[maemo-developers] sensing change in System Clock using Qt

[From: Faheem Pervez]

There are many D-Bus signals emitted when the time zone changes. Try
and make the effort to run dbus-monitor --system, please.

Failing that, the following pages exist:
http://maemo.org/api_refs/5.0/5.0-final/libosso/group__Time.html
http://maemo.org/api_refs/5.0/5.0-final/clockd/

Best Regards,
Faheem

On Sun, Jan 31, 2010 at 9:45 AM, ibrahim <ibrahim.ali at asgatech.com> wrote:
> David Greaves wrote:
>>
>> ibrahim wrote:
>>
>>>
>>> Remi.Denis-Courmont at nokia.com wrote:
>>>
>>>>
>>>>   Hello,
>>>>
>>>> ----- Message d'origine -----
>>>>
>>>>>
>>>>> But the problem that can face me is the case when the user changes his
>>>>> clock settings (i.e adjust phone's time to a different time). in this
>>>>> case, the timer that has been set to some fixed duration can go wrong.
>>>>>
>>>>
>>>> As a general rule, delay measurements should be done with the
>>>> monotonic clock, not the wall clock (the real-time clock). As far as I
>>>> know, Qt timers already do so internally. But of course, your own code
>>>> should never request and use the wall clock for time measurements.
>>>>
>>>>
>>>
>>> I don't think I follow you! What do you mean by monotonic clock ? If I
>>> don't depend on the system's clock to get current time, where else can I
>>> get it from ?
>>> Let me explain my problem again briefly, I want to know the current
>>> time, calculate some future durations  depending on it. Then I figure
>>> out the time left to the upcoming duration and set it as interval to a
>>> QTimer Object. But I'm afraid that user may change the system clock
>>> (adjust the clock) So that my preset time will be invalid.
>>>
>>
>> Just so you know... you're describing an implementation and asking if it
>> does
>> what you want without describing what you want.
>>
>> Example: "At 4am the user wants to play a sound at 8am (in 4hrs). At 6am
>> the
>> user changes timezone and it becomes 7am. The alarm should sound at 8am in
>> the
>> new timezone."
>>
>> My guess is that you know about interval timers but you should be using a
>> wall-clock. Since you haven't specified what you want it's hard to know.
>>
>> David
>>
>>
>
> I am very sorry for not making my question clear enough. But the situation
> you just described is JUST what I want to do! Yes, I want to do something
> exactly as you described; I am now at 4:00 am, I need to make my app do
> something at - say - 8:00 am (the time of the alarm is calculated and varies
> from time to time, so i can't just use cron jobs to schedule the next
> alarm), So, I used a QTimer and set its interval to the duration between now
> and the next alarm. BUT this solution won't work if user decides to adjust
> the system clock/change timezone.
> What I'm asking is there anyway to GET NOTIFIED by the system when its
> clock/timezone changes (in order to recalculate the next alarm and set my
> Qtimer object to a new duration)?? any signal emitted ? anything?
>
> I hope i made my question clear and sorry for any inconvenience.
> thanks again
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