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For a 3D scanner implementation I need to precisely control the output of a projector connected as a second monitor to my graphics card. I would need to issue OpenGL commands in a full screen context on this second monitor using a second X server instance. I am on Ubuntu 13.04 with a Dell Precision T3600 Workstation containing a AMD V7900 GPU.

How do I get one X server with Unity on the main screen and a second X server instance for the projector which contains only a fullscreen OpenGL context?

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OK, I came up with a solution, albeit it is a bit trickery. I have configured my graphics driver for a multi display setup. This way each "monitor" is represented as a separate X screen. Ubuntu Unity does not play nicely with this, as it currently expects a XrandR setup with a single virtual screen. However, by erasing the relative screen location information from my xorg.conf, Unity is ignoring the second screen altogether. Now, I can create a fullscreen OpenGL context on the second X screen without any interference from the OS. The top of my xorg.conf looks like this:

Section "ServerLayout" Identifier "amdcccle Layout" Screen 0 "amdcccle-Screen[5]-0" 0 0 Screen "amdcccle-Screen[5]-1" EndSection

In the old-style multi-screen setup, the second screen would have position specifiers (e.g. 1920 0 or "Right of Screen 0"). By removing them, the second screen is ignored.

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