[MacPorts] #60511: gtk3, pango and cairo: move to quartz as default backend

[MacPorts]

#60511: gtk3, pango and cairo: move to quartz as default backend
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  Reporter:  ra1nb0w             |      Owner:  dbevans
      Type:  enhancement         |     Status:  assigned
  Priority:  Normal              |  Milestone:
 Component:  ports               |    Version:
Resolution:                      |   Keywords:
      Port:  gtk3, pango, cairo  |
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Comment (by ryandesign):

 It's always been recommended that a user make the decision about whether
 to use x11 or quartz before installing any ports. If they want to change
 their mind, we recommend uninstalling all ports. If we are proposing to
 change the default, we would have to do so in all ports that have them,
 not just the few proposed here. (There are over a hundred ports with such
 variants.) We also don't have a mechanism that could be used to assist all
 existing users in upgrading properly. For example, all existing users who
 are using +x11 and want to continue doing so should add +x11 to their
 variants.conf, but we don't have a way of notifying users that they should
 do this, short of the MacPorts release notes and mailing lists and so
 forth.

 Ports that build themselves differently depending on whether a dependency
 was installed with +quartz or +x11 must themselves have +quartz and +x11
 variants. As far as I know we largely do have that already but there could
 be some that have been overlooked (and that is why we make the uninstall-
 and-reinstall recommendation). If we switch defaults, that will surely
 bring such problems to light so that we can fix them.

 I was planning on trying out defaulting to +quartz on my system when I
 upgrade to Catalina since I'll have to reinstall everything then anyway.
 But I haven't really tried it yet so I can't say how well +quartz
 currently works generally.

 Changing the default for only some OS versions seems like it would cause
 confusion. It also has the potential to cause problems during
 [wiki:Migration migration] if the user is migrating between two OS
 versions for which we've chosen different defaults.

-- 
Ticket URL: <https://trac.macports.org/ticket/60511#comment:4>
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