Looking for a "wait until x or timeout" design pattern..

[stephen barncard]

you should check out Dar Scott's primers on Message Mechanics.

Visually and technically informative.

http://pages.swcp.com/dsc/revstacks.html

On 29 January 2012 11:38, Ken Corey <ken at kencorey.com> wrote:

> Here's the basic idea of the code I needed.
>
> the touchMove event arrives in no particular order, and in no particular
> time.
>
> If you absolutely have to have a timeout, you can't just test for a
> timestamp on the next run of touchMove, because there might not be another
> touchMove.
>
> I'm not quite clear on what the "wait 50 milliseconds with messages"
> command does.  Is that a more succinct way of putting it?
>
> -Ken
>
>
> -------------------8<---------**----------------------
> -- Semaphore handling for touch movements
> --
> -- This code is meant to be used to group random events that
> -- happen in a timeframe, group them together, and take action
> -- on those events as a whole.
> --
> -- User input is pseudo-random, and we therefore cannot count on
> -- events coming in a particular order, or even coming at all.
> --
> -- I use code similar to this to group several distinct user inputs and
> -- deal with several at a time.  If no more events come within the
> -- delay period, we fire the handler.
> --
> -- This isn't perfect, as there doesn't seem to be a way to cancel a
> -- pending send...so we guard against the send happening in
> -- performAction.
> --
> -- What this means is that the delay (50 milliseconds below) must
> -- be chosen carefully so that there's only one group of data waiting
> -- to be processed.
> --
> -- If the touchMove event happens but is delayed, and another
> -- touchMove event with immediate execution happens within the
> -- timeout period, the second touchMove event clears the sSemaphore,
> -- so then the delayed performAction from the first touchMove event
> -- is ignored.
> --
>
> local sDetails,sSemaphore
>
> on touchMove pID,pX,pY
>   -- check to see if we've dealt with pID before
>   if pID is in the keys of sSemaphore then
>      -- have seen it before so take action immediately
>      put (pX&comma&pY) into sSemaphore[pID]
>      send "performAction "&pID&","&pX&","&pY
>   else
>      -- haven't seen it, only do it after a delay
>      put (pX&comma&pY) into sSemaphore[pID]
>      send "performAction "&pID&","&pX&","&pY to me in 50 milliseconds
>   end if
> end touchMove
>
> on performAction
>   -- check to see if it's already been handled.
>   if the number of lines in the keys of sSemaphore > 0 then
>      -- nope, let's get busy
>
>      -- code to deal with the data
>
>      delete variable sSemaphore
>   end if
> end performAction
>
>
>
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-- 



Stephen Barncard
San Francisco Ca. USA

more about sqb  <http://www.google.com/profiles/sbarncar>