bug#5809: 23.1.94; cross-reference by anchor yields in accurate position

[Drew Adams]

> No need to blindly trying to click all links.  You can open the file
> `info/elisp' and count all strings that start with "Ref:"
> (they are anchors that put the cursor to a mid-node position).
> 
> There are 66 lines with "Ref:" (that fail to go directly to the
> appropriate place) and 839 lines with "Node:" (that succeed since
> they put the cursor to the beginning of the node).
> 
> The ratio of 66 to 839 is 8%.  So you guess of 10% is closer to the
> actual percentage.

Thanks. I wasn't aware of that. Now we know. Neither "all the time" nor "very
rare". At least in terms of _numbers_ of links (see #2 below).

1. But what do you mean here by "fail to go directly to the appropriate place"?
As I pointed out, failing to go to the precise location is not a problem in the
vast majority of cases, since the link still takes you to the appropriate
paragraph or correct 1-3 line description. Does your measure take that into
account?

IOW, even if 10% of the links do not behave precisely, but 99.9% of those
fail-to-go-directly links still get you to the correct paragraph (or correct 1-2
line function/var description), then the 10% number is far too high as a measure
of the real problem.

2. I'm still assuming, based on experience, that it is mainly the index links
that target mid-node locations. So a secondary question would be how often the
different kinds of links are followed in practice - e.g. index vs other links.
If there is a significant difference (either way), that could be important. This
is a user-practice question, which cannot be answered by counting links.

I myself use the index a lot, at least via `i'. I think it's important that
index links actually take you where they should. But if users generally use
index links less than text-body links, then that reduces the practical problem
still further.