Fix wrong display position computed in _update() after calling setPosition(...) for relative metric mode overlay elements.
Fix wrong display position computed in _update() after calling setPosition(...) for relative metric mode overlay elements.

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branch : v1-8

digimatic/ogre,digimatic/ogre,digimatic/ogre,digimatic/ogre,digimatic/ogre,digimatic/ogre,digimatic/ogre