From Alberto Luaces, "I have updated a bit the pkg-config system:

1. Install the .pc file for osgIntrospection only if it is compiled,
instead of unconditionally.

2. New .pc file for osgQt, also created only if that library is actually
compiled.
"

CMakeLists.txt

@@ -875,9 +875,16 @@ SET(PKGCONFIG_FILES
   openscenegraph-osgShadow
   openscenegraph-osgAnimation
   openscenegraph-osgVolume
-  openscenegraph-osgIntrospection
 )
 
+IF(BUILD_OSG_WRAPPERS)
+  SET(PKGCONFIG_FILES ${PKGCONFIG_FILES} openscenegraph-osgIntrospection)
+ENDIF(BUILD_OSG_WRAPPERS)
+
+IF(QT4_FOUND)
+  SET(PKGCONFIG_FILES ${PKGCONFIG_FILES} openscenegraph-osgQt)
+ENDIF(QT4_FOUND)
+
 FOREACH(PKGCONFIG_FILE ${PKGCONFIG_FILES})
   CONFIGURE_FILE(${PROJECT_SOURCE_DIR}/packaging/pkgconfig/${PKGCONFIG_FILE}.pc.in
     ${PROJECT_BINARY_DIR}/packaging/pkgconfig/${PKGCONFIG_FILE}.pc

packaging/pkgconfig/openscenegraph-osgQt.pc.in

@@ -0,0 +1,14 @@
+# pkg-config source file
+
+prefix=@CMAKE_INSTALL_PREFIX@
+exec_prefix=${prefix}
+libdir=${exec_prefix}/lib@LIB_POSTFIX@
+includedir=${prefix}/include
+
+Name: openscenegraph-osgQt
+Description: osgQt utility library.
+Version: @OPENSCENEGRAPH_VERSION@
+Requires: openscenegraph-osgWidget openscenegraph-osgDB openscenegraph-osgUtil openscenegraph-osg openthreads
+Conflicts:
+Libs: -L${libdir} -losgQt
+Cflags: -I${includedir}