Re: enriched-mode and switching major modes.

[Luc Teirlinck <teirllm@dms.auburn.edu>]

Oliver Scholz wrote:

   I did not spend any thought about overlays, because I thought they
   were too expensive?  The documents could be large and have many nodes.

   Of course, if overlays work better: maybe they could be made more
   efficient in the long run?

Note that, unless you take special steps, there are important
user-visible differences between using text properties and overlays
(for better or for worse, depending on the situation).

Text properties are part of the text, overlays are not.  Hence
changing text properties marks the buffer modified, playing around
with overlays not.  Of course, this has numerous important consequences
in terms of auto-save files, asking or not asking the user to save the
file, auto reverting and so on...

It has been a while ago that I played around extensively with many
overlays in huge buffers, but I found that functions that do that
could be made incredibly faster by executing:

(overlay-recenter (point-max))

before starting to play around with overlays.  I do not know whether
this is still the case, since the overlay code could have changed in
the meantime.

Sincerely,

Luc.