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Why does Gem crash when creating the Gem-window?

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This FAQ applies to: 0.91

When I try to create a Gem-window, my X-server crashes (or worse)? btw, I am using Ubuntu/hoary with fglrx drivers.


try setting the environment variable GEM_SINGLE_CONTEXT to 1


Gem establishes an (invisible) openGL-context at startup, even if no Gem-window is created yet. When you create the Gem-window, a 2nd openGL-context is used (which shares some properties with the invisible context).

For some reasons this seems to be not possible with some gfx-drivers (e.g. ATI's proprietary fglrx drivers) and some window-managers (i suspect compiz/beryll), leading to crashes of the X-server and/or system freezes.

The current workaround is to set the environment variable GEM_SINGLE_CONTEXT=1, which prevents this dual-context magic.


  • if you are starting Pd from the bash, you can start Pd/Gem with GEM_SINGLE_CONTEXT=1 pd -lib Gem
  • on bash, you can also set this permanently by adding a the line export GEM_SINGLE_CONTEXT=1 to either ~/.bashrc (the bash-configuration file in your home-directory) or to /etc/bash.bashrc (to set it for all users)

see also:

Can GEM run on a 3Dfx Voodoo card?
by IOhannes m zmoelnig last modified 2008-05-09 04:05 PM

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