Re: trunk r115472: Make 'configure' work out-of-the-box on Solaris.

[Stephen J. Turnbull]

martin rudalics writes:

 > When I want to check whether a feature works with the GTK or Lucid
 > build, I have to reconfigure in between.

Aside from multiple branches, which are a PITA if conceptually they're
supposed to be identical source IMO, surely Emacs uses the wonderful
support Make has for VPATH aka configure --srcdir builds?  Have a GTK
blddir, a Lucid blddir, etc for any that you regularly build.  After
doing that once, just "make" should win (or perhaps an occasional
"make bootstrap").

 > Still it would be great if I didn't have to care about a missing image
 > library  ...

This is nearly trivial to support, except that it would be bad if
other users were surprised by the absence of features they expect due
to a lack of some *-devel.rpm.  The UI aspect isn't that hard, but I
can't post code because it would be based on XEmacs code of provenance
unknown to me, and anyway it suits of mode of configuration unlike
that of GNU Emacs.  If it *can* be user-optional at configure time it
*is* optional, with --enable-FEATURE={no|auto|yes}, where "auto" means
"use it if you can find it and it's usable", and "yes" means "error if
you can't find a usable library and header".

GNU Emacs might prefer a single --enable-missing-features configure
option, with "no" meaning you get a configure error when a standard
feature is missing.  Preferably attempting to continue configuration
of all features, collecting "missing feature" errors to report at the
end of the run (which of course finishes with a fatal error), and
"yes" meaning you get a warning but configure continues and produces a
buildable tree (as far as configure knows, of course).

Either way, you could add support for it feature by feature without
disturbing current users just by defaulting --enable-missing-features
to "no", or all the --enable-FEATURE options to "yes".