Re: Display question

[Eli Zaretskii]

> From: Michael Welsh Duggan <address@hidden>
> Date: Wed, 08 Jun 2011 01:55:54 -0400
> 
> Afterward, I get a character that looks like a double-boxed RLO.  Image
> included:
> 
> Is this expected?  If I just do (insert RLO RLO RLO) a few times in a
> non-font-locked buffer, I get a box around RLO, with a tiny space
> between the boxes, and not the double box seen here.

The difference between these two use cases is that characters
delivered from display tables are not subject to the treatment we give
to "glyphless characters", which is what u+200b ZERO WIDTH SPACE is.
You expect this character to be displayed as a thin space (probably to
get the boxed "RLO" look prettier), but this thin space will only show
when u+200b is treated as a glyphless character, which can happen when
it comes from the buffer, but not from a display table.

The problem here is that display tables and glyphless character
display are 2 similar, but different features, and we didn't yet
figure out how to mix them, or whether to fuse them into a single
feature.  So now they "fight" each other, and the display table wins
in this case.

We could perhaps find some ad-hoc solution for this particular case,
but I really think we should solve the general issue -- how to combine
display tables and glyphless character display together -- before we
discuss the solutions.

Btw, you cannot expect that u+200b is displayed as a thin space,
because the user could change that via glyphless-char-display-control,
which see.  So this particular use of u+200b is questionable to begin
with, IMO.