Re: WM_TIMER remaining/elapsed time...

From:
"Tom Serface" <tom@camaswood.com>
Newsgroups:
microsoft.public.vc.mfc
Date:
Thu, 29 Apr 2010 09:29:15 -0500
Message-ID:
<eUEJXh65KHA.348@TK2MSFTNGP02.phx.gbl>
"Simon" <bad@example.com> wrote in message
news:#n8kUL55KHA.5476@TK2MSFTNGP06.phx.gbl...

Yes, I am fairly sure I need it.
We have some use cases to 'pause', (or delay), a timer.
Here is a common example.

We have a server application, when it starts, it checks online for new
transactions every 10 minutes.


You could do all of this in the same timer just based on other
flags/sub-timers that you set while in here. What you really need to do is
make the firing of the timer be the shortest resolution you might need.
Having it fire the timer then just returning since enough time has elapsed
is not an expensive operation.

During those 10 minutes the user can start a time consuming process,
(printing of reports, connecting to another app, doing a backup), during
the process we do not want to check for transactions.


I would just set a busy flag in these cases which would preclude doing the
check while something else is going on.

What I could do is:

OnTimer()
{
 if( busy_doing_something_important )
 {
   // check again in 10 seconds
 }
 else
 {
   check_for_transactions()
 }
}

Yeah, like that, only you may want to have it check more than every 10
minutes.

Or I could kill the timer and restart it again, but if the user print a
new report every 9:59 minutes then there will be no checks for a very long
time.


The problem with killing the timer is you'd need a way to restart it. You
could do this when the report finishes printing, or some other operation,
but that may take longer than you want.

On the other hand, if I check for transactions every time we complete a
lengthy transaction then we might end-up checking too often, (during month
end for example we print hundreds of reports).


Unless the check takes a really long time I don't think this will be an
issue.

So on return of a lengthy operation I could check if the timer would have
fired, and in that case check for transactions.


That would work so long as you're only doing one report at a time, or you
could, as you said, stop the timer while a report is printing then restart
it when the report completes or is canceled (assuming there is only one
running).

Tom
 

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