bug#42110: Whitespace Newline Face Doesn't Disappear

[Reuben Thomas]

On Sun, 28 Jun 2020 at 17:28, Basil L. Contovounesios <contovob@tcd.ie> wrote:

found 37467 25.3
forcemerge 37467 42110
quit

> From: Robin Choudhury <robin_choudhury1@protonmail.com>
> To: bug-gnu-emacs@gnu.org
> Subject: 26.3; Whitespace Newline Face Doesn't Disappear
> -----
>
> When typing at the bottom of a document, a newline is inserted. An
> additional newline is then inserted. Upon insertion, a face higlights
> the first newline's emptiness. Typing in the second newline should make
> this face disappear. However, it remains.

Thanks, I can reproduce this in Emacs versions 25.3-28 inclusive, but
not in 24.5.  I think this is a duplicate of bug#37467, and sounds like
it might be related/due to bug#24745; CCing Reuben.

Sorry, I had a look at this and can see how it is related to the bug I fixed, but can't see how, before the fix, the unhighlighting would have happened, i.e. how space highlighted at the end of the document would have been unhighlighted after inserting characters at EOB.

I suppose that would be the logic in the function whitespace-empty-at-eob-regexp? I don't understand how regions are un-highlighted in this mode/in font-lock, though.

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