On 12/18/2012 10:43 AM, Paul Berry wrote: > The nVidia driver violates these parts of the ARB_glx_create_context > extension: > > <attrib_list> specifies a list of attributes for the context. The > list consists of a sequence of <name,value> pairs terminated by the > value None (0). If an attribute is not specified in <attrib_list>, > then the default value specified below is used instead. > > The default values for GLX_CONTEXT_MAJOR_VERSION_ARB and > GLX_CONTEXT_MINOR_VERSION_ARB are 1 and 0 respectively. In this > case, implementations will typically return the most recent version > of OpenGL they support which is backwards compatible with OpenGL 1.0 > (e.g. 3.0, 3.1 + GL_ARB_compatibility, or 3.2 compatibility profile) > > What the nVidia driver does, instead, is: > > - If neither GLX_CONTEXT_MAJOR_VERSION_ARB nor > GLX_CONTEXT_MINOR_VERSION_ARB is specified, it returns a 4.2 context. > - If GLX_CONTEXT_MAJOR_VERSION=1 and GLX_CONTEXT_MINOR_VERSION_ARB=0 are > specified, it returns a 2.1 context. > > It's pretty clear to me that this is a violation of the spec. Perhaps I > should write to my congressman.
Yeah, it's very clear. Calling glXCreateContextAttribs with MAJOR=1 and MINOR=0 should be equivalent to calling it without specifying MAJOR and MINOR. > Anyhow, for the moment I'm working around the problem by modifying > glx_context_fill_attrib_list (waffle/src/waffle/glx/glx_context.c) so that > it only provides attributes these two problematic attributes to the driver > if (attrs->context_major_version != 1 || attrs->context_minor_version != > 0). I can't decide whether I like this as a long term solution, though. According to the GLX_ARB_create_context spec, calling it either way should be equivalent, so I don't view your workaround as dirty. If, in order to accommodate a buggy driver, we must replace one call in waffle with a according-to-the-spec equivalent call, that seems to be an acceptable workaround. _______________________________________________ waffle mailing list waffle@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/waffle
