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https://issues.apache.org/jira/browse/CB-55?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13158873#comment-13158873
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Shazron Abdullah commented on CB-55:
------------------------------------
by: https://github.com/all4ip
Yes, I use the merged version. The major change is the line "Retrieve location
immediately and schedule next retrieval afterwards".
But that's not what I ment.
I was reading now much more of the documentation
(http://dev.w3.org/geo/api/spec-source.html) and was close to admit that I am
wrong, but now again, I don't think so.
Here is my interpretation how the w3c specification is ment:
getCurrentPosition() has its timeout which will be triggered only if no
position is available until then and will return a position earlier otherwise.
watchPosition() will continuously retrieve positions and call the success
callback on a not configurable high frequency while "new position differs
significantly from the previous position". Only if no position is available for
as many seconds as defined by timeout, then the timout error should occur.
So the params.timeout should not be used in "setInterval(intervalFunction,
params.timeout)". There should be used a value like 100 or 500 or 1000 ms.
The w3c doc continues:
"In step 5.2.2 of the watch process, the successCallback is only invoked when a
new position is obtained and this position differs signifficantly from the
previously reported position. The definition of what consitutes a significant
difference is left to the implementation. Furthermore, in steps 5.2.2 and
5.2.3, implementations may impose limitations on the frequency of callbacks so
as to avoid inadvertently consuming a disproportionate amount of resources."
So I would for simplicy reasons return all values and omit calculation of
position differences, as it is done now in the currenty implementation.
But the interval frequency should NOT be set by the params.timeout, it has to
be a static implementation.
When I was close to admit I am wrong I thought, I have to use params.timeout
with 1000 and would be fine with it, because I want updates every second. But I
also want to use a timeout of 30000, to allow the app to start up GPS and
acquire the first position and so on, when the app starts the first time and
allow up to 30 seconds of not receiving a position if the app travels i.e.
through a tunnel. This should be possible with the w3c specification, but is
not with the current PhoneGap implementation. So I still think the timout
options is used at a wrong place.
The conclusion:
1. setInterval(intervalFunction, params.timeout) should be changed to
setInterval(intervalFunction, 500)
2. a filter should be implemented to return only positions, which "position
differs signifficantly from the previously reported position" (this may be done
later)
> Geolocation.prototype.watchPosition uses timeout option in wrong way
> --------------------------------------------------------------------
>
> Key: CB-55
> URL: https://issues.apache.org/jira/browse/CB-55
> Project: Apache Callback
> Issue Type: Bug
> Components: iOS
> Reporter: Shazron Abdullah
>
> reported at: https://github.com/phonegap/phonegap-iphone/issues/305
> by: https://github.com/all4ip
> I have following scenario:
> I want aprox. every second a position update. I do not want cached positions.
> I am willing to wait up to 30 seconds for the first valid position.
> So my params would be:
> var options = { timeout: 30000, maximumAge: 0, enableHighAccuracy: true };
> This is identical to w3c definition.
> But the timout value is also used for the internal endless loop of
> watchPosition. So I can either have updates every second and can wait up to 1
> second for valid position or wait up to 30 seconds for valid position and get
> updates only every 30 seconds, too!
> The timout option should be used like the doc says:
> "The maximum length of time (msec) that is allowed to pass from the call to
> geolocation.getCurrentPosition or geolocation.watchPosition until the
> corresponding geolocationSuccess callback is invoked."
> This happens correctly, when the params are passed to getCurrentPosition().
> But the continuous update in watchPosition uses the same value for the timer,
> too:
> setInterval(intervalFunction, params.timeout);
> The interval should be a static value i.e. 1000 ms or 500 ms or a variable
> frequency.
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