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RE: Advice on troubleshooting function to "unscroll"

From: Drew Adams
Subject: RE: Advice on troubleshooting function to "unscroll"
Date: Sun, 25 Jan 2015 14:45:37 -0800 (PST)

> the "problem" was that C-v was bound to another (older?) function.

The command `scroll-up' is indeed older, and it is still usable.
It is, in fact, the core of the `scroll-up-command' implementation.

(In Emacs, it is often the case that you can use a command
non-interactively, though this is sometimes explicitly not
recommended for certain commands.)

`scroll-up-command' was added in Emacs 24.1, to (a) retain the
`scroll-up' behavior as a separate function, and yet (b) provide
additional behavior when you scroll interactively, in particular
the handling of the new (in 24.1) option `scroll-error-top-bottom'.

> I've hesitated from diving into Edebug because there was no
> "error" as such.  That is, the code "worked" it just didn't do
> what I intended.

Using the debugger (and debugging generally) is not necessarily
about finding why Emacs raises a particular error.  (That is the
particular use of variable `debug-on-error': enter the debugger
to show a backtrace when an error is raised.)

In addition to Edebug, there is the regular Emacs debugger, aka
`debug'.  Some of us prefer to use that.  Others prefer to use
it in some cases but `edebug' in other cases.

Keep in mind too that any debugger does not necessarily tell you
everything that goes on, and its representation of what happens
with debugging turned off is not flawless.  In particular, this
is because using the debugger itself changes what Emacs does.
(Think of the debugger's buffer display and its handling of
input events, for example.)

The regular debugger is what you get with `debug-on-entry' and
by inserting calls to `(debug)' in code to serve more or less as
breakpoints.  See `C-h f debug' for information about evaluating
and displaying the results of sexps (cdr ARGS) upon entry into
the debugger.

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