From ba5316ca8e8e2799a05ab3510c68cdc623896861 Mon Sep 17 00:00:00 2001
From: ehofman <ehofman>
Date: Tue, 17 Jun 2003 16:55:21 +0000
Subject: [PATCH] Add an OpenGL extension query function which should be cross
 platform

---
 simgear/screen/Makefile.am    |  1 +
 simgear/screen/extensions.hxx | 31 +++++++++++++++++++++++++++++++
 2 files changed, 32 insertions(+)
 create mode 100644 simgear/screen/extensions.hxx

diff --git a/simgear/screen/Makefile.am b/simgear/screen/Makefile.am
index c5c05dcc..86a547c5 100644
--- a/simgear/screen/Makefile.am
+++ b/simgear/screen/Makefile.am
@@ -19,6 +19,7 @@ include_HEADERS = \
 	texture.hxx \
 	$(IMAGE_SERVER_INCL) \
 	screen-dump.hxx \
+	extensions.hxx \
 	tr.h
 
 libsgscreen_a_SOURCES = \
diff --git a/simgear/screen/extensions.hxx b/simgear/screen/extensions.hxx
new file mode 100644
index 00000000..949345a8
--- /dev/null
+++ b/simgear/screen/extensions.hxx
@@ -0,0 +1,31 @@
+#ifndef __SG_EXTENSIONS_HXX
+#define __SG_EXTENSIONS_HXX 1
+
+#ifndef WIN32
+#include <dlfcn.h>
+#endif
+
+inline void (*SGLookupFunction(const char *func))() {
+
+#if defined( WIN32 )
+        return (void (*)()) wglGetProcAddress(func);
+
+#else
+
+  // If the target system s UNIX and the ARB_get_proc_address
+  // GLX extension is *not* guaranteed to be supported. An alternative
+  // dlsym-based approach will be used instead.
+  #if defined( linux ) || defined ( sgi )
+        void *libHandle;
+        void (*fptr)();
+        libHandle = dlopen("libGL.so", RTLD_LAZY);
+        fptr = (void (*)()) dlsym(libHandle, func);
+        dlclose(libHandle);
+        return fptr;
+  #else
+        return glXGetProcAddressARB(func);
+  #endif
+#endif
+}
+
+#endif
-- 
2.39.5