[MacPorts] #47808: port:jpeg proposal to prepare for making port:libjpeg-turbo the default jpeg dependency

[MacPorts]

#47808: port:jpeg proposal to prepare for making port:libjpeg-turbo the default
jpeg dependency
-------------------------+--------------------------------
 Reporter:  rjvbertin@…  |      Owner:  macports-tickets@…
     Type:  enhancement  |     Status:  new
 Priority:  Normal       |  Milestone:
Component:  ports        |    Version:
 Keywords:  haspatch     |       Port:  jpeg
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 This is the draft proposal for a change in how port:jpeg installs, helping
 to prepare for a transition to using port:libjpeg-turbo (or mozjpeg) as
 the default "jpeg provider".

 I propose

 - to install to ${prefix}/libexec/jpeg
 - to provide a +transitional variant (default for now) that hides this
 change from the installed ports
 - to provide a grace period (during which +transitional exists and) during
 which even `-transitional` installs a symlink to just libjpeg.9.dylib so
 that existing ports can continue to use that library without requiring a
 rebuild.

 I've tested both `+transitional` and `-transitional`, the latter with
 libjpeg-turbo installed and used by 2 ports (simply by rebuilding them).

 The only anomaly I can think of is the fact that those 2 rebuilt ports are
 declaring to depend on port:jpeg while in fact they depend on a library
 provided by libjpeg-turbo. That's something that I think can get sorted
 out gradually during the grace period.

-- 
Ticket URL: <https://trac.macports.org/ticket/47808>
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