fixed-width japanese renders differently from other GTK/QT apps

[Ahmad Syukri Abdollah]

Binary package hint: firefox

In LibreOffice and Gedit, I'm able to type using fixed-width Japanese fonts (IPA/Takao Mincho/Gothic, without P) such that two half-width characters will line up to a full-width character. That means, if I type 32 full-width letters on one line and 64 half-width letters on the next line, they will be the same length horizontally.

But in Firefox, this seems to be broken. Please see the attached screenshot for clarification. Sorry if it's too big; I have my DPI set to 168. Also, I have hinting disabled.

I've tested typing in qtconfig-qt4, and it also works fine. Maybe only Firefox is affected? This could have something to do with the fact that Firefox doesn't respect Xft/GNOME DPI settings, which suggests it probably renders in a different way.

Also attached is a test HTML file used to produce the screenshot for Firefox.

[Ahmad Syukri Abdollah (syockit)]

Drats, I just found out that it affects other apps as well (except LibreOffice)! The bug only appears on certain font sizes, and it just so happens that the font sizes that cause the bug are different between Firefox and Gedit.

[Ahmad Syukri Abdollah (syockit)]

It could be a freetype bug, seeing that another freetyped-based program for Windows, gdipp, seems to suffer from the same problem? (http://code.google.com/p/gdipp/issues/detail?id=151) And over there, it renders correctly in the word processor too (Microsoft Word).

[Ahmad Syukri Abdollah (syockit)]

Woops, previous attachment mistitled as Gothic. Correct one is Mincho.
Here is the python script for generating dialog in previous attachment. Requires python-gtk2

[Takashi Sakamoto (mocchi)]

This bug also appears in the other Japanese monospace true type font. I tested VL Gothic in "ttf-vlgothic" package. (See attached screenshot) Each of full-width letters don't have the same width as half-width.

The Japanese glyphs of Takao and VL Gothic are not derived from the same source. So this bug is not related to which font is applied but related to the backends of displaying process.