[gtk-i18n-list] Re: On CJK font selection (was Re: [Fwd: Re: Request for review and advice on wqy-bitmap-fonts fontconfig settings])

[Behdad Esfahbod]

On Fri, 2007-12-21 at 01:24 +0900, mpsuzuki at hiroshima-u.ac.jp wrote:
> Sorry, I slipped to attach the picture, here it is.
> 
> On Fri, 21 Dec 2007 01:17:08 +0900
> mpsuzuki at hiroshima-u.ac.jp wrote:
> 
> >On Thu, 20 Dec 2007 10:08:05 -0500
> >Behdad Esfahbod <behdad at behdad.org> wrote:
> >
> >>On Thu, 2007-12-20 at 23:04 +0900, mpsuzuki at hiroshima-u.ac.jp wrote:
> >>> On Thu, 20 Dec 2007 07:48:50 -0500
> >>> Behdad Esfahbod <behdad at behdad.org> wrote:
> >>> >Setting locale is actually enough.  If that's not desired,
> >>> >$PANGO_LANGUAGE can be set as a fallback.  So far seems like most of the
> >>> >issues happen because either the users are not setting locale correctly
> >>> >or are using crappy fonts.  How do I don't care enough about those cases
> >>> >I'm not surprised.
> >>> 
> >>> Excuse me, PANGO_LANGUAGE is the solution to modify the
> >>> Pango's behaviour that Qianqian & Abel ask for fix?
> >>
> >>It's a way to tell Pango which of the CJK languages to prefer.  It's
> >>main use is when running under non-CJK locale (en_US for example) and
> >>the text doesn't have language tags.  It solves most of the "multiple
> >>fonts used in the same line" issues with CJK characters.
> >
> >Excuse me again, please let me know more detail.
> >I attached a picture to describe the behaviour I want to fix.

Thanks for raising a concrete issue.


> >The picture (1), (2), (3) are screenshots under English.
> >
> >If I execute gedit as
> >	$ env LANG=C PANGO_LANGUAGE=en gedit
> >font is not changed during I type "[" then "a".
> >
> >The picture (1'), (2'), (3'), (4') are screenshots under Japanese.
> >
> >If I execute gedit as
> >	$ env LANG=ja_JP.euc-jp PANGO_LANGUAGE=ja gedit

As long as your LANG and PANGO_LANGUAGE are the same, you don't need
both.  PANGO_LANGUAGE is mostly useful when you set LANG to en.  That's
not relevant to your issue here though.


> >and I type "[" then "a" then "あ". The font to display
> >"[" is dynamically changed as (2'), (3'), (4') during
> >typing keys. The dynamically font switching shifts the
> >baseline up and down, it looks as strange zig-zag behaviour.
> >I could not stop this switching by setting PANGO_LANGUAGE=en
> >nor PANGO_LANGUAGE=ja. How can I stop this switching?

I tell you what's happening, you tell me what Pango is doing wrong and
how you think it can be fixed:

  - In image 2', you are running under Japanese locale, you type a
COMMON character ('[') only, Pango assumes you are going to type
Japanese text, your preferred Japanese font has a glyph for '[', so
Pango uses it, hoping that it will use the same font when you enter
Japanese text.

  - In image 3', you entered a Latin letter, not Japanese (an unexpected
event given that you run under Japanese locale), so Pango now associates
the bracket to the Latin text, because, well, that's the only non-COMMON
script there.  You sure have a bracket and Latin text in it.  So it
renders the bracket using the same font that it uses for the Latin text.

  - In image 4', you add a Japanese character.  No surprises here: you
have two fonts, the line takes the height of the taller font.  So the
Latin text is shifted down a bit.


So, the issue comes down to the fact that:

  - It's unexpected to enter Latin under Japanese locale.

  - You have a COMMON character at the beginning of the line.

  - Your Japanese and Latin fonts have different heights.


And this case is rare enough that I normally don't consider it an issue
at all.  But apparently multiplying that by 1 billion makes it quite
visible!


One way one may suggest is that Pango should reserve a minimum line
height that is enough to fit the default Japanese font, because it's
running under Japanese locale after all.  That would fix the jump from
3' to 4', but makes English-only paragraphs look very ugly and badly
spaced vertically, so that's not an option either.

The jump from 2' to 3' can't be fixed.  I already proved that.  If one
fixes it, it would introduce the bug that '[' followed by a Japanese
character will choose a separate fonts for those chars, OR, that font
used for '[' will change when you type a Japanese char.  It's as simple
as this: Pango can't know what you are going to type next.  It can just
guess, and it's guessing pretty good.  It's just not reading your mind
yet :).


I have two suggestions for what you can do that may achieve better
results for you.

  - Run under LC_LANG=en_US LC_MESSAGES=ja_JA

  - Choose a non-generic font family in gedit.  That is, something other
than Sans, Sans-serif, and Monospace.


> >Regards,
> >mpsuzuki


Regards,

-- 
behdad
http://behdad.org/

...very few phenomena can pull someone out of Deep Hack Mode, with two
noted exceptions: being struck by lightning, or worse, your *computer*
being struck by lightning.  -- Matt Welsh