On 2016-06-12 18:58, Dmitry Gutov wrote:
>> I have encountered no such problems in over 15 years of hacking
>> Emacs. I think you're seeing problems somewhere and blaming 
>> narrow-to-region/widen, when the real problem is somewhere else.
> 
> It's been a known problem for a while, and it has come up in multiple
> discussions over the last years.
> 
> The "real problem" is a matter of perspective. Some might argue that
> trying to use narrowing at all, for any purpose, is a bad idea, and
> then, of course, the right choice would be to use something else.

I can share one instance of running into issues with narrow-to-region. I was implementing a simple ‘presenter’ mode, such that special comments were used to delimit ‘slides’. The mode functioned by narrowing the buffer to regions delimited by these special comments. It was a very convenient way to page through code in front of an audience.

Unfortunately, this approach was not robust. I ran into issues with modes using (point-min) and (point-max) without widening, and thereby misplacing overlays. In the end things kept breaking, and I ended up implementing the same feature using two overlays with an invisible property, hiding everything before (respectively after) the region being shown. It was a pain.

Not sure whether this is a useful contribution :) In any case, that's one problem I ran into.

Clément.