[maemo-developers] Optimal battery life considerations in apps

[From: Andrew Flegg]

On Sat, Jul 11, 2009 at 12:09, Andrew Flegg<andrew at bleb.org> wrote:
> On Sat, Jul 11, 2009 at 08:28, Faheem Pervez<trippin1 at gmail.com> wrote:
>
>> FocusOut event, serial 20, synthetic NO, window 0x1600001,
>>    mode NotifyNormal, detail NotifyNonlinear
>
> I had a thought about using focus-in/out and checking
> window.get_property("is-topmost") - unfortunately, the value of that
> property doesn't seem reliable enough (or, rather, the focus-out fires
> before the window is minimised)

Right, my current strategy - which seems to work in Diablo[1] and on a
GTK+ desktop - is as follows, in Pythonesque pseudo-code:

--------8<--------
visible = True
paused  = False

def osso_state_change(shutdown, save_unsaved_data, memory_low,
                 system_inactivity, message, widget):
  paused  = system_inactivity
  set_visible(not paused)


def do_window_state_event(self, window, event):
  set_visible(not event.new_window_state &
                             (gtk.gdk.WINDOW_STATE_ICONIFIED
                             |gtk.gdk.WINDOW_STATE_WITHDRAWN))


def do_focus_in_event(self, widget, event):
  set_visible(True)


def do_expose_event(self, event):
  topmost = self.app_window.get_property('is-topmost')
  self.set_visible(not self.paused and topmost)
  ...


def set_visible(self, visible):
  if (visible == self.visible):
    return

  if (visible):
    my_custom_redraw_and_invalidate()
    gobject.timeout_add(self.freq, my_custom_redraw_and_invalidate)


def my_custom_redraw_and_invalidate():
  ...
  return visible
------->8-------

Since "expose-event" is firing regularly anyway (because of
my_custom_redraw_and_invalidate), it can check the 'is-topmost'
property of HildonWindow[2].

The application can't get focus without it being on top, so if a
"focus-in-event" is received, assume we're visible again.

Comments, as ever, welcome.

Cheers,

Andrew

[1] Fremantle has no app switching, so not easy to test.
[2] Interestingly, is-topmost is still true even when the display
    is blanked.

-- 
Andrew Flegg -- mailto:andrew at bleb.org  |  http://www.bleb.org/
Maemo Community Council chair