ClickableTransparentOverlay/ClickableTransparentOverlay/WinApi.cs

namespace ClickableTransparentOverlay
{
    using System;
    using System.Runtime.InteropServices;

    public static class WinApi
    {
        private const int GWL_EXSTYLE = -20;
        private const int WS_EX_LAYERED = 0x80000;
        private const int WS_EX_TRANSPARENT = 0x20;
        private const int LWA_ALPHA = 0x02;
        private const int LWA_COLORKEY = 0x01;

        private const int SW_HIDE = 0x00;
        private const int SW_SHOW = 0x05;

        public static void EnableTransparent(IntPtr handle, System.Drawing.Rectangle size)
        {
            int windowLong = GetWindowLong(handle, GWL_EXSTYLE) | WS_EX_LAYERED | WS_EX_TRANSPARENT;
            SetWindowLong(handle, GWL_EXSTYLE, new IntPtr(windowLong));
            //SetLayeredWindowAttributes(handle, 0, 255, LWA_ALPHA /*| LWA_COLORKEY*/ );
            Margins margins = Margins.FromRectangle(size);
            DwmExtendFrameIntoClientArea(handle, ref margins);
        }

        #region Structures

        [StructLayout(LayoutKind.Sequential)]
        private struct Margins
        {
            private int left, right, top, bottom;

            public static Margins FromRectangle(System.Drawing.Rectangle rectangle)
            {
                var margins = new Margins
                {
                    left = rectangle.Left,
                    right = rectangle.Right,
                    top = rectangle.Top,
                    bottom = rectangle.Bottom
                };
                return margins;
            }
        }

        [StructLayout(LayoutKind.Sequential)]
        private struct Rect
        {
            private readonly int left, top, right, bottom;

            public System.Drawing.Rectangle ToRectangle(System.Drawing.Point point)
            {
                return new System.Drawing.Rectangle(point.X, point.Y, right - left, bottom - top);
            }
        }

        #endregion Structures

        public static void HideConsoleWindow()
        {
            var handle = GetConsoleWindow();
            ShowWindow(handle, SW_HIDE);
        }

        public static void ShowConsoleWindow()
        {
            var handle = GetConsoleWindow();
            ShowWindow(handle, SW_SHOW);
        }

        [DllImport("dwmapi.dll")]
        private static extern IntPtr DwmExtendFrameIntoClientArea(IntPtr hWnd, ref Margins pMarInset);

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

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

        [DllImport("user32.dll", SetLastError = true)]
        private static extern bool SetLayeredWindowAttributes(IntPtr hWnd, uint crKey, byte bAlpha, uint dwFlags);

        [DllImport("kernel32.dll")]
        static extern IntPtr GetConsoleWindow();

        [DllImport("user32.dll")]
        static extern bool ShowWindow(IntPtr hWnd, int nCmdShow);
    }
}