NOTE : The font for testing "Hiraagino" is Japanese system font on OS X.

http://en.wikipedia.org/wiki/List_of_CJK_fonts#Japanese_2
Hiragino Kaku Gothic (ヒラギノ角ゴ) and Hiragino Maru Gothic (ヒラギノ丸ゴ) – default Japanese system font on Mac OS X.

English Name : "Hiragino Kaku Gothic Pro". (See hiragino_english.png)
Japanese Name : "ヒラギノ角ゴ Pro" (See hiragino_japanese.png)

Steps to reproduce)

Unexpected Case)
1) Change order of "日本語" (it means Japanese) to top most (See language_order_japanese.png)
2) Compile and execute attached sample.
3) Select "ヒラギノ角ゴ Pro" (See select_hiragino_japanese.png) and press OK.

Result)
% ./fontdialog.app/Contents/MacOS/fontdialog
QFontDialog returned : "Lucida Grande"

It is unexpected shown above and an expected result is as follows
QFontDialog returned : "Hiragino Kaku Gothic Pro"

Expected Case in English)
1) Change order of "English" to top most (See language_order_japanese.png)
2) Compile and execute attached sample.
3) Select "Hiragino Kaku Gothic Pro" (See select_hiragino_english.png) and press OK.
Result)
% ./fontdialog.app/Contents/MacOS/fontdialog
QFontDialog returned : "Hiragino Kaku Gothic Pro"

Please check the zip file for images and example application.