[fpc-devel] OpenGL 3.3 Core

[Michalis Kamburelis]

 2017-05-26 18:48 GMT+02:00 Kostas Michalopoulos <badsectoracula at gmail.com>:
> I'd use an enum with values like (glcDefaultProfile, glcCoreProfile,
> glcCompatibilityProfile). Default would leave things as-is (when versioning
> is introduced to backends that currently do not support it, it will either
> use a backend-specific default or leave it unspecified where possible), Core
> will explicitly request a core profile and Compatibility will explicitly
> request a compatibility profile. Under OSes where compatibility isn't
> available, the context creation would fail.
>
> For bonus points, i'd rename glcCoreProfile to glcRequireCoreProfile and
> instead of glcCompatibilityProfile i'd use glcPreferCompatibilityProfile and
> glcRequireCompatibilityProfile. glcRequireCoreProfile would work like above,
> glcPreferCompatibilityProfile will first try to use the compatibility
> profile but fallback to core if not available (so that the drivers avoid the
> extra checks) and glcRequireCompatibilityProfile will fail if the
> compatibility profile doesn't exist - basically having the profiles as
> glcDefaultProfile, glcPreferCompatibilityProfile,
> glcRequireCompatibilityProfile and glcRequireCoreProfile.
>

I like all of these ideas:)

And they are easily implementable by
https://www.khronos.org/registry/OpenGL/extensions/ARB/GLX_ARB_create_context.txt
(used by the GTK implementation):

- glcRequireCoreProfile and glcRequireCompatibilityProfile results in
the appropriate bit set of GLX_CONTEXT_PROFILE_MASK_ARB .
- glcPreferCompatibilityProfile would need to eventually query for
another profile, as you write (I'm not sure do we really need it much?
I see that sometimes it can be useful, if the implementation can adapt
to use either "old fixed-function renderer" or not, but I'm not sure
is this a large need.)
- ForwardCompatible = true sets the
GLX_CONTEXT_FORWARD_COMPATIBLE_BIT_ARB bit in GLX_CONTEXT_FLAGS_ARB .

Not that I'm volunteering to implement them (I'm not having much time,
and I mostly use my own OpenGL context creation in CastleWindow). But
it makes sense and I would gladly test it:)

Regards,
Michalis