Another overly complex function until we reorganize everything into a nice all-in-one helper. This is made more complex because we have dissociated the layout rectangle (pos_min..pos_max) which define _where_ the ellipsis is, from actual clipping of text and limit of the ellipsis display. This is because in the context of tabs we selectively hide part of the text when the Close Button appears, but
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nothing calls this directly
no test coverage detected