Re: Question on bitmap fonts

FROM : Aki Inoue
DATE : Mon Mar 31 20:18:29 2008

Tobia,

It appears that this is the intended behavior.

The font contains glyphs that extend beyond the ascender line (the 
accented glyphs) and Cocoa automatically adjusts the default line 
height accordingly to avoid baseline shifts.

So, basically the system, tools you're using to convert the font, and 
the font itself are all working as designed.

Aki

On 2008/03/31, at 9:23, Tobia Conforto wrote:

> Hello
>
> After 1000 messages to this list and no reply, I'm resubmitting my 
> question about bitmap fonts, hoping to get any bit of help or any 
> pointer at all (docs, other mailing lists, etc.)
>
> Basically, I would like to know what are the best practices and 
> recommended programs for preparing bitmap fonts for use in Cocoa 
> applications.  I'm also reporting what is probably a bug in either 
> OS X or the available font editors.
>
> If there is a list better suited to this question, please point me 
> to it.
>
>
> I'm trying to convert the well known X11 fixed unicode fonts to a 
> format usable in Cocoa text editors and terminal programs.  These 
> fonts are available under a free license on Markus Kuhn's website: http://www.cl.cam.ac.uk/~mgk25/ucs-fonts.html
>  and are provided in source BDF format.
>
> I tried using the free editor Fontforge to convert 9x18.bdf into a 
> so-called (by Fontforge) "Apple bitmap-only .dfont" format.  Mostly 
> it works, but I've run into a problem that Fontforge's programmers 
> can't solve.  See this thread on their list:
> http://www.nabble.com/BDF-to-Apple-bitmap-only-dfont,-wrong-line-height-td15155775.html
>
> The problem is that the generated dfont is rendered by OS X with 4px 
> of additional ascent (or line-height) and we can't figure out where 
> it comes from.  If I convert only the ASCII subset of the original 
> Unicode font, the line-height is correct.  As soon as I add more 
> than a couple of non-ASCII characters, the 4px bug comes out.
>
> I tried doing the same conversion using a trial version of the 
> commercial BitFonter 3.0 editor ($500) and I got the same results as 
> with Fontforge.
>
> I looked into the .dfont file with a hex editor, using this manual 
> as a reference http://developer.apple.com/textfonts/TTRefMan/ but I 
> couldn't find anything out of place.
>
> Here is a zip http://gruppo4.com/~tobia/osx-font-problem.zip where 
> I've put two OS X dfont files I created from 9x18.bdf, using 
> Fontforge, plus a text file with the font tables I extracted using 
> the hex editor.
> In "test3" I converted the full Latin 1 charset (Unicode points < 
> 256) and it shows the 4px bug; in "test7" I deleted all glyphs other 
> than ASCII and a couple of Latin 1 accented letters, and it displays 
> correctly in all Cocoa apps.
>
> What am I doing wrong?  What's different in the two files?  Can you 
> replicate this bug?  Is this a bug in OS X, a weird setting in the 
> original BDF, or a bug shared between Fontforge and BitFonter?
>
> Can you think of any workaround or alternative program I could try?
>
>
> Tobia
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