diff -Nurd -x'*~' plotutils-2.6.orig/configure.ac plotutils-2.6/configure.ac
--- plotutils-2.6.orig/configure.ac	2009-07-29 23:14:09.000000000 -0400
+++ plotutils-2.6/configure.ac	2011-07-10 12:39:00.000000000 -0400
@@ -331,7 +331,7 @@
 fi])
 
 # Do we build libplotter, the C++ library, and other C++ software?
-AC_ARG_ENABLE(libplotter, [  --enable-libplotter     build the C++ Plotter class library and C++ software], echo enabling construction of the C++ class library; no_libplotter="no", no_libplotter="yes"; extralib="")
+AC_ARG_ENABLE(libplotter, [  --enable-libplotter     build the C++ Plotter class library and C++ software], echo enabling construction of the C++ class library; [AC_PROG_CXX] no_libplotter="no", no_libplotter="yes"; extralib="")
 AM_CONDITIONAL(NO_LIBPLOTTER, test "x$no_libplotter" = "xyes")
 
 # Do we build and install a standalone version of the libxmi
diff -Nurd -x'*~' plotutils-2.6.orig/libplot/Makefile.am plotutils-2.6/libplot/Makefile.am
--- plotutils-2.6.orig/libplot/Makefile.am	2009-07-28 22:16:02.000000000 -0400
+++ plotutils-2.6/libplot/Makefile.am	2011-07-10 10:43:38.000000000 -0400
@@ -6,7 +6,7 @@
 
 libplot_la_LDFLAGS = -version-info 4:4:2
 
-INCLUDES = $(X_CFLAGS) -I$(srcdir)/../include -DLIBPLOT
+INCLUDES = -I$(srcdir)/../include $(CPPFLAGS) $(X_CFLAGS) -DLIBPLOT
 
 MISRC = mi_alloc.c mi_api.c mi_arc.c mi_canvas.c mi_fllarc.c mi_fllrct.c \
 mi_fplycon.c mi_gc.c mi_ply.c mi_plycon.c mi_plygen.c mi_plypnt.c	 \
diff -Nurd -x'*~' plotutils-2.6.orig/libplot/z_write.c plotutils-2.6/libplot/z_write.c
--- plotutils-2.6.orig/libplot/z_write.c	2008-07-15 20:54:10.000000000 -0400
+++ plotutils-2.6/libplot/z_write.c	2011-07-10 12:03:45.000000000 -0400
@@ -164,7 +164,7 @@
     }
 
   /* cleanup after libpng errors (error handler does a longjmp) */
-  if (setjmp (png_ptr->jmpbuf))
+  if (setjmp (png_jmpbuf (png_ptr)))
     {
       png_destroy_write_struct (&png_ptr, (png_info **)NULL);
       return -1;
@@ -444,7 +444,11 @@
 #endif
     }
 
+#if (PNG_LIBPNG_VER < 10500)
   longjmp (png_ptr->jmpbuf, 1);
+#else
+  png_longjmp (png_ptr, 1);
+#endif
 }
 
 static void 
@@ -515,7 +519,11 @@
 #endif
     }
 
+#if (PNG_LIBPNG_VER < 10500)
   longjmp (png_ptr->jmpbuf, 1);
+#else
+  png_longjmp (png_ptr, 1);
+#endif
 }
 
 static void 
diff -Nurd -x'*~' plotutils-2.6.orig/libplotter/Makefile.am plotutils-2.6/libplotter/Makefile.am
--- plotutils-2.6.orig/libplotter/Makefile.am	2009-07-28 22:16:18.000000000 -0400
+++ plotutils-2.6/libplotter/Makefile.am	2011-07-10 10:48:44.000000000 -0400
@@ -4,7 +4,7 @@
 
 libplotter_la_LDFLAGS = -version-info 4:4:2
 
-INCLUDES = $(X_CFLAGS) -I$(srcdir)/../include -DLIBPLOT -DLIBPLOTTER
+INCLUDES = -I$(srcdir)/../include $(CPPFLAGS) $(X_CFLAGS) -DLIBPLOT -DLIBPLOTTER
 
 MISRC = mi_alloc.cc mi_api.cc mi_arc.cc mi_canvas.cc mi_fllarc.cc	\
 mi_fllrct.cc mi_fplycon.cc mi_gc.cc mi_ply.cc mi_plycon.cc mi_plygen.cc	\