Re: [Emacs-diffs] scratch/widen-less a4ba846: Replace prog-widen with consolidating widen calls

[Stefan Monnier]

> Why does it need to widen, though?

Because in general, indentation may need to look at the context, and
that context may be outside of the current user-chosen narrowing.

> If the mode's indent-line-function is not supposed to call 'widen',
> why do we do that in indent-according-to-mode?

We do it in indent-according-to-mode specifically so that
indent-line-function doesn't need to do it.

> When you widen, the text that comes into the view will be entirely
> alien syntactically to the sub-mode that is trying to indent, right?

The widening is done in indent-according-to-mode and brings into view
the whole multi-mode buffer, indeed.  Then MMM's indent-line-function is
called, which narrows the buffer to the relevant chunk and then calls
the submode's indent-line-function which hence only sees the part of the
buffer it needs.

>> This change should be harmless because even if the user has narrowed
>> the buffer, the indentation should always be done depending on the
>> whole buffer's content anyway.
> But that's an incompatible change, isn't it?

It's a change that can have visible effects, of course, but these are
fairly rare and I'm hard pressed to come up with scenarios where the
effect is anything but beneficial.


        Stefan