scroll-*-aggressively

scroll-*-aggressively

[Eli Zaretskii]

From the Emacs manual:

     When the window does scroll by a longer distance, you can control
  how aggressively it scrolls by setting the variables
  `scroll-up-aggressively' and `scroll-down-aggressively'.  The value of
  `scroll-up-aggressively' should be either `nil', or a fraction F
  between 0 and 1.  A fraction specifies where on the screen to put point
  when scrolling upward: when a window scrolls up because point is above
  the window start, the new start position is chosen to put point F parts
  of the window height from the top.  Thus, larger F means more aggressive
  scrolling.  The default value, `nil', is equivalent to 0.5.

     Likewise, `scroll-down-aggressively' is used for scrolling down.
  The value specifies how far point should be placed from the bottom of
  the window; thus, as with `scroll-up-aggressively', a larger value is
  more aggressive.

But this is all backwards, isn't it?  "Scrolling up" in this context
means moving point towards larger values, e.g. with C-n or <down>
arrow, which scrolls the _text_ (not the window) up.  Moreover, when
point goes off the window's bottom with C-p, the new point is
positioned `scroll-up-aggressively' parts of the window height from
the window _bottom_, not from its top.  IOW, the above description
confuses "up" with "down".

Am I missing something?

Btw, isn't it confusing that these variables don't affect `scroll-up'
or `scroll-down' in any way?

Re: scroll-*-aggressively

[Chong Yidong]

Eli Zaretskii <eliz@gnu.org> writes:

> But this is all backwards, isn't it?  "Scrolling up" in this context
> means moving point towards larger values, e.g. with C-n or <down>
> arrow, which scrolls the _text_ (not the window) up.  Moreover, when
> point goes off the window's bottom with C-p, the new point is
> positioned `scroll-up-aggressively' parts of the window height from
> the window _bottom_, not from its top.  IOW, the above description
> confuses "up" with "down".
>
> Am I missing something?

It's a mistake in the manual, indeed.  I checked in a fix to emacs-23.

BTW, I think we should replace ye olde "scroll-up" and "scroll-down"
terminology with "scroll-forward" and "scroll-backward".

Re: scroll-*-aggressively

[Óscar Fuentes]

Chong Yidong <cyd@stupidchicken.com> writes:

[snip]

> BTW, I think we should replace ye olde "scroll-up" and "scroll-down"
> terminology with "scroll-forward" and "scroll-backward".

Oh yes.

Extra thanks for replacing split-window-[horizontally|vertically] with
something that means the same for everybody.

proposal to rename scrolling directions up/down as forward/backward [was: scroll-*-aggressively]

[Drew Adams]

> BTW, I think we should replace ye olde "scroll-up" and "scroll-down"
> terminology with "scroll-forward" and "scroll-backward".

1+

In principle, forward/backward has the same problem as up/down (ambiguous,
depending on what is considered to be moving), but in practice it does not.  

In Emacs, forward/backward generally refers to direction of movement through the
buffer.  The `scroll-up' doc refers to scrolling direction of the text/buffer
movement relative to the view, whereas many users think in terms of window (view
port) movement along the buffer (forward and down).

Renaming the commands to use forward/backward will help for this reason alone
(users think of forward as movement through the text/buffer).

Not sure what the best way of making such a change is, however.  In any case, we
no longer bind `scroll-up' - we bind `scroll-up-command' instead.  I just filed
a doc bug (#8349) about this.

Renaming the commands will no doubt help, but many users will never pay
attention to the command names.  They will use `C-h k' and look at the doc, so
it is especially the doc that needs to be clear.  (It is currently clear and
correct, but users can still become confused by the terminology.)