GNU bug report logs - #3454
<SPC> when reading the emacs manual sometimes goes to the wrong node

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Message #5 received at submit <at> emacsbugs.donarmstrong.com (full text, mbox):

From: Shannon Jones <zedzap <at> gmail.com>
To: emacs-pretest-bug <at> gnu.org
Subject: <SPC> when reading the emacs manual sometimes goes to the wrong node
Date: Wed, 3 Jun 2009 00:40:37 -0500

[Message part 1 (text/plain, inline)]

<SPC> when reading the emacs manual sometimes goes to the wrong node.

Emacs version: GNU Emacs 23.0.94.1 (i686-pc-linux-gnu, GTK+ Version 2.10.4)
 of 2009-05-26 (built from pretest source tarball)

Running on CentOS 5.3.
No options given to configure.
Also tested on Windows with same results.


How to reproduce:

Run emacs -Q
C-h r (Reads emacs manual)
g Command Index (takes you to the "Command and Function Index" page of the
manual)
M-> (Go to end of info node)

At this point, your cursor should be at the end of the info node that lists
all commands and functions.  Note that at the top, the next node is listed
as "Variable Index".  I would expect that pressing <SPC> would take you to
this node.  However, if you press <SPC> it takes you to some other node.  It
takes me to the middle of the node "49 Two-Column Editing".

I believe <DEL> has a similar problem, but I didn't narrow down a test case.

According to the manual for Info, "You can read an entire manual top to
bottom by just typing <SPC>".  So it seemed strange to me that pressing
<SPC> went to some place in the middle of the manual instead of the next
node.

This problem also existed in emacs 22.3.

[Message part 2 (text/html, inline)]

Message #10 received at 3454-done <at> emacsbugs.donarmstrong.com (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Shannon Jones <zedzap <at> gmail.com>, 3454-done <at> debbugs.gnu.org
Subject: Re: bug#3454: <SPC> when reading the emacs manual sometimes goes to the
	wrong node
Date: Wed, 03 Jun 2009 11:39:17 -0400

> Date: Wed, 3 Jun 2009 00:40:37 -0500
> From: Shannon Jones <zedzap <at> gmail.com>
> Cc: 
> Reply-To: Shannon Jones <zedzap <at> gmail.com>, 3454 <at> emacsbugs.donarmstrong.com
> 
> Run emacs -Q
> C-h r (Reads emacs manual)
> g Command Index (takes you to the "Command and Function Index" page of the
> manual)
> M-> (Go to end of info node)
> 
> At this point, your cursor should be at the end of the info node that lists
> all commands and functions.  Note that at the top, the next node is listed
> as "Variable Index".  I would expect that pressing <SPC> would take you to
> this node.  However, if you press <SPC> it takes you to some other node.  It
> takes me to the middle of the node "49 Two-Column Editing".

This is not a bug: SPC does _not_ necessarily go to the Next node;
instead, it traverses the nodes as a tree: if there is a menu in the
current node, it takes you to the first menu item of that menu.

If you need to go to the Next node, type `n', not SPC.

> According to the manual for Info, "You can read an entire manual top to
> bottom by just typing <SPC>".

Right, but by going to the Next node you will not end up reading the
whole manual, because Next does not descend to sections, subsections,
subsubsections, etc.  SPC does, so it does indeed guarantee that you
end up reading the whole manual in the logical order: before you move
to the next chapter, you read all the sections and subsections of the
current chapter.

This logic does TRT in nodes that are not indices, because an index is
ordered alphabetically, not in any meaningful order as far as the
sections are concerned.

Morale: do not use SPC at the end of an index, use `n'.

I'm closing this report.

Message #15 received at 3454 <at> emacsbugs.donarmstrong.com (full text, mbox):

From: Shannon Jones <zedzap <at> gmail.com>
To: Eli Zaretskii <eliz <at> gnu.org>, 3454 <at> debbugs.gnu.org
Subject: Re: bug#3454: <SPC> when reading the emacs manual sometimes goes to 
	the wrong node
Date: Wed, 3 Jun 2009 13:15:47 -0500

On Wed, Jun 3, 2009 at 10:39 AM, Eli Zaretskii <eliz <at> gnu.org> wrote:
>> Date: Wed, 3 Jun 2009 00:40:37 -0500
>> From: Shannon Jones <zedzap <at> gmail.com>
>> Cc:
>> Reply-To: Shannon Jones <zedzap <at> gmail.com>, 3454 <at> emacsbugs.donarmstrong.com
>>
>> Run emacs -Q
>> C-h r (Reads emacs manual)
>> g Command Index (takes you to the "Command and Function Index" page of the
>> manual)
>> M-> (Go to end of info node)
>>
>> At this point, your cursor should be at the end of the info node that lists
>> all commands and functions.  Note that at the top, the next node is listed
>> as "Variable Index".  I would expect that pressing <SPC> would take you to
>> this node.  However, if you press <SPC> it takes you to some other node.  It
>> takes me to the middle of the node "49 Two-Column Editing".

> This is not a bug: SPC does _not_ necessarily go to the Next node;
> instead, it traverses the nodes as a tree: if there is a menu in the
> current node, it takes you to the first menu item of that menu.

Thanks for the quick response :-)

I see what my problem was now.  Each item listed in the Index is a
subnode of the Index.  So pressing <SPC> at the bottom of the Index
page will take me to the first item listed in the Index.  I was
expecting it to take me to the Next node in the manual, since I didn't
realize that the index entries were considered subnodes.

>> According to the manual for Info, "You can read an entire manual top to
>> bottom by just typing <SPC>".
>
> Right, but by going to the Next node you will not end up reading the
> whole manual, because Next does not descend to sections, subsections,
> subsubsections, etc.  SPC does, so it does indeed guarantee that you
> end up reading the whole manual in the logical order: before you move
> to the next chapter, you read all the sections and subsections of the
> current chapter.

Unfortunately, pressing <SPC> does not allow you to traverse the whole
emacs manual from top to bottom, like the Info manual says it will.
If you go to the top node of the manual (C-h r) and press space
repeatedly, you follow this path:

Table of Contents
Distribution
Introduction
Glossary
Key (Character) Index
37.8 Shell Commands in Dired
37.9 ... Appendix G
GNU Manifesto
Then cycles back to Distribution

Note that you skip sections 1..36 completely, and most of 37.

By having the index near the beginning, it messes up navigation a bit.
 But it only impacts odd people like me who read the manual from the
beginning :-)  That's how I noticed this.  I was paging through the
manual from the beginning, and suddenly found myself skipping over
most of the manual.

> I'm closing this report.
>

That's fine, I agree it's not a bug.  I'll just remember to hit 'n' at
the bottom of indexes instead of <SPC>.

Message #20 received at submit <at> emacsbugs.donarmstrong.com (full text, mbox):

From: bojohan+news <at> dd.chalmers.se (Johan Bockgård)
To: bug-gnu-emacs <at> gnu.org
Subject: Re: bug#3454: marked as done (<SPC> when reading the emacs manual sometimes goes to the wrong node)
Date: Thu, 04 Jun 2009 01:41:53 +0200

> This logic does TRT in nodes that are not indices, because an index is
> ordered alphabetically, not in any meaningful order as far as the
> sections are concerned.
>
> Morale: do not use SPC at the end of an index, use `n'.

The `]' command does get this case right though.

Message #25 received at 3454 <at> emacsbugs.donarmstrong.com (full text, mbox):

From: Stefan Monnier <monnier <at> iro.umontreal.ca>
To: Shannon Jones <zedzap <at> gmail.com>
Cc: 3454 <at> debbugs.gnu.org, Eli Zaretskii <eliz <at> gnu.org>
Subject: Re: bug#3454: <SPC> when reading the emacs manual sometimes goes to the wrong node
Date: Thu, 04 Jun 2009 12:06:12 -0400

>> This is not a bug: SPC does _not_ necessarily go to the Next node;
>> instead, it traverses the nodes as a tree: if there is a menu in the
>> current node, it takes you to the first menu item of that menu.

> Thanks for the quick response :-)

> I see what my problem was now.  Each item listed in the Index is a
> subnode of the Index.  So pressing <SPC> at the bottom of the Index
> page will take me to the first item listed in the Index.  I was
> expecting it to take me to the Next node in the manual, since I didn't
> realize that the index entries were considered subnodes.

Actually I think that SPC's behavior in index nodes is wrong.
Basically, SPC currently presumes that info nodes linked by menus form
a tree, and it is mostly true, but not for index menus.


        Stefan

Message #30 received at 3454 <at> emacsbugs.donarmstrong.com (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Stefan Monnier <monnier <at> iro.umontreal.ca>
Cc: zedzap <at> gmail.com, 3454 <at> debbugs.gnu.org
Subject: Re: bug#3454: <SPC> when reading the emacs manual sometimes goes to the wrong node
Date: Thu, 04 Jun 2009 12:11:11 -0400

> From: Stefan Monnier <monnier <at> iro.umontreal.ca>
> Cc: 3454 <at> emacsbugs.donarmstrong.com,  Eli Zaretskii <eliz <at> gnu.org>
> Date: Thu, 04 Jun 2009 12:06:12 -0400
> 
> Actually I think that SPC's behavior in index nodes is wrong.
> Basically, SPC currently presumes that info nodes linked by menus form
> a tree, and it is mostly true, but not for index menus.

Index is just a large menu; it's not easy to distinguish the two, and
the decision would be error-prone.  We already tried to ``improve''
Info, and I cannot say that the result looks good.

I don't see why bother in this case: a human can always know that she
is in an index, and not use SPC near the end.

Message #35 received at 3454 <at> emacsbugs.donarmstrong.com (full text, mbox):

From: Stefan Monnier <monnier <at> iro.umontreal.ca>
To: Eli Zaretskii <eliz <at> gnu.org>
Cc: zedzap <at> gmail.com, 3454 <at> debbugs.gnu.org
Subject: Re: bug#3454: <SPC> when reading the emacs manual sometimes goes to the wrong node
Date: Thu, 04 Jun 2009 14:37:05 -0400

>> Actually I think that SPC's behavior in index nodes is wrong.
>> Basically, SPC currently presumes that info nodes linked by menus form
>> a tree, and it is mostly true, but not for index menus.

> Index is just a large menu; it's not easy to distinguish the two, and
> the decision would be error-prone.  We already tried to ``improve''
> Info, and I cannot say that the result looks good.

Wether we should fix the behavior is a different question from whether
it's right or wrong.  I think the behaviro is wrong.  I agree that's
it's not terribly important, so unless we can come up with a fix that is
simple and reliable, it's probably better to leave things as they are.

This said, "recent" versions of makeinfo label index nodes with an
"index cookie", so if we see such a cookie, we know for sure we're in an
index node.  That should make it possible to write a good patch.


        Stefan

Message #40 received at 3454 <at> emacsbugs.donarmstrong.com (full text, mbox):

From: "Drew Adams" <drew.adams <at> oracle.com>
To: "'Stefan Monnier'" <monnier <at> iro.umontreal.ca>,
        <3454 <at> debbugs.gnu.org>, "'Eli Zaretskii'" <eliz <at> gnu.org>
Cc: <zedzap <at> gmail.com>
Subject: RE: bug#3454: <SPC> when reading the emacs manual sometimes goes to thewrong node
Date: Mon, 8 Jun 2009 11:26:51 -0700

> "recent" versions of makeinfo label index nodes with an
> "index cookie", so if we see such a cookie, we know for sure 
> we're in an index node.  That should make it possible to write
> a good patch.

I think this bug should be fixed, no matter how minor it might seem to someone
who understands well the structure of Info or its implementation. It really
should be possible for someone to use a single key (`SPC') to traverse the
manual, with no exceptions.

Even adding a pseudo menu item at the beginning of the index, which would DTRT
(since SPC goes to the first menu item's node), would be useful, if no better
solution can be found. I'm not necessarily proposing such an ugly hack, but it
might be better than nothing.

`n' doesn't go anywhere when there is no `Next' node, and `SPC' doesn't go to
the right place when you are at the end of an index. Users should not need to
sometimes use `n' and sometimes use `SPC', and think consciously about which
might be appropriate and work, in order to simply traverse the manual from front
to back (and then wrap back to the front).

And this attitude is not a great one, IMO:

"Morale: do not use SPC at the end of an index, use `n'.
I'm closing this report."

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