cmake/modules/GtkDoc.cmake, Install.txt - fixes

Install.txt

@@ -73,6 +73,20 @@ For example, say you want to use Clang to build on Linux.
 Then you can set the C and C++ compilers at CMake time, like so:
 % CC=clang CXX=clang++ cmake ..
 
+== Building for OSX (Mac) ==
+Homebrew:
+  A couple of necessary dependencies do not have their headers
+  and development libraries linked into /usr/local/{include,lib} due
+  to possible contamination with the operating system versions of the
+  same name.  This is known to be the case with libffi and libxml2
+  Fix is to export PKG_CONFIG_PATH so CMake can find them, as in:
+    export PKG_CONFIG_PATH=/usr/local/opt/libffi/lib/pkgconfig:\
+                           /usr/local/opt/libxml2/lib/pkgconfig
+
+  Also, if building the gtkdocs you'll need to say where the xml
+  catalog files can be found so the gtk entities are located, like so:
+    export XML_CATALOG_FILES=/usr/local/etc/xml/catalog
+
 == Optional Dependencies ==
 * libicu "International Components for Unicode" development libraries.
   Highly recommended for RSCALE support.

cmake/modules/GtkDoc.cmake

@@ -59,9 +59,10 @@ macro(add_gtkdoc _module _namespace _deprecated_guards _srcdirsvar _depsvar _ign
     list(APPEND _filedeps ${_files})
   endforeach()
 
-  set(_mkhtml_prefix "")
   if(APPLE)
-    set(_mkhtml_prefix "${CMAKE_COMMAND} -E env XML_CATALOG_FILES=\"/usr/local/etc/xml/catalog\"")
+    if(NOT DEFINED ENV{XML_CATALOG_FILES})
+      message(FATAL_ERROR "On OSX, please run \'export XML_CATALOG_FILES=/usr/local/etc/xml/catalog\' first; else the gtk entities cannot be located.")
+    endif()
   endif()
 
   set(_scangobj_deps)
@@ -70,8 +71,8 @@ macro(add_gtkdoc _module _namespace _deprecated_guards _srcdirsvar _depsvar _ign
   set(_scangobj_ldflags "")
   set(_scangobj_ld_lib_dirs "")
 
-  list(APPEND _scangobj_cflags_list -I${INCLUDE_INSTALL_DIR})
-  list(APPEND _scangobj_ldflags -L${LIB_INSTALL_DIR})
+  list(APPEND _scangobj_cflags_list -I${CMAKE_INSTALL_PREFIX}/${INCLUDE_INSTALL_DIR})
+  list(APPEND _scangobj_ldflags -L${CMAKE_INSTALL_PREFIX}/${LIB_INSTALL_DIR})
 
   foreach(opt IN LISTS ${_depsvar})
     if(TARGET ${opt})
@@ -164,7 +165,7 @@ macro(add_gtkdoc _module _namespace _deprecated_guards _srcdirsvar _depsvar _ign
 
     COMMAND ${CMAKE_COMMAND} -E make_directory "${CMAKE_CURRENT_BINARY_DIR}/html"
 
-    COMMAND ${CMAKE_COMMAND} -E chdir "${CMAKE_CURRENT_BINARY_DIR}/html" ${_mkhtml_prefix} ${GTKDOC_MKHTML} --path=.. ${_module} ../${_module}-docs.sgml
+    COMMAND ${CMAKE_COMMAND} -E chdir "${CMAKE_CURRENT_BINARY_DIR}/html" ${GTKDOC_MKHTML} --path=.. ${_module} ../${_module}-docs.sgml
 
     COMMAND ${GTKDOC_FIXXREF}
       --module=${_module}