extents and insert-before-markers
Stephen J. Turnbull
stephen at xemacs.org
Thu Jan 12 11:31:58 EST 2012
Julian Bradfield writes:
> I suppose the general case I have in mind is where you have two extents
> covering adjacent fields:
> and if point is at the first y, there's a clear distinction between
> adding to the end of field x, and adding to the beginning of field y.
Sure. In most applications I can thing of, though, there would be an
"inert" separator such as "|". So the picture I would expect is
(where the square brackets are metacharacters indicating closed extent
endpoints and are not displayed). In fact, you could wrap the
separator in an invisible extent, but that would be a little weird for
users. In many others, the "natural" arrangement would be start-open,
end-closed (aka append-only extents).
> If you were using markers to track the fields (as vm does), then
> insert-before-markers and insert are the way you'd do it. But with
> extents would the only possibility be to change the openness each
There's also explicit set-extent-endpoints, and the insert-then-delete
Does VM really sometimes insert and sometimes insert-before-markers at
the same place?
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