I'm facing RANDR missing problem with Xvfb and firefox.Some people suggested Xvfb :1 -extension RANDR can solve the problem.But I found a also +extension option.In my environment(CentOS6.5), the both fails.But I want to know at least if there is difference between -extension and +extension. I couldn't find entry about it in man Xvfb.Do someone know about it?
Is there difference between Xvfb option `-extension` and `+extension`?
firefox;xvfb
See Xserver(1):  -extension extensionName       disables named extension. If an unknown extension name is specified, a list of accepted extension names is printed.  +extension extensionName       enables named extension. If an unknown extension name is specified, a list of accepted extension names is printed.You should be able to get list of supported extensions from glxinfo or xdpyinfo.