[Dev-luatex] Chars to glyphs. How to?

Taco Hoekwater taco at elvenkind.com
Wed Dec 5 13:51:02 CET 2007



Hans Hagen wrote:
>>
>> Still, why is the subtype ia bitfield anyway? Can a glyph node
>> i.e. be both a character node as well as a ligature node?
> 
> a ligature is not really a character -)
> 
> anyhow, zero means 'nothing done', while other values < 256 means, 
> something done; you can use bits >= 256 for your own usage since luatex 
> only looks at the first 8 bits

A glyph_node is either a pre-hyphenation character (only bit 0 is set
== its value is 1), or it is something else.  Some of the "something
elses" really make more sense when subtype is a bit field (ligatures
and ghosts).

The advantage of using a the first and second bit for "character"
and "glyph", is that we could make tests like: is this a pre-ligkern
node (0 and 1 both unset), or a post-ligkern glyph node (with bit 1
set), or a character (bit 0 set). Such a split allows speedups as
some processing steps can be skipped. Currently however, only the
character test is implemented.

>> - If I handle accented characters this way, I do not have to create
>>   a "ligaturing" callback, do I?

correct.

>> - Does the "char" font command move the output pointer?

yes.

Best wishes,
Taco


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