[maemo-developers] Howto enable portrait mode support on Fremantle

[From: Kimmo Hämäläinen]

On Fri, 2009-08-21 at 15:53 +0200, ext Alberto Garcia wrote:
> On Fri, Aug 21, 2009 at 02:53:01PM +0200, Cornelius Hald wrote:
> 
> I'll try to summarize how it works (I'm adding Kimmo to Cc in case I'm
> forgetting something, as the rotating itself is done by the desktop,
> libhildon only sets a WM hint).
> 
> Let's suppose we open a new window. Before we open that window the
> device might already be in portrait mode.
> 
> If the portrait flags of the new window are:
> 
> 1) No flags -> The screen is rotated to landscape mode.

Correct.  An example: when you are in portrait mode and suddenly a
system-modal dialog pops up without the SUPPORT or REQUEST flag, we go
to the landscape mode.

> 2) _SUPPORT -> The screen keeps its orientation.

Correct ...unless some window has the REQUEST flag. The SUPPORT flag on
your window tells that you support the portrait mode, i.e. your window
can relayout itself for the portrait mode. The REQUEST flag on your
window tells that you want to be in the portrait mode (for whatever
reason, not necessarily just because the device is currently in portrait
orientation!).  Hildon-desktop is not turning the screen to portrait
unless there is at least one visible window with REQUEST and the rest of
the visible windows have the SUPPORT (explicit or implicit) flag. These
flags are inherited to transient windows, and REQUEST implies the
SUPPORT flag.

> 3) _SUPPORT + _REQUEST -> The screen is rotated to portrait mode
> 4) _REQUEST alone -> I don't think we're using that. Kimmo?

REQUEST is the same as REQUEST + SUPPORT. Since there is no sense to
request the portrait mode if you don't support it...

> To detect whether a device is physically rotated I think you need to
> use the DBus API already mentioned in this thread.

Correct, the sig_device_orientation_ind signal from MCE.

> In other words: using this API alone won't change the orientation of
> the screen when the device is physically rotated, am I right Kimmo?

Hildon-desktop looks at these flags, it does not listen to the
orientation signals, so it does not know how the device is oriented
relative to the Earth's crust.  (There is an exception to this, but you
are not affected by it.)

-Kimmo

> 
> Berto