Isuses with timers + fast intervals

[bankai123]

Hi, I have a question about the Windows Forms Timer class. Suppose that the timer's interval is set at say 10ms and the work it does in each tick takes longer than 10ms to complete. Is each tick executed on a separate thread? If not, then what happens?

[kselman]

Im guessing the next Tick will be delayed. Good question.. You can experiment with two timers and two counters .. the one with the lower count would be the delayed function.

[Stathread]

no, executes again.

[bankai123]

So the tick executes again if it cannot complete it's work before the next tick is called?

[Martin 0]

Hello, Here I found a very interesting post at this forum about this question. http://www.codeproject.com/script/comments/forums.asp?msg=1643202&forumid=1649&XtraIDs=1649&searchkw=Timer.Tick&sd=9+Jan+2006&ed=7+Nov+2006&stype=1#xx1643202xx[^] Hope this helps you. All the best, Martin

[Coding C]

Hi, the timer event occurs after 10ms even if the first execution of event is yet to complete. what u can do to cope this prob is set the timer enabled=false once its event execution starts so event doesnt fire again even if 10ms is over. and when ur code execution is complete u can set enabled=true again. Something like this timer1_Tick() { timer1.enabled=false //do ur work here timer1.enabled=true } hope this works... Nitin...

[S Senthil Kumar]

bankai123 wrote:

Is each tick executed on a separate thread?

No, all ticks on a System.Windows.Forms.Timer run on the UI thread.

bankai123 wrote:

If not, then what happens?

Every timer tick runs as a result of a WM_TIMER message being processed by the message dispatcher. Windows doesn't post the WM_TIMER message to the message queue if they are any pending messages (including WM_TIMER) in the queue. This prevents the scenario you described (a tick firing even when processing for the previous tick is executing). Note that any message in the message queue will prevent the timer from ticking, so for example, if your UI button click handler takes one second to execute, then you won't get timer ticks for that one second. Also, note that no queuing of ticks happens, so you won't get ticks one after the other corresponding to the period when no timer ticks executed. In the above example, you won't get timer ticks corresponding to that one second period even after your button handler has completed execution. Hope this helps.

Regards Senthil [MVP - Visual C#] _____________________________ My Blog | My Articles | My Flickr | WinMacro

[Martin 0]

Hello again,

bankai123 wrote:

Is each tick executed on a separate thread?

No, but I think "System.Timers.Timer" does. There you have to use the "Elapsed" event. All the best, Martin

[bankai123]

Thanks for all the info, it has been helpful. I've decided to use the System.Timers.Timer class instead, with a interval of 20ms for processing some information. I tried disabling the timer once i entered the event handler and re-enabling it after all the work is done. ( to avoid re-entrance) However it didn't seem to work for me, It seemed to call the first elapsed event once, and doesn't seem to occur again. I gotta debug more, not really sure where the problem lies at the moment.