[Development] QSystemAlignedTimer to QtCore

[lorn.potter at nokia.com]

On 21/11/2011, at 9:51 PM, ext shane.kearns at accenture.com wrote:

> It should be used to extend the QTimer API.
> Where the system doesn't support this kind of timer, then the in process solution as in Thiago's blog should be used.
> 
> Should there be a preferred interval?
> For some use cases, the timer is allowed to be late but not early (e.g. supervisory timeouts) in which case preferred == minimum
> Whereas for other use cases, the timer is allowed to be late or early

Preferred interval is (maximum + minimum) / 2. Where there is no max value given, then min is preferred, but timeout is not guaranteed to any one specific time with this timer.

> 
> Out of interest, which platforms support this kind of timer? (other than symbian which isn't supported by Qt5)
> 

Besides symbian, only harmattan/meego that I know of.
A working generic backend should/would need to be supplied, IMHO, otherwise this is useless.

> Finally, when this functionality is in QtCore, then the QSystemInfo API should be replaced with a shim over the QtCore implementation.
> I.E. implement a backend that uses the QTimer API and remove any OS specific backends, and mark the API as deprecated.

I disagree. That would mean QtSystemInfo would no longer work on Qt 4.


>> Now I'm thinking of move it to QtCore, and preferably merge it into
>> QTimer. If so, we probably need to add some interface to specify the
>> precision, other than simply tell the type as in [1].
>> Any thoughts?
>> 
>> 

Originally, there were two methods.
something like:

startTimer(minimum, maximum);
startTimer(preferred, timerWindow);

where preferred was most likely the average of max and min, and timerWindow was the length of time allowable to fire (max - min). I preferred the second method, as it seemed more natural to me, but was dropped as it seemed too confusing to some.


I can email you more details if needed.


>> [1] http://codereview.qt-project.org/#change,657
>> 

Personally, I would not tack it on to that change, but it's own change that depends on that one.



Lorn Potter
Senior Software Engineer, Core Enablers/QtSensors