Desktop OpenGL implements a GL_FRAMEBUFFER_SRGB setting; query that instead
of the frambuffer color encoding.
With this change it is no longer necessary to enable FRAMEBUFFER_SRGB
in the macOS setup; remove it.
Signed-off-by: Elias Naur <mail@eliasnaur.com>
macOS is the only platform where desktop OpenGL is used. To support
foreign ANGLE contexts add a setting to override Gio's selection of
OpenGL implementation.
The bulk of this change is making all function pointers per-context
instead of global, and loading the OpenGL library dynamically. As a side
effect we're closer to Gio tolerating a platform without any OpenGL
implementation. For example, Apple has deprecated OpenGL and OpenGL ES
on its platforms and may remove them in the future.
Note that as a side-effect of this change, Gio needs Go 1.16 or newer to
run on iOS.
Signed-off-by: Elias Naur <mail@eliasnaur.com>
There was a special case for optional symbols for macOS/iOS. It turns out
dlsym(3) works as expected, so this change deletes the special case.
The change is required to make Gio work with ANGLE, which emulates
OpenGL ES on top of Metal.
Signed-off-by: Elias Naur <mail@eliasnaur.com>
Elias Naur