[libdmapsharing] configure.ac: clean up checks for mDNS library

[W. Michael Petullo <wmpetullo src gnome org>]

commit 6d933bd2faff96d5d4cdce21f7e2690139e4456b
Author: W. Michael Petullo <mike flyn org>
Date:   Mon Jul 6 00:37:48 2020 -0500

    configure.ac: clean up checks for mDNS library
    
    Closes #35.

 configure.ac | 65 +++++++++++++++++-------------------------------------------
 1 file changed, 18 insertions(+), 47 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 7e0790a..b73c7f7 100644
--- a/configure.ac
+++ b/configure.ac
@@ -213,89 +213,60 @@ AC_ARG_WITH(
 
 HAVE_AVAHI=no
 HAVE_DNS_SD=no # Apple's DNSSD library.
-HAVE_MDNS=no
 USE_AVAHI=no
 USE_DNS_SD=no
 
-PKG_CHECK_MODULES(
-       AVAHI,
-       avahi-client >= 0.6
-       avahi-glib >= 0.6,
-       HAVE_AVAHI=yes,
-       HAVE_AVAHI=no
-)
+if test x"$WITH_MDNS" = xauto || test x"$WITH_MDNS" = xavahi; then
+       PKG_CHECK_MODULES(
+               AVAHI,
+               avahi-client >= 0.6
+               avahi-glib >= 0.6,
+               HAVE_AVAHI=yes,
+               HAVE_AVAHI=no
+       )
+fi
 
-AC_CHECK_HEADERS(dns_sd.h, HAVE_DNS_SD=yes)
-if test x"$HAVE_DNS_SD" = xyes; then
-       AC_CHECK_LIB(dns_sd, DNSServiceRegister, DNS_SD_LIBS="-ldns_sd",)
+if test x"$HAVE_AVAHI" = xno; then
+       if test x"$WITH_MDNS" = xauto || test x"$WITH_MDNS" = xdns_sd; then
+               AC_CHECK_HEADERS(dns_sd.h, HAVE_DNS_SD=yes)
+               if test x"$HAVE_DNS_SD" = xyes; then
+                       AC_CHECK_LIB(dns_sd, DNSServiceRegister, DNS_SD_LIBS="-ldns_sd",)
+               fi
+       fi
 fi
 
 if test x"$WITH_MDNS" = xauto; then
        if test x"$HAVE_AVAHI" = xyes; then
                MDNS_CFLAGS=$AVAHI_CFLAGS
                MDNS_LIBS=$AVAHI_LIBS
-               AC_DEFINE(
-                       WITH_AVAHI,
-                       1,
-                       [Define if mDNS/DNS-SD implementation uses Avahi]
-               )
                USE_AVAHI=yes
                AC_MSG_NOTICE([Detected Avahi; using it for mDNS/DNS-SD])
-               if test x$HAVE_AVAHI = xyes; then
-                       AC_DEFINE(
-                               HAVE_AVAHI,
-                               1,
-                               [Define if mDNS/DNS-SD implementation uses Avahi]
-                       )
-               fi
-
-               HAVE_MDNS=yes
        elif test x"$HAVE_DNS_SD" = xyes; then
                MDNS_CFLAGS=$DNS_SD_CFLAGS
                MDNS_LIBS=$DNS_SD_LIBS
-               AC_DEFINE(
-                       WITH_DNS_SD,
-                       1,
-                       [Define if mDNS/DNS-SD implementation uses Apple's DNSSD]
-               )
                USE_DNS_SD=yes
                AC_MSG_NOTICE([Detected Apple's DNSSD; using it for mDNS/DNS-SD])
-               HAVE_MDNS=yes
        else
                AC_MSG_ERROR([Must have avahi or dns_sd.h development files installed])
        fi
-fi
-
-if test x"$WITH_MDNS" = xavahi; then
+elif test x"$WITH_MDNS" = xavahi; then
        if test x"$HAVE_AVAHI" = xno; then
                AC_MSG_ERROR([Avahi explicitly requested but not found. Install Avahi, or try 
--with-mdns=dns_sd])
        fi
 
        MDNS_CFLAGS=$AVAHI_CFLAGS
        MDNS_LIBS=$AVAHI_LIBS
-       AC_DEFINE(WITH_AVAHI, 1, [Define if mDNS/DNS-SD implementation uses Avahi])
        USE_AVAHI=yes
        AC_MSG_NOTICE([Using Avahi for mDNS/DNS-SD])
-
-       if test x$HAVE_AVAHI = xyes; then
-               AC_DEFINE(HAVE_AVAHI, 1, [Define if mDNS/DNS-SD implementation uses Avahi])
-       fi
-
-       HAVE_MDNS=yes
-fi
-
-if test x"$WITH_MDNS" = xdns_sd; then
+elif test x"$WITH_MDNS" = xdns_sd; then
        if test x"$HAVE_DNS_SD" = xno; then
                AC_MSG_ERROR([Apple DNSSD explicitly requested but not found. Install Apple DNSSD, or try 
--with-mdns=avahi])
        fi
 
        MDNS_CFLAGS=$DNS_SD_CFLAGS
        MDNS_LIBS=$DNS_SD_LIBS
-       AC_DEFINE(WITH_DNS_SD, 1, [Define if mDNS/DNS-SD implementation uses Apple's DNSSD])
        USE_DNS_SD=yes
        AC_MSG_NOTICE([Using Apple's DNSSD for mDNS/DNS-SD])
-
-       HAVE_MDNS=yes
 fi
 
 AM_CONDITIONAL(USE_AVAHI, test "x$USE_AVAHI" = "xyes")