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twistedcubic

Member

Registered: 2012-03-01

Posts: 22

[Solved]dual screen (radeon 9200) not working properly under composite

I am running a radeon 9200 on my desktop with monitors plugged into both the DVI and VGA outputs. I'm using the xf86-radeon-ati driver with no Xorg.conf.

I have been using openbox for a few years now, and for as long as I remember, all I needed was:

xrandr --output DVI-0 --auto --left-of VGA-0

and everything works fine. Seems like xcompmgr and cairo-compmgr also work properly.

I was experimenting with XFCE4, which works fine until I try to also use compiz as the window manager. The right side on the left monitor become jibberish, and the second monitor also becomes just as messed up, and I cannot properly drag any windows.

The same thing happened when I installed KDE4.

I should note two things:

1) If I clone the two monitors, everything works fine.
2) If I change from OpenGL to XRender (under desktop effects in KDE settings), everything works fine, just quite slowly.

Am I right in guessing that compiz works based off of OpenGL? Is there some way to get OpenGL working properly with my setup, or is this not an option?

Last edited by twistedcubic (2012-06-01 15:27:06)

Gusar

Member

Registered: 2009-08-25

Posts: 3,607

Re: [Solved]dual screen (radeon 9200) not working properly under composite

Depends on the resolution. It's quite possible the card's limit when it comes to opengl is 2048x2048. If the combined resolution of your displays is larger than that, you simply can't use an opengl compositor.

twistedcubic

Member

Registered: 2012-03-01

Posts: 22

Re: [Solved]dual screen (radeon 9200) not working properly under composite

Depends on the resolution. It's quite possible the card's limit when it comes to opengl is 2048x2048. If the combined resolution of your displays is larger than that, you simply can't use an opengl compositor.

Does this have anything to do with texture size? If I try to enable composite from terminal, I see some error messages regarding texture size, and after some googling it appears as if it is possible that the max texture size is 2048.

Gusar

Member

Registered: 2009-08-25

Posts: 3,607

Re: [Solved]dual screen (radeon 9200) not working properly under composite

Yes, it's about texture size. Which means you can't use a gl compositor with dual-screen. Except maybe, what exactly is the resolution of your displays? On my netbook, I simply stacked them vertically instead of horizontally (the second output below the first one instead of to the right/left of it), that way they fit into 2048x2048.

Last edited by Gusar (2012-06-01 14:05:02)

twistedcubic

Member

Registered: 2012-03-01

Posts: 22

Re: [Solved]dual screen (radeon 9200) not working properly under composite

Wow, you got it. They are both 1600x900, so if I stack them everything works properly.