RE: Why doesn't Info `T' cache node tree for current file?

["Drew Adams" <drew.adams@oracle.com>]

> > My thought was that if someone uses `T', s?he is likely
> > to do so again, and likely with the same file. Since we
> > have gone to the trouble of building the node tree
> > (graph), why not save it for possible reuse? That's all.
> 
> It is not very quick, since the code has to reread all Info subfiles
> (its slowest part).

That was my thinking - it really does seem to do quite a lot of work.

On the other hand, at least with the manuals I use (Emacs and Elisp), it seems
pretty snappy to me. Do you really see a performance problem, or is this just
hypothetical?

> When the delay after typing `T' is more than 1 sec, this is
> unbearable for many users.

Whoa! That certainly would be unbearable. I don't see anything like that. It
seems instantaneous, to me (which surprises me, since it does all of the
`Info-goto-node' stuff).

Can you give a recipe (e.g. which manual)?

> So we could cache the TOC buffer per Info file, if this costs
> us nothing.

Either the TOC buffer or the node list, depending on performance needs etc.

> I see one problem: how to refresh the cached TOC buffer when
> the Info file changes

Do you mean when you go to a different manual (different file), or do you mean
when someone changes the file on disk?

I think we can ignore the latter (no?).

And I think the former would be easy to take care of. As I see it (and I think I
said this), the file name would be associated with the cached node list (or
buffer). When the current file is different and you hit `T', a new TOC is built.


Should we keep caches already built for previously visted files or just toss
them? Could be a user option - users with lots of resources might opt for
multiple caches; others not.

> - the usual key `g' for buffer refreshing is already
> allocated to `Info-goto-node'.

No - it should be automatic - see above.