From: Richard Wordingham (richard.wordingham@ntlworld.com)
Date: Thu Mar 23 2006 - 02:46:27 CST
Philippe Verdy wrote:
>From: "Richard Wordingham" <richard.wordingham@ntlworld.com>
>> For example, to 'swap' characters K and E with glyphs gK and gE you could
>> try a sequence of rules such as:
>> gK > E_for_K / _ gE
>> gE > gK / E_for_K _
>> E_for_K > gE
>> which converts 'gK gE' to 'gE gK'. However, a process that would
>> normally
>> delete gK would delete E from the backing store, with the result that
>> apparently deleting gK would convert the display 'gE gK' to 'gK'!
> I would not doit this way. "Swapping" doesnot mean that the same glyph ids
> must be used.
In fact I would probably use simply such rule: gK gE > gE_before gK
Which GSUB substitution do you mean by this? Context substitution (code 5)?
The only difference is that the latter might lose you the ability to select
either glyph. The point is that if you can select isolated glyphs, the
first in the display will be associated with the first in backing store, and
vice versa.
> Advanced edition of text (with subselections, selection of grapheme
> clusters, ...) is another issue,and is less important than correct
> rendering of text only for display or print. Editors can still be written
> without any knowledge of the font support, but still can recognize where
> cluster boundaries occur in its backingstore (this is needed anyway to
> allow smart line breaks, and this process does not require any specific
> font support)
Some of us would like to be able to change individual characters. At
present it's reminiscent of the ancient editing situation where you had to
change a line at a time when editing on a teletype. It is frustrating to
have to delete a cluster of 3 or 4 characters just to change the base
character. (I can think of a 6 character cluster - 4 visible, 2 invisible -
in Khmer off the top of my head.) Admittedly changing a character in the
middle of a cluster can be very difficult, but at least one can correct the
base character quite easily in a Graphite font.
Richard.
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