AudioKeepAwake.cs

using System;
using System.Runtime.InteropServices;
using System.Threading;
using System.Windows.Forms;
using System.Drawing;

namespace AudioKeepAwake
{
    class Program
    {
        // Windows API flags to prevent sleep
        [FlagsAttribute]
        public enum EXECUTION_STATE : uint
        {
            ES_CONTINUOUS = 0x80000000,
            ES_SYSTEM_REQUIRED = 0x00000001,
            ES_DISPLAY_REQUIRED = 0x00000002
        }

        [DllImport("kernel32.dll", CharSet = CharSet.Auto, SetLastError = true)]
        static extern EXECUTION_STATE SetThreadExecutionState(EXECUTION_STATE esFlags);

        static NotifyIcon trayIcon;
        static bool wasPlaying = false;

        static Icon activeIcon;
        static Icon inactiveIcon;

        [STAThread]
        static void Main(string[] args)
        {
            // Use a mutex to prevent multiple instances from running concurrently
            bool createdNew;
            using (Mutex mutex = new Mutex(false, "Global\\AudioKeepAwakeMutex", out createdNew))
            {
                if (!createdNew)
                {
                    return; // Another instance is already running
                }

                Application.EnableVisualStyles();
                Application.SetCompatibleTextRenderingDefault(false);

                // Pre-generate icon states
                activeIcon = CreateZzzIcon(Color.LimeGreen, "Zzz");
                inactiveIcon = CreateZzzIcon(Color.Orange, "Zzz");

                // Setup Tray Icon
                trayIcon = new NotifyIcon();
                trayIcon.Icon = inactiveIcon; 
                trayIcon.Text = "AudioKeepAwake: Allowing Sleep";
                trayIcon.Visible = true;

                // Setup Context Menu for right click -> Exit
                ContextMenu trayMenu = new ContextMenu();
                trayMenu.MenuItems.Add("Exit", OnExit);
                trayIcon.ContextMenu = trayMenu;

                // Setup a timer to check audio
                System.Windows.Forms.Timer checkTimer = new System.Windows.Forms.Timer();
                checkTimer.Interval = 60000; // 60 seconds
                checkTimer.Tick += new EventHandler(CheckAudioTick);
                checkTimer.Start();
                
                // Check right away
                CheckAudioTick(null, null);

                // Start message loop so icon appears
                Application.Run();
            }
        }

        static void CheckAudioTick(object sender, EventArgs e)
        {
            bool isPlaying = IsAudioPlaying();
            
            if (isPlaying && !wasPlaying)
            {
                // Prevent sleep and display turn-off
                SetThreadExecutionState(EXECUTION_STATE.ES_CONTINUOUS | EXECUTION_STATE.ES_SYSTEM_REQUIRED | EXECUTION_STATE.ES_DISPLAY_REQUIRED);
                wasPlaying = true;
                trayIcon.Icon = activeIcon;
                trayIcon.Text = "AudioKeepAwake: Preventing Sleep";
            }
            else if (!isPlaying && wasPlaying)
            {
                // Allow sleep
                SetThreadExecutionState(EXECUTION_STATE.ES_CONTINUOUS);
                wasPlaying = false;
                trayIcon.Icon = inactiveIcon;
                trayIcon.Text = "AudioKeepAwake: Allowing Sleep";
            }
        }
        
        static void OnExit(object sender, EventArgs e)
        {
            // Allow sleep before exiting, just in case
            SetThreadExecutionState(EXECUTION_STATE.ES_CONTINUOUS);
            trayIcon.Visible = false;
            Application.Exit();
        }

        static Icon CreateZzzIcon(Color mainColor, string text)
        {
            Bitmap bmp = new Bitmap(16, 16);
            using (Graphics g = Graphics.FromImage(bmp))
            {
                g.TextRenderingHint = System.Drawing.Text.TextRenderingHint.SingleBitPerPixelGridFit;
                g.Clear(Color.Transparent);
                
                using (Brush brush = new SolidBrush(mainColor))
                {
                    // Draw text in a small font fitting 16x16
                    using (Font font = new Font("Tahoma", 7, FontStyle.Bold))
                    {
                        SizeF textSize = g.MeasureString(text, font);
                        float x = (16 - textSize.Width) / 2;
                        float y = (16 - textSize.Height) / 2;
                        g.DrawString(text, font, brush, x, y);
                    }
                }
            }
            return Icon.FromHandle(bmp.GetHicon());
        }

        static bool IsAudioPlaying()
        {
            try
            {
                // Instantiate MMDeviceEnumerator
                Type deviceEnumeratorType = Type.GetTypeFromCLSID(new Guid("BCDE0395-E52F-467C-8E3D-C4579291692E"));
                if (deviceEnumeratorType == null) return false;

                IMMDeviceEnumerator enumerator = (IMMDeviceEnumerator)Activator.CreateInstance(deviceEnumeratorType);
                
                // Get the default audio endpoint for playing sounds (eRender = 0, eConsole = 0)
                IMMDevice device;
                enumerator.GetDefaultAudioEndpoint(0, 0, out device);

                if (device != null)
                {
                    // Activate AudioMeterInformation interface
                    Guid IID_IAudioMeterInformation = new Guid("C02216F6-8C67-4B5B-9D00-D008E73E0064");
                    object meterObject;
                    device.Activate(ref IID_IAudioMeterInformation, 1, IntPtr.Zero, out meterObject);
                    
                    IAudioMeterInformation meter = (IAudioMeterInformation)meterObject;
                    float peakValue;
                    meter.GetPeakValue(out peakValue);

                    // Clean up COM objects
                    Marshal.ReleaseComObject(meter);
                    Marshal.ReleaseComObject(device);
                    Marshal.ReleaseComObject(enumerator);

                    // 0.0001f avoids tiny background noise triggering it
                    return peakValue > 0.0001f;
                }
            }
            catch
            {
                // In case of exceptions (e.g. no audio devices), assume not playing
            }
            
            return false;
        }
    }

    // -- Minimum COM Interop definitions --

    [ComImport]
    [Guid("A95664D2-9614-4F35-A746-DE8DB63617E6")]
    [InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
    interface IMMDeviceEnumerator
    {
        // Pad methods to match vtable
        [PreserveSig] int EnumAudioEndpoints(int dataFlow, int dwStateMask, out IntPtr ppDevices);
        [PreserveSig] int GetDefaultAudioEndpoint(int dataFlow, int role, out IMMDevice ppEndpoint);
    }

    [ComImport]
    [Guid("D666063F-1587-4E43-81F1-B948E807363F")]
    [InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
    interface IMMDevice
    {
        [PreserveSig] int Activate(ref Guid iid, int dwClsCtx, IntPtr pActivationParams, [MarshalAs(UnmanagedType.IUnknown)] out object ppInterface);
    }

    [ComImport]
    [Guid("C02216F6-8C67-4B5B-9D00-D008E73E0064")]
    [InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
    interface IAudioMeterInformation
    {
        [PreserveSig] int GetPeakValue(out float pfPeak);
    }
}