[cairo] Making configure error message more clear

[Owen Taylor]

On Thu, 2010-03-25 at 17:04 -0400, Behdad Esfahbod wrote:
> On 03/22/2010 02:10 PM, Carl Worth wrote:
> > On Thu, 18 Mar 2010 21:15:33 +0100, Arjen Nienhuis <a.g.nienhuis at gmail.com> wrote:
> >>> Below is an exchange I recently had with a new user trying to use cairo
> >>> who got this error and followed its advice, (browsed to the URL, found
> >>> pixman, downloaded it, installed it to the default /usr/local/). But the
> >>> user still got the same message, and never knew to adjust the
> >>> PKG_CONFIG_PATH environment variable.
> >>
> >> Why isn't PKG_CONFIG_PATH set to $PREFIX/lib/pkgconfig by default?
> > 
> > I've often wondered why pkg-config doesn't do that by default.
> > 
> > But I suppose that we could just have cairo's configure script set that
> > environment variable that way if it's not already set. That would be a
> > nice solution for this problem.
> 
> Interesting.  Why pkg-config doesn't do it is not hard to see.  Why shouldn't
> it provide a macro to do that, good q.  I'll fix it in cairo and propose other
> packages doing the same.

It's always been completely clear that configure --prefix=<X> is about
where the package is *installed*, not where the build process looks for
things.

Now, there's maybe no reason that the configure process couldn't guess
that where you are installing is where you want to find things too, but
I'm sort of skeptical that it's a good idea for a few packages to start
doing that in one aspect PKG_CONFIG_PATH (but not other aspects like
include and library paths.)

- Owen