EGL support on MacOS?

[Ken Cunningham]

I am not an expert on OpenGL support on any system, just trying to get
things built, and looking for someone who might know more about it for
ideas...

The linux world seems to be moving towards EGL based on a number of recent
changes I have seen in webkit2-gtk, gtk4, and other places, that I think at
least in part are due to improvements in EGL support, performance, and
moving to Wayland.

Newer software, for example the x11 version of gtk4, seems to assume EGL is
present. Although it might be possible to #ifdef into the source to make
this not happen on Apple, and use what I believe is the fallback of GLX,
that is getting to be work and may not be much tested upstream.

An EGL implementation for Apple would be a more easily supportable fix, it
would seem.

There is one in mesa, currently disabled in our port, that I was able to
get to build with a small patch and a toggle in the Portfile. That allowed
libepoxy to build with EGL support as well (with a toggle and two small
patches). But performance seemed poor, and there were lots of warning
messages and errors running software built with that. Looks quite raw.

Many projects (webkit, etc) seem to be moving to ANGLE for this support.
This is actively maintained and as far as I can see, looks to be the future
for a GL compatibility layer. Some ports (webkit2-gtk at least) bundle
ANGLE and it builds on MacOS. There is no MacPorts port for ANGLE as yet,
at least that I can see.

You can see the ANGLE build in webkit2-gtk like this:

nm /opt/local/lib/libwebkit2gtk-4.0.37.44.4.dylib | grep ANGLE

So - that is where my current knowledge ends. I am imagining that we will
need an EGL implementation, possibly via ANGLE (or mesa, if it is
performant), to allow (reasonably easy) ongoing support of x11 software
builds.

If anyone has a nice depth of knowledge in this area and can shed more
light on it / knows a better plan / knows of a current EGL solution I have
missed so far, please add what you wish.

Ken
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