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if not modules then modules = { } end modules ['typo-pag'] = {
version = 1.001,
comment = "companion to typo-pag.mkiv",
author = "Hans Hagen, PRAGMA-ADE, Hasselt NL",
copyright = "PRAGMA ADE / ConTeXt Development Team",
license = "see context related readme files"
}
builders = builders or { }
local builders = builders
builders.paragraphs = builders.paragraphs or { }
local parbuilders = builders.paragraphs
local nodes = nodes
local nodecodes = nodes.nodecodes
local hlist_code = nodecodes.hlist
local vlist_code = nodecodes.vlist
local glue_code = nodecodes.glue
local kern_code = nodecodes.kern
local penalty_code = nodecodes.penalty
local unsetvalue = attributes.unsetvalue
local a_keeptogether = attributes.private("keeptogether")
local nuts = nodes.nuts
local getnext = nuts.getnext
local getprev = nuts.getprev
local getid = nuts.getid
local getattr = nuts.getattr
local takeattr = nuts.takeattr
local setattr = nuts.setattr
local getwhd = nuts.getwhd
local getkern = nuts.getkern
local setpenalty = nuts.setpenalty
local getwidth = nuts.getwidth
local getdepth = nuts.getdepth
local insert_node_after = nuts.insert_after
local new_penalty = nuts.pool.penalty
local trace_keeptogether = false
local report_keeptogether = logs.reporter("parbuilders","keeptogether")
local enableaction = nodes.tasks.enableaction
local cache = { }
local last = 0
local enabled = false
trackers.register("parbuilders.keeptogether", function(v) trace_keeptogether = v end)
-- todo: also support lines = 3 etc (e.g. dropped caps) but how to set that
-- when no hlists are there ?
function parbuilders.registertogether(line,specification) -- might change
if not specification then
return
end
if not enabled then
enableaction("finalizers","builders.paragraphs.keeptogether")
end
local a = getattr(line,a_keeptogether)
local c = a and cache[a]
if c then
local height = specification.height
local depth = specification.depth
local slack = specification.slack
if height and height > c.height then
c.height = height
end
if depth and depth > c.depth then
c.depth = depth
end
if slack and slack > c.slack then
c.slack = slack
end
else
last = last + 1
cache[last] = specification
if not specification.height then
specification.height = 0
end
if not specification.depth then
specification.depth = 0
end
if not specification.slack then
specification.slack = 0
end
setattr(line,a_keeptogether,last)
end
if trace_keeptogether then
local a = a or last
local c = cache[a]
local noflines = specification.lineheight
local height = c.height
local depth = c.depth
local slack = c.slack
if not noflines or noflines == 0 then
noflines = "unknown"
else
noflines = math.round((height + depth - slack) / noflines)
end
report_keeptogether("registered, index %s, height %p, depth %p, slack %p, noflines %a",a,height,depth,slack,noflines)
end
end
local function keeptogether(start,a,specification)
local current = getnext(start)
local previous = start
local total = getdepth(previous)
local slack = specification.slack
local threshold = specification.depth - slack
if trace_keeptogether then
report_keeptogether("%s, index %s, total %p, threshold %p, slack %p","list",a,total,threshold,slack)
end
while current do
local id = getid(current)
if id == vlist_code or id == hlist_code then
local wd, ht, dp = getwhd(current)
total = total + ht + dp
if trace_keeptogether then
report_keeptogether("%s, index %s, total %p, threshold %p","list",a,total,threshold)
end
if total <= threshold then
if getid(previous) == penalty_code then
setpenalty(previous,10000)
else
insert_node_after(head,previous,new_penalty(10000))
end
else
break
end
elseif id == glue_code then
-- hm, breakpoint, maybe turn this into kern
total = total + getwidth(current)
if trace_keeptogether then
report_keeptogether("%s, index %s, total %p, threshold %p","glue",a,total,threshold)
end
if total <= threshold then
if getid(previous) == penalty_code then
setpenalty(previous,10000)
else
insert_node_after(head,previous,new_penalty(10000))
end
else
break
end
elseif id == kern_code then
total = total + getkern(current)
if trace_keeptogether then
report_keeptogether("%s, index %s, total %s, threshold %s","kern",a,total,threshold)
end
if total <= threshold then
if getid(previous) == penalty_code then
setpenalty(previous,10000)
else
insert_node_after(head,previous,new_penalty(10000))
end
else
break
end
elseif id == penalty_code then
if total <= threshold then
if getid(previous) == penalty_code then
setpenalty(previous,10000)
end
setpenalty(current,10000)
else
break
end
end
previous = current
current = getnext(current)
end
end
-- also look at first non glue/kern node e.g for a dropped caps
function parbuilders.keeptogether(head)
local done = false -- can go
local current = head
while current do
if getid(current) == hlist_code then
local a = takeattr(current,a_keeptogether)
if a and a > 0 then
local specification = cache[a]
if specification then
keeptogether(current,a,specification)
-- this is tricky ... we need a better resetter, maybe some
-- injected latelua or a gc method on a property (interesting
-- experiment)
cache[a] = nil
done = true
end
end
end
current = getnext(current)
end
return head, done
end
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