[gobject-introspection] autotools: Make INTROSPECTION_GIRDIR/INTROSPECTION_TYPELIBDIR respect prefix/datadir/libdir

[Christoph Reiter <creiter src gnome org>]

commit bd3bb463adf6952bcad5de967181a950ca105111
Author: Christoph Reiter <reiter christoph gmail com>
Date:   Sun Nov 10 19:51:33 2019 +0100

    autotools: Make INTROSPECTION_GIRDIR/INTROSPECTION_TYPELIBDIR respect prefix/datadir/libdir
    
    The provided m4 macro uses pkg-config for setting INTROSPECTION_GIRDIR and INTROSPECTION_TYPELIBDIR
    which can be used to install the generated gir/typelib files into. Up until now this always used
    the prefix encoded in the g-i .pc file and ignored the prefix provided by the autotools project using it.
    
    This can be fixed by passing "--define-variable=datadir=/mydatadir" to pkg-config. To get the real value 
of
    datadir include a copy of AS_AC_EXPAND in our m4 and use it to expand the variables we need so we can
    pass the real paths to pkg-config which will use them to generate the new girdir/typelibdir paths.
    
    The reason this hasn't been much of a problem is that the example autotools code suggested using
    "girdir = $(datadir)/gir-1.0" and "typelibsdir = $(libdir)/girepository-1.0" and not using the variables 
defined
    by our macro, so not many projects used it. Now both ways should work.
    
    See !133

 m4/introspection.m4 | 50 ++++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 48 insertions(+), 2 deletions(-)
---
diff --git a/m4/introspection.m4 b/m4/introspection.m4
index d89c3d90..0513a4c8 100644
--- a/m4/introspection.m4
+++ b/m4/introspection.m4
@@ -8,6 +8,47 @@ dnl
 
 # serial 1
 
+dnl This is a copy of AS_AC_EXPAND
+dnl
+dnl (C) 2003, 2004, 2005 Thomas Vander Stichele <thomas at apestaart dot org>
+dnl Copying and distribution of this file, with or without modification,
+dnl are permitted in any medium without royalty provided the copyright
+dnl notice and this notice are preserved.
+m4_define([_GOBJECT_INTROSPECTION_AS_AC_EXPAND],
+[
+  EXP_VAR=[$1]
+  FROM_VAR=[$2]
+
+  dnl first expand prefix and exec_prefix if necessary
+  prefix_save=$prefix
+  exec_prefix_save=$exec_prefix
+
+  dnl if no prefix given, then use /usr/local, the default prefix
+  if test "x$prefix" = "xNONE"; then
+    prefix="$ac_default_prefix"
+  fi
+  dnl if no exec_prefix given, then use prefix
+  if test "x$exec_prefix" = "xNONE"; then
+    exec_prefix=$prefix
+  fi
+
+  full_var="$FROM_VAR"
+  dnl loop until it doesn't change anymore
+  while true; do
+    new_full_var="`eval echo $full_var`"
+    if test "x$new_full_var" = "x$full_var"; then break; fi
+    full_var=$new_full_var
+  done
+
+  dnl clean up
+  full_var=$new_full_var
+  AC_SUBST([$1], "$full_var")
+
+  dnl restore prefix and exec_prefix
+  prefix=$prefix_save
+  exec_prefix=$exec_prefix_save
+])
+
 m4_define([_GOBJECT_INTROSPECTION_CHECK_INTERNAL],
 [
     AC_BEFORE([AC_PROG_LIBTOOL],[$0])dnl setup libtool first
@@ -50,6 +91,11 @@ m4_define([_GOBJECT_INTROSPECTION_CHECK_INTERNAL],
 
     AC_MSG_RESULT([$found_introspection])
 
+    dnl expand datadir/libdir so we can pass them to pkg-config
+    dnl and get paths relative to our target directories
+    _GOBJECT_INTROSPECTION_AS_AC_EXPAND(_GI_EXP_DATADIR, "$datadir")
+    _GOBJECT_INTROSPECTION_AS_AC_EXPAND(_GI_EXP_LIBDIR, "$libdir")
+
     INTROSPECTION_SCANNER=
     INTROSPECTION_COMPILER=
     INTROSPECTION_GENERATE=
@@ -59,8 +105,8 @@ m4_define([_GOBJECT_INTROSPECTION_CHECK_INTERNAL],
        INTROSPECTION_SCANNER=`$PKG_CONFIG --variable=g_ir_scanner gobject-introspection-1.0`
        INTROSPECTION_COMPILER=`$PKG_CONFIG --variable=g_ir_compiler gobject-introspection-1.0`
        INTROSPECTION_GENERATE=`$PKG_CONFIG --variable=g_ir_generate gobject-introspection-1.0`
-       INTROSPECTION_GIRDIR=`$PKG_CONFIG --variable=girdir gobject-introspection-1.0`
-       INTROSPECTION_TYPELIBDIR="$($PKG_CONFIG --variable=typelibdir gobject-introspection-1.0)"
+       INTROSPECTION_GIRDIR=`$PKG_CONFIG --define-variable=datadir="${_GI_EXP_DATADIR}" --variable=girdir 
gobject-introspection-1.0`
+       INTROSPECTION_TYPELIBDIR="$($PKG_CONFIG --define-variable=libdir="${_GI_EXP_LIBDIR}" 
--variable=typelibdir gobject-introspection-1.0)"
        INTROSPECTION_CFLAGS=`$PKG_CONFIG --cflags gobject-introspection-1.0`
        INTROSPECTION_LIBS=`$PKG_CONFIG --libs gobject-introspection-1.0`
        INTROSPECTION_MAKEFILE=`$PKG_CONFIG --variable=datadir 
gobject-introspection-1.0`/gobject-introspection-1.0/Makefile.introspection