From c3880a25b661522cfe95a3d6c745de68929a2590 Mon Sep 17 00:00:00 2001
From: Chris White <chrisw@leehayes.com>
Date: Fri, 3 Aug 2018 17:57:45 -0400
Subject: [PATCH] Remove duplication of REGISTER_WINDOWINGSYSTEMINTERFACE code

Refactor so GraphicsWindowWin32 doesn't duplicate code in
<osg/GraphicsContext>.

Also, add OSGVIEWER_EXPORT to X11WindowingSystemInterface so
X11WindowingSystemInterface examples can build on cygwin.
This change parallels that in commit 0bca415d5af4647da868888c1588b9617dbe3eb8.
---
 include/osg/GraphicsContext           | 9 +++++++--
 src/osgViewer/GraphicsWindowWin32.cpp | 3 +--
 src/osgViewer/GraphicsWindowX11.cpp   | 2 +-
 3 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/include/osg/GraphicsContext b/include/osg/GraphicsContext
index 33d7b0b12..875b0436a 100644
--- a/include/osg/GraphicsContext
+++ b/include/osg/GraphicsContext
@@ -597,10 +597,15 @@ struct WindowingSystemInterfaceProxy
     osg::ref_ptr<T> _wsi;
 };
 
-#define REGISTER_WINDOWINGSYSTEMINTERFACE(ext, classname) \
-    extern "C" void graphicswindow_##ext(void) {} \
+// Internal use only - compile on C90 compilers, which prohibit empty macro arguments.
+#define _OSG_GRAPHICSCONTEXT_NO_ATTRIBS
+
+#define REGISTER_WINDOWINGSYSTEMINTERFACE2(ext, classname, attribs) \
+    extern "C" attribs void graphicswindow_##ext(void) {} \
     static osg::WindowingSystemInterfaceProxy<classname> s_proxy_##classname(#ext);
 
+#define REGISTER_WINDOWINGSYSTEMINTERFACE(ext, classname) \
+    REGISTER_WINDOWINGSYSTEMINTERFACE2(ext, classname, _OSG_GRAPHICSCONTEXT_NO_ATTRIBS)
 }
 
 #endif
diff --git a/src/osgViewer/GraphicsWindowWin32.cpp b/src/osgViewer/GraphicsWindowWin32.cpp
index 91e6c8f49..b38423c1b 100644
--- a/src/osgViewer/GraphicsWindowWin32.cpp
+++ b/src/osgViewer/GraphicsWindowWin32.cpp
@@ -3148,8 +3148,7 @@ static RegisterWindowingSystemInterfaceProxy createWindowingSystemInterfaceProxy
 } // namespace OsgViewer
 
 
-extern "C" OSGVIEWER_EXPORT void graphicswindow_Win32(void) {}
-static osg::WindowingSystemInterfaceProxy<Win32WindowingSystem> s_proxy_Win32WindowingSystem("Win32");
+REGISTER_WINDOWINGSYSTEMINTERFACE2(Win32,Win32WindowingSystem,OSGVIEWER_EXPORT)
 
 void GraphicsWindowWin32::raiseWindow()
 {
diff --git a/src/osgViewer/GraphicsWindowX11.cpp b/src/osgViewer/GraphicsWindowX11.cpp
index 9ee634219..453d38829 100644
--- a/src/osgViewer/GraphicsWindowX11.cpp
+++ b/src/osgViewer/GraphicsWindowX11.cpp
@@ -2277,7 +2277,7 @@ public:
 
 };
 
-REGISTER_WINDOWINGSYSTEMINTERFACE(X11, X11WindowingSystemInterface)
+REGISTER_WINDOWINGSYSTEMINTERFACE2(X11, X11WindowingSystemInterface, OSGVIEWER_EXPORT)
 
 void GraphicsWindowX11::raiseWindow()
 {