inabox/inabox.wpf/OpenWindowGetter.cs

using System.Diagnostics;
using System.Runtime.InteropServices;
using System.Text;
using HWND = System.IntPtr;

namespace InABox.WPF
{
    /// <summary>Contains functionality to get all the open windows.</summary>
    public static class OpenWindowGetter
    {
        [DllImport("USER32.DLL")]
        private static extern bool EnumWindows(EnumWindowsProc enumFunc, int lParam);

        [DllImport("USER32.DLL")]
        private static extern int GetWindowText(HWND hWnd, StringBuilder lpString, int nMaxCount);

        [DllImport("USER32.DLL")]
        private static extern int GetWindowTextLength(HWND hWnd);

        [DllImport("USER32.DLL")]
        private static extern bool IsWindowVisible(HWND hWnd);

        [DllImport("USER32.DLL")]
        private static extern IntPtr GetShellWindow();

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

        [DllImport("user32")]
        private static extern uint GetWindowThreadProcessId(HWND hWnd, out int lpdwProcessId);

        /// <summary>Returns a dictionary that contains the handle and title of all the open windows.</summary>
        /// <returns>A dictionary that contains the handle and title of all the open windows.</returns>
        public static IDictionary<HWND, string> GetOpenWindows()
        {
            var shellWindow = GetShellWindow();
            var windows = new Dictionary<HWND, string>();

            EnumWindows(delegate(HWND hWnd, int lParam)
            {
                if (hWnd == shellWindow) return true;
                if (!IsWindowVisible(hWnd)) return true;

                var length = GetWindowTextLength(hWnd);
                if (length == 0) return true;

                var builder = new StringBuilder(length);
                GetWindowText(hWnd, builder, length + 1);

                windows[hWnd] = builder.ToString();
                return true;
            }, 0);

            return windows;
        }

        public static string GetActiveWindowTitle()
        {
            const int nChars = 256;
            var Buff = new StringBuilder(nChars);
            var handle = GetForegroundWindow();

            if (GetWindowText(handle, Buff, nChars) > 0) return Buff.ToString();
            return null;
        }


        public static string GetActiveWindowProcess()
        {
            var handle = GetForegroundWindow();
            GetWindowThreadProcessId(handle, out var pid);
            var p = Process.GetProcessById(pid);
            return p?.ProcessName;
        }

        private delegate bool EnumWindowsProc(HWND hWnd, int lParam);
    }
}