dnl Copyright © 2012 Nick Bowler
dnl
dnl Definitions to help maintain compatibility with older versions of Automake.
dnl
dnl License WTFPL2: Do What The Fuck You Want To Public License, version 2.
dnl This is free software: you are free to do what the fuck you want to.
dnl There is NO WARRANTY, to the extent permitted by law.

dnl DX_AUTOMAKE_COMPAT
dnl
dnl Provides definitions to help maintain compatibility with older versions of
dnl Automake.  Currently, this means:
dnl
dnl  - AM_V and AM_DEFAULT_V (new in Automake 1.12) are defined and AC_SUBSTed
dnl    if Automake did not already, in a manner compatible with silent-rules
dnl    support from previous versions.
dnl
dnl  - A make variable DX_ALIGN_V is defined which contain printf alignment
dnl    flags for silent-rules output, since the alignment changed between
dnl    Automake 1.11 and 1.12.  It is intended to be used like this:
dnl
dnl      MYGEN_V   = $(MYGEN_V@AM_V@)
dnl      MYGEN_V_  = $(MYGEN_V_@AM_DEFAULT_V)
dnl      MYGEN_V_0 = @printf '  %$(DX_ALIGN_V)s %s\n' 'MYGEN   ' $@
dnl
dnl    The spacing after MYGEN should be defined so that the silent-rules
dnl    alignment is correct for the latest version of Automake if DX_ALIGN_V
dnl    is empty (that way, this definition provides only backwards
dnl    compatibility).  However, it is irrelevant when DX_ALIGN_V is defined
dnl    by this macro, as the spacing will always be correct.  This feature
dnl    maintains alignment by truncating the argument, so it will only work
dnl    properly if your string can actually be aligned in all versions of
dnl    Automake being targeted (this means you are limited to 6 characters
dnl    in Automake 1.11).

AC_DEFUN_ONCE([DX_AUTOMAKE_COMPAT], [dnl
AC_REQUIRE([DX_INIT])

AC_CONFIG_COMMANDS_PRE([dnl
	AS_VAR_SET_IF([AM_V], [], [AC_SUBST([AM_V], ['$(V)'])])
	AS_VAR_SET_IF([AM_DEFAULT_V], [],
		[AC_SUBST([AM_DEFAULT_V], ['$(AM_DEFAULT_VERBOSITY)'])])])

# This will only work if there is a Makefile.in generated at the top srcdir.
AC_CACHE_CHECK([for alignment of silent-rules output], [dx_cv_align_v], [dnl
cat >conftest.sed <<'EOF'
/^am__v_GEN_0 *=/{
	s/@<:@^"@:>@*"  \(GEN *\).*/\1/
	s/ /x/g
	p
}
EOF
if sed -nf conftest.sed Makefile.in >conftest.out 2>/dev/null; then
	read dx_genline <conftest.out
	dx_cv_align_v=`expr "$dx_genline" : '.*'`
	test $dx_cv_align_v -eq 0 && dx_cv_align_v=unknown
fi
: "${dx_cv_align_v:=unknown}"
rm -f conftest*
])

AS_IF([test x"$dx_cv_align_v" != x"unknown"],
	[AC_SUBST([DX_ALIGN_V], [-$dx_cv_align_v.$dx_cv_align_v])])
])