3D [LWN.net]

3D

Posted Jun 23, 2010 0:38 UTC (Wed) by dododge (subscriber, #2870)
In reply to: 3D by drago01
Parent article: A quick grumpy review of Shotwell

I haven't tried this latest gthumb (my system is not handy), but I see in the Clutter README that it depends on the XComposite extension. That can be a problem on multi-head systems.

People with only two displays attached to the same card can get around the problems by using things like NVIDIA's Twinview, which tricks the X server into thinking you only have one display. When you add a second card to get three displays it all falls apart. Twinview doesn't work across cards, so you have to enable Xinerama (or live with not being able to move windows between screens). Enabling Xinerama causes XComposite to be disabled because they're not compatible. Xinerama is supposedly deprecated and replaced by XRandR -- which is compatible with XComposite -- but XRandR also doesn't work with multiple cards and and that capability has been repeatedly delayed for something like 3 years now.

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Posted Jun 23, 2010 9:44 UTC (Wed) by ebassi (subscriber, #54855) [Link]

Disclaimer: I am the Clutter maintainer

I haven't tried this latest gthumb (my system is not handy), but I see in the Clutter README that it depends on the XComposite extension. That can be a problem on multi-head systems.

the XComposite extension is optional.

also, I have a multi-head system (two panels, my LVDS and an external monitor) and it works perfectly fine. granted, I'm not using an extension and X server from 1997 but something designed released in this millenium. ;-)

and yes, I'm using Clutter on this system. actually, it's the system on which Clutter itself is mainly developed.

Posted Jun 23, 2010 21:44 UTC (Wed) by dododge (subscriber, #2870) [Link]

> the XComposite extension is optional.

Sounds good, thanks.

> granted, I'm not using an extension and X server from 1997 but something designed released in this millenium. ;-)

My 3-head system is running the current Xorg in Ubuntu 10.04, which still can't do XComposite (or XRandR) properly across multiple cards. It does at least do OpenGL, and windowed applications such as Google Earth are okay. Anything that tries to go full-screen can get very confused or worse yet trigger bugs in the X server, though.

It seems like every new release gets a little bit worse. For example with this latest Xorg the server chokes if you try to configure a 3-1-2 screen layout (so that screen 1 is in the center), which had worked fine for the past 4-5 years. The only person I've heard of managing to get XComposite to work across multiple cards had to use a several-years-old modified Xgl server -- it's never worked in Xorg.