Re: Industry Thai Cell-Clustering Rules

[Chookij Vanatham <chookij vanatham eng sun com>]

Hi Owen,

] > 
] > This piece of code determines Cell-Clustering for Thai and, of couse,
] > it doesn't use Wtt2.0 Cell-clustering logic.
] >
] > Now, if users want to have Thai displayed as Wtt2.0 Cell-clustering,
] > what will you do ?
] >
] > That's why, we put Cell-clustering to XLFD name, so that, the engine
] > can determine which cell-clustering rule should be used. Then, users
] > would be able to choose what they want.
] > 
] > It's not really clear cut to say that Cell-clustering is not specific to
] > font. Unfortunately, in the industry, there are more than 1 cell-clustering
] > rule.
] 
] I have to disagree here (and, I think, agree with K. Theppitak) - 

Now, I think we get everybody in sync here and what we should say
is that "cell-clustering is not font-specific".

] 
]  - I wrote that code basically to give a simple example of how a
]    shaper can work in Pango, not to say that is how Thai shaping
]    should definitively work in Pango. In fact, I'd be very happy if
]    somebody replaced the code with something more standard and
]    better.

This is the exact point.
I will change the cell-clustering to be Wtt2.0 cell-clustering
standard and of course, will work with K.Theppitak to make sure
that all these ideas are not coming from only one person.

] 
]  - Changing .pangox-aliases to use a different font name is not
]    a good way for users to configure their preferred clustering
]    rules.

Because we are going to change cell-clustering in Thai Pango engine
to be Wtt2.0 cell-clustering and we agree that this cell-clustering
is important, then, I think, we should not mix up .pangox-aliases
with cell-clustering issue. So, then, this should be ok.

] 
]  - I'm not sure if we need to support multiple cell clustering
]    rules in Pango is even necessary. Can't we just say that 
]    we always use wtt-2.0?

That is the whole point and I would say "yes" but we need
to hear from K.Theppitak as well.

] 
]  - It is important in Pango that clustering (in the Pango sense -
]    I'm not sure I quite understand the sense that you mean), is
]    independent of the font.

I think, from a lot of mails we have been talking so far,
I think, we can get the sense that cell-clustering is independent
of the font and it's just if there are more than one rule of
cell-clustering, how we are going to deal with it.
The best case, I hope that, it would be one cell-clustering rule
for each script but I'm not too sure about that.

] 
]    I can have a GtkTextBuffer object with multiple views of the same
]    text with different. Moving one cursor position to the right 
]    should have an unambiguous meaning in this case.
] 
] > ] Let me say:
] > ] - tis620-1 and tis620-2 are proper supersets of tis620-0.
] > ] - So, any rendering engine that works with plain TIS 620 (i.e. tis620-0)
] > ]   can be applied to all above categories of tis620 registry. And WTT 2.0
] > ]   provides one of such engines.
] > ] - So, it's rather a matter of preference to choose the rendering engine
] > ]   than a matter of font encoding.
] > 
] > K.Theppitak, let me make sure that we are not mixing between Cell-clustering
] > and font-shapping. As you mentioned that it's a matter of preference to
] > choose the rendering engine to have either Wtt2.0 cell-clustering or
] > (let's say) non-Wtt2.0 cell-clustering, how would you be able to do that
] > with Pango ?
] 
] What would be the reasons why a user would want to choose one
] clustering rule or another?

Owen, this is the exact point too.

Actually, Thai users who are not in computer-industry might not even hear
about wtt2.0 name but one thing, for sure, when I was a kid and learned
Thai in the school, my teacher taught me how to write Thai script and
for sure, Thai vowel will always follow Thai consonant and Thai tonemark will
always follow Thai vowel. This is the right sequence. We never been taught
to write it in different sequence. That's why Wtt2.0 cell-clustering rule
doesn't allow the illegal sequnence to be displayed as the same as
the right sequence.

Unfortunately, I'm trying not to blame the computer industry in that period
that was mis-leading this interpretation with whatever reason why they
did that.

That's why it causes more problems for both Thai users and Non-Thai users
and that's why we are having this discussion.

Hope this can help answering this question.

Chookij V.

]  
] 
] Still a bit confused...
]                                         Owen
] 
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