ENH: add depend information from qrc files

Modules/FindQt4.cmake

@@ -776,11 +776,21 @@ IF (QT4_QMAKE_FOUND)
     FOREACH (it ${ARGN})
       GET_FILENAME_COMPONENT(outfilename ${it} NAME_WE)
       GET_FILENAME_COMPONENT(infile ${it} ABSOLUTE)
+      GET_FILENAME_COMPONENT(rc_path ${infile} PATH)
       SET(outfile ${CMAKE_CURRENT_BINARY_DIR}/qrc_${outfilename}.cxx)
+      #  parse file for dependencies
+      FILE(READ "${infile}" _RC_FILE_CONTENTS)
+      STRING(REGEX MATCHALL "<file>[^<]*" _RC_FILES "${_RC_FILE_CONTENTS}")
+      SET(_RC_DEPENDS)
+      FOREACH(_RC_FILE ${_RC_FILES})
+        STRING(REGEX REPLACE "^<file>" "" _RC_FILE "${_RC_FILE}")
+        SET(_RC_DEPENDS ${_RC_DEPENDS} "${rc_path}/${_RC_FILE}")
+      ENDFOREACH(_RC_FILE)
       ADD_CUSTOM_COMMAND(OUTPUT ${outfile}
         COMMAND ${QT_RCC_EXECUTABLE}
         ARGS -name ${outfilename} -o ${outfile} ${infile}
-        MAIN_DEPENDENCY ${infile} )
+        MAIN_DEPENDENCY ${infile}
+        DEPENDS ${_RC_DEPENDS})
       SET(${outfiles} ${${outfiles}} ${outfile})
     ENDFOREACH (it)