bug#50424: 27.2; Tab bar button mouse face not clearing entirely

[Eli Zaretskii]

> From: Juri Linkov <juri@linkov.net>
> Cc: alan@idiocy.org,  luangruo@yahoo.com,  50424@debbugs.gnu.org
> Date: Sun, 12 Sep 2021 19:06:57 +0300
> 
> > If we want the default value of tab-bar-button-margin to be a cons
> > cell, let's change the default value to be a cons cell, it's not more
> > complicated than setting it to a scalar, even in C.  But tab-bar.el
> > should use in its image specs the exact value of
> > tab-bar-button-margin, it cannot decide to change it behind the back
> > of the caller.
> 
> I tried a cons cell, but it looks ugly for buttons other than the close 
> button.
> OTOH, margin 1 looks nice for all buttons:

Fine by me.

> diff --git a/src/dispextern.h b/src/dispextern.h
> index f4c7575b35..6aefe43e19 100644
> --- a/src/dispextern.h
> +++ b/src/dispextern.h
> @@ -3202,7 +3202,7 @@ #define IMAGE_CACHE_BUCKETS_SIZE 1001
>  
>  /* Default values of the above variables.  */
>  
> -#define DEFAULT_TAB_BAR_BUTTON_MARGIN 4
> +#define DEFAULT_TAB_BAR_BUTTON_MARGIN 1
>  #define DEFAULT_TAB_BAR_BUTTON_RELIEF 1

Btw, I don't see much sense in keeping the
DEFAULT_TAB_BAR_BUTTON_MARGIN macro: it's used in one place only,
AFAICT, so we could simply have it there literally.