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bug#66942: move-to-column behavior when newlines have a display property
From: |
JD Smith |
Subject: |
bug#66942: move-to-column behavior when newlines have a display property |
Date: |
Sun, 5 Nov 2023 12:18:12 -0500 |
Eli Zaretskii <eliz@gnu.org> writes:
> ...unless someone comes with an idea for how to handle these situations in a
> sensible way (and I thought long and hard about it, but couldn't find such
> ideas), this will remain a limitation of move-to-column, and one of the
> complications introduced by display strings with embedded newlines in general.
Would it not make more sense to place the cursor _before_ the first character
with a `\n` in its replacing-display property, if move-to-column attempts to
move past it? It is true that neither that position nor a position on a
subsequent line is “correct”, but the former at least preserves the expected
move-to-column semantics of “stay on this line”.
The final newline is the only place to add display on blank lines, so this will
be a general problem for any package attempting to do that. Here’s a simple
test of this for people wanting to investigate:
(progn
(insert "\n>>>>\n" (propertize "\n" 'display "xxxxx\n") "SHOULD NOT MOVE
HERE\n<<<<")
(forward-line -2) ; at beginning of xxxxx\n line
(move-to-column 10)) ; should not move past the line