Question

MFC: Thread Trouble to update GUI?

Asked by: SumitKalsait

Hello Everybody, My application captures Ethernet packet and shows all packet data in the Listview control with report view. Right now i am doing it over the main thread of my dialog box. When I handle the GUI (Move or button click or combobox item selection) my packet capture loop which is in do while loop is disturbed (It getting stop).
I have structure which looks like
do
{
   if( Catch _the_Packet() == true)
     {
        Show_Packet_Listview();
      }
  doev ents();
}while(Stop_cpature!= true);

Now I want to make this packet capture mechanism on the other thread and GUI updates or packet display on main thread.

Which threads should i use.? worker thread to capture packet or GUI thread ? How shpuld i handle the message to update packet listview when packet is captured,

Many Many Thanks in Adavance.
 

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Asked On
2009-03-11 at 03:02:39ID24219108
Tags

MFC

,

VC++

,

Threading

Topics

Windows MFC Programming

,

Microsoft Visual C++.Net

,

Microsoft Visual C++

Participating Experts
3
Points
125
Comments
7

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Answers

 

by: ZoppoPosted on 2009-03-11 at 03:10:23ID: 23855285

Hi SumitKalsait,

I would suggest to implement a worker thread to capture the packets, in this thread you can use SendMessage or SendThreadMessage with a self defined message ID to pass the data to be displayed to the main window or thread.

ZOPPO

 

by: alb66Posted on 2009-03-11 at 03:19:07ID: 23855334

 

by: SumitKalsaitPosted on 2009-03-11 at 03:26:00ID: 23855375

Hello Zoppo and alb66

Thanks alot

Which Messages I need to handle if I make this capture on worker threads and how should I synchrinise it with the My main GUI thread. ?
for example
pWnd->PostMessage(WM_SETTEXT, 0, (LPARAM)psztext);

Waiting for your answer. thanks

 

by: alb66Posted on 2009-03-11 at 03:29:12ID: 23855401

You must define your private messages:

#define YOUR_MSG1 WM_APP+1
#define YOUR_MSG1 WM_APP+2

pWnd->PostMessage(YOUR_MSG1 , 0, (LPARAM)psztext);

 

by: SumitKalsaitPosted on 2009-03-11 at 05:14:16ID: 23856134

Do I need synchronisation object? I am sending packets every 1 ms and receiving at next cycle. and show this packets in the Packet listview.
 I need thread synchronization object, such as an event, ? to have the worker thread signal to the main thread when it was done. with recieved packet ?

 

by: alb66Posted on 2009-03-11 at 05:58:28ID: 23856548

 

by: DanRollinsPosted on 2009-03-11 at 15:40:12ID: 23863103

Another option that I've found simplifies things:

In the worker thread, read the packets and save them into a simple queue structure -- don't display anything.  

Then in the GUI thread, create a window timer.  At each timer tick, check to see which items have not been displayed and display them.  The timer interval can be surprising large without causing the user to see jerking, etc.  For instance, even 250ms (4 times a seconds) looks pretty smooth to the human eye.

20120131-EE-VQP-002

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