From: nospam@spamcatchers.com
Thanks Ralph
I will look at the re working of the code you have given me some good ideas
there and thanks for the tip on the different behaviour when running in the
IDE.
The app is one that has grown over the past 6 years and could do with a good
rethink.
Max
"Ralph" wrote in message
news:Gd2dnS7bK4GZtQTYnZ2dnUVZ_rOqnZ2d@arkansas.net...
>
> "Max" wrote in message
> news:4598fc4c$0$5748$afc38c87@news.optusnet.com.au...
>> This may be an elementary question but it's something I have not
> encountered
>> 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
>> 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
>> everything ticking along, however something interesting happens.
>>
>> I have another timer on a very short interval watching for something else
> to
>> happen. This something else is unrelated to the file system, it is
> updating
>> 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
>> 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.
>
> 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.
>
> 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.
>
> hth
> -ralph
>
>
>
>
>
>
>
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