summaryrefslogtreecommitdiff
path: root/Master/texmf-dist/tex/context/base/mkiv/page-mix.lua
blob: 107ac14102c7ce38a5f8616c19967732c0c7d50d (plain)
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
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
if not modules then modules = { } end modules ["page-mix"] = {
    version   = 1.001,
    comment   = "companion to page-mix.mkiv",
    author    = "Hans Hagen, PRAGMA-ADE, Hasselt NL",
    copyright = "PRAGMA ADE / ConTeXt Development Team",
    license   = "see context related readme files"
}

-- inserts.getname(name)

-- local node, tex = node, tex
-- local nodes, interfaces, utilities = nodes, interfaces, utilities
-- local trackers, logs, storage = trackers, logs, storage
-- local number, table = number, table

-- todo: explore vsplit (for inserts)

local next, type = next, type
local concat = table.concat
local ceil = math.ceil

local trace_state  = false  trackers.register("mixedcolumns.trace",  function(v) trace_state  = v end)
local trace_detail = false  trackers.register("mixedcolumns.detail", function(v) trace_detail = v end)

local report_state = logs.reporter("mixed columns")

local context             = context

local nodecodes           = nodes.nodecodes

local hlist_code          = nodecodes.hlist
local vlist_code          = nodecodes.vlist
local kern_code           = nodecodes.kern
local glue_code           = nodecodes.glue
local penalty_code        = nodecodes.penalty
local insert_code         = nodecodes.ins
local mark_code           = nodecodes.mark
local rule_code           = nodecodes.rule

local nuts                = nodes.nuts
local tonode              = nuts.tonode
local listtoutf           = nodes.listtoutf

local hpack               = nuts.hpack
local vpack               = nuts.vpack
local flushnode           = nuts.flush
local concatnodes         = nuts.concat
local slidenodes          = nuts.slide -- ok here as we mess with prev links intermediately

local setlink             = nuts.setlink
local setlist             = nuts.setlist
local setnext             = nuts.setnext
local setprev             = nuts.setprev
local setbox              = nuts.setbox
local setwhd              = nuts.setwhd
local setheight           = nuts.setheight
local setdepth            = nuts.setdepth

local getnext             = nuts.getnext
local getprev             = nuts.getprev
local getid               = nuts.getid
local getlist             = nuts.getlist
local getsubtype          = nuts.getsubtype
local getbox              = nuts.getbox
local getattribute        = nuts.getattribute
local getwhd              = nuts.getwhd
local getkern             = nuts.getkern
local getpenalty          = nuts.getpenalty
local getwidth            = nuts.getwidth
local getheight           = nuts.getheight
local getdepth            = nuts.getdepth
local traverse_id         = nuts.traverse_id
local traverse            = nuts.traverse

local theprop             = nuts.theprop

local nodepool            = nuts.pool

local new_hlist           = nodepool.hlist
local new_vlist           = nodepool.vlist
local new_glue            = nodepool.glue

local points              = number.points

local settings_to_hash    = utilities.parsers.settings_to_hash

local variables           = interfaces.variables
local v_yes               = variables.yes
local v_global            = variables["global"]
local v_local             = variables["local"]
local v_none              = variables.none
local v_halfline          = variables.halfline

local context             = context
local implement           = interfaces.implement

pagebuilders              = pagebuilders or { }
pagebuilders.mixedcolumns = pagebuilders.mixedcolumns or { }
local mixedcolumns        = pagebuilders.mixedcolumns

local a_checkedbreak      = attributes.private("checkedbreak")
local forcedbreak         = -123

-- initializesplitter(specification)
-- cleanupsplitter()

-- Inserts complicate matters a lot. In order to deal with them well, we need to
-- distinguish several cases.
--
-- (1) full page columns: firstcolumn, columns, lastcolumn, page
-- (2) mid page columns : firstcolumn, columns, lastcolumn, page
--
-- We need to collect them accordingly.

local function collectinserts(result,nxt,nxtid)
    local inserts, currentskips, nextskips, inserttotal = { }, 0, 0, 0
    local i = result.i
    if not i then
        i = 0
        result.i = i
    end
    while nxt do
        if nxtid == insert_code then
            i = i + 1
            result.i = i
            inserttotal = inserttotal + getheight(nxt) -- height includes depth (hm, still? needs checking)
            local s = getsubtype(nxt)
            local c = inserts[s]
            if trace_detail then
                report_state("insert of class %s found",s)
            end
            if not c then
                local width = structures.notes.check_spacing(s,i) -- before
                c = { }
                inserts[s] = c
                if not result.inserts[s] then
                    currentskips = currentskips + width
                end
                nextskips = nextskips + width
            end
            c[#c+1] = nxt
        elseif nxtid == mark_code then
            if trace_detail then
                report_state("mark found")
            end
        else
            break
        end
        nxt = getnext(nxt)
        if nxt then
            nxtid = getid(nxt)
        else
            break
        end
    end
    return nxt, inserts, currentskips, nextskips, inserttotal
end

local function appendinserts(ri,inserts)
    for class, collected in next, inserts do
        local ric = ri[class]
        if not ric then
            -- assign to collected
            ri[class] = collected
        else
            -- append to collected
            for j=1,#collected do
                ric[#ric+1] = collected[j]
            end
        end
    end
end

local function discardtopglue(current,discarded)
    local size = 0
    while current do
        local id = getid(current)
        if id == glue_code then
            size = size + getwidth(current)
            discarded[#discarded+1] = current
            current = getnext(current)
        elseif id == penalty_code then
            if getpenalty(current) == forcedbreak then
                discarded[#discarded+1] = current
                current = getnext(current)
                while current and getid(current) == glue_code do
                    size = size + getwidth(current)
                    discarded[#discarded+1] = current
                    current = getnext(current)
                end
            else
                discarded[#discarded+1] = current
                current = getnext(current)
            end
        else
            break
        end
    end
    if current then
        setprev(current) -- prevent look back
    end
    return current, size
end

local function stripbottomglue(results,discarded)
    local height = 0
    for i=1,#results do
        local r = results[i]
        local t = r.tail
        while t and t ~= r.head do
            local prev = getprev(t)
            if not prev then
                break
            end
            local id = getid(t)
            if id == penalty_code then
                if getpenalty(t) == forcedbreak then
                    break
                else
                    discarded[#discarded+1] = t
                    r.tail = prev
                    t = prev
                end
            elseif id == glue_code then
                discarded[#discarded+1] = t
                local width = getwidth(t)
                if trace_state then
                    report_state("columns %s, discarded bottom glue %p",i,width)
                end
                r.height = r.height - width
                r.tail = prev
                t = prev
            else
                break
            end
        end
        if r.height > height then
            height = r.height
        end
    end
    return height
end

local function preparesplit(specification) -- a rather large function
    local box = specification.box
    if not box then
        report_state("fatal error, no box")
        return
    end
    local list = getbox(box)
    if not list then
        report_state("fatal error, no list")
        return
    end
    local head = getlist(list) or specification.originalhead
    if not head then
        report_state("fatal error, no head")
        return
    end
    slidenodes(head) -- we can have set prev's to nil to prevent backtracking
    local discarded      = { }
    local originalhead   = head
    local originalwidth  = specification.originalwidth  or getwidth(list)
    local originalheight = specification.originalheight or getheight(list)
    local current        = head
    local skipped        = 0
    local height         = 0
    local depth          = 0
    local skip           = 0
    local handlenotes    = specification.notes or false
    local splitmethod    = specification.splitmethod or false
    if splitmethod == v_none then
        splitmethod = false
    end
    local options     = settings_to_hash(specification.option or "")
    local stripbottom = specification.alternative == v_local
    local cycle       = specification.cycle or 1
    local nofcolumns  = specification.nofcolumns or 1
    if nofcolumns == 0 then
        nofcolumns = 1
    end
    local preheight  = specification.preheight or 0
    local extra      = specification.extra or 0
    local maxheight  = specification.maxheight
    local optimal    = originalheight/nofcolumns
    local noteheight = specification.noteheight or 0

    maxheight = maxheight - noteheight

    if specification.balance ~= v_yes then
        optimal = maxheight
    end
    local topback   = 0
    local target    = optimal + extra
    local overflow  = target > maxheight - preheight
    local threshold = specification.threshold or 0
    if overflow then
        target = maxheight - preheight
    end
    if trace_state then
        report_state("cycle %s, maxheight %p, preheight %p, target %p, overflow %a, extra %p",
            cycle, maxheight, preheight , target, overflow, extra)
    end
    local results = { }
    for i=1,nofcolumns do
        results[i] = {
            head    = false,
            tail    = false,
            height  = 0,
            depth   = 0,
            inserts = { },
            delta   = 0,
            back    = 0,
        }
    end

    local column      = 1
    local line        = 0
    local result      = results[1]
    local lasthead    = nil
    local rest        = nil
    local lastlocked  = nil
    local lastcurrent = nil
    local lastcontent = nil
    local backtracked = false

    if trace_state then
        report_state("setting collector to column %s",column)
    end

    local function unlock(penalty)
        if lastlocked then
            if trace_state then
                report_state("penalty %s, unlocking in column %s",penalty or "-",column)
            end
            lastlocked  = nil
        end
        lastcurrent = nil
        lastcontent = nil
    end

    local function lock(penalty,current)
        if trace_state then
            report_state("penalty %s, locking in column %s",penalty,column)
        end
        lastlocked  = penalty
        lastcurrent = current or lastcurrent
        lastcontent = nil
    end

    local function backtrack(start)
        local current = start
        -- first skip over glue and penalty
        while current do
            local id = getid(current)
            if id == glue_code then
                if trace_state then
                    report_state("backtracking over %s in column %s","glue",column)
                end
                current = getprev(current)
            elseif id == penalty_code then
                if trace_state then
                    report_state("backtracking over %s in column %s","penalty",column)
                end
                current = getprev(current)
            else
                break
            end
        end
        -- then skip over content
        while current do
            local id = getid(current)
            if id == glue_code then
                if trace_state then
                    report_state("quitting at %s in column %s","glue",column)
                end
                break
            elseif id == penalty_code then
                if trace_state then
                    report_state("quitting at %s in column %s","penalty",column)
                end
                break
            else
                current = getprev(current)
            end
        end
        if not current then
            if trace_state then
                report_state("no effective backtracking in column %s",column)
            end
            current = start
        end
        return current
    end

    local function gotonext()
        if lastcurrent then
            if current ~= lastcurrent then
                if trace_state then
                    report_state("backtracking to preferred break in column %s",column)
                end
                -- todo: also remember height/depth
                current = backtrack(lastcurrent)
                backtracked = true
            end
            lastcurrent = nil
            if lastlocked then
                if trace_state then
                    report_state("unlocking in column %s",column)
                end
                lastlocked = nil
            end
        end
        if head == lasthead then
            if trace_state then
                report_state("empty column %s, needs more work",column)
            end
            rest = current
            return false, 0
        else
            lasthead = head
            result.head = head
            if current == head then
                result.tail = head
            else
                result.tail = getprev(current)
            end
            result.height = height
            result.depth  = depth
        end
        head   = current
        height = 0
        depth  = 0
        if column == nofcolumns then
            column = 0 -- nicer in trace
            rest   = head
            return false, 0
        else
            local skipped
            column = column + 1
            result = results[column]
            if trace_state then
                report_state("setting collector to column %s",column)
            end
            current, skipped = discardtopglue(current,discarded)
            if trace_detail and skipped ~= 0 then
                report_state("check > column 1, discarded %p",skipped)
            end
            head = current
            return true, skipped
        end
    end

    local function checked(advance,where,locked)
        local total   = skip + height + depth + advance
        local delta   = total - target
        local state   = "same"
        local okay    = false
        local skipped = 0
        local curcol  = column
        if delta > threshold then
            result.delta = delta
            okay, skipped = gotonext()
            if okay then
                state = "next"
            else
                state = "quit"
            end
        end
        if trace_detail then
            report_state("%-8s > column %s, delta %p, threshold %p, advance %p, total %p, target %p => %a (height %p, depth %p, skip %p)",
                where,curcol,delta,threshold,advance,total,target,state,height,depth,skip)
        end
        return state, skipped
    end

    current, skipped = discardtopglue(current,discarded)
    if trace_detail and skipped ~= 0 then
        report_state("check > column 1, discarded %p",skipped)
    end

    -- problem: when we cannot break after a list (and we only can expect same-page situations as we don't
    -- care too much about weighted breaks here) we should sort of look ahead or otherwise be able to push
    -- back inserts and so
    --
    -- ok, we could use vsplit but we don't have that one opened up yet .. maybe i should look into the c-code
    -- .. something that i try to avoid so let's experiment more before we entry dirty trick mode

    head = current

    local function process_skip(current,nxt)
        local advance = getwidth(current)
        if advance ~= 0 then
            local state, skipped = checked(advance,"glue")
            if trace_state then
                report_state("%-8s > column %s, state %a, advance %p, height %p","glue",column,state,advance,height)
                if skipped ~= 0 then
                    report_state("%-8s > column %s, discarded %p","glue",column,skipped)
                end
            end
            if state == "quit" then
                return true
            end
            height = height + depth + skip
            depth  = 0
            if advance < 0 then
                height = height + advance
                skip = 0
                if height < 0 then
                    height = 0
                end
            else
                skip = height > 0 and advance or 0
            end
            if trace_state then
                report_state("%-8s > column %s, height %p, depth %p, skip %p","glue",column,height,depth,skip)
            end
        else
            -- what else? ignore? treat as valid as usual?
        end
        if lastcontent then
            unlock()
        end
    end

    local function process_kern(current,nxt)
        local advance = getkern(current)
        if advance ~= 0 then
            local state, skipped = checked(advance,"kern")
            if trace_state then
                report_state("%-8s > column %s, state %a, advance %p, height %p, state %a","kern",column,state,advance,height)
                if skipped ~= 0 then
                    report_state("%-8s > column %s, discarded %p","kern",column,skipped)
                end
            end
            if state == "quit" then
                return true
            end
            height = height + depth + skip + advance
            depth  = 0
            skip   = 0
            if trace_state then
                report_state("%-8s > column %s, height %p, depth %p, skip %p","kern",column,height,depth,skip)
            end
        end
    end

    local function process_rule(current,nxt)
        -- simple variant of h|vlist
        local advance = getheight(current) -- + getdepth(current)
        if advance ~= 0 then
            local state, skipped = checked(advance,"rule")
            if trace_state then
                report_state("%-8s > column %s, state %a, rule, advance %p, height %p","rule",column,state,advance,inserttotal,height)
                if skipped ~= 0 then
                    report_state("%-8s > column %s, discarded %p","rule",column,skipped)
                end
            end
            if state == "quit" then
                return true
            end
            height = height + depth + skip + advance
         -- if state == "next" then
         --     height = height + nextskips
         -- else
         --     height = height + currentskips
         -- end
            depth = getdepth(current)
            skip  = 0
        end
        lastcontent = current
    end

    -- okay, here we could do some badness like magic but we want something
    -- predictable and even better: strategies .. so eventually this will
    -- become installable
    --
    -- [chapter] [penalty] [section] [penalty] [first line]

    local function process_penalty(current,nxt)
        local penalty = getpenalty(current)
        if penalty == 0 then
            unlock(penalty)
        elseif penalty == forcedbreak then
            local needed  = getattribute(current,a_checkedbreak)
            local proceed = not needed or needed == 0
            if not proceed then
                local available = target - height
                proceed = needed >= available
                if trace_state then
                    report_state("cycle: %s, column %s, available %p, needed %p, %s break",cycle,column,available,needed,proceed and "forcing" or "ignoring")
                end
            end
            if proceed then
                unlock(penalty)
                local okay, skipped = gotonext()
                if okay then
                    if trace_state then
                        report_state("cycle: %s, forced column break, same page",cycle)
                        if skipped ~= 0 then
                            report_state("%-8s > column %s, discarded %p","penalty",column,skipped)
                        end
                    end
                else
                    if trace_state then
                        report_state("cycle: %s, forced column break, next page",cycle)
                        if skipped ~= 0 then
                            report_state("%-8s > column %s, discarded %p","penalty",column,skipped)
                        end
                    end
                    return true
                end
            end
        elseif penalty < 0 then
            -- we don't care too much
            unlock(penalty)
        elseif penalty >= 10000 then
            if not lastcurrent then
                lock(penalty,current)
            elseif penalty > lastlocked then
                lock(penalty)
            end
        else
            unlock(penalty)
        end
    end

    local function process_list(current,nxt)
        local nxtid = nxt and getid(nxt)
        line = line + 1
        local inserts, insertskips, nextskips, inserttotal = nil, 0, 0, 0
        local wd, ht, dp = getwhd(current)
        local advance = ht
        local more = nxt and (nxtid == insert_code or nxtid == mark_code)
        if trace_state then
            report_state("%-8s > column %s, content: %s","line (1)",column,listtoutf(getlist(current),true,true))
        end
        if more and handlenotes then
            nxt, inserts, insertskips, nextskips, inserttotal = collectinserts(result,nxt,nxtid)
        end
        local state, skipped = checked(advance+inserttotal+insertskips,more and "line (2)" or "line only",lastlocked)
        if trace_state then
            report_state("%-8s > column %s, state %a, line %s, advance %p, insert %p, height %p","line (3)",column,state,line,advance,inserttotal,height)
            if skipped ~= 0 then
                report_state("%-8s > column %s, discarded %p","line (4)",column,skipped)
            end
        end
        if state == "quit" then
            return true
        end
     -- if state == "next" then -- only when profile
     --     local unprofiled = theprop(current).unprofiled
     --     if unprofiled then
     --         local h = unprofiled.height
     --         local s = unprofiled.strutht
     --         local t = s/2
     -- print("profiled",h,s)
     -- local snapped = theprop(current).snapped
     -- if snapped then
     --     inspect(snapped)
     -- end
     --         if h < s + t then
     --             result.back = - (h - s)
     --             advance     = s
     --         end
     --     end
     -- end
        height = height + depth + skip + advance + inserttotal
        if state == "next" then
            height = height + nextskips
        else
            height = height + insertskips
        end
        depth = dp
        skip  = 0
        if inserts then
            -- so we already collect them ... makes backtracking tricky ... alternatively
            -- we can do that in a separate loop ... no big deal either
            appendinserts(result.inserts,inserts)
        end
        if trace_state then
            report_state("%-8s > column %s, height %p, depth %p, skip %p","line (5)",column,height,depth,skip)
        end
        lastcontent = current
    end

    while current do

        local id  = getid(current)
        local nxt = getnext(current)

        backtracked = false

        if id == hlist_code or id == vlist_code then
            if process_list(current,nxt) then break end
        elseif id == glue_code then
            if process_skip(current,nxt) then break end
        elseif id == kern_code then
            if process_kern(current,nxt) then break end
        elseif id == penalty_code then
            if process_penalty(current,nxt) then break end
        elseif id == rule_code then
            if process_rule(current,nxt) then break end
        else
            -- skip inserts and such
        end

        if backtracked then
            nxt = current
        end

        if nxt then
            current = nxt
        elseif head == lasthead then
            -- to be checked but break needed as otherwise we have a loop
            if trace_state then
                report_state("quit as head is lasthead")
            end
            break
        else
            local r = results[column]
            r.head   = head
            r.tail   = current
            r.height = height
            r.depth  = depth
            break
        end
    end

    if not current then
        if trace_state then
            report_state("nothing left")
        end
        -- needs well defined case
     -- rest = nil
    elseif rest == lasthead then
        if trace_state then
            report_state("rest equals lasthead")
        end
        -- test case: x\index{AB} \index{AA}x \blank \placeindex
        -- makes line disappear: rest = nil
    end

    if stripbottom then
        local height = stripbottomglue(results,discarded)
        if height > 0 then
            target = height
        end
    end

    specification.results        = results
    specification.height         = target
    specification.originalheight = originalheight
    specification.originalwidth  = originalwidth
    specification.originalhead   = originalhead
    specification.targetheight   = target or 0
    specification.rest           = rest
    specification.overflow       = overflow
    specification.discarded      = discarded

    setlist(getbox(specification.box))

    return specification
end

local function finalize(result)
    if result then
        local results  = result.results
        local columns  = result.nofcolumns
        local maxtotal = 0
        for i=1,columns do
            local r = results[i]
            local h = r.head
            if h then
                setprev(h)
                if r.back then
                    local k = new_glue(r.back)
                    setlink(k,h)
                    h = k
                    r.head = h
                end
                local t = r.tail
                if t then
                    setnext(t)
                else
                    setnext(h)
                    r.tail = h
                end
                for c, list in next, r.inserts do
                    local t = { }
                    for i=1,#list do
                        local l = list[i]
                        local h = new_hlist()
                        local g = getlist(l)
                        t[i] = h
                        setlist(h,g)
                        local ht = getheight(l)
                        local dp = getdepth(l)
                        local wd = getwidth(g)
                        setwhd(h,wd,ht,dp)
                        setlist(l)
                    end
                    setprev(t[1])  -- needs checking
                    setnext(t[#t]) -- needs checking
                    r.inserts[c] = t
                end
            end
            local total = r.height + r.depth
            if total > maxtotal then
                maxtotal = total
            end
            r.total = total
        end
        result.maxtotal = maxtotal
        for i=1,columns do
            local r = results[i]
            r.extra = maxtotal - r.total
        end
    end
end

local splitruns = 0

local function report_deltas(result,str)
    local t = { }
    for i=1,result.nofcolumns do
        t[#t+1] = points(result.results[i].delta or 0)
    end
    report_state("%s, cycles %s, deltas % | t",str,result.cycle or 1,t)
end

-- local function xxcollectinserts(h)
--     local skips, total, order = 0, 0, 0
--     print(h)
--     if h then
-- h = getlist(h)
-- for n in traverse(h) do
--     print(tonode(n))
-- end
--         for n in traverse_id(insert_code,h) do
--             order = order + 1
--             total = total + getheight(n)
--             skips = skips + structures.notes.check_spacing(getsubtype(n),order)
--         end
--     end
--     return skips, total
-- end

local function setsplit(specification)
    splitruns = splitruns + 1
    if trace_state then
        report_state("split run %s",splitruns)
    end
    local result = preparesplit(specification)
    if result then
        if result.overflow then
            if trace_state then
                report_deltas(result,"overflow")
            end
            -- we might have some rest
        elseif result.rest and specification.balance == v_yes then
            local step = specification.step or 65536*2
            local cycle = 1
            local cycles = specification.cycles or 100
            while result.rest and cycle <= cycles do
                specification.extra = cycle * step
                result = preparesplit(specification) or result
                if trace_state then
                    report_state("cycle: %s.%s, original height %p, total height %p",
                        splitruns,cycle,result.originalheight,result.nofcolumns*result.targetheight)
                end
                cycle = cycle + 1
                specification.cycle = cycle
            end
            if cycle > cycles then
                report_deltas(result,"too many balancing cycles")
            elseif trace_state then
                report_deltas(result,"balanced")
            end
        elseif trace_state then
            report_deltas(result,"done")
        end
        return result
    elseif trace_state then
        report_state("no result")
    end
end

local function getsplit(result,n)
    if not result then
        report_state("flush, column %s, no result",n)
        return
    end
    local r = result.results[n]
    if not r then
        report_state("flush, column %s, empty",n)
    end
    local h = r.head
    if not h then
        return new_glue(result.originalwidth)
    end

    setprev(h) -- move up
    local strutht    = result.strutht
    local strutdp    = result.strutdp
    local lineheight = strutht + strutdp
    local isglobal   = result.alternative == v_global

    local v = new_vlist()
    setlist(v,h)

 -- local v = vpack(h,"exactly",height)

    if isglobal then -- option
        result.height = result.maxheight
    end

    local ht = 0
    local dp = 0
    local wd = result.originalwidth

    local grid         = result.grid
    local internalgrid = result.internalgrid
    local httolerance  = .25
    local dptolerance  = .50
    local lineheight   = internalgrid == v_halfline and lineheight/2 or lineheight

    local function amount(r,s,t)
        local l = ceil((r-t)/lineheight)
        local a = lineheight * l
        if a > s then
            return a - s
        else
            return s
        end
    end
    if grid then
        -- print(n,result.maxtotal,r.total,r.extra)
        if isglobal then
            local rh = r.height
         -- ht = (lineheight * ceil(result.height/lineheight) - strutdp
            ht = amount(rh,strutdp,0)
            dp = strutdp
        else
            -- natural dimensions
            local rh = r.height
            local rd = r.depth
            if rh > ht then
                ht = amount(rh,strutdp,httolerance*strutht)
            end
            if rd > dp then
                dp = amount(rd,strutht,dptolerance*strutdp)
            end
            -- forced dimensions
            local rh = result.height or 0
            local rd = result.depth or 0
            if rh > ht then
                ht = amount(rh,strutdp,httolerance*strutht)
            end
            if rd > dp then
                dp = amount(rd,strutht,dptolerance*strutdp)
            end
            -- always one line at least
            if ht < strutht then
                ht = strutht
            end
            if dp < strutdp then
                dp = strutdp
            end
        end
    else
        ht = result.height
        dp = result.depth
    end

    setwhd(v,wd,ht,dp)

    if trace_state then
        local id = getid(h)
        if id == hlist_code then
            report_state("flush, column %s, grid %a, width %p, height %p, depth %p, %s: %s",n,grid,wd,ht,dp,"top line",listtoutf(getlist(h)))
        else
            report_state("flush, column %s, grid %a, width %p, height %p, depth %p, %s: %s",n,grid,wd,ht,dp,"head node",nodecodes[id])
        end
    end

    for c, list in next, r.inserts do
        local l = concatnodes(list)
        for i=1,#list-1 do
            setdepth(list[i],0)
        end
        local b = vpack(l) -- multiple arguments, todo: fastvpack
     -- setbox("global",c,b)
        setbox(c,b)
        r.inserts[c] = nil
    end

    return v
end

local function getrest(result)
    local rest = result and result.rest
    result.rest = nil -- to be sure
    return rest
end

local function getlist(result)
    local originalhead = result and result.originalhead
    result.originalhead = nil -- to be sure
    return originalhead
end

local function cleanup(result)
    local discarded = result.discarded
    for i=1,#discarded do
        flushnode(discarded[i])
    end
    result.discarded = { }
end

mixedcolumns.setsplit = setsplit
mixedcolumns.getsplit = getsplit
mixedcolumns.finalize = finalize
mixedcolumns.getrest  = getrest
mixedcolumns.getlist  = getlist
mixedcolumns.cleanup  = cleanup

-- interface --

local result

implement {
    name      = "mixsetsplit",
    actions   = function(specification)
        if result then
            for k, v in next, specification do
                result[k] = v
            end
            result = setsplit(result)
        else
            result = setsplit(specification)
        end
    end,
    arguments = {
        {
           { "box", "integer" },
           { "nofcolumns", "integer" },
           { "maxheight", "dimen" },
           { "noteheight", "dimen" },
           { "step", "dimen" },
           { "cycles", "integer" },
           { "preheight", "dimen" },
           { "prebox", "integer" },
           { "strutht", "dimen" },
           { "strutdp", "dimen" },
           { "threshold", "dimen" },
           { "splitmethod" },
           { "balance" },
           { "alternative" },
           { "internalgrid" },
           { "grid", "boolean" },
           { "notes", "boolean" },
        }
    }
}

implement {
    name      = "mixgetsplit",
    arguments = "integer",
    actions   = function(n)
        if result then
            context(tonode(getsplit(result,n)))
        end
    end,
}

implement {
    name    = "mixfinalize",
    actions = function()
        if result then
            finalize(result)
        end
    end
}

implement {
    name    = "mixflushrest",
    actions = function()
        if result then
            context(tonode(getrest(result)))
        end
    end
}

implement {
    name = "mixflushlist",
    actions = function()
        if result then
            context(tonode(getlist(result)))
        end
    end
}

implement {
    name    = "mixstate",
    actions = function()
        context(result and result.rest and 1 or 0)
    end
}

implement {
    name = "mixcleanup",
    actions = function()
        if result then
            cleanup(result)
            result = nil
        end
    end
}