vtk: Need to explicitly state we are using X11 OpenGL

For a while now OS X vtk has been attempting to use the native
Framework regardless of the Cocoa/X11 setting. It was working because
X11 OpenGL was picked up by default anyhow.

Not tested on Linux (where it was presumably working fine without
any fiddling) so not sure if this patch should only be enabled
on OS X.

thirdparty/kitware/vtk/Makefile.am

@@ -31,6 +31,10 @@ all:
 	        -D TK_INCLUDE_PATH:PATH=$(prefix)/include \
 	        -D TK_LIBRARY:FILEPATH=$(prefix)/lib/libtk8.5$(SHLIB_EXT) \
 	        -D VTK_OPENGL_HAS_OSMESA:BOOL=OFF \
+                -D CMAKE_FIND_FRAMEWORK=NEVER \
+                -D OPENGL_INCLUDE_DIR:PATH=$(X11_INCLUDES) \
+                -D OPENGL_gl_LIBRARY:FILEPATH=$(X11_LIBS)/libGL$(SHLIB_EXT) \
+                -D OPENGL_glu_LIBRARY:FILEPATH=$(X11_LIBS)/libGLU$(SHLIB_EXT) \
 	        -D VTK_USE_CARBON:BOOL=OFF \
 	        -D VTK_USE_COCOA:BOOL=OFF  \
 	        -D VTK_USE_GEOVIS:BOOL=OFF \

thirdparty/kitware/vtk/configure.ac

@@ -9,6 +9,15 @@ AC_PREREQ(2.50)
 dnl    Require Starlink automake
 AM_INIT_AUTOMAKE(1.8.2-starlink)
 
+dnl  Need to work out where the X11 libraries are. On a Mac
+dnl  VTK always looks for the OpenGL framework even if building
+dnl  against X11.
+AC_PATH_XTRA
+X11_INCLUDES=$x_includes
+X11_LIBS=$x_libraries
+AC_SUBST(X11_INCLUDES)
+AC_SUBST(X11_LIBS)
+
 dnl    Get extension for shared libraries.
 dnl    Need to determine the suffix for shareable libraries, as used by
 dnl    Tcl, so we can link against the GAIA dynamic library.