2018-04-13 15:02:00

1 files changed, 172 insertions, 0 deletions

diff --git a/tex/context/base/mkiv/font-imp-reorder.lua b/tex/context/base/mkiv/font-imp-reorder.lua
new file mode 100644
index 000000000..250aa47c6
--- /dev/null
+++ b/tex/context/base/mkiv/font-imp-reorder.lua
@@ -0,0 +1,172 @@
+if not modules then modules = { } end modules ['font-imp-reorder'] = {
+    version   = 1.001,
+    comment   = "companion to font-ini.mkiv and hand-ini.mkiv",
+    author    = "Hans Hagen, PRAGMA-ADE, Hasselt NL",
+    copyright = "PRAGMA ADE / ConTeXt Development Team",
+    license   = "see context related readme files"
+}
+
+local next = next
+local find = string.find
+local sortedhash, sortedkeys, sort = table.sortedhash, table.sortedkeys, table.sort
+
+local fonts              = fonts
+local otf                = fonts.handlers.otf
+local registerotffeature = otf.features.register
+
+-- 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,
+        isol =  2,
+        fina =  3,
+        medi =  4,
+        init =  5,
+        rlig =  6,
+        rclt =  7,
+        calt =  8,
+        liga =  9,
+        dlig = 10,
+        cswh = 11,
+        mset = 12,
+    },
+    gpos = {
+        curs =  1,
+        kern =  2,
+        mark =  3,
+        mkmk =  4,
+    },
+}
+
+local function compare(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
+
+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,compare)
+        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.shared.reorderedsequences = sequences
+        end
+    end
+end
+
+-- maybe delay till ra is filled
+
+local function initialize(tfmdata,key,value)
+    if value then
+        otf.reorderlookups(tfmdata,value)
+    end
+end
+
+registerotffeature {
+    name        = "reorderlookups",
+    description = "reorder lookups",
+    manipulators = {
+        base = initialize,
+        node = initialize,
+    }
+}