[features] conditionally pull in old feature mechanism

Pretty hackish and probably not supported forever, but this is required
on account of the changes to the loader since TL 2014.

1 files changed, 145 insertions, 1 deletions

diff --git a/src/luaotfload-features.lua b/src/luaotfload-features.lua
index 322a020..d212df5 100644
--- a/src/luaotfload-features.lua
+++ b/src/luaotfload-features.lua
@@ -970,7 +970,147 @@ local noflags = { }
 
 local tohash = table.tohash
 
-local function addfeature(data,feature,specifications)
+local function ancient_addfeature (data, feature, specifications)
+    local descriptions = data.descriptions
+    local resources    = data.resources
+    local lookups      = resources.lookups
+    local gsubfeatures = resources.features.gsub
+    if gsubfeatures and gsubfeatures[feature] then
+        -- already present
+    else
+        local sequences    = resources.sequences
+        local fontfeatures = resources.features
+        local unicodes     = resources.unicodes
+        local lookuptypes  = resources.lookuptypes
+        local splitter     = lpeg.splitter(" ",unicodes)
+        local done         = 0
+        local skip         = 0
+        if not specifications[1] then
+            -- so we accept a one entry specification
+            specifications = { specifications }
+        end
+        -- subtables are tables themselves but we also accept flattened singular subtables
+        for s=1,#specifications do
+            local specification = specifications[s]
+            local valid         = specification.valid
+            if not valid or valid(data,specification,feature) then
+                local initialize = specification.initialize
+                if initialize then
+                    -- when false is returned we initialize only once
+                    specification.initialize = initialize(specification) and initialize or nil
+                end
+                local askedfeatures = specification.features or everywhere
+                local subtables     = specification.subtables or { specification.data } or { }
+                local featuretype   = types[specification.type or "substitution"]
+                local featureflags  = specification.flags or noflags
+                local featureorder  = specification.order or { feature }
+                local added         = false
+                local featurename   = stringformat("ctx_%s_%s",feature,s)
+                local st = { }
+                for t=1,#subtables do
+                    local list = subtables[t]
+                    local full = stringformat("%s_%s",featurename,t)
+                    st[t] = full
+                    if featuretype == "gsub_ligature" then
+                        lookuptypes[full] = "ligature"
+                        for code, ligature in next, list do
+                            local unicode = tonumber(code) or unicodes[code]
+                            local description = descriptions[unicode]
+                            if description then
+                                local slookups = description.slookups
+                                if type(ligature) == "string" then
+                                    ligature = { lpegmatch(splitter,ligature) }
+                                end
+                                local present = true
+                                for i=1,#ligature do
+                                    if not descriptions[ligature[i]] then
+                                        present = false
+                                        break
+                                    end
+                                end
+                                if present then
+                                    if slookups then
+                                        slookups[full] = ligature
+                                    else
+                                        description.slookups = { [full] = ligature }
+                                    end
+                                    done, added = done + 1, true
+                                else
+                                    skip = skip + 1
+                                end
+                            end
+                        end
+                    elseif featuretype == "gsub_single" then
+                        lookuptypes[full] = "substitution"
+                        for code, replacement in next, list do
+                            local unicode = tonumber(code) or unicodes[code]
+                            local description = descriptions[unicode]
+                            if description then
+                                local slookups = description.slookups
+                                replacement = tonumber(replacement) or unicodes[replacement]
+                                if descriptions[replacement] then
+                                    if slookups then
+                                        slookups[full] = replacement
+                                    else
+                                        description.slookups = { [full] = replacement }
+                                    end
+                                    done, added = done + 1, true
+                                end
+                            end
+                        end
+                    end
+                end
+                if added then
+                    -- script = { lang1, lang2, lang3 } or script = { lang1 = true, ... }
+                    for k, v in next, askedfeatures do
+                        if v[1] then
+                            askedfeatures[k] = tabletohash(v)
+                        end
+                    end
+                    local sequence = {
+                        chain     = 0,
+                        features  = { [feature] = askedfeatures },
+                        flags     = featureflags,
+                        name      = featurename,
+                        order     = featureorder,
+                        subtables = st,
+                        type      = featuretype,
+                    }
+                    if specification.prepend then
+                        insert(sequences,1,sequence)
+                    else
+                        insert(sequences,sequence)
+                    end
+                    -- register in metadata (merge as there can be a few)
+                    if not gsubfeatures then
+                        gsubfeatures  = { }
+                        fontfeatures.gsub = gsubfeatures
+                    end
+                    local k = gsubfeatures[feature]
+                    if not k then
+                        k = { }
+                        gsubfeatures[feature] = k
+                    end
+                    for script, languages in next, askedfeatures do
+                        local kk = k[script]
+                        if not kk then
+                            kk = { }
+                            k[script] = kk
+                        end
+                        for language, value in next, languages do
+                            kk[language] = value
+                        end
+                    end
+                end
+            end
+        end
+        if trace_loading then
+            report_otf("registering feature %a, affected glyphs %a, skipped glyphs %a",feature,done,skip)
+        end
+    end
+end
+
+local function current_addfeature(data,feature,specifications)
     local descriptions = data.descriptions
     local resources    = data.resources
     local features     = resources.features
@@ -1344,6 +1484,10 @@ return {
             anum = anum_specification,
         }
 
+        --- hack for backwards compat with TL2014 loader
+        local addfeature = otf.version < 2.8 and current_addfeature
+                                              or ancient_addfeature
+
         otf.enhancers.register ("check extra features",
                                 function (data, filename, raw)
                                     for feature, specification in next, extrafeatures do