[maemo-developers] Optimal battery life considerations in apps

[From: Kimmo Hämäläinen]

On Fri, 2009-07-24 at 10:54 +0200, ext Andrew Flegg wrote:
> On Fri, Jul 24, 2009 at 07:55, daniel wilms<daniel.wilms at nokia.com> wrote:
> >
> > there is an API to detect if the window is in the foreground or not (thx to Kimmo
> > for pointing me to this) [1]. If this property is true, then the window is visible
> > on the screen. You can use this parameter directly from your root window. And here

Not "your root window", but "the root window". The property in the root
window is _MB_CURRENT_APP_WINDOW and is-topmost in libhildon tracks that
property.

> > [2] you find the method to get the value of the parameter.
> 
> Yup, indeed. (PyMaemo doesn't expose the method, but you can get the property).
> 
> However, what's the best way of detecting when you come *back* to the
> foreground? I didn't get a property-change event (although this could
> be due to a PyMaemo bug rather than a Hildon one).

The property changes to true when you come back to foreground. Only in
the visible HildonWindow, of course (in case you have a stack of
windows).

> My basic code structure is:
> 
>     * while timer fires:
>           - check is-topmost
>                 - if false, cancel timer and return
>           - update screen
> 
>     * when receiving focus-in event:
>           - check is-topmost
>                 - if true, re-initialise timer
> 
>     * when osso signal for power state received:
>           - cancel, or re-initialise, timer as appropriate
> 
> This works fine on Diablo (can't test on Fremantle due to no app
> switching). The "focus-in" bit seems a bit hacky, though. But if
> there's no better way which the Hildon developers/Nokia recommend,
> that's fine by me.

Probably Python bindings are confused then. You don't need any timers to
use it.

-Kimmo

> 
> Cheers,
> 
> Andrew
>