[aux,characters] import further Context code

this allows loading Context bidi code without importing the whole lot of
``char-def.lua`` and ``char-ini.lua``.

Addresses https://github.com/lualatex/luaotfload/issues/132

2 files changed, 138 insertions, 20 deletions

diff --git a/luaotfload-auxiliary.lua b/luaotfload-auxiliary.lua
index da3f5f2..311fae9 100644
--- a/luaotfload-auxiliary.lua
+++ b/luaotfload-auxiliary.lua
@@ -368,35 +368,124 @@ aux.name_of_slot      = name_of_slot
   resides. The file is huge (>3.7 MB as of 2013) and not part of the
   isolated font loader. Nevertheless, we include a partial version
   generated by the mkcharacters script that contains only the
-  “direction” and “mirror” fields of each character defined.
+  a subset of the fields of each character defined.
+
+  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 = { }
-local chardef   = "luaotfload-characters"
+characters         = characters or { } --- should be created in basics-gen
+characters.data    = nil
+local chardef      = "luaotfload-characters"
 
 do
-  local chardata
-  local index = function (t, k)
+  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
+
+    setmetatable (characters, { __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 ()
+
+    log ("Loading character metadata from %s.", chardef)
+    chardata = dofile (kpse.find_file (chardef, "lua"))
+
     if chardata == nil then
-      log("Loading character metadata from %s.", chardef)
-      chardata = dofile(kpse.find_file(chardef, "lua"))
-      if chardata == nil then
-        warning("Could not load %s; continuing with empty character table.",
+      warning ("Could not load %s; continuing \z
+                with empty character table.",
                 chardef)
-        chardata = { }
-      end
+      chardata    = { }
+      load_failed = true
     end
-    return chardata[k]
+
+    characters      = { } --- nuke metatable
+    characters.data = chardata
+
+    --- 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 mt = getmetatable(characters.data)
-  if mt then
-    mt.__index = index
-  else
-    setmetatable(characters.data, { __index = index })
+  local charindex = function (t, k)
+    if chardata == nil and load_failed ~= true then
+      load_chardef ()
+    end
+
+    return characters [k]
   end
+
+  setmetatableindex (characters, charindex)
+
 end
 
 -----------------------------------------------------------------------
diff --git a/mkcharacters b/mkcharacters
index a1c4204..63c78ed 100755
--- a/mkcharacters
+++ b/mkcharacters
@@ -15,10 +15,39 @@
 --                              config
 -----------------------------------------------------------------------
 local charfile      = "./luaotfload-characters.lua"
-local chardef       = "~phg/base/char-def.lua"
-local import        = {
+local chardef       = "/home/phg/base/char-def.lua"
+
+---  for every code point char-def.lua provides a set of fields. they
+---  are:
+---
+---     * adobename
+---     * category
+---     * cjkwd
+---     * comment
+---     * contextname
+---     * description
+---     * direction
+---     * lccode
+---     * linebreak
+---     * mathclass
+---     * mathextensible
+---     * mathfiller
+---     * mathname
+---     * mathspec
+---     * mathstretch
+---     * mathsymbol
+---     * mirror
+---     * shcode
+---     * specials
+---     * textclass
+---     * uccode
+---     * unicodeslot
+---     * variants
+
+local import = {
   "direction", "mirror", --> πολυγλωσσία/uax9
   "category",            --> https://gist.github.com/phi-gamma/5812290
+  "textclass",           --> https://gist.github.com/phi-gamma/6488187 
 }
 
 -----------------------------------------------------------------------