Hi,

I'm seeing strange bugs in my toolkit after converting my font layout engine to 
harfbuzz-ng shaping. While most fonts work alright, some have wrong X axis 
density as you can see on this (rather big) screenshot: 
http://meeloo.net/~meeloo/nui_harfbuzz.png

At least two fonts have problems: Helvetica.dfont (from Mac OSX Snow Leopard), 
Meiryo.ttf (from OSX too) and the the open source Vera Sans Mono from bitstream.
As you can see on the screenshot, all sizes of Vera Sans Mono don't show the 
same problem, as the 8pt version looks alright.

My toolkit uses harfbuzz + freetype2 with the harfbuzz provided freetype glue 
code. The unicode callbacks are implemented via a mix of custom code (for 
script detection) and ucdata (for code point features).

You can have a look at the code here 
https://github.com/meeloo/nui3/tree/utf8/src/Font . I call harfbuzz only in one 
function: 
https://github.com/meeloo/nui3/blob/utf8/src/Font/nuiFontBase.cpp#L2114

Before using harfbuzz I was using a very naive algorithm (that is just using 
glyph advances) but I was not having these problems (but I couldn't handle 
complex scripts either ;-) ).

I would like to know if this is a bug on my part (most likely) or a problem in 
the shaping algorithm.

Thank you very much if you've read this far.


-- 
Sébastien Métrot
libnui author
http://libnui.net




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