[maemo-developers] sensing change in System Clock using Qt
From: ibrahim ibrahim.ali at asgatech.comDate: Sun Jan 31 11:45:52 EET 2010
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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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