A question about EXCEPT

[fadolatabadi]

Hi all
I made a contextual single positioning lookup in VOLT 1.3 and set the context as EXCEPT <glyphgroupname> (glyphgroupname was one of my predefined glyph groups). In this situation VOLT did not recognize my lookup and when I wanted to compile the font, showed the following message:
"EXCEPT cannot be bound to a glyph set. Please check the expression and all glyphs it references."
I have seen in VOLT Training Video that assigning a glyph group to 'EXCEPT' in contextual lookups is something quite feasible. But in my experience it does not work. I don’t know the cause of this problem. Is there something wrong with me or is it related to VOLT (I mean VOLT cannot accept a glyph group after EXCEPT command)? I would appreciate any help in this issue.
With Thank, F.A. D

[Sergey Malkin (Microsoft)]

EXCEPT should be first word in context string, after it you can put any valid context.

You may have put it after '|', in this case it will be trated like normal input.

Thanks,
Sergey

[tiro_hudson]

I can confirm that the EXCEPT syntax does work, but as Sergey notes the EXCEPT command must be at the beginning of the context string and applies to the whole string.

This means that you can't do this sort of thing

<glyphgroup1> | EXCEPT <glyphgroup2>

But could achieve the same result with

EXCEPT | <glyphgroup2>
<glyphgroup1> |

Contexts involving the EXCEPT command must precede those that do not.

[fadolatabadi]

Thank you very much Sergey and hudson
As you said I put the EXCEPT after | and it was not recognized by VOLT. Again thank you for your advice.
F. A. D.

[sylvain]

Hi.

Fadolatabadi, first thanks for talking about this because I didn't know about the EXCEPT command.
Can you tell me about the VOLT training video you are talking about? Can I find it on the web? As if there are more things like this, I'd be really glad to see it.

Thanks a lot.

Greetings from Berlin to Iran.

Sylvain.

[Sergey Malkin (Microsoft)]

This page on Microsoft Typography website contains various information about VOLT, including training video: http://www.microsoft.com/typography/VOLT.mspx

Thanks,
Sergey

[fadolatabadi]

Hi Sergey
I want to know something else about EXCEPT. Suppose that I have a font containing several scripts (e.g. English, Cyrillic, Greek, Arabic and so on) and I want to use the EXCEPT command in one of them (say, Arabic). The question here is:
Does the EXCEPT command apply to the glyphs only in the specified script (or language) in VOLT or it applies to all other glyphs included in the font?
In normal contextual features, you clearly determine the glyphs and completely know which glyphs are in contexts. Conversely, in contextual features containing EXCEPT you determine the glyphs that do not take part in that feature. My question is about these glyphs. How VOLT deals with them? These glyphs might be only in the range of selected script in the VOLT or might be all other glyphs in the font. Which one of them is true?
With thanks
F.A.D

[Sergey Malkin (Microsoft)]

It seems to me you are confused about how EXCEPT works.

Mathcing for EXCEPT context is the same as for normal one. It is not dealing with glyphs that are "not in the specified group", whatever it may mean. Matching process is absolutely the same. Difference is in what happens after context is matched. If normal context is matched, action specified in the lookup will be executed. If it is EXCEPT context, action will not be executed and we will stop checking following contexts.

Thanks,
Sergey

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