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Subject: |
Documentation bug in the docstring of set-face-attribute? |
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Date: |
Wed, 31 Aug 2022 08:14:00 +0000 |
The docstring of set-face-attribute says:
"As an exception, to reset the value of some attribute to `unspecified' in
a way that overrides the non-`unspecified' value defined by the face's
spec in `defface', for new frames, you must explicitly call this function
with FRAME set to t and the attribute's value set to `unspecified'; just
using FRAME of nil will not affect new frames in this case."
Not only is that sentence hard to parse, it also seems wrong.
Can someone come up with a scenario in which a call
(set-face-attribute 'some-face nil :some-attribute 'unspecified)
only affects existing frames? In my testing it affects all frames
(existing and future ones), and that's also what the code seems to do:
set-face-attribute sets where to 0 when frame is nil, and calls
internal-set-face-attribute
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Subject: |
Re: bug#57499: Documentation bug in the docstring of set-face-attribute? |
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Date: |
Thu, 01 Sep 2022 11:44:48 +0300 |
> Date: Thu, 01 Sep 2022 08:25:35 +0000
> From: Gregory Heytings <gregory@heytings.org>
> cc: 57499@debbugs.gnu.org
>
> >> I just want to make it as clear as possible that to get that special
> >> value `unspecified' one should use the symbol 'unspecified.
> >
> > We have gazillions of such situations everywhere in Emacs where symbol
> > values are documented, and we never say anything beyond the name of the
> > symbol with proper quoting.
>
> For some reason this situation seems different (from a user point of
> view), give that the same question pops again and again. Why is adding
> such a note a problem?
Because we don't say anything like that anywhere else.
> And when one calls
>
> (set-face-attribute 'isearch t :background 'unspecified)
>
> this is what is happening:
>
> (internal-set-lisp-face-attributes 'isearch :background 'unspecified t)
>
> So this call is already included in the previous one. Why should we tell
> users to add such a redundant call in their code?
The new text doesn't say the call with FRAM = t should be an
additional call.
> As far as I understand, the actual and real problem here is some users use
> nil when they should use 'unspecified, because they are not aware that nil
> and 'unspecified are subtly different. The subtle difference is that
> using nil works for frame = #<frame-1> ... #<frame-n>, but does not work
> with frame = t.
That is a backward-compatibility feature that I don't want to mention
in the doc string. Lisp programs should only use valid values that
are documented in the doc string.
> > When a new frame is created, attribute values in the FACE's `defspec'
> > normally override the `unspecified' values in the FACE's default
> > attributes. To avoid that, i.e. to cause ATTRIBUTE's value be reset to
> > `unspecified' when creating new frames, disregarding what the FACE's
> > face spec says, call this function with FRAME set to t and the
> > ATTRIBUTE's value set to `unspecified'.
>
> See above: I really don't understand why the 'unspecified value should be
> detailed as if it were different from the other values, when in fact it
> isn't. The real and actual problem here is that users are confused by the
> fact that a nil value for an attribute is equivalent to an 'unspecified
> value for existing frames, but is not equivalent to 'unspecified for new
> frames.
I give up. I've installed the last text I proposed, and I'm closing
this bug with that.
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