2017-06-27 18:10:00

1 files changed, 161 insertions, 2 deletions

diff --git a/tex/context/base/mkiv/font-ext.lua b/tex/context/base/mkiv/font-ext.lua
index da629c045..85e39e877 100644
--- a/tex/context/base/mkiv/font-ext.lua
+++ b/tex/context/base/mkiv/font-ext.lua
@@ -7,9 +7,9 @@ if not modules then modules = { } end modules ['font-ext'] = {
 }
 
 local next, type, tonumber = next, type, tonumber
-local formatters = string.formatters
-local byte = string.byte
+local byte, find, formatters = string.byte, string.find, string.formatters
 local utfchar = utf.char
+local sortedhash, sortedkeys, sort = table.sortedhash, table.sortedkeys, table.sort
 
 local context            = context
 local fonts              = fonts
@@ -1350,3 +1350,162 @@ do
     }
 
 end
+
+do
+
+    -- This is a rather special test-only feature that I added for the sake of testing
+    -- Idris's husayni. We wanted to know if uniscribe obeys the order of lookups in a
+    -- font, in spite of what the description of handling arabic suggests. And indeed,
+    -- mixed-in lookups of other features (like all these ss* in husayni) are handled
+    -- the same in context as in uniscribe. If one sets reorderlookups=arab then we sort
+    -- according to the "assumed" order so e.g. the ss* move to after the standard
+    -- features. The observed difference in rendering is an indication that uniscribe is
+    -- quite faithful to the font (while e.g. tests with the hb plugin demonstrate some
+    -- interference, apart from some hard coded init etc expectations). Anyway, it means
+    -- that we're okay with the (generic) node processor. A pitfall is that in context
+    -- we can actually control more, so we can trigger an analyze pass with e.g.
+    -- dflt/dflt while the libraries depend on the script settings for that. Uniscribe
+    -- probably also parses the string and when seeing arabic will follow a different
+    -- code path, although it seems to treat all features equal.
+
+    local trace_reorder  = trackers.register("fonts.reorderlookups",function(v) trace_reorder = v end)
+    local report_reorder = logs.reporter("fonts","reorder")
+
+    local vectors = { }
+
+    vectors.arab = {
+        gsub = {
+            ccmp =  1,
+            init =  2,
+            medi =  3,
+            fina =  4,
+            isol =  5,
+            rlig =  6,
+            rclt =  7,
+            calt =  8,
+            liga =  9,
+            dlig = 10,
+            cswh = 11,
+            mset = 12,
+        },
+        gpos = {
+            curs =  1,
+            kern =  2,
+            mark =  3,
+            mkmk =  4,
+        },
+    }
+
+    function otf.reorderlookups(tfmdata,vector)
+        local order = vectors[vector]
+        if not order then
+            return
+        end
+        local oldsequences = tfmdata.resources.sequences
+        if oldsequences then
+            local sequences = { }
+            for i=1,#oldsequences do
+                sequences[i] = oldsequences[i]
+            end
+            for i=1,#sequences do
+                local s = sequences[i]
+                local features = s.features
+                local kind     = s.type
+                local index    = s.index
+                if features then
+                    local when
+                    local what
+                    for feature in sortedhash(features) do
+                        if not what then
+                            what = find(kind,"^gsub") and "gsub" or "gpos"
+                        end
+                        local newwhen = order[what][feature]
+                        if not newwhen then
+                            -- skip
+                        elseif not when then
+                            when = newwhen
+                        elseif newwhen < when then
+                            when = newwhen
+                        end
+                    end
+                    s.ondex = s.index
+                    s.index = i
+                    s.what  = what == "gsub" and 1 or 2
+                    s.when  = when or 99
+                else
+                    s.ondex = s.index
+                    s.index = i
+                    s.what  = 1
+                    s.when  = 99
+                end
+            end
+            sort(sequences,function(a,b)
+                local what_a = a.what
+                local what_b = b.what
+                if what_a ~= what_b then
+                    return a.index < b.index
+                end
+                local when_a = a.when
+                local when_b = b.when
+                if when_a == when_b then
+                    return a.index < b.index
+                else
+                    return when_a < when_b
+                end
+            end)
+            local swapped = 0
+            for i=1,#sequences do
+                local sequence = sequences[i]
+                local features = sequence.features
+                if features then
+                    local index = sequence.index
+                    if index ~= i then
+                        swapped = swapped + 1
+                    end
+                    if trace_reorder then
+                        if swapped == 1 then
+                            report_reorder()
+                            report_reorder("start swapping lookups in font %!font:name!",tfmdata)
+                            report_reorder()
+                            report_reorder("gsub order: % t",table.swapped(order.gsub))
+                            report_reorder("gpos order: % t",table.swapped(order.gpos))
+                            report_reorder()
+                        end
+                        report_reorder("%03i : lookup %03i, type %s, sorted %2i, moved %s, % t",
+                            i,index,sequence.what == 1 and "gsub" or "gpos",sequence.when or 99,
+                            (index > i and "-") or (index < i and "+") or "=",sortedkeys(features))
+                    end
+                end
+                sequence.what  = nil
+                sequence.when  = nil
+                sequence.index = sequence.ondex
+            end
+            if swapped > 0 then
+                if trace_reorder then
+                    report_reorder()
+                    report_reorder("stop swapping lookups, %i lookups swapped",swapped)
+                    report_reorder()
+                end
+                tfmdata.resources.sequences = sequences
+            end
+        end
+    end
+
+    -- maybe delay till ra is filled
+
+    local function reorderlookups(tfmdata,key,value)
+        if value then
+            otf.reorderlookups(tfmdata,value)
+        end
+    end
+
+    registerotffeature {
+        name        = "reorderlookups",
+        description = "reorder lookups",
+        manipulators = {
+            base = reorderlookups,
+            node = reorderlookups,
+        }
+    }
+
+end