[waffle] [PATCH] glx: Add glXCreateContextAttribs workaround for NVidia bug

[Paul Berry]

On 19 December 2012 12:21, Chad Versace <chad.versace at linux.intel.com>wrote:

> With NVidia, calling glXCreateContextAttribsARB with MAJOR=1 and MINOR=0
> returns an OpenGL 2.1 context. Calling it with MAJOR and MINOR unspecified
> returns a context of the latest supported OpenGL version. However,
> according to
> the GLX_ARB_create_context spec, the two calls should behave identically.
> Calling with MAJOR and MINOR unspecified produces the expected behavior.
>
> As a workaround, do not specify GLX_CONTEXT_MAJOR_VERSION_ARB and
> GLX_CONTEXT_MINOR_VERSION_ARB in the call to glXCreateContextAttribsARB if
> the
> user requested an OpenGL context of unspecified version or if the user
> explicitly requested an OpenGL 1.0 context.
>
> Reported-by: Paul Berry <stereotype441 at gmail.com>
> Signed-off-by: Chad Versace <chad.versace at linux.intel.com>
>

Reviewed-and-tested-by: Paul Berry <stereotype441 at gmail.com>.


> ---
>  src/waffle/glx/glx_context.c | 37 ++++++++++++++++++++++++++++++++-----
>  1 file changed, 32 insertions(+), 5 deletions(-)
>
> diff --git a/src/waffle/glx/glx_context.c b/src/waffle/glx/glx_context.c
> index bc218af..ffb79a4 100644
> --- a/src/waffle/glx/glx_context.c
> +++ b/src/waffle/glx/glx_context.c
> @@ -72,11 +72,38 @@ glx_context_fill_attrib_list(struct glx_config *config,
>      struct wcore_config_attrs *attrs = &config->wcore.attrs;
>      int i = 0;
>
> -    attrib_list[i++] = GLX_CONTEXT_MAJOR_VERSION_ARB;
> -    attrib_list[i++] = attrs->context_major_version;
> -
> -    attrib_list[i++] = GLX_CONTEXT_MINOR_VERSION_ARB;
> -    attrib_list[i++] = attrs->context_minor_version;
> +    // As a workaround for NVidia, do not specify
> +    // GLX_CONTEXT_MAJOR_VERSION_ARB and GLX_CONTEXT_MINOR_VERSION_ARB in
> the
> +    // call to glXCreateContextAttribsARB if the user requested an OpenGL
> +    // context of unspecified version or if the user explicitly requested
> an
> +    // OpenGL 1.0 context.
> +    //
> +    // Calling glXCreateContextAttribARB with MAJOR=1 and MINOR=0,
> according
> +    // to the spec, is equivalent to calling it with MAJOR and MINOR
> +    // unspecified.  From the GLX_ARB_create_context spec:
> +    //
> +    //     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)
> +    //
> +    // However, NVidia's libGL, circa 2012-12-19, is not compliant.
> Calling
> +    // glXCreateContextAttribsARB with MAJOR=1 and MINOR=0 returns an
> OpenGL
> +    // 2.1 context. Calling it with MAJOR and MINOR unspecified returns
> +    // a context of the latest supported OpenGL version.
> +    if (attrs->context_api == WAFFLE_CONTEXT_OPENGL &&
> +        attrs->context_full_version != 10)
> +    {
> +        attrib_list[i++] = GLX_CONTEXT_MAJOR_VERSION_ARB;
> +        attrib_list[i++] = attrs->context_major_version;
> +
> +        attrib_list[i++] = GLX_CONTEXT_MINOR_VERSION_ARB;
> +        attrib_list[i++] = attrs->context_minor_version;
> +    }
>
>      switch (attrs->context_api) {
>          case WAFFLE_CONTEXT_OPENGL:
> --
> 1.7.11.7
>
>
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