Re: [ft] lsb/rsb_delta and vertical text (again)

[Brady Duga]

On May 9, 2007, at 7:25 AM, Werner LEMBERG wrote:

> Sorry for the late reply.

No problem - I will take all the help I can get!

> > I am still trying to work out some issues with glyph spacing and
> > vertical fonts.  I have implemented the lsb/rsb_deltas for
> > horizontal text and that seems to be working fine.  The issue I am
> > now having is with some Japanese fonts that are intended to be drawn
> > vertically with very little space between the glyphs.  Essentially,
> > the spacing is really bad :( In some cases glyphs actually touch
> > each other.  However, if I render with FT_LOAD_NO_HINTING then the
> > spacing is fine.  I have some sample images here:
> > http://www.ljug.com/vertsamples.html
>
> IMHO, the spacing for unhinted text you actually use is too tight.
> Just look at the `上' glyph in the rightmost column: The base line of
> this glyph gets overwritten by the glyph below.

Actually, I don't think that is true. Take at look at the same glyph  
at the bottom of the column third from the left. Notice that it is  
also missing the line across the bottom, even though it is the last  
character on the line. I think this is just a general problem with  
drawing East Asian fonts with auto-hinting disabled.

> Japanese companies
> like Morisawa provide special fonts intended for tight vertical
> writing; essentially, those fonts are slightly compressed vertically,
> together with a lot of vertical kerning pairs.

Actually, I have such a font, but the metrics in it appear to be  
wrong. I was going to try it again with  
'FT_LOAD_IGNORE_GLOBAL_ADVANCE_WIDTH' and see if that helped (since  
it appears to be a buggy CJK font). Certainly the font I showed is  
not designed for this compressed look, but it does seem to have small  
errors in placing the characters when auto-hinting is on.

> > I made a feeble attempt to add tsb/bsb_delta values to my local copy
> > of FreeType, but it didn't seem to make a difference.
>
> Can you post a patch so that we can look at it?

Sure. First I have to figure out how to do that, but I can certainly  
give it a shot.

--Brady