Re: Automatic face re-application with frame-set-background-mode

Good morning,

Eli Zaretskii <[email protected]> writes:
> That still signals an error about an unknown theme 'mve'.

Ouch. The summer heat may have got me.

--8<---------------cut here---------------start------------->8---
(custom-theme-set-faces
 'mve ; <--- here, instead of 'mve-theme
 ...
--8<---------------cut here---------------end--------------->8---

Not handy with the theming facilities syntax. But anyway, that's not
relevant anymore. See below.

>
> I think the intended usage is that the background mode is set _before_
> the theme's faces are applied.
>
>> «...»
>
> Again, you have it backwards: AFAIU, the background mode should be
> known _before_ the default faces are determined.
>

I see.  Upon closer inspection of `frame-background-mode':

  The brightness of the background.
  _Set this to the symbol ‘dark’ if your background color is dark, ‘light’ if your background is light,_ ...

So it is intended to be set according to the background _already_ is, not
the desired background. I thought otherwise, and the fact that
`frame-background-mode' had a setter function made me believe that even
more.

>
> It's the other way around, actually: the background color is the
> source for determining the background mode.
>

I was quite confused to your mentioning "background color" until i
figured out it is an actual frame parameter (that is actually also
superseded by the `default' face's background)

>> >> >Are there plans or best practices for making theme faces reactive to
>> >> >background-mode changes without manually reapplying the theme?
>> >
>> > I don't understand the question, please elaborate.
>> 
>> Implying that `frame-background-mode` is a user option (which is
>> debatable), how should one make a theme that accounts for such
>> specification? With what I've seen above, this acts in inconsistent
>> ways, or maybe I'm just abusing or misusing it.
>
> Load the theme after the background mode is set.  Does that behave as
> expected?

Yes, it does, but that seemed to me quite hacky a-la "have you tried
turning the PC off and on"? Also, what about faces that are customized
through M-x customize-face? You can't reload them as easily.

So, once I've defined the light and dark specific faces, when changing
the background mode on an existing frame I must also reload the theme,
right?

But then, what about `frame-set-background-mode` 's docstring?

    _Set up display-dependent faces_ on FRAME.
    Display-dependent faces are those which have different definitions
    according to the ‘background-mode’ and ‘display-type’ frame parameters.

    If optional arg KEEP-FACE-SPECS is non-nil, _don’t recalculate
    face specs_ for the new background mode.


It says it does recalculate faces, but that's not always the case as
we've just said that reloading the theme is needed.