Anybody can explain for me. If we install public headers to /usr/include/qtxdg/, what should the variable QTXDG_INCLUDE_DIR contain?

Variant 1.
   The QTXDG_INCLUDE_DIR is equal "/usr/include". In this case in the code we use "#include <qtxdg/XdgDirs>". The X11 behave so.

Variant 2.
   The QTXDG_INCLUDE_DIR is equal "/usr/include/qtxdg". In this case in the code we use "#include <XdgDirs>". The Qt4 behave so.

What is right?

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Best regards,
Alexander.