* bug#31204: 25.3; Make word motion more customizable
@ 2018-04-18 8:55 Yuri Khan
2022-05-18 12:03 ` Lars Ingebrigtsen
0 siblings, 1 reply; 3+ messages in thread
From: Yuri Khan @ 2018-04-18 8:55 UTC (permalink / raw)
To: 31204
While trying to make word motion commands (Ctrl+left/right, M-f/b) more
similar to that implemented in other editors:
http://lists.gnu.org/archive/html/help-gnu-emacs/2018-04/msg00230.html
I encountered a difficulty.
The function ‘forward-word’ behaves as follows:
1. Skip to the nearest character having word constituent syntax.
2. Skip to the nearest word boundary.
Step 2, by default, finds:
* a non-word-constituent character, OR
* a transition between two adjacent characters of different scripts
(subject to exceptions controlled by ‘word-combining-categories’ and
‘word-separating-categories’),
whichever comes first.
Step 2 can also be customized by modifying
‘find-word-boundary-function-table’. This enables various useful
behaviors such as ‘subword-mode’, ‘superword-mode’, and possibly CJK
word breaking rules.
Step 1, on the other hand, is not customizable at all.
The specific behavior that I was trying to implement was to find the
nearest transition:
* from a word character to a non-word character, OR
* from a non-word non-whitespace character to a word character, OR
* from a non-word non-whitespace character to a whitespace character.
As an illustration (where ‘|’ specifies word motion stops when going
left to right):
foo| ***| +++| (|bar|)|
^
When cursor is after ‘foo’, step 1 of ‘forward-word’ skips to directly
before ‘bar’, missing two stops.
As a result, implementing the desired behavior requires either:
* defining separate functions ‘my-forward-word’, ‘my-backward-word’,
‘my-left-word’, ‘my-right-word’, ‘my-kill-word’,
‘my-backward-kill-word’, and possibly more, and remapping their key
bindings; OR
* advising ‘forward-word’ with an :override.
Perhaps it would be nice to have an optional hook for step 1 of
‘forward-word’, a function that would take two arguments POS and LIMIT,
and returning the starting word boundary position from which step 2 would
then work.
In GNU Emacs 25.3.2 (x86_64-pc-linux-gnu, GTK+ Version 3.18.9)
of 2017-09-13 built on lcy01-32
Windowing system distributor 'The X.Org Foundation', version 11.0.11905000
System Description: Ubuntu 16.04.4 LTS
Configured using:
'configure --build=x86_64-linux-gnu --prefix=/usr
'--includedir=${prefix}/include' '--mandir=${prefix}/share/man'
'--infodir=${prefix}/share/info' --sysconfdir=/etc --localstatedir=/var
--disable-silent-rules '--libdir=${prefix}/lib/x86_64-linux-gnu'
'--libexecdir=${prefix}/lib/x86_64-linux-gnu' --disable-maintainer-mode
--disable-dependency-tracking --prefix=/usr --sharedstatedir=/var/lib
--program-suffix=25 --with-modules --with-x=yes --with-x-toolkit=gtk3
'CFLAGS=-g -O2 -fstack-protector-strong -Wformat
-Werror=format-security' 'CPPFLAGS=-Wdate-time -D_FORTIFY_SOURCE=2'
'LDFLAGS=-Wl,-Bsymbolic-functions -Wl,-z,relro''
Configured features:
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Important settings:
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value of $LC_NUMERIC: en_US.UTF-8
value of $LC_TIME: en_DK.utf8
value of $LANG: en_US.UTF-8
locale-coding-system: utf-8-unix
Major mode: Lisp Interaction
Minor modes in effect:
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global-eldoc-mode: t
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blink-cursor-mode: t
auto-composition-mode: t
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auto-compression-mode: t
line-number-mode: t
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Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.
Load-path shadows:
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^ permalink raw reply [flat|nested] 3+ messages in thread
* bug#31204: 25.3; Make word motion more customizable
2018-04-18 8:55 bug#31204: 25.3; Make word motion more customizable Yuri Khan
@ 2022-05-18 12:03 ` Lars Ingebrigtsen
2022-06-15 15:03 ` Lars Ingebrigtsen
0 siblings, 1 reply; 3+ messages in thread
From: Lars Ingebrigtsen @ 2022-05-18 12:03 UTC (permalink / raw)
To: Yuri Khan; +Cc: 31204
Yuri Khan <yuri.v.khan@gmail.com> writes:
> While trying to make word motion commands (Ctrl+left/right, M-f/b) more
> similar to that implemented in other editors:
>
> http://lists.gnu.org/archive/html/help-gnu-emacs/2018-04/msg00230.html
>
> I encountered a difficulty.
[...]
> Step 1, on the other hand, is not customizable at all.
>
> The specific behavior that I was trying to implement was to find the
> nearest transition:
>
> * from a word character to a non-word character, OR
> * from a non-word non-whitespace character to a word character, OR
> * from a non-word non-whitespace character to a whitespace character.
>
> As an illustration (where ‘|’ specifies word motion stops when going
> left to right):
>
> foo| ***| +++| (|bar|)|
> ^
[...]
> Perhaps it would be nice to have an optional hook for step 1 of
> ‘forward-word’, a function that would take two arguments POS and LIMIT,
> and returning the starting word boundary position from which step 2 would
> then work.
(I'm going through old bug reports that unfortunately weren't resolved
at the time.)
I think this sounds like it could be useful. If we added such a hook to
`forward-word', what would the rest of the code look like to make
`C-<right>' work this way?
--
(domestic pets only, the antidote for overdose, milk.)
bloggy blog: http://lars.ingebrigtsen.no
^ permalink raw reply [flat|nested] 3+ messages in thread
* bug#31204: 25.3; Make word motion more customizable
2022-05-18 12:03 ` Lars Ingebrigtsen
@ 2022-06-15 15:03 ` Lars Ingebrigtsen
0 siblings, 0 replies; 3+ messages in thread
From: Lars Ingebrigtsen @ 2022-06-15 15:03 UTC (permalink / raw)
To: Yuri Khan; +Cc: 31204
Lars Ingebrigtsen <larsi@gnus.org> writes:
>> As an illustration (where ‘|’ specifies word motion stops when going
>> left to right):
>>
>> foo| ***| +++| (|bar|)|
[...]
> I think this sounds like it could be useful. If we added such a hook to
> `forward-word', what would the rest of the code look like to make
> `C-<right>' work this way?
I've played a bit at the patch below, but I tend to think that this is
going about things the wrong way. That is, for something like this to
work meaningfully, it would require a lot of setup (because
Vfind_word_boundary_function_table) would also have to be altered in
conjunction with this.
I.e., it's really about changing the definition of what a "word" is, and
in that case, I think it would be easier to just do that in a syntax
table, and then everything would work automatically.
(Or by advising the functions here.)
So I don't think it'd be worth it to proceed with something like the
below, and I'm therefore closing this bug report.
diff --git a/src/syntax.c b/src/syntax.c
index f9022d18d2..02d4dd4b9a 100644
--- a/src/syntax.c
+++ b/src/syntax.c
@@ -1462,20 +1462,33 @@ scan_words (ptrdiff_t from, EMACS_INT count)
while (count > 0)
{
- while (true)
+ if (!NILP (Vfind_word_start_function))
{
- if (from == end)
+ Lisp_Object np = call2 (Vfind_word_start_function,
+ make_fixnum (from), make_fixnum (end));
+ if (!FIXNUMP (np))
return 0;
- UPDATE_SYNTAX_TABLE_FORWARD (from);
+ from = XFIXNUM (np);
+ from_byte = CHAR_TO_BYTE (from);
ch0 = FETCH_CHAR_AS_MULTIBYTE (from_byte);
- code = SYNTAX (ch0);
- inc_both (&from, &from_byte);
- if (words_include_escapes
- && (code == Sescape || code == Scharquote))
- break;
- if (code == Sword)
- break;
- rarely_quit (from);
+ }
+ else
+ {
+ while (true)
+ {
+ if (from == end)
+ return 0;
+ UPDATE_SYNTAX_TABLE_FORWARD (from);
+ ch0 = FETCH_CHAR_AS_MULTIBYTE (from_byte);
+ code = SYNTAX (ch0);
+ inc_both (&from, &from_byte);
+ if (words_include_escapes
+ && (code == Sescape || code == Scharquote))
+ break;
+ if (code == Sword)
+ break;
+ rarely_quit (from);
+ }
}
/* Now CH0 is a character which begins a word and FROM is the
position of the next character. */
@@ -3792,6 +3805,12 @@ syms_of_syntax (void)
In both cases, LIMIT bounds the search. */);
Vfind_word_boundary_function_table = Fmake_char_table (Qnil, Qnil);
+ DEFVAR_LISP ("find-word-start-function",
+ Vfind_word_start_function,
+ doc: /* Function called to find the start of a word.
+It's called with two parameters, POS and LIMIT. */);
+ Vfind_word_start_function = Qnil;
+
DEFVAR_BOOL ("comment-end-can-be-escaped", comment_end_can_be_escaped,
doc: /* Non-nil means an escaped ender inside a comment doesn't end the comment. */);
comment_end_can_be_escaped = false;
--
(domestic pets only, the antidote for overdose, milk.)
bloggy blog: http://lars.ingebrigtsen.no
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2018-04-18 8:55 bug#31204: 25.3; Make word motion more customizable Yuri Khan
2022-05-18 12:03 ` Lars Ingebrigtsen
2022-06-15 15:03 ` Lars Ingebrigtsen
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