specification for hardware/vo OSD support?

Hi,
I wanted to ask if there are already any ideas concerning the way vos=20
can support OSD drawing, e.g. if there is hardware support for drawing=20
pictures with alpha (like in OpenGL..)
I personally have been thinking about a few things (something like a=20
"very first draft"):

1) The vos should be able to give a "virtual" resolution for the OSD, so=20
they can vary it independently from video size (very usefull if the OSD=20
will be displayed on a different display, or there is some kind of=20
overlay mechanism that supports only a different resolution than for the=20
video).

2) Not giving x, y coordinates for different parts of the OSD, but=20
instead specifying
left, horizontal center or right and
top, vertical center or bottom
This would allow the driver to e.g. always put the subtitles in the=20
black border below the picture when it's big enough...
The vo would maintain a buffer for each of these locations (3*3=3D9=20
altogether), and the interface functions would allow to set the size and=20
contents of these buffers or mark them as unused.

Greetings,
Reimar D=F6ffinger