From 5b56596df794ed09319c69dc9e7d93c8a8e4050b Mon Sep 17 00:00:00 2001
From: ManoloFLTK <41016272+ManoloFLTK@users.noreply.github.com>
Date: Wed, 6 Dec 2023 15:37:04 +0100
Subject: [PATCH] configure+macOS: enforce local zlib when local libpng is
 active

---
 configure.ac | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/configure.ac b/configure.ac
index 55362e007..0c6958b0a 100644
--- a/configure.ac
+++ b/configure.ac
@@ -694,6 +694,14 @@ if test x$enable_localzlib != xyes; then
 	    syszlib_ok=yes
 	fi])
 fi
+case "$host_os" in
+  darwin*)
+# macOS: enforce local zlib when local libpng is active
+    if test x$syszlib_ok = xyes -a x$enable_localpng != xno; then
+      syszlib_ok=no
+    fi
+    ;;
+esac
 # Now set the Z lib and include flags according to the requested mode and availability
 if test x$enable_localzlib = xyes -o x$syszlib_ok = xno ; then
     ZLIBINC="-I../zlib"