/// <c>ContextMenu</c> costs the whole rendering stack in the background process.
+/// </remarks>
+internal static class MenuNative
+{
+    private const uint MF_STRING = 0x00000000;
+    private const uint MF_SEPARATOR = 0x00000800;
+    private const uint MF_GRAYED = 0x00000001;
+
+    private const uint TPM_LEFTALIGN = 0x0000;
+    private const uint TPM_RIGHTBUTTON = 0x0002;
+    private const uint TPM_RETURNCMD = 0x0100;
+
+    /// <summary>An item of the menu being built.</summary>
+    /// <param name="Id">What <see cref="Track"/> gives back when the item is chosen.</param>
+    /// <param name="Caption">The text, or <c>null</c> for a separator.</param>
+    /// <param name="IsEnabled">A greyed item is shown but cannot be chosen.</param>
+    internal readonly record struct Item(int Id, string? Caption, bool IsEnabled = true)
+    {
+        internal static Item Separator => new(0, null);
+    }
+
+    /// <summary>
+    /// Raises the menu at a screen point and returns the identifier of the chosen item,
+    /// or zero when the user dismissed it.
+    /// </summary>
+    /// <remarks>
+    /// <c>TPM_RETURNCMD</c> means the answer comes back from the call itself instead of
+    /// as a <c>WM_COMMAND</c> later, which keeps the whole menu in one place. The call
+    /// does not return until the user is done with the menu — that is how a modal menu
+    /// works, and the message loop keeps running inside it.
+    ///
+    /// The window is brought to the foreground first and poked with an empty message
+    /// afterwards: without the first the menu never closes on a click elsewhere, and
+    /// without the second it stays on screen after the choice is made. Both are
+    /// long-standing quirks of a menu owned by a window the user cannot see.
+    /// </remarks>
+    internal static int Track(IntPtr owner, PopupWindowNative.Point at, IReadOnlyList<Item> items)
+    {
+        IntPtr menu = CreatePopupMenu();
+        if (menu == IntPtr.Zero)
+        {
+            return 0;
+        }
+
+        try
+        {
+            foreach (Item item in items)
+            {
+                if (item.Caption is null)
+                {
+                    AppendMenu(menu, MF_SEPARATOR, IntPtr.Zero, null);
+                    continue;
+                }
+
+                uint flags = MF_STRING | (item.IsEnabled ? 0 : MF_GRAYED);
+                AppendMenu(menu, flags, new IntPtr(item.Id), item.Caption);
+            }
+
+            TrayIconNative.BringToForeground(owner);
+
+            int chosen = TrackPopupMenuEx(
+                menu, TPM_LEFTALIGN | TPM_RIGHTBUTTON | TPM_RETURNCMD,
+                at.X, at.Y, owner, IntPtr.Zero);
+
+            WindowNative.PostMessage(owner, WindowNative.WM_NULL, IntPtr.Zero, IntPtr.Zero);
+
+            return chosen;
+        }
+        finally
+        {
+            DestroyMenu(menu);
+        }
+    }
+
+    [DllImport("user32.dll")]
+    private static extern IntPtr CreatePopupMenu();
+
+    [DllImport("user32.dll")]
+    private static extern bool DestroyMenu(IntPtr hMenu);
+
+    [DllImport("user32.dll", CharSet = CharSet.Unicode, EntryPoint = "AppendMenuW")]
+    private static extern bool AppendMenu(IntPtr hMenu, uint uFlags, IntPtr uIDNewItem, string? lpNewItem);
+
+    [DllImport("user32.dll")]
+    private static extern int TrackPopupMenuEx(IntPtr hMenu, uint uFlags, int x, int y,
+        IntPtr hwnd, IntPtr lptpm);
+}
@@ -0,0 +1,229 @@
+using System.Runtime.InteropServices;
+using CursorLang.Core.Interop;
+
+namespace CursorLang.Agent.Interop;
+
+/// <summary>
+/// Win32 API for the notification area: the icon itself, the messages it sends
+/// and the icon image taken from the executable.
+/// </summary>
+/// <remarks>
+/// The icon is asked for at version 4 of the protocol. It is the only version that
+/// reports a request for the context menu as such — by the keyboard as well as by
+/// the right button — and passes the point of the click along with it. The
+/// notification then arrives in the low word of <c>lParam</c>, and the point in
+/// <c>wParam</c>, which is the opposite of the earlier versions.
+/// </remarks>
+internal static class TrayIconNative
+{
+    /// <summary>The message the icon sends to its window. WM_APP is free for the app.</summary>
+    internal const int CallbackMessage = 0x8000 + 1;
+
+    /// <summary>The user chose the icon: a click of the left button or Enter on it.</summary>
+    internal const int SelectNotification = 0x0400;
+
+    /// <summary>The same by the space bar — Windows tells the two apart.</summary>
+    internal const int KeySelectNotification = 0x0403;
+
+    /// <summary>The context menu is asked for: the right button or the menu key.</summary>
+    internal const int ContextMenuNotification = 0x007B;
+
+    private const int NIM_ADD = 0x00000000;
+    private const int NIM_DELETE = 0x00000002;
+    private const int NIM_SETVERSION = 0x00000004;
+
+    private const uint NIF_MESSAGE = 0x00000001;
+    private const uint NIF_ICON = 0x00000002;
+    private const uint NIF_TIP = 0x00000004;
+    private const uint NIF_SHOWTIP = 0x00000080;
+
+    private const uint NotifyIconVersion4 = 4;
+
+    private const uint IMAGE_ICON = 1;
+    private const uint LR_DEFAULTCOLOR = 0x00000000;
+
+    private const int SM_CXSMICON = 49;
+    private const int SM_CYSMICON = 50;
+
+    /// <summary>The resource the .NET build puts the application icon under.</summary>
+    private const int ApplicationIconResource = 32512;
+
+    /// <summary>
+    /// Explorer says it has restarted this way. The icons of every application are
+    /// gone by then and have to be put back.
+    /// </summary>
+    internal static int TaskbarCreatedMessage { get; } = RegisterWindowMessage("TaskbarCreated");
+
+    /// <summary>Puts the icon into the notification area.</summary>
+    internal static bool Add(IntPtr window, int id, IntPtr icon, string tooltip)
+    {
+        NotifyIconData data = Describe(window, id, icon, tooltip);
+
+        if (!Shell_NotifyIcon(NIM_ADD, ref data))
+        {
+            return false;
+        }
+
+        // The version is asked for after the icon is added and applies to it alone
+        data.uVersion = NotifyIconVersion4;
+        Shell_NotifyIcon(NIM_SETVERSION, ref data);
+
+        return true;
+    }
+
+    /// <summary>Takes the icon away. A forgotten icon stays in the tray until hovered.</summary>
+    internal static void Remove(IntPtr window, int id)
+    {
+        var data = new NotifyIconData
+        {
+            cbSize = Marshal.SizeOf<NotifyIconData>(),
+            hWnd = window,
+            uID = (uint)id,
+        };
+
+        Shell_NotifyIcon(NIM_DELETE, ref data);
+    }
+
+    /// <summary>
+    /// The icon of the application at the size the tray asks for.
+    /// </summary>
+    /// <remarks>
+    /// The image comes from the executable itself, so the tray shows what the user
+    /// sees in Explorer. The build puts the icon under the standard resource; should
+    /// it end up elsewhere, the first icon of the file is taken, and failing that —
+    /// the icon Windows gives to an application without one. An icon is needed
+    /// either way: without it the tray shows an empty spot.
+    /// </remarks>
+    internal static IntPtr LoadApplicationIcon()
+    {
+        int width = GetSystemMetrics(SM_CXSMICON);
+        int height = GetSystemMetrics(SM_CYSMICON);
+
+        IntPtr icon = LoadImage(
+            GetModuleHandle(null), ApplicationIconResource, IMAGE_ICON, width, height, LR_DEFAULTCOLOR);
+
+        if (icon == IntPtr.Zero && Environment.ProcessPath is { Length: > 0 } path)
+        {
+            icon = ExtractIconEx(path, 0, out IntPtr large, out IntPtr small, 1) > 0 ? small : IntPtr.Zero;
+
+            if (large != IntPtr.Zero)
+            {
+                DestroyIcon(large);
+            }
+        }
+
+        return icon != IntPtr.Zero ? icon : LoadIcon(IntPtr.Zero, ApplicationIconResource);
+    }
+
+    /// <summary>Releases an icon loaded by <see cref="LoadApplicationIcon"/>.</summary>
+    internal static void ReleaseIcon(IntPtr icon)
+    {
+        if (icon != IntPtr.Zero)
+        {
+            DestroyIcon(icon);
+        }
+    }
+
+    /// <summary>The notification the icon has sent: it sits in the low word of lParam.</summary>
+    internal static int NotificationOf(IntPtr lParam) => (int)(lParam.ToInt64() & 0xFFFF);
+
+    /// <summary>
+    /// The point of the click. Version 4 of the protocol reports it in screen pixels
+    /// in <c>wParam</c> — exactly what <c>TrackPopupMenuEx</c> expects.
+    /// </summary>
+    internal static PopupWindowNative.Point PointOf(IntPtr wParam) => new()
+    {
+        X = (short)(wParam.ToInt64() & 0xFFFF),
+        Y = (short)((wParam.ToInt64() >> 16) & 0xFFFF),
+    };
+
+    /// <summary>
+    /// Brings the window to the foreground.
+    /// </summary>
+    /// <remarks>
+    /// Windows takes a menu down when its owner window loses the foreground. A tray
+    /// icon belongs to a window that is never shown, so the foreground has to be
+    /// asked for by hand — otherwise the menu stays on screen after the user has
+    /// clicked past it.
+    /// </remarks>
+    internal static void BringToForeground(IntPtr window) => SetForegroundWindow(window);
+
+    private static NotifyIconData Describe(IntPtr window, int id, IntPtr icon, string tooltip) => new()
+    {
+        cbSize = Marshal.SizeOf<NotifyIconData>(),
+        hWnd = window,
+        uID = (uint)id,
+        uFlags = NIF_MESSAGE | NIF_ICON | NIF_TIP | NIF_SHOWTIP,
+        uCallbackMessage = CallbackMessage,
+        hIcon = icon,
+        szTip = tooltip,
+    };
+
+    [DllImport("shell32.dll", CharSet = CharSet.Unicode)]
+    private static extern bool Shell_NotifyIcon(int dwMessage, ref NotifyIconData lpData);
+
+    [DllImport("user32.dll", CharSet = CharSet.Unicode)]
+    private static extern int RegisterWindowMessage(string lpString);
+
+    [DllImport("user32.dll")]
+    private static extern IntPtr LoadImage(IntPtr hInst, IntPtr name, uint type, int cx, int cy, uint fuLoad);
+
+    private static IntPtr LoadImage(IntPtr hInst, int resource, uint type, int cx, int cy, uint fuLoad) =>
+        LoadImage(hInst, new IntPtr(resource), type, cx, cy, fuLoad);
+
+    [DllImport("user32.dll")]
+    private static extern IntPtr LoadIcon(IntPtr hInstance, IntPtr lpIconName);
+
+    private static IntPtr LoadIcon(IntPtr hInstance, int resource) =>
+        LoadIcon(hInstance, new IntPtr(resource));
+
+    [DllImport("shell32.dll", CharSet = CharSet.Unicode)]
+    private static extern int ExtractIconEx(string lpszFile, int nIconIndex,
+        out IntPtr phiconLarge, out IntPtr phiconSmall, int nIcons);
+
+    [DllImport("user32.dll")]
+    private static extern bool DestroyIcon(IntPtr hIcon);
+
+    [DllImport("user32.dll")]
+    private static extern int GetSystemMetrics(int nIndex);
+
+    [DllImport("user32.dll")]
+    private static extern bool SetForegroundWindow(IntPtr hWnd);
+
+    [DllImport("kernel32.dll", CharSet = CharSet.Unicode)]
+    private static extern IntPtr GetModuleHandle(string? lpModuleName);
+
+    /// <summary>
+    /// NOTIFYICONDATAW. The whole structure is described even though only its first
+    /// half is used: Windows reads its size and refuses one it does not know.
+    /// </summary>
+    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
+    private struct NotifyIconData
+    {
+        public int cbSize;
+        public IntPtr hWnd;
+        public uint uID;
+        public uint uFlags;
+        public int uCallbackMessage;
+        public IntPtr hIcon;
+
+        [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 128)]
+        public string szTip;
+
+        public uint dwState;
+        public uint dwStateMask;
+
+        [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 256)]
+        public string szInfo;
+
+        /// <summary>A timeout in the older versions and the protocol version here.</summary>
+        public uint uVersion;
+
+        [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 64)]
+        public string szInfoTitle;
+
+        public uint dwInfoFlags;
+        public Guid guidItem;
+        public IntPtr hBalloonIcon;
+    }
+}
@@ -0,0 +1,180 @@
+using System.Runtime.InteropServices;
+using CursorLang.Core.Interop;
+
+namespace CursorLang.Agent.Interop;
+
+/// <summary>
+/// The Win32 pieces a window needs when there is no framework to make one:
+/// the class, the window itself, the message loop.
+/// </summary>
+internal static class WindowNative
+{
+    /// <summary>The window procedure. Windows keeps the only reference to it.</summary>
+    internal delegate IntPtr WindowProc(IntPtr hWnd, uint message, IntPtr wParam, IntPtr lParam);
+
+    internal const int WS_POPUP = unchecked((int)0x80000000);
+
+    internal const int WS_EX_LAYERED = 0x00080000;
+    internal const int WS_EX_TOOLWINDOW = 0x00000080;
+    internal const int WS_EX_NOACTIVATE = 0x08000000;
+    internal const int WS_EX_TRANSPARENT = 0x00000020;
+    internal const int WS_EX_TOPMOST = 0x00000008;
+
+    internal const int SW_HIDE = 0;
+    internal const int SW_SHOWNOACTIVATE = 4;
+
+    internal const uint WM_DESTROY = 0x0002;
+    internal const uint WM_CLOSE = 0x0010;
+    internal const uint WM_QUIT = 0x0012;
+    internal const uint WM_NULL = 0x0000;
+    internal const uint WM_ENDSESSION = 0x0016;
+
+    /// <summary>WM_APP and up belong to the application; the tray takes WM_APP + 1.</summary>
+    internal const uint WM_APP = 0x8000;
+
+    /// <summary>
+    /// Registers a window class. A class already there is not an error: the name is
+    /// unique per window kind, and a second agent in the same process would meet its
+    /// own registration.
+    /// </summary>
+    internal static void RegisterClass(string className, WindowProc windowProc)
+    {
+        var description = new WindowClass
+        {
+            cbSize = Marshal.SizeOf<WindowClass>(),
+            lpfnWndProc = windowProc,
+            hInstance = GetModuleHandle(null),
+            lpszClassName = className,
+        };
+
+        if (RegisterClassEx(ref description) == 0 &&
+            Marshal.GetLastWin32Error() != ErrorClassAlreadyExists)
+        {
+            throw new InvalidOperationException(
+                $"RegisterClassExW failed for '{className}': {Marshal.GetLastWin32Error()}");
+        }
+    }
+
+    private const int ErrorClassAlreadyExists = 1410;
+
+    /// <summary>Creates a window of a registered class. It is not shown.</summary>
+    internal static IntPtr CreateWindow(string className, string title, int style, int exStyle)
+    {
+        IntPtr window = CreateWindowEx(
+            exStyle, className, title, style,
+            0, 0, 0, 0,
+            IntPtr.Zero, IntPtr.Zero, GetModuleHandle(null), IntPtr.Zero);
+
+        if (window == IntPtr.Zero)
+        {
+            throw new InvalidOperationException(
+                $"CreateWindowExW failed for '{className}': {Marshal.GetLastWin32Error()}");
+        }
+
+        return window;
+    }
+
+    /// <summary>
+    /// Puts a finished picture into a layered window, together with where it goes and
+    /// how see-through it is.
+    /// </summary>
+    /// <remarks>
+    /// One call replaces moving the window, resizing it, painting it and setting its
+    /// opacity, and it works while the window is still hidden. That is the point: the
+    /// content is ready before anyone can see the window, so it can never be shown
+    /// holding the picture of the previous time.
+    /// </remarks>
+    internal static bool SetContent(
+        IntPtr window, PopupWindowNative.Point at, Size size, IntPtr sourceDc, byte alpha)
+    {
+        var source = new PopupWindowNative.Point { X = 0, Y = 0 };
+        var blend = new BlendFunction
+        {
+            BlendOp = AC_SRC_OVER,
+            SourceConstantAlpha = alpha,
+            AlphaFormat = AC_SRC_ALPHA,
+        };
+
+        return UpdateLayeredWindow(
+            window, IntPtr.Zero, ref at, ref size, sourceDc, ref source, 0, ref blend, ULW_ALPHA);
+    }
+
+    private const byte AC_SRC_OVER = 0;
+    private const byte AC_SRC_ALPHA = 1;
+    private const uint ULW_ALPHA = 0x00000002;
+
+    /// <summary>
+    /// BLENDFUNCTION. <c>BlendFlags</c> is never assigned and must stay all the same:
+    /// Windows reads the structure by its layout, and dropping a byte from the middle
+    /// of it would shift everything after.
+    /// </summary>
+    [StructLayout(LayoutKind.Sequential)]
+    private struct BlendFunction
+    {
+        public byte BlendOp;
+        public byte BlendFlags;
+        public byte SourceConstantAlpha;
+        public byte AlphaFormat;
+    }
+
+    [StructLayout(LayoutKind.Sequential)]
+    internal struct Size
+    {
+        public int Width;
+        public int Height;
+    }
+
+    [DllImport("user32.dll", SetLastError = true)]
+    private static extern bool UpdateLayeredWindow(IntPtr hWnd, IntPtr hdcDst,
+        ref PopupWindowNative.Point pptDst, ref Size psize, IntPtr hdcSrc,
+        ref PopupWindowNative.Point pptSrc, uint crKey, ref BlendFunction pblend, uint dwFlags);
+
+    [DllImport("user32.dll", CharSet = CharSet.Unicode, SetLastError = true)]
+    private static extern ushort RegisterClassEx(ref WindowClass lpwcx);
+
+    [DllImport("user32.dll", CharSet = CharSet.Unicode, SetLastError = true, EntryPoint = "CreateWindowExW")]
+    private static extern IntPtr CreateWindowEx(int dwExStyle, string lpClassName, string lpWindowName,
+        int dwStyle, int x, int y, int nWidth, int nHeight,
+        IntPtr hWndParent, IntPtr hMenu, IntPtr hInstance, IntPtr lpParam);
+
+    [DllImport("user32.dll", CharSet = CharSet.Unicode, EntryPoint = "DefWindowProcW")]
+    internal static extern IntPtr DefWindowProc(IntPtr hWnd, uint message, IntPtr wParam, IntPtr lParam);
+
+    [DllImport("user32.dll")]
+    internal static extern bool DestroyWindow(IntPtr hWnd);
+
+    [DllImport("user32.dll")]
+    internal static extern bool ShowWindow(IntPtr hWnd, int nCmdShow);
+
+    [DllImport("user32.dll")]
+    internal static extern bool IsWindowVisible(IntPtr hWnd);
+
+    [DllImport("user32.dll", CharSet = CharSet.Unicode, EntryPoint = "PostMessageW")]
+    internal static extern bool PostMessage(IntPtr hWnd, uint message, IntPtr wParam, IntPtr lParam);
+
+    [DllImport("user32.dll")]
+    internal static extern void PostQuitMessage(int nExitCode);
+
+    [DllImport("kernel32.dll", CharSet = CharSet.Unicode)]
+    private static extern IntPtr GetModuleHandle(string? lpModuleName);
+
+    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
+    private struct WindowClass
+    {
+        public int cbSize;
+        public uint style;
+
+        [MarshalAs(UnmanagedType.FunctionPtr)]
+        public WindowProc lpfnWndProc;
+
+        public int cbClsExtra;
+        public int cbWndExtra;
+        public IntPtr hInstance;
+        public IntPtr hIcon;
+        public IntPtr hCursor;
+        public IntPtr hbrBackground;
+        public string? lpszMenuName;
+        public string lpszClassName;
+        public IntPtr hIconSm;
+    }
+}