[PATCH 6/8] ephyr: Create 3.3 core profile context if possible (v3)

[Matt Turner]

On Mon, Jan 18, 2016 at 11:02 PM, Dave Airlie <airlied at gmail.com> wrote:
> From: Keith Packard <keithp at keithp.com>
>
> On desktop GL, Ask for a 3.3 core profile context if that's available,
> otherwise create a generic context.
>
> v2: tell glamor the profile is a core one.
> v2.1: add/use GL version defines
> v3: let glamor work out core itself
>
> Signed-off-by: Keith Packard <keithp at keithp.com>
> Signed-off-by: Dave Airlie <airlied at redhat.com>
> ---
>  hw/kdrive/ephyr/ephyr_glamor_glx.c | 18 +++++++++++++++++-
>  1 file changed, 17 insertions(+), 1 deletion(-)
>
> diff --git a/hw/kdrive/ephyr/ephyr_glamor_glx.c b/hw/kdrive/ephyr/ephyr_glamor_glx.c
> index 30c5245..b9fe8d1 100644
> --- a/hw/kdrive/ephyr/ephyr_glamor_glx.c
> +++ b/hw/kdrive/ephyr/ephyr_glamor_glx.c
> @@ -41,6 +41,10 @@
>  #include "os.h"
>  #include <X11/Xproto.h>
>
> +/* until we need geometry shaders GL3.1 should suffice. */
> +/* Xephyr has it's own copy of this for build reasons */
> +#define GLAMOR_GL_CORE_VER_MAJOR 3
> +#define GLAMOR_GL_CORE_VER_MINOR 1
>  /** @{
>   *
>   * global state for Xephyr with glamor.
> @@ -319,7 +323,19 @@ ephyr_glamor_glx_screen_init(xcb_window_t win)
>                         "GLX_EXT_create_context_es2_profile\n");
>          }
>      } else {
> -        ctx = glXCreateContext(dpy, visual_info, NULL, True);
> +        static const int context_attribs[] = {
> +            GLX_CONTEXT_PROFILE_MASK_ARB,
> +            GLX_CONTEXT_CORE_PROFILE_BIT_ARB,
> +            GLX_CONTEXT_MAJOR_VERSION_ARB,
> +            GLAMOR_GL_CORE_VER_MAJOR,
> +            GLX_CONTEXT_MINOR_VERSION_ARB,
> +            GLAMOR_GL_CORE_VER_MINOR,
> +            0,
> +        };
> +        ctx = glXCreateContextAttribsARB(dpy, fb_config, NULL, True,
> +                                         context_attribs);
> +        if (!ctx)
> +            ctx = glXCreateContext(dpy, visual_info, NULL, True);
>      }
>      if (ctx == NULL)
>          FatalError("glXCreateContext failed\n");
> --

GL 3.2 adds profiles -- they're not available in GL 3.1. The
GLX_ARB_create_context_profile spec says:

     If the requested OpenGL version is less than 3.2,
     GLX_CONTEXT_PROFILE_MASK_ARB is ignored and the functionality
     of the context is determined solely by the requested version.


If you simply ask for 3.1, you may get GL_ARB_compatibility... The spec says:

    If version 3.1 is requested, the context returned may implement
    any of the following versions:

      * Version 3.1. The GL_ARB_compatibility extension may or may not
        be implemented, as determined by the implementation.
      * The core profile of version 3.2 or greater.

It's probably a safe bet that no driver we care about glamor running
on will implement GL_ARB_compatibility, so maybe asking for 3.1 is the
best thing to do. The lack of profiles in 3.1 is a real pain in the
ass.