different fonts and different heights

[Kiwon Um]

Hello. Let's discuss about follows.

When we use a combination font-setting of over two fonts in emacs, it
may be due to the multi-language editing support. Those different
fonts have varieties in their size, e.g. many Asian glyphs occupy
double width space of an alphabet. (Even though the wide font is not
perfectly double wide space of one alphabet, many users want that the
occupied size of one wide character such as Asian character to be
exactly same with two alphabet characters, namely fixed font setting)

However, we must consider the line spacing, I mean the height of the
fonts. Although the width between different fonts have variation along
each other, the height (or line spacing) should keep same, or, at
least, user must be able to set the base height, IMO.

To keep the consistency in the height spacing with various widths,
emacs needs to check the largest height value along each specified
charset(fontset). Currently, emacs seems to set the base height as the
value of the default fontset. Then, if the height value of other user-
specified charset's font is larger, it may cause inconsistent result
in line spacing. (This is exactly now happening.)

So, how can users specify different fontsets with different sizes for
each, but with consistent height?
As you all already know, users can set the line-spacing value to
control the space between lines. But this
works only for the space between lines, not for the height of a line
itself.

Here is one case with the problem:
    (set-face-font 'default (font-spec :family "terminus" :size 12.0))
    (set-fontset-font nil 'korean-ksc5601
                      (font-spec :family "Guseul" :registry "unicode-
bmp" :lang "ko" :size 14.0)))

Thanks.