$NetBSD: patch-configure,v 1.1 2020/08/08 22:18:27 brook Exp $

Using == with test is not portable; replace with =.

Use pkg-config to define compiler flags for libpng.

--- configure.orig	2020-08-07 23:28:40.807171000 +0000
+++ configure
@@ -4218,7 +4218,7 @@ else
 $as_echo "libraries $x_libraries, headers $x_includes" >&6; }
 fi
 
-if test "x$no_x" == "xyes"; then
+if test "x$no_x" = "xyes"; then
 	echo "------------------------------------------------------------------------------------"
 	echo "Error, the X libraries and development headers must be installed for ncview to work!"
 	echo "------------------------------------------------------------------------------------"
@@ -5496,6 +5496,10 @@ fi
 
 
 fi
+if test x$PNG_INCDIR = x; then
+	PNG_INC_PRESENT=yes
+        PNG_CPPFLAGS=`pkg-config --cflags-only-I libpng`
+else
 PNG_INC_PRESENT=no
 if test x$PNG_INCDIR != x; then
 	PNG_INC_PRESENT=yes
@@ -5504,6 +5508,7 @@ else
 	echo "** Could not find the png.h file, so -frames support will not be included  **"
 	echo "** Install the PNG library (and development headers) to fix this           **"
 fi
+fi
 PNG_LIBNAME=libpng.so
 
 # Check whether --with-png_libdir was given.
@@ -5708,6 +5713,13 @@ if test $PNG_INC_PRESENT = yes; then
 
 $as_echo "#define HAVE_PNG 1" >>confdefs.h
 
+	else
+		PNG_PRESENT=yes
+		PNG_LIBS=`pkg-config --libs-only-l libpng`
+		PNG_LDFLAGS=`pkg-config --libs libpng`
+
+$as_echo "#define HAVE_PNG 1" >>confdefs.h
+
 	fi
 fi