CURSORPOS etc. directives

[Rem@IMSSS]

ELIOT's proposed clear-to-EOL is ambiguous for bitmapped displays.
Do you clear a swath from the bitmap equal in height to the current font
height on the current line? (What is the current font if you have just
done a cursorpos without printing anything?) Or do you clear only text
that is exactly on the same line in the same font and not text from
neighboring lines that slightly overlaps the current line? Perhaps ELIOT
wants this feature only for character-only displays or other devices
that support only fixed-width fixed-height fonts in character arrays with
non-overlapping character positions, or any window that is emulating a
printing terminal with no graphics or cursor positionning (i.e. maybe
cursorpos and erase-eol are mutually exclusive on bitmapped displays)?

Actually I'd like to see somebody propose a simple set of user-interface
primitives that handle all usual kinds of terminals/displays with and
without multiple windows/panes. ELIOT's proposal is merely deficient,
not in the right direction, probably...
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