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if not modules then modules = { } end modules ['lpdf-tag'] = {
version = 1.001,
comment = "companion to lpdf-tag.mkiv",
author = "Hans Hagen, PRAGMA-ADE, Hasselt NL",
copyright = "PRAGMA ADE / ConTeXt Development Team",
license = "see context related readme files"
}
local next = next
local format, match, concat = string.format, string.match, table.concat
local lpegmatch = lpeg.match
local utfchar = utf.char
local trace_tags = false trackers.register("structures.tags", function(v) trace_tags = v end)
local report_tags = logs.reporter("backend","tags")
local backends = backends
local lpdf = lpdf
local nodes = nodes
local nodeinjections = backends.pdf.nodeinjections
local codeinjections = backends.pdf.codeinjections
local tasks = nodes.tasks
local pdfdictionary = lpdf.dictionary
local pdfarray = lpdf.array
local pdfboolean = lpdf.boolean
local pdfconstant = lpdf.constant
local pdfreference = lpdf.reference
local pdfunicode = lpdf.unicode
local pdfstring = lpdf.string
local pdfflushobject = lpdf.flushobject
local pdfreserveobject = lpdf.reserveobject
local pdfpagereference = lpdf.pagereference
local addtocatalog = lpdf.addtocatalog
local addtopageattributes = lpdf.addtopageattributes
local texgetcount = tex.getcount
local nodecodes = nodes.nodecodes
local hlist_code = nodecodes.hlist
local vlist_code = nodecodes.vlist
local glyph_code = nodecodes.glyph
local a_tagged = attributes.private('tagged')
local a_image = attributes.private('image')
local nuts = nodes.nuts
local tonut = nuts.tonut
local tonode = nuts.tonode
local nodepool = nuts.pool
local pdfliteral = nodepool.pdfliteral
local getid = nuts.getid
local getattr = nuts.getattr
local getprev = nuts.getprev
local getnext = nuts.getnext
local getlist = nuts.getlist
local setfield = nuts.setfield
local traverse_nodes = nuts.traverse
local tosequence = nuts.tosequence
local copy_node = nuts.copy
local slide_nodelist = nuts.slide
local insert_before = nuts.insert_before
local insert_after = nuts.insert_after
local structure_stack = { }
local structure_kids = pdfarray()
local structure_ref = pdfreserveobject()
local parent_ref = pdfreserveobject()
local root = { pref = pdfreference(structure_ref), kids = structure_kids }
local tree = { }
local elements = { }
local names = pdfarray()
local taglist = structures.tags.taglist
local usedlabels = structures.tags.labels
local properties = structures.tags.properties
local usedmapping = { }
local colonsplitter = lpeg.splitat(":")
local dashsplitter = lpeg.splitat("-")
local add_ids = false -- true
-- function codeinjections.maptag(original,target,kind)
-- mapping[original] = { target, kind or "inline" }
-- end
local function finishstructure()
if #structure_kids > 0 then
local nums, n = pdfarray(), 0
for i=1,#tree do
n = n + 1 ; nums[n] = i - 1
n = n + 1 ; nums[n] = pdfreference(pdfflushobject(tree[i]))
end
local parenttree = pdfdictionary {
Nums = nums
}
-- we need to split names into smaller parts (e.g. alphabetic or so)
if add_ids then
local kids = pdfdictionary {
Limits = pdfarray { names[1], names[#names-1] },
Names = names,
}
local idtree = pdfdictionary {
Kids = pdfarray { pdfreference(pdfflushobject(kids)) },
}
end
--
local rolemap = pdfdictionary()
for k, v in next, usedmapping do
k = usedlabels[k] or k
local p = properties[k]
rolemap[k] = pdfconstant(p and p.pdf or "Span") -- or "Div"
end
local structuretree = pdfdictionary {
Type = pdfconstant("StructTreeRoot"),
K = pdfreference(pdfflushobject(structure_kids)),
ParentTree = pdfreference(pdfflushobject(parent_ref,parenttree)),
IDTree = (add_ids and pdfreference(pdfflushobject(idtree))) or nil,
RoleMap = rolemap,
}
pdfflushobject(structure_ref,structuretree)
addtocatalog("StructTreeRoot",pdfreference(structure_ref))
--
local markinfo = pdfdictionary {
Marked = pdfboolean(true),
-- UserProperties = pdfboolean(true),
-- Suspects = pdfboolean(true),
}
addtocatalog("MarkInfo",pdfreference(pdfflushobject(markinfo)))
--
for fulltag, element in next, elements do
pdfflushobject(element.knum,element.kids)
end
end
end
lpdf.registerdocumentfinalizer(finishstructure,"document structure")
local index, pageref, pagenum, list = 0, nil, 0, nil
local pdf_mcr = pdfconstant("MCR")
local pdf_struct_element = pdfconstant("StructElem")
local function initializepage()
index = 0
pagenum = texgetcount("realpageno")
pageref = pdfreference(pdfpagereference(pagenum))
list = pdfarray()
tree[pagenum] = list -- we can flush after done, todo
end
local function finishpage()
-- flush what can be flushed
addtopageattributes("StructParents",pagenum-1)
end
-- here we can flush and free elements that are finished
local function makeelement(fulltag,parent)
local tag, n = lpegmatch(dashsplitter,fulltag)
local tg, detail = lpegmatch(colonsplitter,tag)
local k, r = pdfarray(), pdfreserveobject()
usedmapping[tg] = true
tg = usedlabels[tg] or tg
local d = pdfdictionary {
Type = pdf_struct_element,
S = pdfconstant(tg),
ID = (add_ids and fulltag) or nil,
T = detail and detail or nil,
P = parent.pref,
Pg = pageref,
K = pdfreference(r),
-- Alt = " Who cares ",
-- ActualText = " Hi Hans ",
}
local s = pdfreference(pdfflushobject(d))
if add_ids then
names[#names+1] = fulltag
names[#names+1] = s
end
local kids = parent.kids
kids[#kids+1] = s
elements[fulltag] = { tag = tag, pref = s, kids = k, knum = r, pnum = pagenum }
end
local function makecontent(parent,start,stop,slist,id)
local tag = parent.tag
local kids = parent.kids
local last = index
if id == "image" then
local d = pdfdictionary {
Type = pdf_mcr,
Pg = pageref,
MCID = last,
Alt = "image",
}
kids[#kids+1] = d
elseif pagenum == parent.pnum then
kids[#kids+1] = last
else
local d = pdfdictionary {
Type = pdf_mcr,
Pg = pageref,
MCID = last,
}
-- kids[#kids+1] = pdfreference(pdfflushobject(d))
kids[#kids+1] = d
end
--
local bliteral = pdfliteral(format("/%s <</MCID %s>>BDC",tag,last))
local eliteral = pdfliteral("EMC")
-- use insert instead:
local prev = getprev(start)
if prev then
setfield(prev,"next",bliteral)
setfield(bliteral,"prev",prev)
end
setfield(start,"prev",bliteral)
setfield(bliteral,"next",start)
-- use insert instead:
local next = getnext(stop)
if next then
setfield(next,"prev",eliteral)
setfield(eliteral,"next",next)
end
setfield(stop,"next",eliteral)
setfield(eliteral,"prev",stop)
--
if slist and getlist(slist) == start then
setfield(slist,"list",bliteral)
elseif not getprev(start) then
report_tags("this can't happen: injection in front of nothing")
end
index = index + 1
list[index] = parent.pref
return bliteral, eliteral
end
-- -- --
local level, last, ranges, range = 0, nil, { }, nil
local function collectranges(head,list)
for n in traverse_nodes(head) do
local id = getid(n) -- 14: image, 8: literal (mp)
if id == glyph_code then
local at = getattr(n,a_tagged)
if not at then
range = nil
elseif last ~= at then
range = { at, "glyph", n, n, list } -- attr id start stop list
ranges[#ranges+1] = range
last = at
elseif range then
range[4] = n -- stop
end
elseif id == hlist_code or id == vlist_code then
local at = getattr(n,a_image)
if at then
local at = getattr(n,a_tagged)
if not at then
range = nil
else
ranges[#ranges+1] = { at, "image", n, n, list } -- attr id start stop list
end
last = nil
else
local nl = getlist(n)
slide_nodelist(nl) -- temporary hack till math gets slided (tracker item)
collectranges(nl,n)
end
end
end
end
function nodeinjections.addtags(head)
-- no need to adapt head, as we always operate on lists
level, last, ranges, range = 0, nil, { }, nil
initializepage()
head = tonut(head)
collectranges(head)
if trace_tags then
for i=1,#ranges do
local range = ranges[i]
local attr, id, start, stop = range[1], range[2], range[3], range[4]
local tags = taglist[attr]
if tags then -- not ok ... only first lines
report_tags("%s => %s : %05i % t",tosequence(start,start),tosequence(stop,stop),attr,tags)
end
end
end
for i=1,#ranges do
local range = ranges[i]
local attr, id, start, stop, list = range[1], range[2], range[3], range[4], range[5]
local tags = taglist[attr]
local prev = root
local noftags, tag = #tags, nil
for j=1,noftags do
local tag = tags[j]
if not elements[tag] then
makeelement(tag,prev)
end
prev = elements[tag]
end
local b, e = makecontent(prev,start,stop,list,id)
if start == head then
report_tags("this can't happen: parent list gets tagged")
head = b
end
end
finishpage()
-- can be separate feature
--
-- injectspans(tonut(head)) -- does to work yet
--
head = tonode(head)
return head, true
end
-- this belongs elsewhere (export is not pdf related)
function codeinjections.enabletags(tg,lb)
structures.tags.handler = nodeinjections.addtags
tasks.enableaction("shipouts","structures.tags.handler")
tasks.enableaction("shipouts","nodes.handlers.accessibility")
tasks.enableaction("math","noads.handlers.tags")
-- maybe also textblock
if trace_tags then
report_tags("enabling structure tags")
end
end
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