Re: "Pager" page-up and -down, why not merge?

[Juanma Barranquero]

> In what way is it different from setting scroll-preserve-screen-position?

It preserves the column, too, which is the whole point of pager.el.

> I suggest we reuse temporary-goal-column instead.

>> (defconst pager-keep-column-commands
>>   '(pager-row-down pager-row-up row-dn row-up
>>                  pager-page-down pager-page-up pg-dn pg-up)
>>   "Commands which when called without any other intervening command should
>> keep the `pager-temporary-goal-column'")
>
> What are those extra commands?

pager-row-* are scrolling commands, not needed in Emacs (which has
scroll-lock-mode). pg-dn, pg-up, etc. are aliases for pager 1.0
compatibility.

> Since this doesn't doesn't use scroll-up or scroll-down, it's very much
> unclear whether it's going to behave sufficiently well in all cases.
>
> I'm especially uncomfortable with the use of vertical-motion, which
> doesn't actually use the redisplay's code, but some approximation of its
> behavior, (so it doesn't pay attention to images and other things like
> that, for example).

The original pager.el, which I'm using, does not use
`vertical-motion', but `forward-line', `scroll-down' and `scroll-up'.
Please take a look at http://user.it.uu.se/~mic/pager.el

> PS: Here's a patch to window.c which makes
> scroll-preserve-screen-position preserve the column position as well as
> the line position, tho it only applies to GUI frames, not to tty frames
> (which use another piece of code which I haven't bothered to adjust
> accordingly).

That is a great change, please install it!

 Juanma