bug#373: scroll-up, scroll-down don't respect current column

bug#373: scroll-up, scroll-down don't respect current column

[Joe Wells]

jidanni@jidanni.org writes:

> The nerve of scroll-up and scroll-down, always putting the cursor back
> in column 0 no matter what column we were in. There should be a
> variable to control this, documented in scroll-up and scroll-down's
> docstrings. Same with scroll-*-*mark.
>
> Test in a buffer made with (compile "yes 01234567|sed 333q").

WARNING: The behavior you request can be seriously problematic in
buffers with long lines.  Suppose you are at column 378952 (yes, this
happened to me two days ago) and you scroll forward.  First, I hope if
the scrolling keeps you on the same line, the column tracking would
not be so stupid as to take you back to where you were.  Suppose you
were near the end of the (very long) line and a new line was
displayed.  Suppose this new line had 9191917 columns.  Should we
really go to column 378952 on the new line?  The standard (and quite
useful) behavior of scroll forward is to display another screenful of
material, regardless of whether it is on a new line or not.  Your
proposed behavior would really break this.

Just a cautionary note.

-- 
Joe


-- 
Heriot-Watt University is a Scottish charity
registered under charity number SC000278.

bug#373: scroll-up, scroll-down don't respect current column

[jidanni]

Maybe all this should be related to if 'truncate long lines' is
enabled, or if there is the danger that Joe Wells mentioned on the
current line(s). Anyway "why a prejudice for column 0 if column 23 was
where we were". If the column we want doesn't exist on the current
line, temporarily go the nearest column to it.

bug#373: scroll-up, scroll-down don't respect current column

[jidanni]

> As luck would have it, I installed a few days ago a change that
> preserves the column position (if you set
> scroll-preserve-screen-position).

Please document scroll-preserve-screen-position in the scroll-up and
scroll-down docstrings.

In emacs-version "22.2.1" one can set scroll-preserve-screen-position
to t, but it is broken as it does not correct the behavior stated in
this bug. I assume you have made fixes to address this. Thanks.

bug#373: scroll-up, scroll-down don't respect current column

[jidanni]

The nerve of scroll-up and scroll-down, always putting the cursor back
in column 0 no matter what column we were in. There should be a
variable to control this, documented in scroll-up and scroll-down's
docstrings. Same with scroll-*-*mark.

Test in a buffer made with (compile "yes 01234567|sed 333q").