From 0c7b1419ff5b1dc7fd7a27ff221785bafa5ca4c1 Mon Sep 17 00:00:00 2001
From: Matt Turner <mattst88@gmail.com>
Date: Mon, 20 Aug 2012 14:44:01 -0700
Subject: build: Allow linking against OSMesa instead of libGL

---
 Makefile.am  |  6 +++---
 configure.ac | 24 +++++++++++++++++++++---
 2 files changed, 24 insertions(+), 6 deletions(-)

diff --git a/Makefile.am b/Makefile.am
index 23ae5e7..332b96c 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -30,8 +30,8 @@ AM_CPPFLAGS = -DLIBRARYBUILD \
 	-I$(top_srcdir)/src/libnurbs/internals \
 	-I$(top_srcdir)/src/libnurbs/interface \
 	-I$(top_srcdir)/src/libnurbs/nurbtess
-AM_CFLAGS = $(GL_CFLAGS) $(WARNCFLAGS)
-AM_CXXFLAGS = $(GL_CFLAGS) $(WARNCXXFLAGS)
+AM_CFLAGS = $(GL_CFLAGS) $(OSMESA_CFLAGS) $(WARNCFLAGS)
+AM_CXXFLAGS = $(GL_CFLAGS) $(OSMESA_CFLAGS) $(WARNCXXFLAGS)
 
 GLU_LIBRARY_VERSION=1:3:1
 lib_LTLIBRARIES = libGLU.la
@@ -125,5 +125,5 @@ libGLU_la_SOURCES =						\
 	src/libnurbs/nurbtess/sampleMonoPoly.cc			\
 	src/libnurbs/nurbtess/sampledLine.cc			\
 	src/libnurbs/nurbtess/searchTree.cc
-libGLU_la_LIBADD = $(GL_LIBS)
+libGLU_la_LIBADD = $(GL_LIBS) $(OSMESA_LIBS)
 libGLU_la_LDFLAGS = -version-number $(GLU_LIBRARY_VERSION) -no-undefined -export-symbols-regex '^glu'
diff --git a/configure.ac b/configure.ac
index e0ee467..68ff97a 100644
--- a/configure.ac
+++ b/configure.ac
@@ -47,9 +47,26 @@ m4_ifndef([PKG_PROG_PKG_CONFIG],
   ACLOCAL="aclocal -I/other/macro/dir" before running autoreconf.])])
 PKG_PROG_PKG_CONFIG()
 
-dnl Get the pkg-config definitions for libGL.  We include a fallback
-dnl path for GL implementation that don't provide a .pc file
-PKG_CHECK_MODULES(GL, [gl], [], [
+AC_ARG_ENABLE(osmesa,
+              AS_HELP_STRING([--enable-osmesa],
+                [Enable use of OSMesa instead of libGL]),
+              [OSMESA="$enableval"],
+              [OSMESA=no])
+
+dnl Get the pkg-config definitions for libGL/OSMesa.  We include a fallback
+dnl path for implementations that don't provide a .pc file
+if test "x$OSMESA" = "xyes"; then
+    PKG_CHECK_MODULES(OSMESA, [osmesa], [], [
+          AC_CHECK_HEADER([GL/osmesa.h],
+                  [],
+                  AC_MSG_ERROR([OSMesa not found]))
+          AC_CHECK_LIB([OSMesa],
+                   [glBegin],
+                   [OSMESA_LIBS=-lOSMesa],
+                   AC_MSG_ERROR([OSMesa required]))
+          ])
+else
+    PKG_CHECK_MODULES(GL, [gl], [], [
           AC_CHECK_HEADER([GL/gl.h],
                   [],
                   AC_MSG_ERROR([GL not found]))
@@ -58,6 +75,7 @@ PKG_CHECK_MODULES(GL, [gl], [], [
                    [GL_LIBS=-lGL],
                    AC_MSG_ERROR([GL required]))
           ])
+fi
 
 dnl Set up C warning flags.
 if test "x$GCC" = xyes; then
-- 
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