[PATCH weston] configure.ac: make use of wayland-scanner.pc

[Bryce Harrington]

On Sat, Feb 21, 2015 at 11:04:13AM +0000, Emil Velikov wrote:
> Hi Bryce
> 
> On 20 February 2015 at 23:26, Bryce Harrington <bryce at osg.samsung.com> wrote:
> > On Tue, Feb 17, 2015 at 03:13:32PM +0000, Emil Velikov wrote:
> >> Currently we use the wayland-scanner executable as found with
> >> AC_PATH_PROG, and then check the presence of wayland-scanner.pc
> >>
> >> Currently the latter is unused even if AC_PATH_PROG fails to find the
> >> binary. Rework things to use the pkg-config variable as a fall-back.
> >
> > Sorry to have to ask some rather stupid questions, but I want to make
> > sure I understand the effects of this before landing.
> >
> >> Cc: Andrew Oakley <aoakley at espial.com>
> >> Cc: Bill Spitzak <spitzak at gmail.com>
> >> Cc: Daniel Stone <daniel at fooishbar.org>
> >> Signed-off-by: Emil Velikov <emil.l.velikov at gmail.com>
> >> ---
> >>  configure.ac | 5 ++---
> >>  1 file changed, 2 insertions(+), 3 deletions(-)
> >>
> >> diff --git a/configure.ac b/configure.ac
> >> index 1db9f79..b44675f 100644
> >> --- a/configure.ac
> >> +++ b/configure.ac
> >> @@ -503,11 +503,10 @@ AM_CONDITIONAL(HAVE_LCMS, [test "x$have_lcms" = xyes])
> >>
> >>  AC_PATH_PROG([wayland_scanner], [wayland-scanner])
> >>  if test x$wayland_scanner = x; then
> >> -     AC_MSG_ERROR([wayland-scanner is needed to compile weston])
> >
> > Shouldn't there still be an error message generated if the $PKG_CONFIG
> > run (below) fails?
> >
> The macro has an optional [action-if-not-found]. If it's missing (as
> below) we will error out by default.
> 
> >> +     PKG_CHECK_MODULES(WAYLAND_SCANNER, [wayland-scanner])
> >
> > Here's where I think I'm confused.  The main purpose of
> > PKG_CHECK_MODULES as I understand it is to define CFLAGS and LIBS
> > variables, so this would be e.g. WAYLAND_SCANNER_CFLAGS and
> > WAYLAND_SCANNER_LIBS.  Yet I'm not spotting where either of these are
> > actually used.  We only need the binary, not the library stuff, right?
> > Is it declaring any other variables or doing other work we need?
> >
> Afaik the macro does three things
>  1 Check for the presence of the required package(s)
>  2 Sets the relevant _CFLAGS and _LIBS variables.
>  3 Errors out with a very informative message, when
> action-if-not-found is not set.
> 
> Here we're using it for 1 & 3. One can use PKG_CHECK_EXISTS() and then
> manually add the error message, but that is rather uncommon afaict.
> 
> Hope that clears things up a bit.

Thank you, yes that does.

I'll give Bill and Daniels a chance to comment, but meanwhile:

Reviewed-by: Bryce Harrington <bryce at osg.samsung.com>

> -Emil
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