bug#23574: 24.5; Overzealous underlining in emacs-nox

[Noam Postavsky <npostavs@users.sourceforge.net>]

On Mon, Jun 6, 2016 at 3:18 PM, Eli Zaretskii <eliz@gnu.org> wrote:
> And I don't think what you get is the desired effect, you just get a
> side effect of a particular implementation detail.  E.g., what happens
> if a line fits exactly on a line, i.e. the cursor at its end will be
> displayed on the fringe?

The underlining does reach the end of the screen in this case, but it
still looks okay because the underlining doesn't extend too far away
from the text.

>
>> In TTY this places the face over everything, which we don't agree is a bug or not.
>
> It isn't a bug, because that's how the display engine was coded to
> work.  Of course, we can make it behave differently if we want.

I think it makes sense to not do the face extension by default. If I
take a sheet of paper and underline lines 3 to 10, I'm going to stop
drawing at the end of the text, not go all the way to end of the
paper.

For the case I mentioned earlier, magit isn't actually underlining
text, it just wants to make some horizontal lines. It would be nice to
have some way to ask the display engine to do this directly.