[Qemu-devel] Various VGA / VNC fixes and cleanups to prep for multiheaded graphics

[Zachary Amsden]

These patches grew from a very strange process, but nonetheless they exist now.
All of the initial patches are robustness / bugfixes / cleanups.  The final
result is that we can use multiple Cirrus VGA adapters simultaneously.

Note the last patch is a complete hack.  It is not meant to be designed this
way, and is included for demonstration purposes only.  You will also need to
know how to hack your xorg.conf file to setup multihead properly, but it does
work, at least under SDL, for me.  You can switch using the standard qemu
ctrl-alt-1 / ctrl-alt-2 to switch between both graphic consoles.

I would attach a screenshot to demonstrate this if I could, but the patch mail
program, or my skills at manipulating it are not sufficient to do that.

Not that this is very useful, but it was possible, and a consequence of what
I had been working on, so I felt compelled to release it.

The next step if anyone were to be interested in multiheaded machine simulation
would be to create a console.h abstraction designed to support this; it would
at least require a 'display_state_init' and 'run' callback, and would need
differentiation to determine whether all displays should be multiplexed on
one console; or whether there should be multiple consoles supporting all
displays; or whether there should be a master console with access to all
monitor targets and slave displays for secondary graphics consoles.

Multiple concurrent SDL displays would require a much deeper design, with a
separate process for each display, given the current state of SDL does not
support multiple windows.  This may or may not be possible under Cocoa, which
I have access to but have not fully investigated.

This might be more useful when applied to a VNC or other remote display target.
Initial attempts to get multiple simultaneous VNC displays did not work, but
there is no obvious technical obstacle to the progress.

Enjoy.  I was going to include a screenshot of 4 simultaneous heads on a
<unspecified name> distro with a giant image of a heavily modified and
ridiculously finned Honda Civic, but sorry, I don't have the patience to
recompile the X server again.

Cheers,

Zach