bug#6922: 23.1; Setting read-only property in an overlay has no effect

[Marcin Borkowski <mbork@mbork.pl>]

On 2016-02-07, at 23:24, John Wiegley <jwiegley@gmail.com> wrote:

>>>>>> Eli Zaretskii <eliz@gnu.org> writes:
>
>> What is the current consensus? should we adjust the documentation or fix the
>> code? John? Richard?
>
> I think read-only overlays could be very useful. For example:
>
>  1. Create a command called `mask-regexp'. It creates read-only overlays for
>     matching text throughout the buffer.
>  2. There should also be a way to add manual masks, using `mask-region'.
>  3. Now use `replace-string' or any other command to bulk transform text.
>     However, masked text is not changed.
>  4. Then execute unmask-all, and the mask disappears.
>
> This method of editing is key to video editing workflows. I think the only
> reason I never thought to use it in Emacs is because it's never been there
> (and so never occurred to me until now).

Hi,

I just realized that this idea could be /extremely/ useful.  Here's the
case: I start a clock in Org-mode (C-c C-x C-i), and an entry with the
starting time is added in the :LOGBOOK: drawer (and btw, it is
invisible).  While working on the file, I hit C-/ (undo) once too many,
and the entry disappears (and this fact is still invisible to me!).
Then, after some more work, I stop the clock only to see "org-clock-out:
Clock start time is gone", and my clock is still going on (!).

While the last thing (about the clock still going on) is probably an
Org-mode bug (I'll propbably report it later "officially", I'm now
Cc-ing this message to the Org-mode ML), the whole experience (and yes,
it happened to me) is /very/ confusing.

When read-only properties and masking are here, Org could just mark the
half-done entry as read-only.  I suspect that trying to undo it would
perhaps trigger some error, which could be confusing, but it would be
still better than silently removing a vital information.

Best,

-- 
Marcin Borkowski
http://octd.wmi.amu.edu.pl/en/Marcin_Borkowski
Faculty of Mathematics and Computer Science
Adam Mickiewicz University