add function to detect if we are running on a XO

[tomeu]

On Fri, 2009-08-14 at 17:28 -0400, Walter Bender wrote:
> I determine whether or not I am on an XO with:
> 
>     if os.path.exists('/sys/power/olpc-pm'): # then assume you are on an XO
> 

Shouldn't we encapsulate this method (is_xo?()) somewhere? I've seen it
spread in a couple of places so far.. 

[sascha_silbe]

What exactly is this function supposed to be used for?

[walter]

From the activity developer POV, there are situations where you want to know if you are using the XO hardware: (1) to adjust the font sizes since there is a funny scaling factor; (2) know if the special sensor input modes are available; (3) exploit the extra OLPC keyboard and panel buttons.

[sascha_silbe]

Replying to walter:

From the activity developer POV, there are situations where you want to know if you are using the XO hardware:
(1) to adjust the font sizes since there is a funny scaling factor;

In that case the scaling factor should be read and used either directly or more appropriately via GTK style / sugar.graphics.style. I'm setting SUGAR_SCALING on non-XO hardware as well and even intend to extend it to take values other than 72 and 100.

(2) know if the special sensor input modes are available;

These should be discoverable by checking for the corresponding mixer controls. To be of any use the activity needs to be able to toggle them anyway.

(3) exploit the extra OLPC keyboard and panel buttons.

I don't see a reason to make this conditional, other than maybe ignoring keybinding errors if the X server doesn't know the corresponding keysyms - i.e. the same way we handle global hotkeys.