[parsers,features] parse combo requests

Highly experimental at this point. The font request parser has been
extended to handle combinations of already defined fonts. Nothing else
has been implemented yet, so the request handler will simply error out
with a message.

2 files changed, 42 insertions, 2 deletions

diff --git a/src/luaotfload-features.lua b/src/luaotfload-features.lua
index fd43e58..6df04b2 100644
--- a/src/luaotfload-features.lua
+++ b/src/luaotfload-features.lua
@@ -993,7 +993,10 @@ local import_values = {
     { "mode",   true },
 }
 
-local lookup_types = { "anon", "file", "kpse", "my", "name", "path" }
+local lookup_types = { "anon"  , "file", "kpse"
+                     , "my"    , "name", "path"
+                     , "combo"
+                     }
 
 local select_lookup = function (request)
     for i=1, #lookup_types do
@@ -1049,6 +1052,7 @@ end
 local handle_request = function (specification)
     local request = lpegmatch(luaotfload.parsers.font_request,
                               specification.specification)
+----inspect(request)
     if not request then
         --- happens when called with an absolute path
         --- in an anonymous lookup;
@@ -1077,7 +1081,13 @@ local handle_request = function (specification)
         specification.lookup = "path"
         return specification
     end
+
     local lookup, name  = select_lookup(request)
+    if lookup == "combo" then
+        report ("both", 0, "load",
+                "‘combo’ lookup not implemented at this stage.")
+        os.exit(-42)
+    end
     request.features    = apply_default_features(request.features)
 
     if name then
@@ -1749,4 +1759,4 @@ return {
     end
 }
 
--- vim:tw=71:sw=4:ts=4:expandtab
+-- vim:tw=79:sw=4:ts=4:expandtab
diff --git a/src/luaotfload-parsers.lua b/src/luaotfload-parsers.lua
index 0349cdc..5ebe8d5 100644
--- a/src/luaotfload-parsers.lua
+++ b/src/luaotfload-parsers.lua
@@ -45,6 +45,7 @@ local lfsisdir          = lfs.isdir
 ---                         COMMON PATTERNS
 -------------------------------------------------------------------------------
 
+local asterisk          = P"*"
 local dot               = P"."
 local colon             = P":"
 local semicolon         = P";"
@@ -72,6 +73,8 @@ local digit             = R"09"
 local alpha             = R("az", "AZ")
 local anum              = alpha + digit
 local decimal           = digit^1 * (dot * digit^0)^-1
+local hexdigit          = R("09", "af", "AF")
+local hex               = P"0x" * hexdigit^1
 
 -------------------------------------------------------------------------------
 ---                                FONTCONFIG
@@ -560,9 +563,35 @@ local modifier          = slash * (other_modifier      --> ignore
                                  + garbage_modifier)   --> warn
 local modifier_list     = Cg(Ct(modifier^0), "modifiers")
 
+--- combining ---------------------------------------------------------
+---
+--- \font \three = combo:1/42,2/99/0xdeadbeef,3/1/U+2a-U+1337*42
+---                      v +~ v +~ +~~~~~~~~~ v v +~~~ +~~~~~ +~
+---                      | |  | |  |          | | |    |      |
+---                      | |  | |  |          | | |    |      |
+---        idx   :     --+-÷--+-÷--÷----------+ | +----+      |
+---                        |    |  |            | |           |
+---        id    :     ----+----+--÷------------+ +-----------+
+---                                |              |
+---        chars :     ------------+--------------+
+---
+local combohex          = hex     / tonumber
+local combouint         = digit^1 / tonumber
+local tonumber16        = function (s) return tonumber (s, 16) end
+local combouni          = P"U+" * (digit^1 / tonumber16)
+local combonum          = combohex + combouni + combouint
+local comborange        = Ct(combonum * dash * combonum) + combonum
+local combochars        = comborange * (asterisk * comborange)^0
+local combodef1         = Ct(          Cg(combouint, "idx") --> no chars
+                             * slash * Cg(combouint, "id" ))
+local combodef          = Ct(          Cg(combouint, "idx"  )
+                             * slash * Cg(combouint, "id"   )
+                             * slash * Cg(Ct(combochars^1), "chars"))
+local combolist         = Ct(combodef1 * (comma * combodef)^1)
 --- lookups -----------------------------------------------------------
 local fontname          = C((1-S":(/")^1)  --- like luatex-fonts
 local unsupported       = Cmt((1-S":(")^1, check_garbage)
+local combo             = P"combo:" * ws * Cg(combolist, "combo")
 local prefixed          = P"name:" * ws * Cg(fontname, "name")
 --- initially we intended file: to emulate the behavior of
 --- luatex-fonts, i.e. no paths allowed. after all, we do have XeTeX
@@ -626,6 +655,7 @@ local specification     = (prefixed + unprefixed)
                         * subfont^-1
                         * modifier_list^-1
 local font_request      = Ct(path_lookup   * (colon^-1 * features)^-1
+                           + combo --> TODO: feature list needed?
                            + specification * (colon    * features)^-1)
 
 --  lpeg.print(font_request)