Timer Events

Originally Posted by

This may be an elementary question but it's something I have not

Originally Posted by

in about 10 years writing code in VB 5 / 6
>
I have a timer that using the API checks if there has been a change to one
of several watched directories in the file system, if there has been a
change a rather long running process is started.
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The long running process loops through all files comparing the last

Originally Posted by

attributes on each to those in the database if there is a change the
database is updated.
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Simple so far right ?
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Just prior to the loop statement in that routine there is a DoEvents to

Originally Posted by

everything ticking along, however something interesting happens.
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I have another timer on a very short interval watching for something else

Originally Posted by

happen. This something else is unrelated to the file system, it is

Originally Posted by

the status of an out of process com component.
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This second timer is not firing while the long running process is taking
place, the do events is working because the status of the long running
process is updated in the status bar of the application and that works.
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Is there a rule that I have missed that says only one timer event can be
running at any one time ?
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Come to think of it over the years I have only ever put very short

Originally Posted by

in timers so have never faced such a problem.
>
I can think of a few ways to get around this but am wondering if you agree
with my reasoning?
>
All the best for the new year
>
Max
>

Originally Posted by

>
This second timer is not firing while the long running process is taking
place, the do events is working because the status of the long running process
is updated in the status bar of the application and that works.
>

Originally Posted by

>
"Max" <nospam@spamcatchers.comwrote in message
news:4598fc4c$0$5748$afc38c87@news.optusnet.com.au ...

Quote: Originally Posted by >> >This second timer is not firing while the long running process is taking >place, the do events is working because the status of the long running >process is updated in the status bar of the application and that works. >>

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I would bet that the second timer is firing with each DoEvents (unless you
just have the code mangled up).
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It is more likely that it is is firing, but you are not seeing the out of
process component updated as you expect.
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It should be easy to put in a visual queue that the second short timer is
indeed firing during the long loop - a debug statement, a character added
to a text box on a form, whatever works.
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You might well find that the issue is more to do with the out of process
component not getting any processing time to update itself, since your app
is so busy when it is in the long loop.
>
>

Originally Posted by

>
"Max" <nospam@spamcatchers.comwrote in message
news:4598fc4c$0$5748$afc38c87@news.optusnet.com.au ...

Quote: Originally Posted by >This may be an elementary question but it's something I have not

encountered

Quote: Originally Posted by >in about 10 years writing code in VB 5 / 6 >> >I have a timer that using the API checks if there has been a change to >one >of several watched directories in the file system, if there has been a >change a rather long running process is started. >> >The long running process loops through all files comparing the last

modified

Quote: Originally Posted by >attributes on each to those in the database if there is a change the >database is updated. >> >Simple so far right ? >> >Just prior to the loop statement in that routine there is a DoEvents to

keep

Quote: Originally Posted by >everything ticking along, however something interesting happens. >> >I have another timer on a very short interval watching for something else

to

Quote: Originally Posted by >happen. This something else is unrelated to the file system, it is

updating

Quote: Originally Posted by >the status of an out of process com component. >> >This second timer is not firing while the long running process is taking >place, the do events is working because the status of the long running >process is updated in the status bar of the application and that works. >> >Is there a rule that I have missed that says only one timer event can be >running at any one time ? >> >Come to think of it over the years I have only ever put very short

routines

Quote: Originally Posted by >in timers so have never faced such a problem. >> >I can think of a few ways to get around this but am wondering if you >agree >with my reasoning? >> >All the best for the new year >> >Max >>

>
The short answer is no - there is no 'rule' that says you can't have more
than one timer running at a time. However, you can occasionally arrange
things such that you can experience 'unexpected' behavior. <g>
>
As Timers are not hard interupts and a Timer event has to wait for its
turn
to run, just like any other event, a long running process in one timer can
definitely effect results. The usual fix is to install judicious DoEvents
in
a long running process - it sounds like you have tried that. You may just
need to do some re-arranging.
>
Without knowing more about your particular situation I wouldn't venture a
specific solution. But you can take heart that one is likely possible.
>
As a sidenote: Just in case, be aware that timers act differently when run
in debug mode (in an IDE) than when released. They also can react
strangely
with MsgBoxes/Modal dialogs. So do your testing with release versions and
monitor the behavior with logs or DebugOutputString and DebugViewers.
>
Placing Timers in a Control Array and thus having only one event (point of
entry)can often simplify the coding and make it easier to monitor the
behavior.
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At the other end of the spectrum you might consider reworking your
application to using
FindFirstChangeNotification/FindNextChangeNotification
functions with the WaitForMultipleObjects function, and eliminate one of
the
timers entirely.
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hth
-ralph
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