[maemo-developers] Optimal battery life considerations in apps

[From: Thomas Perl]

2009/7/8 Andrew Flegg <andrew at bleb.org>:
>    2) Stop updating the screen when your app isn't in the
>       foreground.
--------- 8< -----------
> I'm willing to put together this wiki page but have two questions:
>
>    1) What is the best way of implementing (2) in C/Python/whatever?

For GTK+ (all languages), you probably want the window-state-event signal:

http://library.gnome.org/devel/gtk/unstable/GtkWidget.html#GtkWidget-window-state-event

This signal makes use of the following structure:

http://library.gnome.org/devel/gdk/unstable/gdk-Event-Structures.html#GdkEventWindowState

which in turn uses the following enum:

http://library.gnome.org/devel/gdk/unstable/gdk-Event-Structures.html#GdkWindowState

You would probably have to write a sample app and check which window
events are received and then document which ones the developer has to
consume and process. One thing I noted with the GTK+ flavour on Diablo
is that iconify events are not sent/received correctly - at least in a
way different than on stock Desktop GTK+.

>    2) In Fremantle, there's a compositing window manager. On a
>       desktop this means you never receive an "expose" event
>       since your window is always exposed on an off-screen
>       buffer. What is the best way of implementing (2) in
>       Maemo 5?

The same window-state-event signal should still be relevant on Maemo 5.

HTH.
thp