1 files changed, 131 insertions, 3 deletions

diff --git a/src/luaotfload-init.lua b/src/luaotfload-init.lua
index 096d778..5fafceb 100644
--- a/src/luaotfload-init.lua
+++ b/src/luaotfload-init.lua
@@ -319,6 +319,137 @@ local init_adapt = function ()
 
 end --- [init_adapt]
 
+--[[doc--
+
+  In Context, characters.data is where the data from char-def.lua
+  resides. The file is huge (>4.4 MB as of 2016) and only a stripped
+  down version is part of the isolated font loader. Nevertheless, we
+  include an excerpt generated by the mkcharacters script that contains
+  a subset of the fields of each character defined and some extra
+  metadata.
+
+  Currently, these are (compare the mkcharacters script!)
+
+    · "direction"
+    · "mirror"
+    · "category"
+    · "textclass"
+
+  The directional information is required for packages like Simurgh [0]
+  to work correctly. In an early stage [1] it was necessary to load
+  further files from Context directly, including the full blown version
+  of char-def.  Since we have no use for most of the so imported
+  functionality, the required parts have been isolated and are now
+  instated along with luaotfload-characters.lua. We can extend the set
+  of imported features easily should it not be enough.
+
+  [0] https://github.com/persian-tex/simurgh
+  [1] http://tex.stackexchange.com/a/132301/14066
+
+--doc]]--
+
+characters         = characters or { } --- should be created in basics-gen
+characters.data    = nil
+local chardef      = "luaotfload-characters"
+
+do
+  local setmetatableindex = function (t, f)
+    local mt = getmetatable (t)
+    if mt then
+      mt.__index = f
+    else
+      setmetatable (t, { __index = f })
+    end
+  end
+
+  --- there are some special tables for each field that provide access
+  --- to fields of the character table by means of a metatable
+
+  local mkcharspecial = function (characters, tablename, field)
+
+    local chardata = characters.data
+
+    if chardata then
+      local newspecial        = { }
+      characters [tablename]  = newspecial --> e.g. “characters.data.mirrors”
+
+      local idx = function (t, char)
+        local c = chardata [char]
+        if c then
+          local m = c [field] --> e.g. “mirror”
+          if m then
+            t [char] = m
+            return m
+          end
+        end
+        newspecial [char] = false
+        return char
+      end
+
+      setmetatableindex (newspecial, idx)
+    end
+
+  end
+
+  local mkcategories = function (characters) -- different from the others
+
+    local chardata         = characters.data
+    local categories       = characters.categories or { }
+    characters.categories  = categories
+
+    setmetatable (categories, { __index = function (t, char)
+      if char then
+        local c = chardata [char]
+        c = c.category or char
+        t [char] = c
+        return c
+      end
+    end})
+
+  end
+
+  local load_failed = false
+  local chardata --> characters.data; loaded on demand
+
+  local load_chardef = function ()
+
+    logreport ("both", 1, "aux", "Loading character metadata from %s.", chardef)
+    chardata = dofile (kpse.find_file (chardef, "lua"))
+
+    if chardata == nil then
+      logreport ("both", 0, "aux",
+                 "Could not load %s; continuing with empty character table.",
+                 chardef)
+      chardata    = { }
+      load_failed = true
+    end
+
+    characters             = { } --- nuke metatable
+    characters.data        = chardata
+    characters.classifiers = chardata.classifiers
+    chardata.classifiers   = nil
+
+    --- institute some of the functionality from char-ini.lua
+
+    mkcharspecial (characters, "mirrors",     "mirror")
+    mkcharspecial (characters, "directions",  "direction")
+    mkcharspecial (characters, "textclasses", "textclass")
+    mkcategories  (characters)
+
+  end
+
+  local charindex = function (t, k)
+    if chardata == nil and load_failed ~= true then
+      load_chardef ()
+    end
+
+    return characters [k]
+  end
+
+  setmetatableindex (characters, charindex)
+
+end
+
 local init_main = function ()
 
   local load_fontloader_module = luaotfload.loaders.fontloader
@@ -338,9 +469,6 @@ local init_main = function ()
                                         or "reference"
   fontloader = tostring (fontloader)
 
-  --- Preload the characters table. This may vanish later.
-  characters = luaotfload.loaders.luaotfload "characters"
-
   if fontloader == "reference" then
     logreport ("log", 0, "init", "Using reference fontloader.")
     load_fontloader_module (luaotfload.fontloader_package)