From b84dba3fd00575830d302ee6ff2d2a8426c99945 Mon Sep 17 00:00:00 2001
From: Philipp Gesang <phg@phi-gamma.net>
Date: Sat, 16 Apr 2016 18:26:02 +0200
Subject: [fontloader] sync with Context as of 2016-04-16

---
 src/fontloader/misc/fontloader-font-map.lua | 89 +++++++++++++++++++++++++++++
 1 file changed, 89 insertions(+)

(limited to 'src/fontloader/misc/fontloader-font-map.lua')

diff --git a/src/fontloader/misc/fontloader-font-map.lua b/src/fontloader/misc/fontloader-font-map.lua
index a91e523..ce84ca6 100644
--- a/src/fontloader/misc/fontloader-font-map.lua
+++ b/src/fontloader/misc/fontloader-font-map.lua
@@ -438,6 +438,95 @@ function mappings.addtounicode(data,filename,checklookups)
         checklookups(data,missing,nofmissing)
     end
     -- todo: go lowercase
+
+    local unset = { }
+    for unic, glyph in next, descriptions do
+        if not glyph.unicode and glyph.class == "ligature" then
+            unset[unic] = glyph
+        end
+    end
+    if next(unset) then
+        local sequences = resources.sequences
+        local collected = { }
+        for i=1,#sequences do
+            local sequence = sequences[i]
+            if sequence.type == "gsub_ligature" then
+                local steps  = sequence.steps
+                if steps then
+                    local l = { }
+                    local function traverse(p,k,v)
+                        if k == "ligature" then
+                            collected[v] = { unpack(l) }
+                        else
+                            table.insert(l,k)
+                            for k, vv in next, v do
+                                traverse(p,k,vv)
+                            end
+                            table.remove(l)
+                        end
+                    end
+                    for i=1,#steps do
+                    -- we actually had/have this in base mode
+                        local coverage = steps[i].coverage
+                        if coverage then
+                            for k, v in next, coverage do
+                                traverse(k,k,v)
+                            end
+                        end
+                    end
+                end
+            end
+        end
+        if next(collected) then
+            while true do
+                local done = false
+                for k, v in next, collected do
+                    for i=1,#v do
+                        local vi = v[i]
+                        if vi == k then
+                            collected[k] = nil
+                            unset[k] = nil
+                        else
+                            local c = collected[vi]
+                            if c then
+                                done = true
+                                local t = { }
+                                local n = i - 1
+                                for j=1,n do
+                                    t[j] = t[j]
+                                end
+                                for j=1,#c do
+                                    n = n + 1
+                                    t[n] = c[j]
+                                end
+                                for j=i+1,#v do
+                                    n = n + 1
+                                    t[n] = t[j]
+                                end
+                                collected[k] = t
+                                break
+                            end
+                        end
+                    end
+                end
+                if not done then
+                    break
+                end
+            end
+            local n = 0
+            for k, v in next, unset do
+                u = collected[k]
+                if u then
+                    v.unicode = u
+                    n = n + 1
+                end
+            end
+            if trace_mapping and n > 0 then
+                report_fonts("%n ligature tounicode mappings deduced from gsub ligature feaures",n)
+            end
+        end
+    end
+
     if trace_mapping then
         for unic, glyph in table.sortedhash(descriptions) do
             local name    = glyph.name
-- 
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