path: root/tex/context/base/typo-dir.lua

if not modules then modules = { } end modules ['typo-dir'] = {
    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"
}

-- todo: also use end_of_math here?
-- todo: use lpeg instead of match

local next, type = next, type
local format, insert, sub, find, match = string.format, table.insert, string.sub, string.find, string.match
local utfchar = utf.char
local formatters = string.formatters

-- vertical space handler

local nodes, node = nodes, node

local trace_directions = false  trackers.register("typesetters.directions", function(v) trace_directions = v end)

local report_directions = logs.reporter("typesetting","directions")

local traverse_id        = node.traverse_id
local insert_node_before = node.insert_before
local insert_node_after  = node.insert_after
local remove_node        = nodes.remove

local texsetattribute    = tex.setattribute
local unsetvalue         = attributes.unsetvalue

local nodecodes          = nodes.nodecodes
local whatcodes          = nodes.whatcodes
local mathcodes          = nodes.mathcodes

local tasks              = nodes.tasks

local glyph_code         = nodecodes.glyph
local whatsit_code       = nodecodes.whatsit
local math_code          = nodecodes.math
local penalty_code       = nodecodes.penalty
local kern_code          = nodecodes.kern
local glue_code          = nodecodes.glue

local localpar_code      = whatcodes.localpar
local dir_code           = whatcodes.dir

local nodepool           = nodes.pool

local new_textdir        = nodepool.textdir

local beginmath_code     = mathcodes.beginmath
local endmath_code       = mathcodes.endmath

local fonthashes         = fonts.hashes
local fontdata           = fonthashes.identifiers
local fontchar           = fonthashes.characters

local chardata           = characters.data
local chardirs           = characters.directions -- maybe make a special mirror table

--~ Analysis by Idris:
--~
--~ 1. Assuming the reading- vs word-order distinction (bidi-char types) is governing;
--~ 2. Assuming that 'ARAB' represents an actual arabic string in raw input order, not word-order;
--~ 3. Assuming that 'BARA' represent the correct RL word order;
--~
--~ Then we have, with input: LATIN ARAB
--~
--~ \textdir TLT LATIN ARAB => LATIN BARA
--~ \textdir TRT LATIN ARAB => LATIN BARA
--~ \textdir TRT LRO LATIN ARAB => LATIN ARAB
--~ \textdir TLT LRO LATIN ARAB => LATIN ARAB
--~ \textdir TLT RLO LATIN ARAB => NITAL ARAB
--~ \textdir TRT RLO LATIN ARAB => NITAL ARAB

--  elseif d == "es"  then -- European Number Separator
--  elseif d == "et"  then -- European Number Terminator
--  elseif d == "cs"  then -- Common Number Separator
--  elseif d == "nsm" then -- Non-Spacing Mark
--  elseif d == "bn"  then -- Boundary Neutral
--  elseif d == "b"   then -- Paragraph Separator
--  elseif d == "s"   then -- Segment Separator
--  elseif d == "ws"  then -- Whitespace
--  elseif d == "on"  then -- Other Neutrals

typesetters.directions = typesetters.directions or { }
local directions       = typesetters.directions

local a_state          = attributes.private('state')
local a_directions     = attributes.private('directions')

local skipmath         = true
local strip            = false

-- todo: delayed inserts here
-- todo: get rid of local functions here

-- beware, math adds whatsits afterwards so that will mess things up

local finish, autodir, embedded, override, done = nil, 0, 0, 0, false
local list, glyphs = nil, false
local finished, finidir, finipos = nil, nil, 1
local head, current, inserted = nil, nil, nil

local function finish_auto_before()
    local fdir = "-" .. finish
    head, inserted = insert_node_before(head,current,new_textdir(fdir))
    finished, finidir, autodir = inserted, finish, 0
    if trace_directions then
        insert(list,#list,formatters["auto %a inserted before, autodir %a, embedded %a"](fdir,autodir,embedded))
        finipos = #list - 1
    end
    finish, done = nil, true
end

local function finish_auto_after()
    local fdir = "-" .. finish
    head, current = insert_node_after(head,current,new_textdir(fdir))
    finished, finidir, autodir = current, finish, 0
    if trace_directions then
        list[#list+1] = formatters["auto %a inserted after, autodir %a, embedded %a"](fdir,autodir,embedded)
        finipos = #list
    end
    finish, done = nil, true
end

local function force_auto_left_before(d)
    if finish then
        finish_auto_before()
    end
    if embedded >= 0 then
        finish, autodir, done = "TLT", 1, true
    else
        finish, autodir, done = "TRT", -1, true
    end
    if finidir == finish then
        head = remove_node(head,finished,true)
        if trace_directions then
            list[finipos] = list[finipos] .. ", deleted afterwards"
            insert(list,#list,formatters["start text dir %a, auto left before, embedded %a, autodir %a, triggered by class %a"](finish,embedded,autodir,d))
        end
    else
        head, inserted = insert_node_before(head,current,new_textdir("+"..finish))
        if trace_directions then
            insert(list,#list,formatters["start text dir %a, auto left before, embedded %a, autodir %a, triggered by class %a"](finish,embedded,autodir,d))
        end
    end
end

local function force_auto_right_before(d)
    if finish then
        finish_auto_before()
    end
    if embedded <= 0 then
        finish, autodir, done = "TRT", -1, true
    else
        finish, autodir, done = "TLT", 1, true
    end
    if finidir == finish then
        head = remove_node(head,finished,true)
        if trace_directions then
            list[finipos] = list[finipos] .. ", deleted afterwards"
            insert(list,#list,formatters["start text dir %a, auto right before, embedded %a, autodir %a, triggered by class %a"](finish,embedded,autodir,d))
        end
    else
        head, inserted = insert_node_before(head,current,new_textdir("+"..finish))
        if trace_directions then
            insert(list,#list,formatters["start text dir %a, auto right before, embedded %a, autodir %a, triggered by class %a"](finish,embedded,autodir,d))
        end
    end
end

local function nextisright(current)
    repeat
        current = current.next
        local id = current.id
        if id == glyph_code then
            local char = current.char
            local d = chardirs[char]
            return d == "r" or d == "al" or d == "an" and current
--         elseif id == glue_code or id == kern_code or id == penalty_code then
--             -- too complex
        else
            return
        end
    until not current
end

local function previsright(current)
    repeat
        current = current.prev
        local id = current.id
        if id == glyph_code then
            local char = current.char
            local d = chardirs[char]
            return d == "r" or d == "al" or d == "an"
--         elseif id == glue_code or id == kern_code or id == penalty_code then
--             -- too complex
        else
            return
        end
    until not current
end

-- todo: use new dir functions

-- todo: use end_of_math

local s_isol = fonts.analyzers.states.isol

function directions.process(namespace,attribute,start) -- todo: make faster
    if not start.next then
        return start, false
    end
    head, current, inserted = start, start, nil
    finish, autodir, embedded, override, done = nil, 0, 0, 0, false
    list, glyphs = trace_directions and { }, false
    finished, finidir, finipos = nil, nil, 1
    local stack, top, obsolete = { }, 0, { }
    local lro, rlo, prevattr, inmath = false, false, 0, false
    while current do
        local id = current.id
-- list[#list+1] = formatters["state: node %a, finish %a, autodir %a, embedded %a"](nutstring(current),finish or "unset",autodir,embedded)
        if skipmath and id == math_code then
            local subtype = current.subtype
            if subtype == beginmath_code then
                inmath = true
            elseif subtype == endmath_code then
                inmath = false
            else
                -- todo
            end
            current = current.next
        elseif inmath then
            current = current.next
        else
            local attr = current[attribute]
            if attr and attr > 0 then
             -- current[attribute] = unsetvalue -- slow, needed?
                if attr == 1 then
                    -- bidi parsing mode
                elseif attr ~= prevattr then
                    -- no pop, grouped driven (2=normal,3=lro,4=rlo)
                    if attr == 3 then
                        if trace_directions then
                            list[#list+1] = formatters["override right -> left (lro), bidi %a"](attr)
                        end
                        lro, rlo = true, false
                    elseif attr == 4 then
                        if trace_directions then
                            list[#list+1] = formatters["override left -> right (rlo), bidi %a"](attr)
                        end
                        lro, rlo = false, true
                    else
                        if trace_directions and
                            current ~= head then list[#list+1] = formatters["override reset, bidi %a"](attr)
                        end
                        lro, rlo = false, false
                    end
                    prevattr = attr
                end
            end
            if id == glyph_code then
                glyphs = true
                if attr and attr > 0 then
                    local char = current.char
                    local d = chardirs[char]
                    if rlo or override > 0 then
                        if d == "l" then
                            if trace_directions then
                                list[#list+1] = formatters["char %C of class %a overridden to r, bidi %a)"](char,d,attr)
                            end
                            d = "r"
                        elseif trace_directions then
                            if d == "lro" or d == "rlo" or d == "pdf" then -- else side effects on terminal
                                list[#list+1] = formatters["override char of class %a, bidi %a"](d,attr)
                            else -- todo: rle lre
                                list[#list+1] = formatters["char %C of class %a, bidi %a"](char,d,attr)
                            end
                        end
                    elseif lro or override < 0 then
                        if d == "r" or d == "al" then
                            current[a_state] = s_isol -- maybe better have a special bidi attr value -> override (9) -> todo
                            if trace_directions then
                                list[#list+1] = formatters["char %C of class %a overridden to l, bidi %a, state 'isol'"](char,d,attr)
                            end
                            d = "l"
                        elseif trace_directions then
                            if d == "lro" or d == "rlo" or d == "pdf" then -- else side effects on terminal
                                list[#list+1] = formatters["override char of class %a, bidi %a"](d,attr)
                            else -- todo: rle lre
                                list[#list+1] = formatters["char %C of class %a, bidi %a"](char,d,attr)
                            end
                        end
                    elseif trace_directions then
                        if d == "lro" or d == "rlo" or d == "pdf" then -- else side effects on terminal
                            list[#list+1] = formatters["override char of class %a, bidi %a"](d,attr)
                        else -- todo: rle lre
                            list[#list+1] = formatters["char %C of class %a, bidi %a"](char,d,attr)
                        end
                    end
                    if d == "on" then
                        local cdata  = chardata[char]
                        local mirror = cdata.mirror -- maybe make a special mirror table
                        if mirror and fontchar[current.font][mirror] then
                            -- todo: set attribute
                            local class = cdata.textclass
                            if class == "open" then
                                if nextisright(current) then
                                    if autodir >= 0 then
                                        force_auto_right_before(d)
                                    end
                                    current.char = mirror
                                    done = true
                                else
                                    mirror = nil
                                    if autodir <= 0 then
                                        force_auto_left_before(d)
                                    end
                                end
                            elseif class == "close" then
                                if previsright(current) then
                                    current.char = mirror
                                    done = true
                                else
                                    mirror = nil
                                end
                            elseif autodir < 0 then
                                current.char = mirror
                                done = true
                            else
                                mirror = nil
                            end
                            if trace_directions then
                                if mirror then
                                    list[#list+1] = formatters["mirroring char %C of class %a to %C, autodir %a, bidi %a"](char,d,mirror,autodir,attr)
                                else
                                    list[#list+1] = formatters["not mirroring char %C of class %a, autodir %a, bidi %a"](char,d,autodir,attr)
                                end
                            end
                        end
                    elseif d == "l" or d == "en" then -- european number
                        if autodir <= 0 then -- could be option
                            force_auto_left_before(d)
                        end
                    elseif d == "r" or d == "al" then -- arabic number
                        if autodir >= 0 then
                            force_auto_right_before(d)
                        end
                    elseif d == "an" then -- arabic number
                        -- actually this is language dependent ...
--                         if autodir <= 0 then
--                             force_auto_left_before(d)
--                         end
                        if autodir >= 0 then
                            force_auto_right_before(d)
                        end
                    elseif d == "lro" then -- Left-to-Right Override -> right becomes left
                        if trace_directions then
                            list[#list+1] = "override right -> left"
                        end
                        top = top + 1
                        stack[top] = { override, embedded }
                        override = -1
                        obsolete[#obsolete+1] = current
                    elseif d == "rlo" then -- Right-to-Left Override -> left becomes right
                        if trace_directions then
                            list[#list+1] = "override left -> right"
                        end
                        top = top + 1
                        stack[top] = { override, embedded }
                        override = 1
                        obsolete[#obsolete+1] = current
                    elseif d == "lre" then -- Left-to-Right Embedding -> TLT
                        if trace_directions then
                            list[#list+1] = "embedding left -> right"
                        end
                        top = top + 1
                        stack[top] = { override, embedded }
                        embedded = 1
                        obsolete[#obsolete+1] = current
                    elseif d == "rle" then -- Right-to-Left Embedding -> TRT
                        if trace_directions then
                            list[#list+1] = "embedding right -> left"
                        end
                        top = top + 1
                        stack[top] = { override, embedded }
                        embedded = -1 -- was 1
                        obsolete[#obsolete+1] = current
                    elseif d == "pdf" then -- Pop Directional Format
                    --  override = 0
                        if top > 0 then
                            local s = stack[top]
                            override, embedded = s[1], s[2]
                            top = top - 1
                            if trace_directions then
                                list[#list+1] = formatters["state: override %a, embedded %a, autodir %a"](override,embedded,autodir)
                            end
                        else
                            if trace_directions then
                                list[#list+1] = "pop error: too many pops"
                            end
                        end
                        obsolete[#obsolete+1] = current
                    end
                elseif trace_directions then
                    local char = current.char
                    local d = chardirs[char]
                    list[#list+1] = formatters["char %C of class %a, bidi %a"](char,d or "?")
                end
            elseif id == whatsit_code then
                if finish then
                    finish_auto_before()
                end
                local subtype = current.subtype
                if subtype == localpar_code then
-- if false then
                    local dir = current.dir
                    local d = sub(dir,2,2)
                    if d == 'R' then -- find(dir,".R.") / dir == "TRT"
                        autodir = -1
                    else
                        autodir = 1
                    end
                 -- embedded = autodir
                    if trace_directions then
                        list[#list+1] = formatters["pardir %a"](dir)
                    end
-- end
                elseif subtype == dir_code then
                    local dir = current.dir
                 -- local sign = sub(dir,1,1)
                 -- local dire = sub(dir,3,3)
                    local sign, dire = match(dir,"^(.).(.)") -- splitter
                    if dire == "R" then
                        if sign == "+" then
                            finish, autodir = "TRT", -1
                        else
                            finish, autodir = nil, 0
                        end
                    else
                        if sign == "+" then
                            finish, autodir = "TLT", 1
                        else
                            finish, autodir = nil, 0
                        end
                    end
                    if trace_directions then
                        list[#list+1] = formatters["textdir %a, autodir %a"](dir,autodir)
                    end
                end
            else
                if trace_directions then
                    list[#list+1] = formatters["node %a, subtype %a"](nodecodes[id],current.subtype)
                end
                if finish then
                    finish_auto_before()
                end
            end
            local cn = current.next
            if not cn then
                if finish then
                    finish_auto_after()
                end
            end
            current = cn
        end
    end
    if trace_directions and glyphs then
        report_directions("start log")
        for i=1,#list do
            report_directions("%02i: %s",i,list[i])
        end
        report_directions("stop log")
    end
    if done and strip then
        local n = #obsolete
        if n > 0 then
            for i=1,n do
                remove_node(head,obsolete[i],true)
            end
            report_directions("%s character nodes removed",n)
        end
    end
    return head, done
end

-- function directions.enable()
--     tasks.enableaction("processors","directions.handler")
-- end

local enabled = false

function directions.set(n) -- todo: names and numbers
    if not enabled then
        if trace_directions then
            report_breakpoints("enabling directions handler")
        end
        tasks.enableaction("processors","typesetters.directions.handler")
        enabled = true
    end
    if not n or n == 0 then
        n = unsetvalue
        -- maybe tracing
    end
    texsetattribute(a_directions,n)
end

commands.setdirection = directions.set

directions.handler = nodes.installattributehandler {
    name = "directions",
    namespace = directions,
    processor = directions.process,
}