Gentoo Haven

Xinerama + Composite

by admin on Apr.13, 2010, under Composite, Development, Xinerama

So today I received my second Nvidia 9500 GT 512MB PCI-X video card.  The plan was simple – stick the card in, attach two more monitors to it, tell X to drive those monitors, and everything should work.  Right?  Wrong!

Turns out that in order for X to drive 4 monitors (2 on each Nvidia 9500 GT), Xinerama needs to be enabled.  What’s bad about that?  Because it’s mutually exclusive with Composite.  That means I can have 2 small & pretty Compiz desktops or 1 large & ugly Metacity desktop.

I did some digging around as to why this is and here’s what I found out:

  <JKac3BEq> Could someone explain why the COMPOSITE extension is not revealed by X.org when XINERAMA is enabled, even though the logs show it is loaded?
  <ajax> because loaded and enabled mean different things.
and the "loaded" message is basically just a list of the things that were built into the server, not what’s actually configured.
  <JKac3BEq> Understood about loaded…. but why isn’t it being enabled then?
X 1.7.6 FYI
  <ajax> because xinerama and composite are mutually exclusive at the moment.
the code is broken, so it’s disabled so you don’t do something that’s not going to work.
  <JKac3BEq> You say at the moment… does that mean that the end goal is for both to work together?
  <ajax> sure.
  <JKac3BEq> Is any work being done to resolve this currently?
  <ajax> meh.
i had a branch a while ago, it still didn’t work, and i haven’t touched it in a few months.
feel free to send patches.
  <JKac3BEq> Is there a list of what doesn’t work somewhere ?
  <ajax> no.
  <JKac3BEq> Or is it a matter of try to compile and run and fix segfaults as you find them?
  <ajax> and fix broken rendering, and deadlocks, and event generation, and…
  <JKac3BEq> Thanks for the info
Can you point me at the branch you started?
  <ajax> it was up on fdo until a disk crash.  it’s currently on a laptop that’s at home.
  <JKac3BEq> ajax: thanks

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