winapi - Prevent windows from going into sleep when my program is running?

Question

I have to stop windows from going into sleep when my program is running.

And I don't only want to prevent the sleep-timer, I also want to cancel the sleep-event if I press the sleep-button or in any other way actively tell the computer to sleep. Therefore SetThreadExecutionState is not enough.

Or...I don't actually have to prevent the sleep completely, only delay it 5-10sec to allow my program to finish a task.

(I know that this is bad program behavior but it's only for personal use.)

Answer 1

After considering vim's answer

"Using PowerCreateRequest, PowerSetRequest, and PowerClearRequest functions is the preferred method."

with the linked AvailabilityRequests.docx on msdn which is exhausting to get into it (too much to read), I have searched the web for a concrete example in c# that is based on the PowerCreateRequest and found http://go4answers.webhost4life.com/Example/problem-monitor-wakeup-service-windows7-12092.aspx [EDIT 2016 - isn't available anymore]

Copied and adapted it to my needs (PInvoke of CloseHandle copied from msdn):

using System.Runtime.InteropServices;

    #region prevent screensaver, display dimming and automatically sleeping
    POWER_REQUEST_CONTEXT _PowerRequestContext;
    IntPtr _PowerRequest; //HANDLE

    // Availability Request Functions
    [DllImport("kernel32.dll")]
    static extern IntPtr PowerCreateRequest(ref POWER_REQUEST_CONTEXT Context);

    [DllImport("kernel32.dll")]
    static extern bool PowerSetRequest(IntPtr PowerRequestHandle, PowerRequestType RequestType);

    [DllImport("kernel32.dll")]
    static extern bool PowerClearRequest(IntPtr PowerRequestHandle, PowerRequestType RequestType);

    [DllImport("kernel32.dll", CharSet = CharSet.Auto, SetLastError = true, ExactSpelling = true)]
    internal static extern int CloseHandle(IntPtr hObject);

    // Availablity Request Enumerations and Constants
    enum PowerRequestType
    {
        PowerRequestDisplayRequired = 0,
        PowerRequestSystemRequired,
        PowerRequestAwayModeRequired,
        PowerRequestMaximum
    }

    const int POWER_REQUEST_CONTEXT_VERSION = 0;
    const int POWER_REQUEST_CONTEXT_SIMPLE_STRING = 0x1;
    const int POWER_REQUEST_CONTEXT_DETAILED_STRING = 0x2;

    // Availablity Request Structures
    // Note:  Windows defines the POWER_REQUEST_CONTEXT structure with an
    // internal union of SimpleReasonString and Detailed information.
    // To avoid runtime interop issues, this version of 
    // POWER_REQUEST_CONTEXT only supports SimpleReasonString.  
    // To use the detailed information,
    // define the PowerCreateRequest function with the first 
    // parameter of type POWER_REQUEST_CONTEXT_DETAILED.
    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
    public struct POWER_REQUEST_CONTEXT
    {
        public UInt32 Version;
        public UInt32 Flags;
        [MarshalAs(UnmanagedType.LPWStr)]
        public string
            SimpleReasonString;
    }

    [StructLayout(LayoutKind.Sequential)]
    public struct PowerRequestContextDetailedInformation
    {
        public IntPtr LocalizedReasonModule;
        public UInt32 LocalizedReasonId;
        public UInt32 ReasonStringCount;
        [MarshalAs(UnmanagedType.LPWStr)]
        public string[] ReasonStrings;
    }

    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
    public struct POWER_REQUEST_CONTEXT_DETAILED
    {
        public UInt32 Version;
        public UInt32 Flags;
        public PowerRequestContextDetailedInformation DetailedInformation;
    }
    #endregion



    /// <summary>
    /// Prevent screensaver, display dimming and power saving. This function wraps PInvokes on Win32 API. 
    /// </summary>
    /// <param name="enableConstantDisplayAndPower">True to get a constant display and power - False to clear the settings</param>
    private void EnableConstantDisplayAndPower(bool enableConstantDisplayAndPower)
    {
        if (enableConstantDisplayAndPower)
        {
            // Set up the diagnostic string
            _PowerRequestContext.Version = POWER_REQUEST_CONTEXT_VERSION;
            _PowerRequestContext.Flags = POWER_REQUEST_CONTEXT_SIMPLE_STRING;
            _PowerRequestContext.SimpleReasonString = "Continuous measurement"; // your reason for changing the power settings;

            // Create the request, get a handle
            _PowerRequest = PowerCreateRequest(ref _PowerRequestContext);

            // Set the request
            PowerSetRequest(_PowerRequest, PowerRequestType.PowerRequestSystemRequired);
            PowerSetRequest(_PowerRequest, PowerRequestType.PowerRequestDisplayRequired);
        }
        else
        {
            // Clear the request
            PowerClearRequest(_PowerRequest, PowerRequestType.PowerRequestSystemRequired);
            PowerClearRequest(_PowerRequest, PowerRequestType.PowerRequestDisplayRequired);

            CloseHandle(_PowerRequest);
        }
    }