bug#39656: 27.0.60; ordering of fonts in fontset is ignored

[Alan Third <alan@idiocy.org>]

On Tue, Feb 18, 2020 at 10:13:47PM +0900, ynyaaa@gmail.com wrote:
> 
> If font list in fontset includes the font for ASCII,
> the ordering may be ignored and the font for ASCII is used prior to
> front fonts.
> 
> I tried to setup fontset to display "MS Gothic" as a primary font,
> and "SimHei" as a secondary font, except for ASCII characters.
> And "SimHei" is used for ASCII characters.
> ("MS Gothic" has YEN SIGN glyph for #x5C(\).)
> 
> Evaluating the form below, every character is displayed with "SimHei"
> if glyphs are defined in both "SImHei" and "MS Gothic".
> For example, most of CJK Ideographs are displayed with "SimHei".
> "MS Gothic" is not used between U+3400 and U+9FA5.
> 
> (let* ((ascii "SimHei")
>        (primary "MS Gothic")
>        (secondary ascii))
>   (setq use-default-font-for-symbols nil)
>   (set-frame-font ascii)
>   (set-fontset-font nil '(#x80 . #x10FFFF) primary)
>   (set-fontset-font nil '(#x80 . #x10FFFF) secondary nil 'append))

As I understand it the fontsets are used as fallbacks if the default
font doesn’t contain the desired glyph. Since SimHei DOES contain the
glyph and has been set as the default (set-frame-font) we would expect
to see it displayed with SimHei.
-- 
Alan Third