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1if
 not
 modules
 then
 modules
 =
 {
 }
 end
 modules
 [
'
font-imp-ligatures
'
]
 =
 {
2    version
   =
 1
.
001
,
3    comment
   =
 "
companion to font-ini.mkiv
"
,
4    author
    =
 "
Hans Hagen, PRAGMA-ADE, Hasselt NL
"
,
5    copyright
 =
 "
PRAGMA ADE / ConTeXt Development Team
"
,
6    license
   =
 "
see context related readme files
"
7}
8
9local
 lpegmatch
 =
 lpeg
.
match
10local
 utfsplit
 =
 utf
.
split
11local
 settings_to_array
 =
 utilities
.
parsers
.
settings_to_array
12
13local
 fonts
              =
 fonts
14local
 otf
                =
 fonts
.
handlers
.
otf
15local
 registerotffeature
 =
 otf
.
features
.
register
16local
 addotffeature
      =
 otf
.
addfeature
17
18-- This is a quick and dirty hack.
19
20local
 lookups
 =
 {
 }
21local
 protect
 =
 {
 }
22local
 revert
  =
 {
 }
23local
 zwjchar
 =
 0x200C
24local
 zwj
     =
 {
 zwjchar
 }
25
26addotffeature
 {
27    name
    =
 "
blockligatures
"
,
28    type
    =
 "
chainsubstitution
"
,
29    nocheck
 =
 true
,
 -- because there is no 0x200C in the font
30    prepend
 =
 true
,
 -- make sure we do it early
31    future
  =
 true
,
 -- avoid nilling due to no steps yet
32    lookups
 =
 {
33        {
34            type
 =
 "
multiple
"
,
35            data
 =
 lookups
,
36        }
,
37    }
,
38    data
 =
 {
39        rules
 =
 protect
,
40    }
41}
42
43addotffeature
 {
44    name
     =
 "
blockligatures
"
,
45    type
     =
 "
chainsubstitution
"
,
46    nocheck
  =
 true
,
  -- because there is no 0x200C in the font
47    append
   =
 true
,
  -- this is done late
48    overload
 =
 false
,
 -- we don't want to overload the previous definition
49    lookups
  =
 {
50        {
51            type
 =
 "
ligature
"
,
52            data
 =
 lookups
,
53        }
,
54    }
,
55    data
 =
 {
56        rules
 =
 revert
,
57    }
58}
59
60registerotffeature
 {
61    name
        =
 '
blockligatures
'
,
62    description
 =
 '
block certain ligatures
'
,
63}
64
65local
 splitter
 =
 lpeg
.
splitat
(
"
:
"
)
66
67local
 function
 blockligatures
(
str
)
68
69    local
 t
 =
 settings_to_array
(
str
)
70
71    for
 i
=
1
,
#
t
 do
72        local
 ti
 =
 t
[
i
]
73        local
 before
,
 current
,
 after
 =
 lpegmatch
(
splitter
,
ti
)
74        if
 current
 and
 after
 then
 -- before is returned when no match
75            -- experimental joke
76            if
 before
 then
77                before
 =
 utfsplit
(
before
)
78                for
 i
=
1
,
#
before
 do
79                    before
[
i
]
 =
 {
 before
[
i
]
 }
80                end
81            end
82            if
 current
 then
83                current
 =
 utfsplit
(
current
)
84            end
85            if
 after
 then
86                after
 =
 utfsplit
(
after
)
87                for
 i
=
1
,
#
after
 do
88                    after
[
i
]
 =
 {
 after
[
i
]
 }
89                end
90            end
91        else
92            before
  =
 nil
93            current
 =
 utfsplit
(
ti
)
94            after
   =
 nil
95        end
96        if
 #
current
 >
 1
 then
97            local
 one
 =
 current
[
1
]
98            local
 two
 =
 current
[
2
]
99            lookups
[
one
]
 =
 {
 one
,
 zwjchar
 }
100            local
 one
 =
 {
 one
 }
101            local
 two
 =
 {
 two
 }
102            local
 new
 =
 #
protect
 +
 1
103            protect
[
new
]
 =
 {
104                before
  =
 before
,
105                current
 =
 {
 one
,
 two
 }
,
106                after
   =
 after
,
107                lookups
 =
 {
 1
 }
,
 -- not shared !
108            }
109            revert
[
new
]
 =
 {
110             -- before = before,
111                current
 =
 {
 one
,
 zwj
 }
,
112             -- after   = { two, unpack(after) },
113                after
   =
 {
 two
 }
,
114                lookups
 =
 {
 1
 }
,
 -- not shared !
115            }
116        end
117    end
118end
119
120-- blockligatures("\0\0")
121
122otf
.
helpers
.
blockligatures
 =
 blockligatures
123
124-- blockligatures("fi,ff")
125-- blockligatures("fl")
126-- blockligatures("u:fl:age")
127
128if
 context
 then
129
130    interfaces
.
implement
 {
131        name
      =
 "
blockligatures
"
,
132        arguments
 =
 "
string
"
,
133        actions
   =
 blockligatures
,
134    }
135
136end
137
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