Re: add-face-text-property destructively modified properties

[Lars Ingebrigtsen <larsi@gnus.org>]

Stefan Monnier <monnier@iro.umontreal.ca> writes:

>> When I added add-face-text-property, it was for shr, which only uses it
>> for buffers where this isn't a problem (I think...?),
>
> I'm pretty sure the problem can occur in buffers as well.
> E.g. if you (put-text-property X Y 'face '(a b c d)) at variable places
> (hence using the exact same list object as `face` property at various
> places) and then use add-face-text-property on some of those places.
> [ both within a given buffer and between different buffers.  ]

Ah, yes, that's true.  Mixing and matching put-text-property with
add-face-text-property could also lead to similar problems as in
strings.

But can `buffer-substring' give us the same problems, or are the text
properties deep-copied in that case?

(I've now changed add-face-text-property to be non-destructive when
changing buffer face properties, too.)

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   bloggy blog: http://lars.ingebrigtsen.no