Weston: DIfferent background image on each output

[Sebert, Holger.ext]

Hi,

in another thread I asked if it is possible to selectively enable or
disable different connectors (HDMI, DisplayPort, etc.) in Weston. Since
this is not possible (thanks for the answers, though!), I am thinking of 
another solution. --

Suppose there are multiple monitors connected and Weston configures an
independent desktop for each. Note that it may also happen that the
user connects one and the same monitor on multiple connectors (e.g.
both HDMI and DisplayPort). I need to avoid showing an empty desktop to
the user.

So, my first question is: How do I decide or control on which desktop
my application will pop up? (It's a Qt application that is started
in /etc/init.d on boot).

I would like to show a message (for example in the form of a
background-image) on all desktops on which my application is NOT shown
telling the user to check or switch monitor inputs.

I am thinking of scanning /sys/class/drm for connected outputs and
creating a suitable weston.ini in a start-up script. For this, however,
Weston needs to support different background images on different
outputs.

Is this possible? Does it make sense?

Best,
Holger