Re: Adding tis620.2533-0 into Thai Pango engine

[Steve Underwood <steveu coppice org>]

Owen Taylor wrote:

> In fact, if I understand the problem you are running to be
> the problem that Thai fonts vary in their conventions for:
>
>  - The advance widths
>  - Where the glyph falls with respect to the drawing origin
>
> Then I've seen at least three different sets of conventions for
> freely available Thai fonts on Linux; I tried to make the Thai
> shaper a little bit robust against this. If I recall correctly,
> it worked with two out of the three sets of fonts.

A similar thing happens with the Indic languages. An I/O developer in Bangalore
told me this came from quirks in Windows. He said TrueType has a problem which
won't allow correct spacing. However, bugs in the Windows 3.1 implementation meant
there was a workaround that disobeyed the TrueType spec., but got the job done.
Windows 95 fixed the bugs, and broke the fonts. He was waiting for the
availability of OpenType to provide a clean solution. In the meantime, some
not-quite-correct fudges have been used to get something usable under Windows 95
and NT. I never pursued the fine detail.

If this is the source of the incomsistencies in Thai, might it be possible to
detect something about the font, and sense which spacing convention it uses?

Regards,
Steve