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Re: Sensor API feedback: watch function

Date: Fri, 09 Mar 2012 17:32:38 +0100
To: Jonas Sicking <jonas@sicking.cc>, "public-device-apis@w3.org" <public-device-apis@w3.org>
Message-id: <CB7FEE7C.257F7%jmcf@tid.es>
Responses inline

El 02/03/12 13:19, "Jonas Sicking" <jonas@sicking.cc> escribió:

>Hi All,
>I have a couple of questions regarding the watch function.
>First off, what's interaction between the 'interval' and 'threshold'
>parameters? I.e. what happens if you set both parameters? Is the
>intent that the onsensordata function should fire whenever the
>threshold is cross, but at least every x milliseconds? Or is the
>intent that the interval specifies how often the implementation is
>supposed to sample the sensor, but only fire the onsensordata event if
>the threshold has been crossed? Or are you simply not allowed to
>specify threshold and interval at the same time?
>I think my preference would be that if both parameters are specified,
>the threshold argument is the one that controls when onsensordata is
>fired, and the interval is a hint which tells the implementation how
>often it should check the sensor.

Make sense.

>Also, the spec says that the threshold only applies on sensors which
>have a numeric reading which makes sense (and is also a good place to
>start). But it doesn't define what happens if the page specifies a
>threshold for a sensor which is not numeric. Should the argument be
>ignored? Should we throw an exception?
>My preference would be for an exception.

>Also, the spec currently says that we should fire an event whenever a
>sensor reading goes below the threshold. Shouldn't we also fire it
>when the reading goes back up above the threshold? I.e. if a page
>specifies .watch({threshold: 10}) on a temperature sensor, I would
>expect to get an event both when the temperature changes from above 10
>deg C to below 10 deg C, as well as when it changes from below 10 deg
>C to above 10 deg C.

Yes. Otherwise We would need to complicate the API with Ranges and the like

>/ Jonas

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Received on Friday, 9 March 2012 16:33:11 UTC

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