[tbb-dev] Fwd: Intent to ship: Changing default Japanese fonts to modern fonts

[Tom Ritter]

Some input on Asian font preferences we could consider.

-tom
---------- Forwarded message ----------
From: "Masayuki Nakano" <masayuki at d-toybox.com>
Date: Aug 23, 2017 12:20 AM
Subject: Intent to ship: Changing default Japanese fonts to modern fonts
To: <dev-platform at lists.mozilla.org>
Cc:

Hi,

We decided that we should change our default Japanese fonts from legacy "MS
PGothic" (sans-serif) and "MS PMincho" (serif) which have bitmap glyph to
modern "Meiryo" or "Yu Gothic" (sans-serif) and "Yu Mincho" (serif).

This has been enabled on Nightly and early Beta since 55 [1].

Then, I removed the |#ifdef EARLY_BETA_OR_EARLIER| in Nightly yesterday
[2].  I.e., the new default settings are enabled on release build starting
from 57.

I'd like to introduce some backgrounds:

"Meiryo" is installed on Vista or later (but not installed on Win10 unless
you add Japanese in system language settings). "Yu Gothic" and "Yu Mincho"
is installed on Win8.1 or later.

Both Edge and Chrome already started to use "Meiryo" as their default
Japanese fonts. So, using "Meiryo" improves the compatibility between
browsers and just looks better and is easier to read than bitmap glyph.

One of the reason why we didn't use "Meiryo" as default fonts is, "Meiryo"
has normal style glyph as italic style glyph. E.g., |a<i>b</i>c| looks like
|abc|, not |a/b/c|. The other browsers have this issue, but I see many
users who complain about this issue. For solving this issue, we added a
hack to ignore italic style family of "Meiryo" at loading fonts [3]. So,
now, Gecko is the only one engine which supports italic style Japanese text
with default fonts!

On the other hand, there are still some problems.

"Meiryo" has too big internal leading for supporting accent marks of
Western languages. This causes increasing normal line height than other
fonts. Additionally, Gecko's normal line height computation is not same as
the other browsers. Therefore, this may cause compatibility issue with the
other browsers. For example, our <input> allows to scroll its content.
Therefore, if user drags text in <input> vertically, the text may be
scrolled [4].

If we could use "Yu Gothic" as Japanese default font, it'd be really nicer
except compatibility with the other browsers because it has nicer glyph
than "Meiryo" ("Meiryo" was designed for UI, not for document. Therefore,
it was designed as easier to read even if the font size is small) and does
not have too big leading like "Meiryo".  However, there is a big problem.
Text renderer of Windows has a bug. Text of "Yu Gothic" is rendered as too
light [5]. So, the contrast between text and background color may not be
enough for some users. Therefore, currently, we use "Yu Gothic" as a
fallback font only when "Meiryo" isn't available.

Anyway, I believe that this makes 57 look nicer for Japanese users!

[1] https://bugzilla.mozilla.org/show_bug.cgi?id=548311
[2] https://bugzilla.mozilla.org/show_bug.cgi?id=1354004
[3] https://bugzilla.mozilla.org/show_bug.cgi?id=1351332
[4] https://bugzilla.mozilla.org/show_bug.cgi?id=1378065
[5] https://bug548311.bmoattachments.org/attachment.cgi?id=8848439

-- 
Masayuki Nakano <masayuki at d-toybox.com>
Software Engineer, Mozilla
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