How to delay 3 seconds and do NOT to hang Current Metro Windows?

Question

My Scenario is like that:

There is a interface in my WinRT Components ( using C++ ), I do need to query some status each 20ms, and after 3s, Stoping query and return result to Metro windows by callback function, but this operation DO NOT hang Metro windows( using C#).

so How can I implement this function?

Answer 1

Seems like it would be easier to:

1. Have a C++ component that only does the status query (hardware, I assume?)

2. Use CreatePeriodicTimer in C# and have your C# WorkItem call the C++ component periodically

That way you keep all the timer manipulation and notification stuff in C#.

Answer 2

Hello,

I found two way to achieve this,

 1. You can use Background task, using the TimeTrigger as trigger. Please follow these document.
 http://msdn.microsoft.com/en-us/library/windows/apps/xaml/hh977055.aspx
 http://msdn.microsoft.com/en-us/library/windows/apps/xaml/windows.applicationmodel.background.timetrigger.aspx
 
 2. You can use a loop, in every loop you can sleep 20ms and run this loop 150 times.
 
Best regards,
Jesse

---

Jesse Jiang [MSFT]
MSDN Community Support | Feedback to us

Answer 3

Hi Henador:

I don't think your idea is suitable for my condition, I need to encapsulate this (including timer and query) to WinRT components and privode to metro.

Hi Jesse:

I think the second way is suitable for my condition; but, problem is how to implement a loop in C++ WinRT? As I known, there must be thread. and the point is here is a timer in loop; I found the timer is big different with Win32 API; Oppss, I'm not good at this.

Is that a correct way to create timer?

"DelayTimer =

Windows::System::Threading::

ThreadPoolTimer::CreateTimer

(refnewWindows::System::Threading::TimerElapsedHandler(timerDelegate), delay);"

Answer 4

Note that I'm a newbie to WinRT/Metro so I don't know if this will work properly! If you're going to stay in C++ for the whole thing, I would implement the C++ part of Jesse's #2 suggestion like this:

static HANDLE hEventAbort;

unsigned int _stdcall QueryThreadProc( void *args )
 {
  for( int i = 0; i < 150; i++ )
   {
    DWORD dwrc;

    dwrc = WaitForSingleObjectEx( hEventAbort, 20, FALSE );
    if( dwrc == WAIT_OBJECT_0 )
     {
      return 1; // aborted
     }

    // do query here, notify c# and return if TRUE

   }

  // notify c# of timeout
  return 2;
 }


void StartQueryLoop()
 {
  hEventAbort = CreateEventEx( 0, 0, 0, 0 );
  _beginthreadex( 0, 0, QueryThreadProc, 0, 0, 0 );
 }


void AbortQueryLoop()
 {
  SetEvent( hEventAbort );
 } 

I have no idea how to notify a C# app from a thread in a C++ component.

Answer 5

Hi Henador:

In Win8 Metro WinRT Components, it don't allow that syntax like that: _beginthreadex, WatiForSingleObject, e.g.;

and I finally got the right way to implement those requirement:

////////////////////////////////////////

static void OnTimerChanged(ThreadPoolTimer^ DelayTimer);
static TimerElapsedHandler^ g_hTimerElapsed = ref new TimerElapsedHandler(OnTimerChanged);
static ThreadPoolTimer^ g_DelayTimer = nullptr;

static void OnTimerChanged(ThreadPoolTimer^ DelayTimer)
{
 try
 {
  //Do your jobs
 }
 catch( ... )
 {
 }
}

static void ThreadProc(  )
{
 try
 {
  
  TimeSpan delay;
  delay.Duration = TIME_REVOLUTION * 10000;//TIME_REVOLUTION is your delay times, unit is second.
  g_lpfCallback = lpCallback;
  g_lpfProtocol = lpProtocol;

  if (g_DelayTimer == nullptr )
  {  
   g_DelayTimer = ThreadPoolTimer::CreatePeriodicTimer( g_hTimerElapsed, delay);
  }
 }
 catch( ... )
 {
 }
}

static concurrency::task<void> StartThreadProcTask(  )
{
 auto workItemHandler = ref new WorkItemHandler([=](IAsyncAction^)
    {
        try
        {
   ThreadProc( lpProtocol, lpCallback );
  }
        catch (...) { }

    }, CallbackContext::Same);//I don't know what means about "Same" and "Any";

    ThreadPool::RunAsync(workItemHandler, WorkItemPriority::Normal, WorkItemOptions::TimeSliced);

 return concurrency::task<void>( );
}