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bug#70077: An easier way to track buffer changes
From: |
Stefan Monnier |
Subject: |
bug#70077: An easier way to track buffer changes |
Date: |
Fri, 29 Mar 2024 18:59:38 -0400 |
User-agent: |
Gnus/5.13 (Gnus v5.13) |
> If I remember correctly, I think this wouldn't be enough for my
> use. You keep two buffers in sync, you have to use
> before-change-function -- it is only before any change that the two
> buffers are guaranteed to be in sync and it is this that allows you to
> work out what the `start' and `end' positions mean in the copied
> buffer. Afterward, you cannot work out what the end position because
> you don't know if the change is a change, insertion, deletion or both.
I believe the API I propose does provide that information: you can
recover the state of the buffer before the change (or more specifically,
the state of the buffer as of the last time you called
track-changes-fetch) from the BEG/END/BEFORE arguments as follows:
(concat (buffer-substring (point-min) beg)
before
(buffer-substring end (point-max)))
I don't mean to suggest to do that, since it's costly for large
buffers, but to illustrate that the information is properly preserved.
> Last time I checked, I did find relatively few primitives that were guilty
> of being inconsistent -- in the case of `subst-char-in-region', it returned
> the maximal area of effect before the and the minimal area of effect
> after. Would it not be easier to fix these?
[ IIRC `revert-buffer` has a similar behavior, and in that case the
difference can be large since the "before" covers the whole buffer. ]
Also, it would fix only the problem of pairing, and not the other ones.
Stefan