Re: Thai fonts small compared to regular characters

[Theppitak Karoonboonyanan <thep linux thai net>]

On Sat, Jul 24, 2004 at 01:48:29PM +0200, Ruben Vermeersch wrote:
> On Sat, 24 Jul 2004 13:48:52 +0200, Pablo Saratxaga
> <pablo mandrakesoft com> wrote:
> > Kaixo!
> >
> > On Sat, Jul 24, 2004 at 01:12:53PM +0200, Ruben Vermeersch wrote:
> > >
> > > display of thai fonts on my gnome desktop. For some reason, thai fonts
> > > are rendered a lot smaller then regular characters. Since the regular
> >
> > > http://files.lambda1.be/screenshots/thai.png
> >
> > Could it be you are using the "Norasi" thai fonts?
> >
> > If yes; the problem is in the fonts themselves.
> >
> > If someone know of better freely distributable fonts for Thai
> > I'll be happy to hear about it.
> >
> > Or maybe is there a possibility to cheat with fontconfig (eg tell
> > fontconfig that when user requests size "x", then size "x+4" has to
> > be used instead).
> >
> 
> Most of my thai fonts come from http://linux.thai.net
> 
> But i have no idea which font my X uses

The font in the screenshot appears to be TLWG PseudoMono.

I would like to say, the relatively small size is currently inevitable,
unless the same font is chosen to render both Thai and English
characters.

The reason is that Thai font designs have to reserve upper and lower
space for placing combining characters [1]. So, with the same point size,
Thai base characters are always smaller than those of typical Latin fonts.
This is true for other multi-level scripts, such as Laos, Khmer, Tibetan
as well. However, those fonts always provide English glyphs with proper
relative size. So, if the same font is chosen, the relative size would fit
well.

On the other hand, some fonts, such as FreeSerif, try to cope with this
problem by scaling up Thai glyphs instead, letting the upper/lower marks
be placed beyond the ascender/descender. While this works in some
cases, the marks just get clipped in some others. Breaking the rule is
always not safe.

So, the ideal is to extend the "point size" definition to cover other
scripts than Latin as well.

Regarding the fontconfig cheat, this is what I have tried to do, without
success. As a rule of thumb, an English font of n points is suitable with
Thai font with n*1.3 points.

Reference:
[1] Thai font standardization working group. Recommendations for Thai
    font construction. (in Thai) pp. 80.
    http://www.swpark.or.th/opensource/download/Thaifont%20for%20Linux3.pdf

Regards,
-Thep.
-- 
Theppitak Karoonboonyanan
http://linux.thai.net/~thep/