Re: no good way to highlight rectangle while region is highlighted

[Richard Stallman <rms@gnu.org>]

    Summary of this message: This is a feature request for (1) the
    possibility that some overlays can have priority over the use of the
    region face, and/or (2) a variant of the ?box? face feature where the
    vertical lines of the box take no extra space.

(2) sounds terribly low-level.  (1) is cleaner.

I think (1) could be implemented with a change in face_at_buffer_position.
For instance, we could define a certain priority for the region,
so that overlays whose priority exceeds that cover the region.
It doesn't look terribly hard, but you need to think carefully
to prove that you store the value into *ENDPTR in all cases.

      It contains some
    code to make Emacs operations that normally operate on the region
    switch between operating on the region and the rectangle.  When
    operating on the region (in transient mark mode), the region is
    highlighted.  When operating on the rectangle, the rectangle is
    highlighted.

If you only want to show the region OR a rectangle,
why do you need any new display features?  You'd need a new
feature only to show both at once.

      I ran into these problems in trying to highlight the
    region and rectangle simultaneously:

Why do you want to highlight them both simultaneously?