pinvoke.net: Edit: user32.GetLastInputInfo

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Summary: Gets the time of the last user input (in ms since the system started)
!!!!C# Signature:
 [DllImport("user32.dll")]
 static extern bool GetLastInputInfo(ref LASTINPUTINFO plii);
!!!!VB Signature:
 <DllImport("user32.dll")>
 Shared Function GetLastInputInfo(ByRef plii As LASTINPUTINFO) As Boolean
 End Function
!!!!C++ Signature:
 [DllImport("user32.dll")]
 static bool GetLastInputInfo(LASTINPUTINFO* plii);
!!!!F# Signature
   [<Struct; CLIMutable; StructLayout(LayoutKind.Sequential)>]
   type LastInputInfo = {
     size : int
     dwTime : uint32
   }

[<DllImport("user32")>]
   extern int GetLastInputInfo(LastInputInfo& lpi);

!!!!User-Defined Types:
[LASTINPUTINFO]

!!!!Notes:
Very useful to detect user-idle state of an application.
Minimum operating systems: Windows 2000

!!!!Tips & Tricks:
Compare to Environment.TickCount to get the time since the last user input.

!!!!Sample Code:
These samples do not take into account the rollover of the tick counter which will occur after ~50 days of uptime.
This function retrieves the time in seconds since last user input
        static uint GetLastInputTime()
        {
            uint idleTime = 0;
            LASTINPUTINFO lastInputInfo = new LASTINPUTINFO();
            lastInputInfo.cbSize = (uint)Marshal.SizeOf( lastInputInfo );
            lastInputInfo.dwTime = 0;

uint envTicks = (uint)Environment.TickCount;

if ( GetLastInputInfo( ref lastInputInfo ) )
            {
                uint lastInputTick = lastInputInfo.dwTime;

idleTime = envTicks - lastInputTick;
            }
            
            return (( idleTime > 0 ) ? ( idleTime / 1000 ) : 0);
        }

!!!!Sample Code vb.net: 
This function retrieves the time in seconds since last user input
 Dim idletime As Integer
 Dim lastInputInf As New LASTINPUTINFO()

Public Function GetLastInputTime() As Integer

idletime = 0
        lastInputInf.cbSize = Marshal.SizeOf(lastInputInf)
        lastInputInf.dwTime = 0

If GetLastInputInfo(lastInputInf) Then
            idletime = Environment.TickCount - lastInputInf.dwTime
        End If

If idletime > 0 Then
            Return idletime / 1000
        Else : Return 0
        End If

End Function

!!!!Sample Code C++ .net: 
This function retrieves the time in seconds since last user input
 public: static double getSystemIdleTime()
 {					
	int systemUptime = Environment::TickCount;
	int idleTicks = 0;
	LASTINPUTINFO lastInputInfo;
	lastInputInfo.cbSize = (UInt32)Marshal::SizeOf(lastInputInfo);
	lastInputInfo.dwTime = 0;
	if (GetLastInputInfo(&lastInputInfo))
	{                
		int lastInputTicks = (int)lastInputInfo.dwTime;
		idleTicks = systemUptime - lastInputTicks;
	}
	return (( idleTicks > 0 ) ? ( idleTicks / 1000 ) : idleTicks );
 }

!!!!Sample code F#
 let idleTimeSeconds() =
     let size = sizeof<LastInputInfo>
     let now = uint32 Environment.TickCount
     let mutable info = { size = size; dwTime = 0u }
     match GetLastInputInfo(&info) with
     | 0 -> 0.
     | _ -> (now - info.dwTime) / 1000.

!!!!Sample code gcc Cygwin:
Prints time in seconds since last user input.
Save to idle.c
Compile at bash command line with: gcc -Wall idle.c
Test it with: sleep 15; ./a.exe
Moving the mouse or pressing the keyboard during the test will alter the result, as expected!
 #include <w32api/windef.h>
 #include <w32api/winbase.h>
 #include <w32api/winuser.h>
 
 #include <stdio.h>
 #include <stdlib.h>
 #include <unistd.h>
 
 int main() {
 	int systemUptime = GetTickCount();	// was Environment.TickCount
 	int idleTicks = 0;
 
 	LASTINPUTINFO lastInputInfo;
 	lastInputInfo.cbSize = sizeof (lastInputInfo);
 	lastInputInfo.dwTime = 0;
 	if (GetLastInputInfo(&lastInputInfo)) {		
 		int lastInputTicks = (int)lastInputInfo.dwTime;
 		idleTicks = systemUptime - lastInputTicks;
 	}
 	printf("%d seconds\n", (idleTicks > 0)? idleTicks/1000: 0);
 	return 0;
 }
Contributed by John Refling

!!!!Alternative Managed API:
Do you know one?  Please contribute it!

Documentation: GetLastInputInfo@msdn on MSDN