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bug#42552: 28.0.50; Overlay 'face' property doesn't set the "underlying
bug#42552: 28.0.50; Overlay 'face' property doesn't set the "underlying face" for 'after-string'
Fri, 7 Aug 2020 02:16:12 +0300
Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0
On 05.08.2020 17:58, Eli Zaretskii wrote:
Should the "overlay string" obey the underlying face, though? It doesn't
obey the 'face' property, like you explained. Seems inconsistent.
Emacs always worked this way, so changing it now is probably a big
deal. AFAIU, the reason for this behavior is so that overlay strings
which specify no faces use the same face as the surrounding text.
Which sounds reasonable.
Do you imagine creating a better consistency the other way (by having
the 'face' property affect overlay strings) would be as likely to create
Emacs 26 and before simply extended the face of the last character of
the line. Emacs 27 doesn't do that, it examines the faces in effect
anew, filtering out those which don't have the :extend attribute set,
so the result is different. This is exactly the change in behavior
that was intended, not a bug.
But it should obey :extend set to nil, shouldn't it?
It does, but :extend nil doesn't override :extend t, it just says that
the face with a nil :extend attribute should not be considered when
computing the face for the empty space past EOL.
BTW, are there other attributes with a similar property? For example, I
find that I have to add (:inverse-video nil) explicitly to the computed
face which would be appended to the overlay string's 'face' properties.
Otherwise, the newlines are still "extended" with the "inverse video"
effect. Try this for an example:
(insert (propertize "abc"
'((:background "green" :extend t)
( :inverse-video t
The "extended" newline is yellow.
That seems to work. It also has the significant benefit on working in
Emacs 27, so if that's the approach you recommend in the end, the fix
you already pushed to master might be unnecessary.
The fix I pushed might not be necessary for company's sake, but it is
necessary for other use cases, because without it we don't behave as
documented when :extend attribute is not present: we extend using the
wrong background color.
All right, thank you.
I'll try to implement this all as suggested, and will come back after.