Native.cs

using System;
using System.Runtime.InteropServices;

namespace WinTextCapture;

/// <summary>All Win32 interop in one place.</summary>
internal static class Native
{
    // ---- low-level keyboard hook ----
    public const int WH_KEYBOARD_LL = 13;
    public const int WM_KEYDOWN = 0x0100;
    public const int WM_SYSKEYDOWN = 0x0104;
    public const int WM_KEYUP = 0x0101;
    public const int WM_SYSKEYUP = 0x0105;

    public delegate IntPtr HookProc(int nCode, IntPtr wParam, IntPtr lParam);

    [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
    public static extern IntPtr SetWindowsHookEx(int idHook, HookProc lpfn, IntPtr hMod, uint dwThreadId);

    [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
    [return: MarshalAs(UnmanagedType.Bool)]
    public static extern bool UnhookWindowsHookEx(IntPtr hhk);

    [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
    public static extern IntPtr CallNextHookEx(IntPtr hhk, int nCode, IntPtr wParam, IntPtr lParam);

    [DllImport("kernel32.dll", CharSet = CharSet.Auto, SetLastError = true)]
    public static extern IntPtr GetModuleHandle(string? lpModuleName);

    [DllImport("user32.dll")]
    public static extern short GetAsyncKeyState(int vKey);

    // virtual-key codes used for modifier polling
    public const int VK_SHIFT = 0x10, VK_CONTROL = 0x11, VK_MENU = 0x12, VK_LWIN = 0x5B, VK_RWIN = 0x5C, VK_LCONTROL = 0xA2;

    public static bool IsDown(int vk) => (GetAsyncKeyState(vk) & 0x8000) != 0;

    // ---- SendInput (used to mask the Win key so it doesn't open the Start menu) ----
    public const uint INPUT_KEYBOARD = 1;
    public const uint KEYEVENTF_KEYUP = 0x0002;
    // sentinel stamped on our own injected input so we can recognise/ignore it
    public static readonly IntPtr InjectedTag = (IntPtr)0x57544558; // "WTEX"

    [StructLayout(LayoutKind.Sequential)]
    public struct MOUSEINPUT { public int dx, dy; public uint mouseData, dwFlags, time; public IntPtr dwExtraInfo; }

    [StructLayout(LayoutKind.Sequential)]
    public struct KEYBDINPUT { public ushort wVk, wScan; public uint dwFlags, time; public IntPtr dwExtraInfo; }

    [StructLayout(LayoutKind.Explicit)]
    public struct INPUTUNION
    {
        [FieldOffset(0)] public MOUSEINPUT mi;
        [FieldOffset(0)] public KEYBDINPUT ki;
    }

    [StructLayout(LayoutKind.Sequential)]
    public struct INPUT { public uint type; public INPUTUNION u; }

    [DllImport("user32.dll", SetLastError = true)]
    public static extern uint SendInput(uint nInputs, INPUT[] pInputs, int cbSize);

    /// <summary>
    /// Tap Left-Ctrl (down+up). When a Win-key hotkey is consumed, the trailing lone Win key-up would
    /// otherwise pop the Start menu; injecting a masking key while Win is held cancels that.
    /// </summary>
    public static void MaskWinKey()
    {
        var inputs = new INPUT[2];
        inputs[0].type = INPUT_KEYBOARD;
        inputs[0].u.ki = new KEYBDINPUT { wVk = VK_LCONTROL, dwExtraInfo = InjectedTag };
        inputs[1].type = INPUT_KEYBOARD;
        inputs[1].u.ki = new KEYBDINPUT { wVk = VK_LCONTROL, dwFlags = KEYEVENTF_KEYUP, dwExtraInfo = InjectedTag };
        SendInput(2, inputs, Marshal.SizeOf<INPUT>());
    }

    // ---- virtual screen metrics (physical pixels in a PerMonitorV2 process) ----
    public const int SM_XVIRTUALSCREEN = 76, SM_YVIRTUALSCREEN = 77, SM_CXVIRTUALSCREEN = 78, SM_CYVIRTUALSCREEN = 79;

    [DllImport("user32.dll")]
    public static extern int GetSystemMetrics(int nIndex);

    public static readonly IntPtr DPI_AWARENESS_CONTEXT_PER_MONITOR_AWARE_V2 = new(-4);

    [DllImport("user32.dll", SetLastError = true)]
    [return: MarshalAs(UnmanagedType.Bool)]
    public static extern bool SetProcessDpiAwarenessContext(IntPtr value);

    // ---- window positioning / focus ----
    public static readonly IntPtr HWND_TOPMOST = new(-1);
    public const uint SWP_SHOWWINDOW = 0x0040;

    [DllImport("user32.dll", SetLastError = true)]
    [return: MarshalAs(UnmanagedType.Bool)]
    public static extern bool SetWindowPos(IntPtr hWnd, IntPtr hWndInsertAfter, int X, int Y, int cx, int cy, uint uFlags);

    [DllImport("user32.dll")]
    [return: MarshalAs(UnmanagedType.Bool)]
    public static extern bool SetForegroundWindow(IntPtr hWnd);

    // ---- dark title bar ----
    public const int DWMWA_USE_IMMERSIVE_DARK_MODE = 20;
    public const int DWMWA_WINDOW_CORNER_PREFERENCE = 33;   // Windows 11; ignored on Windows 10
    public const int DWMWCP_ROUND = 2, DWMWCP_ROUNDSMALL = 3;

    [DllImport("dwmapi.dll")]
    public static extern int DwmSetWindowAttribute(IntPtr hwnd, int attr, ref int value, int size);
}