1 files changed, 158 insertions, 0 deletions
diff --git a/tex/context/base/mkxl/font-imp-ligatures.lmt b/tex/context/base/mkxl/font-imp-ligatures.lmt
new file mode 100644
index 000000000..da5282428
--- /dev/null
+++ b/tex/context/base/mkxl/font-imp-ligatures.lmt
@@ -0,0 +1,158 @@
+if not modules then modules = { } end modules ['font-imp-ligatures'] = {
+    version   = 1.001,
+    comment   = "companion to font-ini.mkiv",
+    author    = "Hans Hagen, PRAGMA-ADE, Hasselt NL",
+    copyright = "PRAGMA ADE / ConTeXt Development Team",
+    license   = "see context related readme files"
+}
+
+-- Not perfect (disc) but we have allternatives.
+
+local lpegmatch = lpeg.match
+local utfsplit = utf.split
+local settings_to_array = utilities.parsers.settings_to_array
+
+local fonts              = fonts
+local otf                = fonts.handlers.otf
+local registerotffeature = otf.features.register
+local addotffeature      = otf.addfeature
+
+-- This is a quick and dirty hack.
+
+local lookups = { }
+local protect = { }
+local revert  = { }
+local zwjchar = 0x200C
+local zwj     = { zwjchar }
+
+addotffeature {
+    name    = "blockligatures",
+    type    = "chainsubstitution",
+    nocheck = true, -- because there is no 0x200C in the font
+    prepend = true, -- make sure we do it early
+    future  = true, -- avoid nilling due to no steps yet
+    lookups = {
+        {
+            type = "multiple",
+            data = lookups,
+        },
+    },
+    data = {
+        rules = protect,
+    }
+}
+
+addotffeature {
+    name     = "blockligatures",
+    type     = "chainsubstitution",
+    nocheck  = true,  -- because there is no 0x200C in the font
+    append   = true,  -- this is done late
+    overload = false, -- we don't want to overload the previous definition
+    lookups  = {
+        {
+            type = "ligature",
+            data = lookups,
+        },
+    },
+    data = {
+        rules = revert,
+    }
+}
+
+registerotffeature {
+    name        = 'blockligatures',
+    description = 'block certain ligatures',
+}
+
+-- local splitter = lpeg.splitat(":")
+--
+-- local function blockligatures(str)
+--     local t = settings_to_array(str)
+--     for i=1,#t do
+--         local ti = t[i]
+--         local before, current, after = lpegmatch(splitter,ti)
+--         if current and after then -- before is returned when no match
+--             -- experimental joke
+--             if before then
+--                 before = utfsplit(before)
+--                 for i=1,#before do
+--                     before[i] = { before[i] }
+--                 end
+--             end
+--             if current then
+--                 current = utfsplit(current)
+--             end
+--             if after then
+--                 after = utfsplit(after)
+--                 for i=1,#after do
+--                     after[i] = { after[i] }
+--                 end
+--             end
+--         else
+--             before  = nil
+--             current = utfsplit(ti)
+--             after   = nil
+--         end
+--         if #current > 1 then
+--             local one = current[1]
+--             local two = current[2]
+--             lookups[one] = { one, zwjchar }
+--             local one = { one }
+--             local two = { two }
+--             local new = #protect + 1
+--             protect[new] = {
+--                 before  = before,
+--                 current = { one, two },
+--                 after   = after,
+--                 lookups = { 1, false }, -- not shared !
+--             }
+--             revert[new] = {
+--                 current = { one, zwj },
+--                 after   = { two },
+--                 lookups = { 1, false }, -- not shared !
+--             }
+--         end
+--     end
+-- end
+
+local function blockligatures(str)
+    local t = settings_to_array(str)
+    for i=1,#t do
+        local ti = t[i]
+        local current = utfsplit(ti)
+        if #current > 1 then
+            local one = current[1]
+            local two = current[2]
+            lookups[one] = { one, zwjchar }
+            local one = { one }
+            local two = { two }
+            local new = #protect + 1
+            protect[new] = {
+                current = { one, two },
+                lookups = { 1, false }, -- not shared !
+            }
+            revert[new] = {
+                current = { one, zwj },
+                after   = { two },
+                lookups = { 1, false }, -- not shared !
+            }
+        end
+    end
+end
+
+-- blockligatures("\0\0")
+
+otf.helpers.blockligatures = blockligatures
+
+-- blockligatures("fi,ff")
+-- blockligatures("fl")
+
+if context then
+
+    interfaces.implement {
+        name      = "blockligatures",
+        arguments = "string",
+        actions   = blockligatures,
+    }
+
+end