[MacPorts] #70137: gtk4: "No provider of glGenSamplers found" error on older systems

[MacPorts]

#70137: gtk4: "No provider of glGenSamplers found" error on older systems
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  Reporter:  barracuda156  |      Owner:  (none)
      Type:  defect        |     Status:  new
  Priority:  Normal        |  Milestone:
 Component:  ports         |    Version:  2.9.3
Resolution:                |   Keywords:
      Port:  gtk4          |
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Comment (by RJVB):

 Replying to [comment:6 mohd-akram]:
 > They seem to be trying to fix it, they haven't closed the issue at
 least.
 >

 Don't count on it. The attitude of Gnome devs is well-known in this
 regard, and last week or so I was told that 1) GTk4/X11 apps would need
 compositing X11 servers (XQuartz isn't) and 2) don't use the X11 backend
 on Mac.

 To the best of my knowledge Apple's OpenGL has remained stuck at 2.1 so
 there's that too. MAYBE an avenue would be to add a +egl variant to
 port:mesa (I hear it's trivial to get EGL to build on Mac in recent days;
 it was already not very difficult in v19.x). Performance for GUI effects
 should be good enough with the llvmpipe renderer, and this approach stands
 a chance to support remote displaying too (a main reason to use GTk/X11?).
 A word of warning: the EGL code path would have to initialise GLX too on
 Mac, to be certain that Mesa's libGL.dylib gets loaded/initialised instead
 of Apple's own. I ran into that with my testing of updated webkit2-gtk
 (2.40.x) with EGL enabled; at best the application crashes but I also had
 a few KPs that were probably due to messing the wrong way with OpenGL.

 Either way, I think the best approach here is to start providing `-gtk4`
 or so (sub)ports (or `-gtk3` legacy (sub)ports) at least for the most
 popular ports. Heck, even the further loss of theme choice would justify
 that in my book!

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Ticket URL: <https://trac.macports.org/ticket/70137#comment:9>
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