GNU bug report logs - #65632
30.0.50; Proposal to improve `faces--attribute-at-point'.

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Message #14 received at 65632 <at> debbugs.gnu.org (full text, mbox):

From: David Ponce <da_vid <at> orange.fr>
To: Eli Zaretskii <eliz <at> gnu.org>
Cc: 65632 <at> debbugs.gnu.org
Subject: Re: bug#65632: 30.0.50; Proposal to improve
 `faces--attribute-at-point'.
Date: Thu, 31 Aug 2023 00:30:43 +0200

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

On 30/08/2023 21:22, Eli Zaretskii wrote:
>> Cc: 65632 <at> debbugs.gnu.org
>> Date: Wed, 30 Aug 2023 21:35:11 +0300
>> From: Eli Zaretskii <eliz <at> gnu.org>
>>
>>> ;; Display "TEST" in red, bold, italic on yellow background.
>>> (insert
>>>    (propertize
>>>     "TEST" 'font-lock-face
>>>     '(bold ((:background "yellow") "italic"
>>>             ((foreground-color . "red") underline)))))
>>
>> This is not a valid face, AFAIU.  That it works is sheer luck (because
>> Emacs is very lenient with this stuff).  The correct face definition
>> for what you want is this (see 'set-face-attribute's doc string):
>>
>>    (insert
>>      (propertize
>>       "TEST" 'font-lock-face
>>       '(:weight bold :background "yellow" :slant italic
>> 	     :foreground "red" :underline t)))
>>
>> If you use the above, foreground-color-at-point etc. will work as
>> expected.
>>
>> I'm not sure we want to go out of our way to support the kind of face
>> specifications that you used.
> 
> However, if we do want that, we already have the technology:
> 
>    (face-attributes-as-vector (get-char-property (point) 'font-lock-face))
> 
> This will return a vector of face attribute values, where you can find
> the value of any attribute you like.  For example, to get the
> foreground color, evaluate:
> 
>    (aref 9
>      (face-attributes-as-vector (get-char-property (point) 'font-lock-face)))

Hi Eli,

Thank you very much for letting me know about `face-attributes-as-vector'
(maybe its doc string could be improved?).  It is exactly the function I need :-)

In case you are interested, I attached an updated patch to faces.el that use
this function to lookup face attribute, which improves and simplify  the
functions `faces--attribute-at-point', `foreground-color-at-point' and
`background-color-at-point'.

Regards

[faces-attribute-lookup-V1.patch (text/x-patch, attachment)]

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