2016-04-11 19:08:00

1 files changed, 1035 insertions, 0 deletions

diff --git a/tex/context/base/mkiv/typo-duc.lua b/tex/context/base/mkiv/typo-duc.lua
new file mode 100644
index 000000000..6f388eb34
--- /dev/null
+++ b/tex/context/base/mkiv/typo-duc.lua
@@ -0,0 +1,1035 @@
+if not modules then modules = { } end modules ['typo-duc'] = {
+    version   = 1.001,
+    comment   = "companion to typo-dir.mkiv",
+    author    = "Hans Hagen, PRAGMA-ADE, Hasselt NL",
+    copyright = "PRAGMA ADE / ConTeXt Development Team",
+    license   = "see context related readme files",
+    comment   = "Unicode bidi (sort of) variant b",
+}
+
+-- This is a follow up on typo-uba which itself is a follow up on t-bidi by Khaled Hosny which
+-- in turn is based on minibidi.c from Arabeyes. This is a further optimizations, as well as
+-- an update on some recent unicode bidi developments. There is (and will) also be more control
+-- added. As a consequence this module is somewhat slower than its precursor which itself is
+-- slower than the one-pass bidi handler. This is also a playground and I might add some plugin
+-- support. However, in the meantime performance got a bit better and this third variant is again
+-- some 10% faster than the two variant.
+
+-- todo (cf html):
+--
+-- normal            The element does not offer a additional level of embedding with respect to the bidirectional algorithm. For inline elements implicit reordering works across element boundaries.
+-- embed             If the element is inline, this value opens an additional level of embedding with respect to the bidirectional algorithm. The direction of this embedding level is given by the direction property.
+-- bidi-override     For inline elements this creates an override. For block container elements this creates an override for inline-level descendants not within another block container element. This means that inside the element, reordering is strictly in sequence according to the direction property; the implicit part of the bidirectional algorithm is ignored.
+-- isolate           This keyword indicates that the element's container directionality should be calculated without considering the content of this element. The element is therefore isolated from its siblings. When applying its bidirectional-resolution algorithm, its container element treats it as one or several U+FFFC Object Replacement Character, i.e. like an image.
+-- isolate-override  This keyword applies the isolation behavior of the isolate keyword to the surrounding content and the override behavior o f the bidi-override keyword to the inner content.
+-- plaintext         This keyword makes the elements directionality calculated without considering its parent bidirectional state or the value of the direction property. The directionality is calculated using the P2 and P3 rules of the Unicode Bidirectional Algorithm.
+--                   This value allows to display data which has already formatted using a tool following the Unicode Bidirectional Algorithm.
+--
+-- todo: check for introduced errors
+-- todo: reuse list, we have size, so we can just change values (and auto allocate when not there)
+-- todo: reuse the stack
+-- todo: no need for a max check
+-- todo: collapse bound similar ranges (not ok yet)
+-- todo: combine some sweeps
+-- todo: removing is not needed when we inject at the same spot (only chnage the dir property)
+-- todo: isolated runs (isolating runs are similar to bidi=local in the basic analyzer)
+
+-- todo: check unicode addenda (from the draft):
+--
+-- Added support for canonical equivalents in BD16.
+-- Changed logic in N0 to not check forwards for context in the case of enclosed text opposite the embedding direction.
+-- Major extension of the algorithm to allow for the implementation of directional isolates and the introduction of new isolate-related values to the Bidi_Class property.
+-- Adds BD8, BD9, BD10, BD11, BD12, BD13, BD14, BD15, and BD16, Sections 2.4 and 2.5, and Rules X5a, X5b, X5c and X6a.
+-- Extensively revises Section 3.3.2, Explicit Levels and Directions and its existing X rules to formalize the algorithm for matching a PDF with the embedding or override initiator whose scope it terminates.
+-- Moves Rules X9 and X10 into a separate new Section 3.3.3, Preparations for Implicit Processing.
+-- Modifies Rule X10 to make the isolating run sequence the unit to which subsequent rules are applied.
+-- Modifies Rule W1 to change an NSM preceded by an isolate initiator or PDI into ON.
+-- Adds Rule N0 and makes other changes to Section 3.3.5, Resolving Neutral and Isolate Formatting Types to resolve bracket pairs to the same level.
+
+local insert, remove, unpack, concat = table.insert, table.remove, table.unpack, table.concat
+local utfchar = utf.char
+local setmetatable = setmetatable
+local formatters = string.formatters
+
+local directiondata       = characters.directions
+local mirrordata          = characters.mirrors
+local textclassdata       = characters.textclasses
+
+local nuts                = nodes.nuts
+local tonut               = nuts.tonut
+local tonode              = nuts.tonode
+local nutstring           = nuts.tostring
+
+local getnext             = nuts.getnext
+local getid               = nuts.getid
+local getsubtype          = nuts.getsubtype
+local getlist             = nuts.getlist
+local getattr             = nuts.getattr
+local getfield            = nuts.getfield
+local getprop             = nuts.getprop
+local isglyph             = nuts.isglyph -- or ischar
+
+local setfield            = nuts.setfield
+local setprop             = nuts.setprop
+local setchar             = nuts.setchar
+
+local properties          = nodes.properties
+
+local remove_node         = nuts.remove
+local insert_node_after   = nuts.insert_after
+local insert_node_before  = nuts.insert_before
+
+local nodepool            = nuts.pool
+local new_textdir         = nodepool.textdir
+
+local nodecodes           = nodes.nodecodes
+local skipcodes           = nodes.skipcodes
+
+local glyph_code          = nodecodes.glyph
+local glue_code           = nodecodes.glue
+local hlist_code          = nodecodes.hlist
+local vlist_code          = nodecodes.vlist
+local math_code           = nodecodes.math
+local dir_code            = nodecodes.dir
+local localpar_code       = nodecodes.localpar
+local parfillskip_code    = skipcodes.skipcodes
+
+local maximum_stack       = 0xFF -- unicode: 60, will be jumped to 125, we don't care too much
+
+local directions          = typesetters.directions
+local setcolor            = directions.setcolor
+local getfences           = directions.getfences
+
+local a_directions        = attributes.private('directions')
+local a_textbidi          = attributes.private('textbidi')
+----- a_state             = attributes.private('state')
+
+----- s_isol              = fonts.analyzers.states.isol
+
+----- current[a_state] = s_isol -- maybe better have a special bidi attr value -> override (9) -> todo
+
+local remove_controls     = true  directives.register("typesetters.directions.removecontrols",function(v) remove_controls  = v end)
+----- analyze_fences      = true  directives.register("typesetters.directions.analyzefences", function(v) analyze_fences   = v end)
+
+local trace_directions    = false trackers  .register("typesetters.directions.two",           function(v) trace_directions = v end)
+local trace_details       = false trackers  .register("typesetters.directions.two.details",   function(v) trace_details    = v end)
+local trace_list          = false trackers  .register("typesetters.directions.two.list",      function(v) trace_list       = v end)
+
+local report_directions   = logs.reporter("typesetting","directions two")
+
+-- strong (old):
+--
+-- l   : left to right
+-- r   : right to left
+-- lro : left to right override
+-- rlo : left to left override
+-- lre : left to right embedding
+-- rle : left to left embedding
+-- al  : right to legt arabic (esp punctuation issues)
+
+-- weak:
+--
+-- en  : english number
+-- es  : english number separator
+-- et  : english number terminator
+-- an  : arabic number
+-- cs  : common number separator
+-- nsm : nonspacing mark
+-- bn  : boundary neutral
+
+-- neutral:
+--
+-- b  : paragraph separator
+-- s  : segment separator
+-- ws : whitespace
+-- on : other neutrals
+
+-- interesting: this is indeed better (and more what we expect i.e. we already use this split
+-- in the old original (also these isolates)
+
+-- strong (new):
+--
+-- l   : left to right
+-- r   : right to left
+-- al  : right to left arabic (esp punctuation issues)
+
+-- explicit: (new)
+--
+-- lro : left to right override
+-- rlo : left to left override
+-- lre : left to right embedding
+-- rle : left to left embedding
+-- pdf : pop dir format
+-- lri : left to right isolate
+-- rli : left to left isolate
+-- fsi : first string isolate
+-- pdi : pop directional isolate
+
+local whitespace = {
+    lre = true,
+    rle = true,
+    lro = true,
+    rlo = true,
+    pdf = true,
+    bn  = true,
+    ws  = true,
+}
+
+local b_s_ws_on = {
+    b   = true,
+    s   = true,
+    ws  = true,
+    on  = true
+}
+
+-- tracing
+
+local function show_list(list,size,what)
+    local what   = what or "direction"
+    local joiner = utfchar(0x200C)
+    local result = { }
+    for i=1,size do
+        local entry     = list[i]
+        local character = entry.char
+        local direction = entry[what]
+        if character == 0xFFFC then
+            local first = entry.id
+            local last  = entry.last
+            local skip  = entry.skip
+            if last then
+                result[i] = formatters["%-3s:%s %s..%s (%i)"](direction,joiner,nodecodes[first],nodecodes[last],skip or 0)
+            else
+                result[i] = formatters["%-3s:%s %s (%i)"](direction,joiner,nodecodes[first],skip or 0)
+            end
+        elseif character >= 0x202A and character <= 0x202C then
+            result[i] = formatters["%-3s:%s %U"](direction,joiner,character)
+        else
+            result[i] = formatters["%-3s:%s %c %U"](direction,joiner,character,character)
+        end
+    end
+    return concat(result,joiner .. " | " .. joiner)
+end
+
+-- preparation
+
+local function show_done(list,size)
+    local joiner = utfchar(0x200C)
+    local result = { }
+    for i=1,size do
+        local entry     = list[i]
+        local character = entry.char
+        local begindir  = entry.begindir
+        local enddir    = entry.enddir
+        if begindir then
+            result[#result+1] = formatters["<%s>"](begindir)
+        end
+        if entry.remove then
+            -- continue
+        elseif character == 0xFFFC then
+            result[#result+1] = formatters["<%s>"]("?")
+        elseif character == 0x0020 then
+            result[#result+1] = formatters["<%s>"](" ")
+        elseif character >= 0x202A and character <= 0x202C then
+            result[#result+1] = formatters["<%s>"](entry.original)
+        else
+            result[#result+1] = utfchar(character)
+        end
+        if enddir then
+            result[#result+1] = formatters["<%s>"](enddir)
+        end
+    end
+    return concat(result,joiner)
+end
+
+-- keeping the list and overwriting doesn't save much runtime, only a few percent
+-- char is only used for mirror, so in fact we can as well only store it for
+-- glyphs only
+
+-- tracking what direction is used and skipping tests is not faster (extra kind of
+-- compensates gain)
+
+local mt_space  = { __index = { char = 0x0020, direction = "ws",  original = "ws",  level = 0 } }
+local mt_lre    = { __index = { char = 0x202A, direction = "lre", original = "lre", level = 0 } }
+local mt_lre    = { __index = { char = 0x202B, direction = "rle", original = "rle", level = 0 } }
+local mt_pdf    = { __index = { char = 0x202C, direction = "pdf", original = "pdf", level = 0 } }
+local mt_object = { __index = { char = 0xFFFC, direction = "on",  original = "on",  level = 0 } }
+
+local function build_list(head) -- todo: store node pointer ... saves loop
+    -- P1
+    local current = head
+    local list    = { }
+    local size    = 0
+    while current do
+        size = size + 1
+        local chr, id = isglyph(current)
+        local t
+        local p = properties[current]
+        if p and p.directions then
+            local skip = 0
+            local last = id
+            current    = getnext(current)
+            while current do
+                local id = getid(current)
+                if p and p.directions then
+                    skip    = skip + 1
+                    last    = id
+                    current = getnext(current)
+                else
+                    break
+                end
+            end
+            if id == last then -- the start id
+--                 t = { level = 0, skip = skip, id = id }
+                t = { skip = skip, id = id }
+            else
+                t = { skip = skip, id = id, last = last }
+--                 t = { level = 0, skip = skip, id = id, last = last }
+            end
+            setmetatable(t,mt_object)
+        elseif chr or id == glyph_code then
+            local dir = directiondata[chr]
+--             t = { level = 0, char = chr, direction = dir, original = dir, level = 0 }
+            t = { char = chr, direction = dir, original = dir, level = 0 }
+            current = getnext(current)
+         -- if not list[dir] then list[dir] = true end -- not faster when we check for usage
+        elseif id == glue_code then -- and how about kern
+--             t = { level = 0 }
+            t = { }
+            setmetatable(t,mt_space)
+            current = getnext(current)
+        elseif id == dir_code then
+            local dir = getfield(current,"dir")
+            if dir == "+TLT" then
+--                 t = { level = 0 }
+                t = { }
+                setmetatable(t,mt_lre)
+            elseif dir == "+TRT" then
+--                 t = { level = 0 }
+                t = { }
+                setmetatable(t,mt_rle)
+            elseif dir == "-TLT" or dir == "-TRT" then
+--                 t = { level = 0 }
+                t = { }
+                setmetatable(t,mt_pdf)
+            else
+--                 t = { level = 0, id = id }
+                t = { id = id }
+                setmetatable(t,mt_object)
+            end
+            current = getnext(current)
+        elseif id == math_code then
+            local skip = 0
+            current    = getnext(current)
+            while getid(current) ~= math_code do
+                skip    = skip + 1
+                current = getnext(current)
+            end
+            skip       = skip + 1
+            current    = getnext(current)
+--             t = { level = 0, id = id, skip = skip }
+            t = { id = id, skip = skip }
+            setmetatable(t,mt_object)
+        else
+            local skip = 0
+            local last = id
+            current    = getnext(current)
+            while n do
+                local id = getid(current)
+                if id ~= glyph_code and id ~= glue_code and id ~= dir_code then
+                    skip    = skip + 1
+                    last    = id
+                    current = getnext(current)
+                else
+                    break
+                end
+            end
+            if skip == 0 then
+                t = { id = id }
+            elseif id == last then -- the start id
+--                 t = { level = 0, id = id, skip = skip }
+                t = { id = id, skip = skip }
+            else
+--                 t = { level = 0, id = id, skip = skip, last = last }
+                t = { id = id, skip = skip, last = last }
+            end
+            setmetatable(t,mt_object)
+        end
+        list[size] = t
+    end
+    return list, size
+end
+
+-- new
+
+-- we could support ( ] and [ ) and such ...
+
+-- ש ) ל ( א       0-0
+-- ש ( ל ] א       0-0
+-- ש ( ל ) א       2-4
+-- ש ( ל [ א ) כ ] 2-6
+-- ש ( ל ] א ) כ   2-6
+-- ש ( ל ) א ) כ   2-4
+-- ש ( ל ( א ) כ   4-6
+-- ש ( ל ( א ) כ ) 2-8,4-6
+-- ש ( ל [ א ] כ ) 2-8,4-6
+
+local function resolve_fences(list,size,start,limit)
+    -- N0: funny effects, not always better, so it's an option
+    local stack = { }
+    local top   = 0
+    for i=start,limit do
+        local entry = list[i]
+        if entry.direction == "on" then
+            local char   = entry.char
+            local mirror = mirrordata[char]
+            if mirror then
+                local class = textclassdata[char]
+                entry.mirror = mirror
+                entry.class  = class
+                if class == "open" then
+                    top = top + 1
+                    stack[top] = { mirror, i, false }
+                elseif top == 0 then
+                    -- skip
+                elseif class == "close" then
+                    while top > 0 do
+                        local s = stack[top]
+                        if s[1] == char then
+                            local open  = s[2]
+                            local close = i
+                            list[open ].paired = close
+                            list[close].paired = open
+                            break
+                        else
+                            -- do we mirror or not
+                        end
+                        top = top - 1
+                    end
+                end
+            end
+        end
+    end
+end
+
+-- local function test_fences(str)
+--     local list  = { }
+--     for s in string.gmatch(str,".") do
+--         local b = utf.byte(s)
+--         list[#list+1] = { c = s, char = b, direction = directiondata[b] }
+--     end
+--     resolve_fences(list,#list,1,#size)
+--     inspect(list)
+-- end
+--
+-- test_fences("a(b)c(d)e(f(g)h)i")
+-- test_fences("a(b[c)d]")
+
+-- the action
+
+local function get_baselevel(head,list,size) -- todo: skip if first is object (or pass head and test for localpar)
+    local id = getid(head)
+    if id == localpar_code then
+        if getfield(head,"dir") == "TRT" then
+            return 1, "TRT", true
+        else
+            return 0, "TLT", true
+        end
+    else
+        -- P2, P3
+        for i=1,size do
+            local entry     = list[i]
+            local direction = entry.direction
+            if direction == "r" or direction == "al" then -- and an ?
+                return 1, "TRT", true
+            elseif direction == "l" then
+                return 0, "TLT", true
+            end
+        end
+        return 0, "TLT", false
+    end
+end
+
+local function resolve_explicit(list,size,baselevel)
+-- if list.rle or list.lre or list.rlo or list.lro then
+    -- X1
+    local level    = baselevel
+    local override = "on"
+    local stack    = { }
+    local nofstack = 0
+    for i=1,size do
+        local entry     = list[i]
+        local direction = entry.direction
+        -- X2
+        if direction == "rle" then
+            if nofstack < maximum_stack then
+                nofstack        = nofstack + 1
+                stack[nofstack] = { level, override }
+                level           = level + (level % 2 == 1 and 2 or 1) -- least_greater_odd(level)
+                override        = "on"
+                entry.level     = level
+                entry.direction = "bn"
+                entry.remove    = true
+            elseif trace_directions then
+                report_directions("stack overflow at position %a with direction %a",i,direction)
+            end
+        -- X3
+        elseif direction == "lre" then
+            if nofstack < maximum_stack then
+                nofstack        = nofstack + 1
+                stack[nofstack] = { level, override }
+                level           = level + (level % 2 == 1 and 1 or 2) -- least_greater_even(level)
+                override        = "on"
+                entry.level     = level
+                entry.direction = "bn"
+                entry.remove    = true
+            elseif trace_directions then
+                report_directions("stack overflow at position %a with direction %a",i,direction)
+            end
+        -- X4
+        elseif direction == "rlo" then
+            if nofstack < maximum_stack then
+                nofstack        = nofstack + 1
+                stack[nofstack] = { level, override }
+                level           = level + (level % 2 == 1 and 2 or 1) -- least_greater_odd(level)
+                override        = "r"
+                entry.level     = level
+                entry.direction = "bn"
+                entry.remove    = true
+            elseif trace_directions then
+                report_directions("stack overflow at position %a with direction %a",i,direction)
+            end
+        -- X5
+        elseif direction == "lro" then
+            if nofstack < maximum_stack then
+                nofstack        = nofstack + 1
+                stack[nofstack] = { level, override }
+                level           = level + (level % 2 == 1 and 1 or 2) -- least_greater_even(level)
+                override        = "l"
+                entry.level     = level
+                entry.direction = "bn"
+                entry.remove    = true
+            elseif trace_directions then
+                report_directions("stack overflow at position %a with direction %a",i,direction)
+            end
+        -- X7
+        elseif direction == "pdf" then
+            if nofstack < maximum_stack then
+                local stacktop  = stack[nofstack]
+                nofstack        = nofstack - 1
+                level           = stacktop[1]
+                override        = stacktop[2]
+                entry.level     = level
+                entry.direction = "bn"
+                entry.remove    = true
+            elseif trace_directions then
+                report_directions("stack overflow at position %a with direction %a",i,direction)
+            end
+        -- X6
+        else
+            entry.level = level
+            if override ~= "on" then
+                entry.direction = override
+            end
+        end
+    end
+-- else
+--     for i=1,size do
+--         list[i].level = baselevel
+--     end
+-- end
+    -- X8 (reset states and overrides after paragraph)
+end
+
+local function resolve_weak(list,size,start,limit,orderbefore,orderafter)
+    -- W1: non spacing marks get the direction of the previous character
+-- if list.nsm then
+    for i=start,limit do
+        local entry = list[i]
+        if entry.direction == "nsm" then
+            if i == start then
+                entry.direction = orderbefore
+            else
+                entry.direction = list[i-1].direction
+            end
+        end
+    end
+-- end
+    -- W2: mess with numbers and arabic
+-- if list.en then
+    for i=start,limit do
+        local entry = list[i]
+        if entry.direction == "en" then
+            for j=i-1,start,-1 do
+                local prev = list[j]
+                local direction = prev.direction
+                if direction == "al" then
+                    entry.direction = "an"
+                    break
+                elseif direction == "r" or direction == "l" then
+                    break
+                end
+            end
+        end
+    end
+-- end
+    -- W3
+-- if list.al then
+    for i=start,limit do
+        local entry = list[i]
+        if entry.direction == "al" then
+            entry.direction = "r"
+        end
+    end
+-- end
+    -- W4: make separators number
+-- if list.es or list.cs then
+        -- skip
+    if false then
+        for i=start+1,limit-1 do
+            local entry     = list[i]
+            local direction = entry.direction
+            if direction == "es" then
+                if list[i-1].direction == "en" and list[i+1].direction == "en" then
+                    entry.direction = "en"
+                end
+            elseif direction == "cs" then
+                local prevdirection = list[i-1].direction
+                if prevdirection == "en" then
+                    if list[i+1].direction == "en" then
+                        entry.direction = "en"
+                    end
+                elseif prevdirection == "an" and list[i+1].direction == "an" then
+                    entry.direction = "an"
+                end
+            end
+        end
+    else -- only more efficient when we have es/cs
+        local runner = start + 2
+        local before = list[start]
+        local entry  = list[start + 1]
+        local after  = list[runner]
+        while after do
+            local direction = entry.direction
+            if direction == "es" then
+                if before.direction == "en" and after.direction == "en" then
+                    entry.direction = "en"
+                end
+            elseif direction == "cs" then
+                local prevdirection = before.direction
+                if prevdirection == "en" then
+                    if after.direction == "en" then
+                        entry.direction = "en"
+                    end
+                elseif prevdirection == "an" and after.direction == "an" then
+                    entry.direction = "an"
+                end
+            end
+            before  = current
+            current = after
+            after   = list[runner]
+            runner  = runner + 1
+        end
+    end
+-- end
+    -- W5
+-- if list.et then
+    local i = start
+    while i <= limit do
+        if list[i].direction == "et" then
+            local runstart = i
+            local runlimit = runstart
+            for i=runstart,limit do
+                if list[i].direction == "et" then
+                    runlimit = i
+                else
+                    break
+                end
+            end
+            local rundirection = runstart == start and sor or list[runstart-1].direction
+            if rundirection ~= "en" then
+                rundirection = runlimit == limit and orderafter or list[runlimit+1].direction
+            end
+            if rundirection == "en" then
+                for j=runstart,runlimit do
+                    list[j].direction = "en"
+                end
+            end
+            i = runlimit
+        end
+        i = i + 1
+    end
+-- end
+    -- W6
+-- if list.es or list.cs or list.et then
+    for i=start,limit do
+        local entry     = list[i]
+        local direction = entry.direction
+        if direction == "es" or direction == "et" or direction == "cs" then
+            entry.direction = "on"
+        end
+    end
+-- end
+    -- W7
+    for i=start,limit do
+        local entry = list[i]
+        if entry.direction == "en" then
+            local prev_strong = orderbefore
+            for j=i-1,start,-1 do
+                local direction = list[j].direction
+                if direction == "l" or direction == "r" then
+                    prev_strong = direction
+                    break
+                end
+            end
+            if prev_strong == "l" then
+                entry.direction = "l"
+            end
+        end
+    end
+end
+
+local function resolve_neutral(list,size,start,limit,orderbefore,orderafter)
+    -- N1, N2
+    for i=start,limit do
+        local entry = list[i]
+        if b_s_ws_on[entry.direction] then
+            -- this needs checking
+            local leading_direction, trailing_direction, resolved_direction
+            local runstart = i
+            local runlimit = runstart
+--             for j=runstart,limit do
+            for j=runstart+1,limit do
+                if b_s_ws_on[list[j].direction] then
+--                     runstart = j
+                    runlimit = j
+                else
+                    break
+                end
+            end
+            if runstart == start then
+                leading_direction = orderbefore
+            else
+                leading_direction = list[runstart-1].direction
+                if leading_direction == "en" or leading_direction == "an" then
+                    leading_direction = "r"
+                end
+            end
+            if runlimit == limit then
+                trailing_direction = orderafter
+            else
+                trailing_direction = list[runlimit+1].direction
+                if trailing_direction == "en" or trailing_direction == "an" then
+                    trailing_direction = "r"
+                end
+            end
+            if leading_direction == trailing_direction then
+                -- N1
+                resolved_direction = leading_direction
+            else
+                -- N2 / does the weird period
+                resolved_direction = entry.level % 2 == 1 and "r" or "l"
+            end
+            for j=runstart,runlimit do
+                list[j].direction = resolved_direction
+            end
+            i = runlimit
+        end
+        i = i + 1
+    end
+end
+
+-- local function resolve_implicit(list,size,start,limit,orderbefore,orderafter)
+--     -- I1
+--     for i=start,limit do
+--         local entry = list[i]
+--         local level = entry.level
+--         if level % 2 ~= 1 then -- not odd(level)
+--             local direction = entry.direction
+--             if direction == "r" then
+--                 entry.level = level + 1
+--             elseif direction == "an" or direction == "en" then
+--                 entry.level = level + 2
+--             end
+--         end
+--     end
+--     -- I2
+--     for i=start,limit do
+--         local entry = list[i]
+--         local level = entry.level
+--         if level % 2 == 1 then -- odd(level)
+--             local direction = entry.direction
+--             if direction == "l" or direction == "en" or direction == "an" then
+--                 entry.level = level + 1
+--             end
+--         end
+--     end
+-- end
+
+local function resolve_implicit(list,size,start,limit,orderbefore,orderafter,baselevel)
+    for i=start,limit do
+        local entry     = list[i]
+        local level     = entry.level
+        local direction = entry.direction
+        if level % 2 ~= 1 then -- even
+            -- I1
+            if direction == "r" then
+                entry.level = level + 1
+            elseif direction == "an" or direction == "en" then
+                entry.level = level + 2
+            end
+        else
+            -- I2
+            if direction == "l" or direction == "en" or direction == "an" then
+                entry.level = level + 1
+            end
+        end
+    end
+end
+
+local function resolve_levels(list,size,baselevel,analyze_fences)
+    -- X10
+    local start = 1
+    while start < size do
+        local level = list[start].level
+        local limit = start + 1
+        while limit < size and list[limit].level == level do
+            limit = limit + 1
+        end
+        local prev_level  = start == 1    and baselevel or list[start-1].level
+        local next_level  = limit == size and baselevel or list[limit+1].level
+        local orderbefore = (level > prev_level and level or prev_level) % 2 == 1 and "r" or "l"
+        local orderafter  = (level > next_level and level or next_level) % 2 == 1 and "r" or "l"
+        -- W1 .. W7
+        resolve_weak(list,size,start,limit,orderbefore,orderafter)
+        -- N0
+        if analyze_fences then
+            resolve_fences(list,size,start,limit)
+        end
+        -- N1 .. N2
+        resolve_neutral(list,size,start,limit,orderbefore,orderafter)
+        -- I1 .. I2
+        resolve_implicit(list,size,start,limit,orderbefore,orderafter,baselevel)
+        start = limit
+    end
+    -- L1
+    for i=1,size do
+        local entry     = list[i]
+        local direction = entry.original
+        -- (1)
+        if direction == "s" or direction == "b" then
+            entry.level = baselevel
+            -- (2)
+            for j=i-1,1,-1 do
+                local entry = list[j]
+                if whitespace[entry.original] then
+                    entry.level = baselevel
+                else
+                    break
+                end
+            end
+        end
+    end
+    -- (3)
+    for i=size,1,-1 do
+        local entry = list[i]
+        if whitespace[entry.original] then
+            entry.level = baselevel
+        else
+            break
+        end
+    end
+    -- L4
+    if analyze_fences then
+        for i=1,size do
+            local entry = list[i]
+            if entry.level % 2 == 1 then -- odd(entry.level)
+                if entry.mirror and not entry.paired then
+                    entry.mirror = false
+                end
+                -- okay
+            elseif entry.mirror then
+                entry.mirror = false
+            end
+        end
+    else
+        for i=1,size do
+            local entry = list[i]
+            if entry.level % 2 == 1 then -- odd(entry.level)
+                local mirror = mirrordata[entry.char]
+                if mirror then
+                    entry.mirror = mirror
+                end
+            end
+        end
+    end
+end
+
+local function insert_dir_points(list,size)
+    -- L2, but no actual reversion is done, we simply annotate where
+    -- begindir/endddir node will be inserted.
+    local maxlevel = 0
+    local finaldir = false
+    for i=1,size do
+        local level = list[i].level
+        if level > maxlevel then
+            maxlevel = level
+        end
+    end
+    for level=0,maxlevel do
+        local started  = false
+        local begindir = nil
+        local enddir   = nil
+        if level % 2 == 1 then
+            begindir = "+TRT"
+            enddir   = "-TRT"
+        else
+            begindir = "+TLT"
+            enddir   = "-TLT"
+        end
+        for i=1,size do
+            local entry = list[i]
+            if entry.level >= level then
+                if not started then
+                    entry.begindir = begindir
+                    started        = true
+                end
+            else
+                if started then
+                    list[i-1].enddir = enddir
+                    started          = false
+                end
+            end
+        end
+        -- make sure to close the run at end of line
+        if started then
+            finaldir = enddir
+        end
+    end
+    if finaldir then
+        list[size].enddir = finaldir
+    end
+end
+
+local function apply_to_list(list,size,head,pardir)
+    local index   = 1
+    local current = head
+    local done    = false
+    if trace_list then
+        report_directions("start run")
+    end
+    while current do
+        if index > size then
+            report_directions("fatal error, size mismatch")
+            break
+        end
+        local id       = getid(current)
+        local entry    = list[index]
+        local begindir = entry.begindir
+        local enddir   = entry.enddir
+        local p = properties[current] if p then p.directions = true else properties[current] = { directions = true } end
+        if id == glyph_code then
+            local mirror = entry.mirror
+            if mirror then
+                setchar(current,mirror)
+            end
+            if trace_directions then
+                local direction = entry.direction
+                if trace_list then
+                    local original = entry.original
+                    local char     = entry.char
+                    local level    = entry.level
+                    if direction == original then
+                        report_directions("%2i : %C : %s",level,char,direction)
+                    else
+                        report_directions("%2i : %C : %s -> %s",level,char,original,direction)
+                    end
+                end
+                setcolor(current,direction,false,mirror)
+            end
+        elseif id == hlist_code or id == vlist_code then
+            setfield(current,"dir",pardir) -- is this really needed?
+        elseif id == glue_code then
+            if enddir and getsubtype(current) == parfillskip_code then
+                -- insert the last enddir before \parfillskip glue
+                local d = new_textdir(enddir)
+                local p = properties[d] if p then p.directions = true else properties[d] = { directions = true } end
+             -- setfield(d,"attr",getfield(current,"attr"))
+                head = insert_node_before(head,current,d)
+                enddir = false
+                done = true
+            end
+        elseif begindir then
+            if id == localpar_code then
+                -- localpar should always be the 1st node
+                local d = new_textdir(begindir)
+                local p = properties[d] if p then p.directions = true else properties[d] = { directions = true } end
+             -- setfield(d,"attr",getfield(current,"attr"))
+                head, current = insert_node_after(head,current,d)
+                begindir = nil
+                done = true
+            end
+        end
+        if begindir then
+            local d = new_textdir(begindir)
+            local p = properties[d] if p then p.directions = true else properties[d] = { directions = true } end
+         -- setfield(d,"attr",getfield(current,"attr"))
+            head = insert_node_before(head,current,d)
+            done = true
+        end
+        local skip = entry.skip
+        if skip and skip > 0 then
+            for i=1,skip do
+                current = getnext(current)
+                local p = properties[current] if p then p.directions = true else properties[current] = { directions = true } end
+            end
+        end
+        if enddir then
+            local d = new_textdir(enddir)
+            local p = properties[d] if p then p.directions = true else properties[d] = { directions = true } end
+         -- setfield(d,"attr",getfield(current,"attr"))
+            head, current = insert_node_after(head,current,d)
+            done = true
+        end
+        if not entry.remove then
+            current = getnext(current)
+        elseif remove_controls then
+            -- X9
+            head, current = remove_node(head,current,true)
+            done = true
+        else
+            current = getnext(current)
+        end
+        index = index + 1
+    end
+    if trace_list then
+        report_directions("stop run")
+    end
+    return head, done
+end
+
+local function process(head)
+    head = tonut(head)
+    -- for the moment a whole paragraph property
+    local attr = getattr(head,a_directions)
+    local analyze_fences = getfences(attr)
+    --
+    local list, size = build_list(head)
+    local baselevel, pardir, dirfound = get_baselevel(head,list,size) -- we always have an inline dir node in context
+    if not dirfound and trace_details then
+        report_directions("no initial direction found, gambling")
+    end
+    if trace_details then
+        report_directions("before : %s",show_list(list,size,"original"))
+    end
+    resolve_explicit(list,size,baselevel)
+    resolve_levels(list,size,baselevel,analyze_fences)
+    insert_dir_points(list,size)
+    if trace_details then
+        report_directions("after  : %s",show_list(list,size,"direction"))
+        report_directions("result : %s",show_done(list,size))
+    end
+    head, done = apply_to_list(list,size,head,pardir)
+    return tonode(head), done
+end
+
+directions.installhandler(interfaces.variables.three,process)