bug#54285: 29.0.50; Scrolling the calc help buffer

bug#54285: 29.0.50; Scrolling the calc help buffer

[Rudolf Adamkovič via Bug reports for GNU Emacs, the Swiss army knife of text editors]

Reproduction steps:

1. emacs -Q
2. C-x * ? ?

At this point:

- the frame splits vertically, and
- the bottom window shows help with a scroll bar.

Scenario 1:

The user starts reading help and as they reach the end of the visible
part of the buffer, they scroll the window *with the mouse wheel*.

Expected: the window scrolls, the user continues reading
Actual: Emacs beeps and closes the window

Scenario 2:

The user starts reading help and as they reach the end of the visible
part of the buffer, they scroll the window *with the scroll bar*.

Expected: the window scrolls, the user continues reading
Actual: Emacs beeps, closes the window, and tells the user:

"Wrong type argument: stringp, nil"

Scenario 3 (optional):

The user starts reading help and as they reach the end of the visible
part of the buffer, they move the cursor with C-n.

Expected: the cursor in the window advances to the next line
Actual: Emacs beeps, closes the window, and tells the user:

"No active formulas in the buffer"

Note:

Emacs should never abruptly close any help window just because the user
typed some "bad" key or performed some "bad" mouse interaction.  Doing
so frustrates the user and prevents them from learning.

Rudy


In GNU Emacs 29.0.50 (build 11, x86_64-apple-darwin21.2.0, NS appkit-2113.20 Version 12.1 (Build 21C52))
 of 2022-03-01 built on Workstation.local
Repository revision: caae254bb478ad83ba9caec6ec94b54e9abfb4c9
Repository branch: master
Windowing system distributor 'Apple', version 10.3.2113
System Description:  macOS 12.1

Configured using:
 'configure --with-json --with-native-compilation'

Configured features:
ACL DBUS GIF GLIB GMP GNUTLS JPEG JSON LCMS2 LIBXML2 MODULES NATIVE_COMP
NOTIFY KQUEUE NS PDUMPER PNG RSVG SQLITE3 THREADS TIFF
TOOLKIT_SCROLL_BARS WEBP XIM ZLIB

Important settings:
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Major mode: Org

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Load-path shadows:
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-- 
"The introduction of suitable abstractions is our only mental aid to
organize and master complexity."
-- Edsger Wybe Dijkstra, 1930-2002

Rudolf Adamkovič <salutis@me.com> [he/him]
Studenohorská 25
84103 Bratislava
Slovakia

bug#54285: 29.0.50; Scrolling the calc help buffer

[Lars Ingebrigtsen]

Rudolf Adamkovič <salutis@me.com> writes:

> The user starts reading help and as they reach the end of the visible
> part of the buffer, they scroll the window *with the scroll bar*.
>
> Expected: the window scrolls, the user continues reading
> Actual: Emacs beeps, closes the window, and tells the user:
>
> "Wrong type argument: stringp, nil"

calc-dispatch-help is basically just looping over `read-event' and
responding only to the keyboard scroll keys.  Perhaps a better way to
implement this would be to use the normal help functions (which are less
modal) so that these things work better?


-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

bug#54285: 29.0.50; Scrolling the calc help buffer

[Michael Heerdegen]

Lars Ingebrigtsen <larsi@gnus.org> writes:

> calc-dispatch-help is basically just looping over `read-event' and
> responding only to the keyboard scroll keys.  Perhaps a better way to
> implement this would be to use the normal help functions (which are less
> modal) so that these things work better?

From what I know: This particular help command is intended to be used
intermediately while reading a key binding: you are supposed to look up
the next key and hit it directly, without interruption.  It's using
`read-event' on purpose.

I also don't like that much, but there are other good help commands to
use instead.  I fear that if you try to change this it will make things
worse or less consistent, the Calc help system is complex, and you might
end up with a non-trivial redesign.  Dunno if the result would be much
of an improvement.

Maybe it's not that bad, dunno, but please be careful.

Michael.

bug#54285: 29.0.50; Scrolling the calc help buffer

[Michael Heerdegen]

Michael Heerdegen <michael_heerdegen@web.de> writes:

> > calc-dispatch-help is basically just looping over `read-event' and
> > responding only to the keyboard scroll keys.  Perhaps a better way to
> > implement this would be to use the normal help functions (which are less
> > modal) so that these things work better?

Or did you mean: like `help-for-help'?  That's similar.  Scrolling
`help-for-help' with the mouse wheel loses the prompt for a key, btw,
only scrolling with the scroll bar works as expected for me.

Note that `help-for-help' is a front end for help commands, while
`calc-dispatch-help' more or less only summarizes the commands reachable
from the outside Calc C-x * prefix.  The Calc help stuff doesn't even
seem to be reachable from C-x *.

BTW, there is a way to get that buffer directly and without a key prompt:
C-h f calc-dispatch-help RET.


Michael.

bug#54285: 29.0.50; Scrolling the calc help buffer

[Lars Ingebrigtsen]

Michael Heerdegen <michael_heerdegen@web.de> writes:

> Or did you mean: like `help-for-help'?  That's similar.  Scrolling
> `help-for-help' with the mouse wheel loses the prompt for a key, btw,
> only scrolling with the scroll bar works as expected for me.

Yes, more like `help-for-help'.  Or rather, I'd like to see a little
library/function for these kinds of things, that allow the immediate
response of a `read-event' loop, but which doesn't disable scrolling
with the scroll bar and mouse wheel.  And which has, as an option, the
possibility of not exiting when entering a non-bound key.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no