sile 0.14.8

Simon’s Improved Layout Engine
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local base = require("pagebuilders.base")

local pagebuilder = pl.class(base)
pagebuilder._name = "grid"

function pagebuilder:_init()
  base._init(self)
end

function pagebuilder.findBestBreak (_, options)
  local vboxlist = SU.required(options, "vboxlist", "in findBestBreak")
  local target   = SU.required(options, "target", "in findBestBreak")
  local i = 0
  local totalHeight = SILE.length()
  local bestBreak = 0
  SU.debug("pagebuilder", "Page builder for frame", SILE.typesetter.frame.id, "called with", #vboxlist, "nodes,", target)
  if SU.debugging("vboxes") then
    for j, box in ipairs(vboxlist) do
      SU.debug("vboxes", (j == i and " >" or "  ") .. j .. ": " .. box)
    end
  end
  while i < #vboxlist do
    i = i + 1
    if not vboxlist[i].is_vglue then
      i = i - 1
      break
    end
  end
  while i < #vboxlist do
    i = i + 1
    local node = vboxlist[i]
    SU.debug("pagebuilder", "Dealing with VBox", node)
    if node.is_vbox then
      totalHeight = totalHeight + node.height:absolute() + node.depth:absolute()
    elseif node.is_vglue then
      totalHeight = totalHeight + node.height:absolute()
    elseif node.is_insertion then
      -- TODO: refactor as hook and without side effects!
      target = SILE.insertions.processInsertion(vboxlist, i, totalHeight, target)
      node = vboxlist[i]
    end
    local left = target - totalHeight
    local _left = left:tonumber()
    SU.debug("pagebuilder", "I have", left, "left")
    SU.debug("pagebuilder", "totalHeight", totalHeight, "with target", target)
    local badness = 0
    if _left < 0 then badness = 1000000 end
    if node.is_penalty then
      if node.penalty < -3000 then badness = 100000
      else badness = -_left * _left - node.penalty
      end
    end
    if badness > 0 then
      local onepage = {}
      for j = 1, bestBreak do
        onepage[j] = table.remove(vboxlist, 1)
      end
      while #onepage > 1 and onepage[#onepage].discardable do
        onepage[#onepage] = nil
      end
      return onepage, 1000
    end
    bestBreak = i
  end
  return false, false
end

return pagebuilder