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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"
}
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 insert_node_after = node.insert_after
local new_penalty = nodes.pool.penalty
local has_attribute = node.has_attribute
local unset_attribute = node.unset_attribute
local set_attribute = node.set_attribute
local points = number.points
local a_keeptogether = attributes.private("keeptogether")
local trace_keeptogether = false trackers.register("parbuilders.keeptogether", function(v) trace_keeptogether = v end)
local report_keeptogether = logs.reporter("parbuilders","keeptogether")
local cache = { }
local last = 0
local enabled = false
-- todo: also support lines = 3 etc (e.g. dropped caps) but how to set that
-- when no hlists are there ? ... maybe the local_par
function builders.paragraphs.registertogether(line,specification) -- might change
if not enabled then
nodes.tasks.enableaction("finalizers","builders.paragraphs.keeptogether")
end
local a = has_attribute(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
set_attribute(line,a_keeptogether,last)
end
if trace_keeptogether then
local a = a or last
local c = cache[a]
if trace_keeptogether then
report_keeptogether("registered, index: %s, height: %s, depth: %s, slack: %s",
a,points(c.height),points(c.depth),points(c.slack))
end
end
end
local function keeptogether(start,a)
if start then
local specification = cache[a]
if a then
local current = start.next
local previous = start
local total = previous.depth
local slack = specification.slack
local threshold = specification.depth - slack
if trace_keeptogether then
report_keeptogether("list, index: %s, total: %s, threshold: %s, slack: %s",a,points(total),points(threshold),points(slack))
end
while current do
local id = current.id
if id == vlist_code or id == hlist_code then
total = total + current.height + current.depth
if trace_keeptogether then
report_keeptogether("list, index: %s, total: %s, threshold: %s",a,points(total),points(threshold))
end
if total <= threshold then
if previous.id == penalty_code then
previous.penalty = 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 + current.spec.width
if trace_keeptogether then
report_keeptogether("glue, index: %s, total: %s, threshold: %s",a,points(total),points(threshold))
end
if total <= threshold then
if previous.id == penalty_code then
previous.penalty = 10000
else
insert_node_after(head,previous,new_penalty(10000))
end
else
break
end
elseif id == kern_code then
total = total + current.kern
if trace_keeptogether then
report_keeptogether("kern, index: %s, total: %s, threshold: %s",a,points(total),points(threshold))
end
if total <= threshold then
if previous.id == penalty_code then
previous.penalty = 10000
else
insert_node_after(head,previous,new_penalty(10000))
end
else
break
end
elseif id == penalty_code then
if total <= threshold then
if previous.id == penalty_code then
previous.penalty = 10000
end
current.penalty = 10000
else
break
end
end
previous = current
current = current.next
end
end
end
end
-- also look at first non glue/kern node e.g for a dropped caps
function builders.paragraphs.keeptogether(head)
local done = false
local current = head
while current do
if current.id == hlist_code then
local a = has_attribute(current,a_keeptogether)
if a and a > 0 then
keeptogether(current,a)
unset_attribute(current,a_keeptogether)
cache[a] = nil
done = true
end
end
current = current.next
end
return head, done
end
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