Re: bidi-display-reordering is now non-nil by default

[Stefan Monnier]

>> >> So embeddings should not be used too much, and/or should only be used
>> >> dynamically (jit-lock-style) and implicitly (e.g. not copied by
>> >> kill-region).
>> > It depends.  If only part of the embedded text is copied, then the
>> > directional formats should be dropped, indeed.  But if all of it is
>> > copied, they should be kept, to preserve the visual appearance.
>> Sounds difficult to implement reliably.
> What difficulties do you have in mind?

See below.

>> > So I guess we will need to set filter-buffer-substring-functions to
>> > something non-nil by default?  Or maybe modify filter-buffer-substring
>> > itself to remove these characters as needed?
>> Maybe that can be made to work, but we'd need to add a corresponding
>> filter-substring
> What for? strings aren't copied by C-w and friends.

Most substrings are created non-interactively, many of them via
buffer-substring but others via just substring (sometimes/often on the
result of buffer-subtring).

>> and I'm not sure that we wouldn't get into bugs where we need to
>> change the code from buffer-substring to filter-buffer-substring.
> Which bugs, and why will we get into them?

Just think of the "Foo (default bar): " prompts, where `bar' often comes
from some buffer via buffer-substring/match-string.


        Stefan