Re: [NTG-context] ligatures/substituation at word boundaries

30 Jul 2017


      On 7/30/2017 11:39 AM, Ulrike Fischer wrote:
...
Am Fri, 28 Jul 2017 23:21:18 +0200 schrieb Hans Hagen:
...
...
Is it possible to refer in fonts.handlers.otf.addfeature to the word
boundary? The luatex manual speaks of a virtual "left_boundary"
char, but I couldn't find a way to use it.
...
It is possible to check against spaces in contextual lookups. There
isn't something like left boundary. I added some test code to the beta
but keep in mind that this will only work with self-made features.
Thanks. It seems to work quite good and after some playing around I
also got the knack of the syntax.
A few questions:
1. "lookups = { 1 }," refers to the first lookup. Is it possible to
name the lookups and to refer to this name?.
no, because order matters
...
2. 0xFFFC refers more or less to the begin and end of line, right?
Why doesn't it interfere with hyphenations? I tried to get
       ab-
ab
and the second wasn't replaced (as wanted) and I wondered how it
worked.
0xFFFC is just the same as "anything other than glyph or discretionary"
...
3. Why is in the following example "abcd" not replaced by "12"?
i'll have a look at this (advancing in somewhat messy defined)
...
\startluacode
      fonts.handlers.otf.addfeature {
          name    = "test-a",
          type    = "chainsubstitution",
          lookups = {
              {
                  type = "ligature",
                  data = {
                      ['1'] = { "a", "b" },
                      ['2'] = { "c", "d" },
                  },
              },
          },
          data = {
              rules = {
                  {
                      before  = { { " ", 0xFFFC } },
                      current = { { "a" }, { "b" } },
                      lookups = { 1 },
                  },
                  {
                      current = { { "c" }, { "d" } },
                      after   = { { 0xFFFC, " " } },
                      lookups = { 1 },
                  },
              },
          },
      }
\stopluacode
\definefontfeature[test-a][test-a=yes]
\startbuffer
xxx abcd abxcd xxx
\stopbuffer
\starttext
\typebuffer
\definedfont[file:dejavu-serif.ttf*default] \getbuffer \blank
\definedfont[file:dejavu-serif.ttf*default,test-a] \getbuffer \blank
\stoptext
-- 

-----------------------------------------------------------------
                                           Hans Hagen | PRAGMA ADE
               Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
        tel: 038 477 53 69 | www.pragma-ade.nl | www.pragma-pod.nl
-----------------------------------------------------------------