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 <masay...@d-toybox.com>
Software Engineer, Mozilla
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