>>>
>>>>Interrupt handlers fire at indeterminate times.
>>>
>>>Not strictly true. The interrupt may fire at any time, when or whether your handler processes it is up to you (i.e. VFP). Your point about well-behaved interrupt handlers is valid but the question here is simply whether Peter can safely rely on _TALLY immediately following a select. AFAIK a timer message just gets stuck in the windows message queue along with everything else (albeit possibly with a higher priority). The documentation for Autoyield=.F. clearly states :
>>>
>>>"The instance of Visual FoxPro does not process pending Windows events between each line of user program code.
>>>All pending Windows events are placed in a queue, and the events in the queue are processed when DOEVENTS is issued or a wait state occurs. A wait state occurs when Visual FoxPro is waiting for input from the user. The WAIT command does not create a wait state."
>>>
>>>and my test seems to bear this out. Like you I'm prepared to err on the side of caution but unless someone can demonstrate that it *CAN BE* rather than just *MAY BE* a problem I'll categorise it as 'Fear and Superstition'
>>>
>>>Regards,
>>>Viv
>>
>>Viv,
>>
>>I think that a timer may fire between each line of code, provided autoyield is TRUE. (Maybe a timer is set up in such a way that it uses a windows event)
>>
>>I've had the case where a grid refesh used some dynamic* and the dynamic* used functions to return eg the forecolour.
>>
>>The timer interrupted those functions
>
>Greg, I'm quite interested in a piece of code that demonstrates this...

I cannot. Not with a 100%. You can have a go at it if you want, nothing fancy

I remember it very well (vfp6sp5). Sometimes, in the timer event, this was referring to the grid and gave errors on unkown properties

I have put code in to skip a cycle if that was the case (by testing this.Class = 'thetimerclass')

Well, as I said, I cannot reproduce it. It happened very rarely and then on some computers only

So, you'll have to take my word for it or live with the risk