bug#60080: 28.2; Double-click selection cannot be customized

bug#60080: 28.2; Double-click selection cannot be customized

[Sean Devlin]

Hi folks,

In GUI Emacs, you can double-click to select some region of text. The
rules for double-click selection are documented in (info "(emacs) Word
and Line Mouse"). Here are the relevant bits:

  Select the text around the word or character which you click on.

  Double-clicking on a character with symbol syntax (such as
  underscore, in C mode) selects the symbol surrounding that
  character.

I'd like to customize Emacs such that when I double-click on a word,
the entire enclosing symbol is selected. In other words, it should
behave more like the latter case of double-clicking on a character with
symbol syntax.

Here is a recipe to show what I am talking about:

1. Open GUI Emacs with -Q flag.
2. In the scratch buffer, type "this-is-a-symbol".
3. With the mouse, double-click on "this".
4. Observe that only "this" is selected in the active region.
5. C-g to deactive the region.
6. Double-click on the "-" following "this".
7. Observe that the entire symbol "this-is-a-symbol" is selected.

I want to select the full symbol "this-is-a-symbol" in both cases.

Note that this is the default behavior in some other editors that I am
aware of.

I understand that I can get the behavior I want by double-clicking the
"-", but "-" is a small target, and selecting the entire symbol is by
far the more common use case for me.

In the short term, I have a workaround where I advise the
mouse-skip-word function.

Thanks!

In GNU Emacs 28.2
System Description:  macOS 13

Configured using:
'configure --with-ns '--enable-locallisppath=/Library/Application
Support/Emacs/${version}/site-lisp:/Library/Application
Support/Emacs/site-lisp' --with-modules'

Configured features:
ACL GMP GNUTLS JSON LIBXML2 MODULES NOTIFY KQUEUE NS PDUMPER THREADS
TOOLKIT_SCROLL_BARS ZLIB

Important settings:
  value of $LANG: en_US.UTF-8
  locale-coding-system: utf-8-unix

Major mode: Lisp Interaction

Minor modes in effect:
  tooltip-mode: t
  global-eldoc-mode: t
  eldoc-mode: t
  show-paren-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  indent-tabs-mode: t
  transient-mark-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message rmc puny dired dired-loaddefs
rfc822 mml mml-sec epa derived epg rfc6068 epg-config gnus-util rmail
rmail-loaddefs auth-source cl-seq eieio eieio-core cl-macs
eieio-loaddefs password-cache json map text-property-search seq byte-opt
gv bytecomp byte-compile cconv mm-decode mm-bodies mm-encode mail-parse
rfc2231 mailabbrev gmm-utils mailheader sendmail rfc2047 rfc2045
ietf-drums mm-util mail-prsvr mail-utils time-date subr-x cl-loaddefs
cl-lib iso-transl tooltip eldoc paren electric uniquify ediff-hook
vc-hooks lisp-float-type elisp-mode mwheel term/ns-win ns-win
ucs-normalize mule-util term/common-win tool-bar dnd fontset image
regexp-opt fringe tabulated-list replace newcomment text-mode lisp-mode
prog-mode register page tab-bar menu-bar rfn-eshadow isearch easymenu
timer select scroll-bar mouse jit-lock font-lock syntax font-core
term/tty-colors frame minibuffer cl-generic cham georgian utf-8-lang
misc-lang vietnamese tibetan thai tai-viet lao korean japanese eucjp-ms
cp51932 hebrew greek romanian slovak czech european ethiopic indian
cyrillic chinese composite emoji-zwj charscript charprop case-table
epa-hook jka-cmpr-hook help simple abbrev obarray cl-preloaded nadvice
button loaddefs faces cus-face macroexp files window text-properties
overlay sha1 md5 base64 format env code-pages mule custom widget
hashtable-print-readable backquote threads kqueue cocoa ns multi-tty
make-network-process emacs)

Memory information:
((conses 16 49949 6483)
(symbols 48 6552 1)
(strings 32 18286 1523)
(string-bytes 1 606914)
(vectors 16 12898)
(vector-slots 8 184857 11573)
(floats 8 21 51)
(intervals 56 198 0)
(buffers 992 10))

bug#60080: 28.2; Double-click selection cannot be customized

[Eli Zaretskii]

> From: Sean Devlin <spd@toadstyle.org>
> Date: Wed, 14 Dec 2022 19:40:22 -0500
> 
> I'd like to customize Emacs such that when I double-click on a word,
> the entire enclosing symbol is selected. In other words, it should
> behave more like the latter case of double-clicking on a character with
> symbol syntax.

Does the patch below do what you want?

If it does, we could provide this as an optional behavior, conditioned
by some new user option.

diff --git a/lisp/mouse.el b/lisp/mouse.el
index f72ab4f..ced7a92 100644
--- a/lisp/mouse.el
+++ b/lisp/mouse.el
@@ -1803,7 +1803,11 @@ mouse-skip-word
 If DIR is positive skip forward; if negative, skip backward."
   (let* ((char (following-char))
 	 (syntax (char-to-string (char-syntax char))))
-    (cond ((string= syntax "w")
+    (cond ((bounds-of-thing-at-point 'symbol)
+           (goto-char (if (< dir 0)
+                          (car (bounds-of-thing-at-point 'symbol))
+                        (cdr (bounds-of-thing-at-point 'symbol)))))
+          ((string= syntax "w")
 	   ;; Here, we can't use skip-syntax-forward/backward because
 	   ;; they don't pay attention to word-separating-categories,
 	   ;; and thus they will skip over a true word boundary.  So,

bug#60080: 28.2; Double-click selection cannot be customized

[Sean Devlin]

Hi Eli,

> On Dec 15, 2022, at 2:33 AM, Eli Zaretskii <eliz@gnu.org> wrote:
> 
>> From: Sean Devlin <spd@toadstyle.org>
>> Date: Wed, 14 Dec 2022 19:40:22 -0500
>> 
>> I'd like to customize Emacs such that when I double-click on a word,
>> the entire enclosing symbol is selected. In other words, it should
>> behave more like the latter case of double-clicking on a character with
>> symbol syntax.
> 
> Does the patch below do what you want?
> 
> If it does, we could provide this as an optional behavior, conditioned
> by some new user option.

Yes, this seems to do the trick.

I agree that a user option would make sense.

Thanks for looking at this so quickly!

> 
> diff --git a/lisp/mouse.el b/lisp/mouse.el
> index f72ab4f..ced7a92 100644
> --- a/lisp/mouse.el
> +++ b/lisp/mouse.el
> @@ -1803,7 +1803,11 @@ mouse-skip-word
> If DIR is positive skip forward; if negative, skip backward."
>   (let* ((char (following-char))
> 	 (syntax (char-to-string (char-syntax char))))
> -    (cond ((string= syntax "w")
> +    (cond ((bounds-of-thing-at-point 'symbol)
> +           (goto-char (if (< dir 0)
> +                          (car (bounds-of-thing-at-point 'symbol))
> +                        (cdr (bounds-of-thing-at-point 'symbol)))))
> +          ((string= syntax "w")
> 	   ;; Here, we can't use skip-syntax-forward/backward because
> 	   ;; they don't pay attention to word-separating-categories,
> 	   ;; and thus they will skip over a true word boundary.  So,

bug#60080: 28.2; Double-click selection cannot be customized

[Eli Zaretskii]

> From: Sean Devlin <spd@toadstyle.org>
> Date: Thu, 15 Dec 2022 14:19:16 -0500
> Cc: 60080@debbugs.gnu.org
> 
> >> I'd like to customize Emacs such that when I double-click on a word,
> >> the entire enclosing symbol is selected. In other words, it should
> >> behave more like the latter case of double-clicking on a character with
> >> symbol syntax.
> > 
> > Does the patch below do what you want?
> > 
> > If it does, we could provide this as an optional behavior, conditioned
> > by some new user option.
> 
> Yes, this seems to do the trick.
> 
> I agree that a user option would make sense.

Thanks, so I installed the change with the new option on the master
branch, and I'm therefore closing this bug.