[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 barracuda156):

 Replying to [comment:9 RJVB]:
 > EDIT: re: legacy/pegged ports that encumber the tree: why not move them
 to their own ports tree, with a bit of documentation how to install them?
 Defining trees the right way in `sources.conf` will make pegged legacy
 port versions "hide" the current ones.

 That would probably make life easier. Even better if a tree can be
 automatically picked for specific criteria.
 Thus we could at the same time get rid of overly complex portfiles with
 chains of fallbacks, make maintaining ports easier (both for new systems
 and for legacy ones), actually fix some ports which got unnecessarily
 broken by updates and avoid subsequent breakages (for example, until
 Qt5/Qt6 is fixed for powerpc, all Qt4 ports could be pegged in its tree,
 much simpler way than monitoring every PR in the queue) and hopefully stop
 preventing fixing something merely because not many people use that.

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Ticket URL: <https://trac.macports.org/ticket/70137#comment:10>
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