sile 0.15.8

Simon’s Improved Layout Engine
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149

--- SILE pagebuilder class.
-- @interfaces pagebuilders

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

function pagebuilder:_init ()
   self.awful_bad = 1073741823
   self.inf_bad = 10000
   self.eject_penalty = -self.inf_bad
   self.deplorable = 100000
end

function pagebuilder.collateVboxes (_, vboxlist)
   local output = SILE.types.node.vbox()
   output:append(vboxlist)
   return output
end

-- Note: Almost 1/3 of the time in a typical SILE in taken iterating through
-- this function. As a result there are some micro-optimizations here that
-- make it a-typical of preferred coding styles. In particular note that
-- we absolutize heavily iterated lengths as early as possible and make
-- make direct calls to their integer amounts, assumed to be in points by
-- the point they are called **without actually checking**!
function pagebuilder:findBestBreak (options)
   local vboxlist = SU.required(options, "vboxlist", "in findBestBreak")
   local target = SU.required(options, "target", "in findBestBreak", "length")
   local restart = options.restart or false
   local force = options.force or false
   local i = 0
   local totalHeight = SILE.types.length()
   local bestBreak = nil
   local started = false
   if restart and restart.target == target then
      totalHeight = restart.totalHeight
      i = restart.i
      started = restart.started
   end
   local leastC = self.inf_bad
   SU.debug("pagebuilder", function ()
      return "Page builder for frame "
         .. SILE.typesetter.frame.id
         .. " called with "
         .. #vboxlist
         .. " nodes, "
         .. tostring(target)
   end)
   if SU.debugging("vboxes") then
      for j, box in ipairs(vboxlist) do
         SU.debug("vboxes", function ()
            return (j == i and " >" or "  ") .. j .. ": " .. box
         end)
      end
   end
   while not started and i < #vboxlist do
      i = i + 1
      if not vboxlist[i].is_vglue then
         started = true
         i = i - 1
         break
      end
   end
   local pi
   while i < #vboxlist do
      i = i + 1
      local vbox = vboxlist[i]
      SU.debug("pagebuilder", "Dealing with VBox", vbox)
      if vbox.is_vbox then
         totalHeight:___add(vbox.height)
         totalHeight:___add(vbox.depth)
      elseif vbox.is_vglue then
         totalHeight:___add(vbox.height)
      elseif vbox.is_insertion then
         -- TODO: refactor as hook and without side effects!
         target = SILE.insertions.processInsertion(vboxlist, i, totalHeight, target)
         vbox = vboxlist[i]
      end
      local left = target - totalHeight
      SU.debug("pagebuilder", "I have", left, "left")
      -- if left < -20 then SU.error("\nCatastrophic page breaking failure!"); end
      pi = 0
      if vbox.is_penalty then
         pi = vbox.penalty
      end
      if
         vbox.is_penalty and vbox.penalty < self.inf_bad
         or (vbox.is_vglue and i > 1 and not vboxlist[i - 1].discardable)
      then
         local badness
         SU.debug("pagebuilder", "totalHeight", totalHeight, "with target", target)
         if totalHeight.length.amount < target.length.amount then -- TeX #1039
            -- Account for infinite stretch?
            badness = SU.rateBadness(self.inf_bad, left.length.amount, totalHeight.stretch.amount)
         elseif left.length.amount < totalHeight.shrink.amount then
            badness = self.awful_bad
         else
            badness = SU.rateBadness(self.inf_bad, -left.length.amount, totalHeight.shrink.amount)
         end

         local c
         if badness < self.awful_bad then
            if pi <= self.eject_penalty then
               c = pi
            elseif badness < self.inf_bad then
               c = badness + pi -- plus insert
            else
               c = self.deplorable
            end
         else
            c = badness
         end
         if c < leastC then
            leastC = c
            bestBreak = i
         else
            restart = { totalHeight = totalHeight, i = i, started = started, target = target }
         end

         SU.debug("pagebuilder", "Badness:", c)
         if c == self.awful_bad or pi <= self.eject_penalty then
            SU.debug("pagebuilder", "outputting")
            local onepage = {}
            if not bestBreak then
               bestBreak = i
            end
            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, pi
         end
      end
   end
   SU.debug("pagebuilder", "No page break here")
   if force and bestBreak then
      local onepage = {}
      for j = 1, bestBreak do
         onepage[j] = table.remove(vboxlist, 1)
      end
      return onepage, pi
   end
   return false, restart
end

return pagebuilder