[SailfishDevel] Scheduling code for execution at x seconds since epoch

[Thomas Tanghus]

On Saturday 15 March 2014 23:55 Arvid Fahlström Myrman wrote:
> Hi,
> 
> Thanks, I didn't think of starting a Timer during an iphb wake-up. It still
> gets a bit difficult though having to juggle both Insomniac and a Timer at
> the same time, especially as I need to chain a bunch of timers, some with
> intervals as short as five seconds, and I need to make sure that they're
> all triggered at the right time reliably. Some abstraction should take away
> most of the pain though.
> 
> While testing I did have some trouble with the timer not triggering reliably
> though, possible due to Insomniac triggering a bit late (since as you said,
> libiphb isn't guaranteed to be accurate), or perhaps due to the device
> entering suspend too early. My test works roughly like so:
> 
> 1. Set timer & insomniac to repeat: false
> 2. Set triggerTime to ~5 s from now (Math.round((Date.now() + 5000) / 1000))
> 3. Set insomniac.interval to run three seconds earlier (triggerTime - 3),
> with timerWindow set to 2 -- which, unless I'm sorely mistaken on what
> iphb_wait's mintime and maxtime actually do, should tell Insomniac to
> trigger sometime between 1 and 3 seconds from now.

I have timerWindow set to 10 and set it to wake up 10 seconds before needed.
It's not mission critical for my Kitchen Timer if it misses a couple of 
seconds, but you could have the timer window a bit smaller than trigger 
time to be sure.

https://github.com/tanghus/kitchen-timer-qml/blob/master/qml/harbour-kitchentimer.qml#L121

> 5. Start insomniac
> 4. When insomniac triggers, set timer.interval to triggerTime*1000 -
> Date.now()
> 5. Start timer
> 6. When timer triggers, go to 2
> 
> I'm thinking about trying my luck with nemo-keepalive's KeepAlive, and
> setting its enabled property to true when insomniac triggers to guarantee
> that timer also triggers. I'm also considering not using Insomniac at all
> whenever the next timer has an interval of less than 10 seconds or so, and
> instead just having KeepAlive.enabled set to true for the whole duration of
> the interval. 

If interval is so short, Insomniac is probably not the right tool.

> Or is disabling suspend for 10 seconds a bit too long for the
> Powers That Be to be pleased?

I got past the harbour master with my premature ejacu^W wakeup ;)

> Regards,
> Arvid
> 
> On Thursday 13 March 2014 21:33:53 Thomas Tanghus wrote:
> > On Thursday 13 March 2014 20:45 Arvid Fahlström Myrman wrote:
> > > Hi,
> > > 
> > > Does anyone know if it is possible to schedule code for execution at x
> > > seconds since epoch, with guaranteed execution even when in sleep mode?
> > > Currently I am using libiphb (through tanghus's Insomniac QML plugin),
> > > but
> > > libiphb only seems to support waiting for a specified number of seconds,
> > > meaning that if iphb_wait is called when the time is 1394730709733
> > > milliseconds since epoch and is instructed to wait for 5 seconds, the
> > > code
> > > will be executed sometime around 1394730714733 milliseconds since epoch.
> > > I
> > > want to be able to schedule code to be run at e.g. 1394730715000 (±50 ms
> > > or
> > > some such small margin), i.e. whole seconds since epoch, no matter the
> > > current time. That way for example WallClock from org.nemomobile.time
> > > would
> > > be in sync with my timer, and I could accurately reflect the remaining
> > > time
> > > in the GUI by updating on onTimeChanged without having to update the GUI
> > > unnecessarily often, in addition to other simplifications I would be
> > > able
> > > to make.
> > > 
> > > Using the standard QtQuick Timer type would work, since it supports
> > > specifying the interval in milliseconds, so you could do something like
> > > timer.interval = 1394730715000 - Date.now(), however Timer doesn't work
> > > when in sleep mode.
> > 
> > As libiphb is not guaranteed to be accurate, I set the Insomniac to wake
> > up
> > a few seconds before I need the alarm to trigger, then start a Timer. You
> > could do the same: Wake up, check time and start a normal Timer.
> > Or am I missing something?
> 
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-- 
Med venlig hilsen / Best Regards

Thomas Tanghus