summaryrefslogtreecommitdiff
path: root/Master/texmf-dist/source/latex/l3experimental/xgalley/xgalley.dtx
blob: 92368b98a7eb60b316ff81ebd9372f1b3e758c26 (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
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
% \iffalse
%
%% File: xgalley.dtx Copyright (C) 1999-2001, 2004-2009 Frank Mittelbach
%%                             (C) 2010-2012,2014,2016-2018 The LaTeX3 Project
%
% It may be distributed and/or modified under the conditions of the
% LaTeX Project Public License (LPPL), either version 1.3c of this
% license or (at your option) any later version.  The latest version
% of this license is in the file
%
%    https://www.latex-project.org/lppl.txt
%
% This file is part of the "l3experimental bundle" (The Work in LPPL)
% and all files in that bundle must be distributed together.
%
% -----------------------------------------------------------------------
%
% The development version of the bundle can be found at
%
%    https://github.com/latex3/latex3
%
% for those people who are interested.
%
%<*driver|package>
\RequirePackage{xparse}
%</driver|package>
%<*driver>
\documentclass[full]{l3doc}
\begin{document}
  \DocInput{\jobname.dtx}
\end{document}
%</driver>
% \fi
%
% \title{^^A
%   The \textsf{xgalley} package\\ Galley^^A
% }
%
% \author{^^A
%  The \LaTeX3 Project\thanks
%    {^^A
%      E-mail:
%        \href{mailto:latex-team@latex-project.org}
%          {latex-team@latex-project.org}^^A
%    }^^A
% }
%
% \date{Released 2018-11-19}
%
% \maketitle
%
% \begin{documentation}
%
% \section{Introduction}
%
% In \LaTeX3 terminology a galley is a rectangular area which receives
% text and other material filling it from top. The vertically extend of
% a galley is normally not restricted: instead certain chunks are taken
% off the top of an already partially filled galley to form columns or
% similar areas on a page. This process is typically asynchronous but
% there are ways to control or change its behaviour.
%
% Examples for galleys are \enquote{the main galley}, where the
% continuous document data gets formatted into  and from which columns
% and pages are constructed, and \enquote{vertical box galleys}, such
% as the body of a minipage environment. The latter galleys are
% typically not split after formatting, though there can be exceptions.
%
% \section{Formatting layers}
%
% The present module is mainly concerned with the formatting of text
% in galleys. The mechanism by which this is achieved uses four
% (somewhat) distinct layers, some of which can be addressed using the
% templates provided here.
%
% \subsection{Layer one: external dimensions}
%
% The bottom layer of the system is the external dimensions of the
% galley. Normally only the horizontal dimension is fixed externally,
% while the vertical (filling) dimension is unspecified. The external
% dimensions are fixed when starting a new galley, and are therefore
% not modifiable within the galley.
%
% There are no templates for setting this layer directly, although the
% external values are influenced by other parts of the system (for
% example when creating minipage environments).
%
% \subsection{Layer two: internal dimensions}
%
% The second layer is the internal dimensions of the galley: the
% \emph{measure} used for paragraph text and the position of the
% paragraph relative to the edges of the galley.
%
% This layer is normally accessed by higher-level templates
% \emph{via} the object type \texttt{measure}. Changes made using
% level two templates will often extend for large parts of a document
% (up to and including the entire document).
%
% \subsection{Layer three: paragraph shape}
%
% The third layer defines the paragraph shape within the measure as
% provided by the second layer. In the absence of any specification
% for that layer the paragraph shape used will be that of a
% rectangular area of the width of the current measure.
%
% There are some restrictions imposed on the shape of a paragraph by the
% underlying \TeX{} mechanisms. For example, cut out sections in
% paragraphs can be specified from the top of the paragraph but not from
% the bottom.
%
% \subsection{Layer four: formatting inside the paragraph}
%
% The forth layer deals with the paragraph formatting aspects such as
% hyphenation and justification within the paragraph (this is sometimes
% referred to as \enquote{\texttt{h\&j}} or \enquote{\texttt{hj}}).
%
% \section{Templates}
%
% \subsection{Layer two: internal dimensions}
%
% \begin{TemplateInterfaceDescription}{measure}
%   \TemplateArgument{}{} ^^A A hack
%   \TemplateSemantics
%   Sets the width available to typeset material within the galley.
%   The \meta{left margin} and \meta{right margin} values are used in the
%   adjustment to over-ride any given in the template. Depending upon
%   the template in use, the margins may be absolute (relative only to the
%   edges of the galley) or relative (taking account of |measure| adjustments
%   already made). The template applies to the galley from the point of
%   us forward, unless over-ridden by another use of the |measure|
%   object type.
% \end{TemplateInterfaceDescription}
%
% \begin{TemplateDescription}{measure}{absolute}
%   \TemplateKey{left-margin}{length}
%     {^^A
%       The distance from the left edge of the galley to the left edge of
%       the area for typeset material. A negative value will cause the
%       typeset material to extend beyond the edge of the galley.^^A
%     }
%     {0pt}
%   \TemplateKey{right-margin}{length}
%     {^^A
%       The distance from the right edge of the galley to the right edge of
%       the area for typeset material. A negative value will cause the
%       typeset material to extend beyond the edge of the galley.^^A
%     }
%     {0pt}
%   \TemplateSemantics
%   This template sets up the typesetting area such that typeset material
%   runs from |left-margin| away from the left edge of the galley to
%   |right-margin| away from the right edge of the galley. Both of these
%   distances are absolute, \emph{i.e.}~no account is taken of previous
%   |measure| settings. Either on or both values may be negative, in which
%   case the typeset material will protrude outside of the edges of the
%   galley.
% \end{TemplateDescription}
%
% \begin{TemplateDescription}{measure}{relative}
%   \TemplateKey{left-margin}{length}
%     {^^A
%       The distance from the previous left margin of the typeset material
%       within the galley to the new position of the left margin. A negative
%       value will cause the new margin to be \enquote{outside} of the
%       previous one, and \emph{may} cause the typeset material to
%       protrude outside of the edge of the galley.
%     }
%     {0pt}
%   \TemplateKey{right-margin}{length}
%     {^^A
%       The distance from the previous right margin of the typeset material
%       within the galley to the new position of the right margin. A negative
%       value will cause the new margin to be \enquote{outside} of the
%       previous one, and \emph{may} cause the typeset material to
%       protrude outside of the edge of the galley.
%     }
%     {0pt}
%   \TemplateSemantics
%   This template sets up the typesetting area such that it has margins
%   |left-margin| and |right-margin| within those previously set. For a
%   galley within no previous margins, this will result in margins relative
%   to the edges of the galley. Within a galley in which the |measure| has
%   already been set, using the |relative| template will indent the typeset
%   material relative to the existing margins.
%   Either on or both values may be negative, in which
%   case the typeset material may protrude outside of the edges of the
%   galley.
% \end{TemplateDescription}
%
% \subsection{Layer three: paragraph shape}
%
% \begin{TemplateInterfaceDescription}{parshape}
%   \TemplateArgument{}{}^^A A hack
%   \TemplateSemantics
%   Template of this type define any shaping of the paragraph within the
%   current measure of the galley. Thus they are used to generate
%   \enquote{special} paragraph shapes, for example placing a cutout
%   in one side of the paragraph. Typically, \texttt{parshape} templates
%   will apply in a limited sense (to a single paragraph or a defined number of
%   lines). However, \texttt{parshape} templates may also apply in an
%   \enquote{ongoing} manner.
%
%   Note that \texttt{parshape} templates do not alter any first-line
%   indent for paragraphs (or any other \enquote{in paragraph} setting).
%   Instead, they define a shape inside which the paragraph material will be
%   placed.
% \end{TemplateInterfaceDescription}
%
% \begin{TemplateDescription}{parshape}{hang}
%   \TemplateKey{indent}{length}
%     {^^A
%       The hanging indent from either the left- or right-hand margin
%       (as determined by \texttt{on-left-side}).^^A
%     }
%     {0pt}
%   \TemplateKey{on-left-side}{boolean}
%     {^^A
%       If \texttt{true}, causes the hanging indent to be on the left-hand
%       side of the paragraph.^^A
%     }
%     {true}
%   \TemplateKey{lines}{integer}
%     {The number of lines of full width before hanging begins.}
%     {1}
%  \TemplateSemantics
%  Sets the paragraph shape such that the after a number of full-width
%  lines, specified by |lines|, the paragraph is indented by the
%  |indent| from a margin. If |on-left-side| is |true| this indent will be
%  from the left-hand margin, otherwise it will be from the right. In either
%  case, the indent is relative to the edge of the current |measure| and
%  may be negative (in which case an outdent will result).
%  This template type applies only to a single paragraph.
% \end{TemplateDescription}
%
% \begin{TemplateDescription}{parshape}{initial}
%   \TemplateKey{indent}{length}
%     {^^A
%       The indent for the initial lines from either the left- or right-hand
%       margin (as determined by \texttt{on-left-side}).^^A
%     }
%     {0pt}
%   \TemplateKey{on-left-side}{boolean}
%     {^^A
%       If \texttt{true}, causes the indent to be on the left-hand
%       side of the paragraph.^^A
%     }
%     {true}
%   \TemplateKey{lines}{integer}
%     {The number of lines of indented lines before full-width line begins.}
%     {2}
%   \TemplateSemantics
%   Sets the paragraph shape such that the first |lines| lines
%   are indented by the |indent| given, before lines of full width begin.
%   If |on-left-side| is |true| this indent will be
%   from the left-hand margin, otherwise it will be from the right. In either
%   case, the indent is relative to the edge of the current |measure| and
%   may be negative (in which case an outdent will result).
%   This template type applies only to a single paragraph.
% \end{TemplateDescription}
%
% \begin{TemplateDescription}{parshape}{std}
%   \TemplateKey{}{}{}{} ^^A hack
%   \TemplateSemantics
%   Sets a rectangular paragraph shape which occupies the full width
%   specified by the |measure|. It is therefore intended as a
%   \enquote{do nothing} template for use where a paragraph shape is required
%   but where no special formatting is needed. This template type applies only
%   to a single paragraph.
% \end{TemplateDescription}
%
% \subsection{Layer four: formatting inside the paragraph}
%
% \begin{TemplateInterfaceDescription}{hyphenation}
%   \TemplateArgument{}{} ^^A Hack
%   \TemplateSemantics
%   Controls whether hyphenation is attempted within the current
%   galley. This object type may also alter the degree to which hyphenation
%   is encouraged by manipulating the underlying \TeX{} parameters. This
%   object type applies to the galley from the point of use forward.
% \end{TemplateInterfaceDescription}
%
% \begin{TemplateDescription}{hyphenation}{std}
%   \TemplateKey{enable}{boolean}
%     {Switches all hyphenation on or off.}
%     {true}
%   \TemplateKey{enable-upper-case}
%     {boolean}
%     {^^A
%       Switches hyphenation on or off for words beginning with upper case
%       letters.^^A
%     }
%     {true}
%   \TemplateKey{penalty}{choice}
%     {^^A
%       Sets the degree to which \TeX{} is discouraged from undertaking
%       hyphenation, from the choices |low|, |medium| and |high|.^^A
%     }
%     {low}
%   \TemplateSemantics
%   Determines both whether hyphenation is allowed at all, and if so to
%   what degree it is discouraged. Setting |penalty| to |high| does not
%   prevent hyphenation: this is only done if |enable| is set |false|.
% \end{TemplateDescription}
%
% \begin{TemplateInterfaceDescription}{justification}
%   \TemplateArgument{}{} ^^A Hack
%   \TemplateSemantics
%   Controls the nature of justification undertaken within the galley.
%   The template applies from the point of use forward.
% \end{TemplateInterfaceDescription}
%
% \begin{TemplateDescription}{justification}{std}
%   \TemplateKey{end-skip}{skip}
%     {The skip inserted to fill the last line of a paragraph.}
%     {0pt plus 1fil}
%   \TemplateKey{fixed-word-spacing}{boolean}
%     {^^A
%       Determines whether inter-word spacing has a stretch component (for
%       non-monospaced fonts.^^A
%     }
%     {false}
%   \TemplateKey{indent-width}{length}
%     {^^A
%       The length of the indent inserted at the start of the first line of a
%       new paragraph.^^A
%     }
%     {}
%   \TemplateKey{left-skip}{skip}
%     {^^A
%       The skip between the left margin of the galley and the left edge of a
%       paragraph.^^A
%     }
%     {0pt}
%   \TemplateKey{right-skip}{skip}
%     {^^A
%       The skip between the right margin of the galley and the right edge of a
%       paragraph.^^A
%     }
%     {0pt}
%   \TemplateKey{start-skip}{skip}
%     {^^A
%       The skip inserted in addition to |indent-width| at the start of a
%       paragraph.^^A
%     }
%     {0pt}
%   \TemplateSemantics
%   The |std| template for justification provides rubber lengths
%   at the start and end of the paragraph and at each side of the paragraph.
%   It also allows for both flexible and fixed inter-word spacing. The
%   interaction between the settings is demonstrated in the selection of
%   standard instances provided.
% \end{TemplateDescription}
%
% \begin{InstanceDescription}{justification}{justified}{std}
%   \InstanceKey{indent-width}{15pt}
%   \InstanceSemantics
%   Sets paragraphs fully-justified with the first line indented by
%   |15pt|.
% \end{InstanceDescription}
%
% \begin{InstanceDescription}{justification}{noindent}{std}
%   \InstanceKey{end-skip}{15pt plus 1fil}
%   \InstanceKey{indent-width}{0pt}
%   \InstanceSemantics
%   Sets paragraphs fully-justified with no indent for the first line. To
%   ensure that paragraphs have some visual distinction, the |end-skip| is
%   set to insert some space in all cases.
% \end{InstanceDescription}
%
% \begin{TemplateDescription}{justification}{single}
%   \TemplateKey{end-skip}{skip}
%     {The skip inserted to fill the last line of a paragraph.}
%     {0pt plus 1fil}
%   \TemplateKey{fixed-word-spacing}{boolean}
%     {^^A
%       Determines whether inter-word spacing has a stretch component (for
%       non-monospaced fonts.^^A
%     }
%     {false}
%   \TemplateKey{indent-width}{length}
%     {^^A
%       The length of the indent inserted at the start of the first line of a
%       new paragraph.^^A
%     }
%     {}
%   \TemplateKey{left-skip}{skip}
%     {^^A
%       The skip between the left margin of the galley and the left edge of a
%       paragraph.^^A
%     }
%     {0pt}
%   \TemplateKey{right-skip}{skip}
%     {^^A
%       The skip between the right margin of the galley and the right edge of a
%       paragraph.^^A
%     }
%     {0pt}
%   \TemplateKey{start-skip}{skip}
%     {^^A
%       The skip inserted in addition to |indent-width| at the start of a
%       paragraph.^^A
%     }
%     {0pt}
%   \TemplateKey{stretch-last-line}{boolean}
%     {
%       Determines whether inter-word spacing in the last line is stretched.
%       If \texttt{true}, the spacing in the last line is stretched in the
%       by the same factor as that in the penultimate line.^^A
%     }
%     {false}
%   \TemplateSemantics
%   The |single| template for justification provides rubber lengths
%   at the start and end of the paragraph and at each side of the paragraph.
%   It also allows for both flexible and fixed inter-word spacing. The
%   interaction between the settings is demonstrated in the selection of
%   standard instances provided. The template applies only to a single
%   paragraph.
% \end{TemplateDescription}
%
% \begin{InstanceDescription}[fixed-word-spacing-xxx]{justification}{ragged-left}{std}
%   \InstanceKey{end-skip}{0pt}
%   \InstanceKey{fixed-word-spacing}{true}
%   \InstanceKey{indent-width}{0pt}
%   \InstanceKey{left-skip}{0pt plus 2em}
%   \InstanceKey{right-skip}{0pt}
%   \InstanceSemantics
%   Typesets material with a ragged left margin such that hyphenation will
%   still occur and such that very short lines are discouraged. This is
%   similar to the \LaTeXe{} \pkg{ragged2e} \env{RaggedLeft} environment.
% \end{InstanceDescription}
%
% \begin{InstanceDescription}[fixed-word-spacing-xxx]{justification}{ragged-right}{std}
%   \InstanceKey{end-skip}{0pt}
%   \InstanceKey{fixed-word-spacing}{true}
%   \InstanceKey{indent-width}{0pt}
%   \InstanceKey{left-skip}{0pt}
%   \InstanceKey{right-skip}{0pt plus 2em}
%   \InstanceSemantics
%   Typesets material with a ragged right margin such that hyphenation will
%   still occur and such that very short lines are discouraged. This is
%   similar to the \LaTeXe{} \pkg{ragged2e} \env{RaggedLeft} environment.
% \end{InstanceDescription}
%
% \begin{InstanceDescription}[fixed-word-spacing-xxx]{justification}{center}{std}
%   \InstanceKey{end-skip}{0pt}
%   \InstanceKey{fixed-word-spacing}{true}
%   \InstanceKey{indent-width}{0pt}
%   \InstanceKey{left-skip}{0pt plus 1fil}
%   \InstanceKey{right-skip}{0pt plus 1fil}
%   \InstanceSemantics
%   Centres typeset material such that hyphenation is discouraged and short
%   lines are allowed.
% \end{InstanceDescription}
%
% \begin{TemplateDescription}{justification}{compound}
%   \TemplateKey{first-paragraph}{instance}
%     {Justification for the first paragraph.}
%     {}
%   \TemplateKey{other-paragraphs}{instance}
%     {Justification for the remaining paragraphs.}
%     {}
%   \TemplateSemantics
%   Here, both keys should themselves be instances of the |justification|
%   template. The |compound| template is used to set up a single
%   \enquote{non-standard} paragraph followed by \enquote{standard} ones.
%   For example, it can be used to ensure that one |noindent| paragraph is
%   then followed by |std| justification.
% \end{TemplateDescription}
%
% \begin{TemplateInterfaceDescription}{line-breaking}
%   \TemplateArgument{}{} ^^A Hack
%   \TemplateSemantics
%   Controls the line breaking attempted by \TeX{} when typesetting
%   material for the galley. This does not include whether words are
%   hyphenated, which is handled separately.
% \end{TemplateInterfaceDescription}
%
% \begin{TemplateDescription}{line-breaking}{std}
%   \TemplateKey{badness}{integer}
%      {^^A
%        Boundary that if exceeded will cause \TeX{} to report an
%        underfull line.^^A
%      }
%      {1000}
%   \TemplateKey{binop-penalty}{integer}
%      {^^A
%        Penalty charged if an inline math formula is broken at a
%        binary operator.^^A
%      }
%      {700}
%   \TemplateKey{double-hyphen-demerits}{integer}
%      {^^A
%        Extra demerit charge of two (or more) lines in succession end
%        in a hyphen.^^A
%      }
%      {10000}
%   \TemplateKey{emergency-stretch}{skip}
%      {^^A
%        Additional stretch assumed for each line if no better line breaking
%        can be found without it. This stretch is not actually added to lines,
%        so its use may result in underfull box warnings.^^A
%      }
%      {0pt}
%   \TemplateKey{final-hyphen-demerits}{integer}
%      {Extra demerit charge if the second last line is hyphenated.}
%      {5000}
%   \TemplateKey{fuzz}{length}
%      {Boundary below overfull lines are not reported.}
%      {0.1pt}
%   \TemplateKey{mismatch-demerits}{integer}
%      {^^A
%        Extra demerit charge if two visually incompatible lines follow
%        each other.^^A
%      }
%      {10000}
%   \TemplateKey{line-penalty}{integer}
%      {^^A
%        Extra penalty charged per line in the paragraph. By making
%        this penalty higher \TeX{} will try harder to produce compact
%        paragraphs.^^A
%      }
%      {10}
%   \TemplateKey{pretolerance}{integer}
%      {^^A
%        Maximum tolerance allowed for individual lines to break the
%        paragraph without attempting hyphenation.^^A
%      }
%      {100}
%   \TemplateKey{relation-penalty}{integer}
%      {^^A
%        Penalty charged if an inline math formula is broken at a
%        relational symbol.^^A
%      }
%      {500}
%   \TemplateKey{tolerance}{integer}
%      {^^A
%        Maximum tolerance allowed for individual lines when breaking a
%        paragraph while attempting hyphenation (if this limit can't be
%        met \texttt{emergency-stretch} comes into play).^^A
%      }
%      {200}
%   \TemplateSemantics
%   This is an interface to the underlying \TeX{} system for determining
%   line breaking.
% \end{TemplateDescription}
%
% \subsection{Between paragraphs}
%
% \begin{TemplateInterfaceDescription}{paragraph-breaking}
%   \TemplateArgument{}{} ^^A Hack
%   \TemplateSemantics
%   This object type determines how \TeX{} determines the behaviour when
%   the paragraph-breaking algorithm is calculating whether to break up a
%   paragraph.  Thus for example an instance of this object type may prevent
%   breaks within a paragraph, forbid widows or orphans, \emph{etc.}
% \end{TemplateInterfaceDescription}
%
% \begin{TemplateDescription}{paragraph-breaking}{std}
%   \TemplateKey{badness}{integer}
%      {^^A
%        Boundary that if exceeded will cause \TeX{} to report an
%        underfull vertical box.^^A
%      }
%      {1000}
%   \TemplateKey{broken-penalty}{integer}
%      {Penalty for page breaking after a hyphenated line.}
%      {100}
%   \TemplateKey{club-penalty}{integer}
%      {Penalty for generating a club line when page breaking.}
%      {150}
%   \TemplateKey{display-club-penalty}{integer}
%      {^^A
%        Penalty for breaking between to leave a club line after display
%        math.^^A
%      }
%      {150}
%   \TemplateKey{display-widow-penalty}{integer}
%      {^^A
%        Penalty for breaking between to leave a widow line before display
%        math.^^A
%      }
%      {150}
%   \TemplateKey{fuzz}{length}
%      {Boundary below which overfull vertical boxes are not reported.}
%      {0.1pt}
%   \TemplateKey{interline-penalty}{integer}
%      {Penalty for breaking between lines in a paragraph.}
%      {0}
%   \TemplateKey{pre-display-penalty}{integer}
%      {Penalty for breaking between immediately before display math material.}
%      {10000}
%   \TemplateKey{post-display-penalty}{integer}
%      {Penalty for breaking between immediately after display math material.}
%      {0}
%   \TemplateKey{widow-penalty}{integer}
%      {Penalty for generating a widow line when page breaking.}
%      {150}
%   \TemplateSemantics
%   This template provides an interface to the underlying \TeX{} mechanism for
%   controlling page breaking. The template applies on an ongoing basis to all
%   paragraphs after the template is used.
% \end{TemplateDescription}
%
% \begin{InstanceDescription}{paragraph-breaking}{std}{std}
%   \InstanceSemantics
%   Sets paragraphs such that they can break with widows and orphans
%   discouraged but not prevented. Breaks are possible after display math
%   material but no immediately before it.
% \end{InstanceDescription}
%
% \begin{InstanceDescription}[post-display-penalty-xxxx]{paragraph-breaking}{nobreak}{std}
%   \InstanceKey{interline-penalty}{10000}
%   \InstanceKey{post-display-penalty}{10000}
%   \InstanceSemantics
%   Sets paragraphs such that they cannot be broken at all (as far as is
%   possible in \TeX{}).
% \end{InstanceDescription}
%
% \begin{InstanceDescription}[post-display-penalty-xxxx]{paragraph-breaking}{nolone}{std}
%   \InstanceKey{club-penalty}{10000}
%   \InstanceKey{display-widow-penalty}{10000}
%   \InstanceKey{widow-penalty}{10000}
%   \InstanceSemantics
%   Sets paragraphs such that they cannot be broken to leave a club or
%   widow line (as far as is possible in \TeX{}).
% \end{InstanceDescription}
%
% \begin{TemplateDescription}{paragraph-breaking}{single}
%   \TemplateKey{badness}{integer}
%      {^^A
%        Boundary that if exceeded will cause \TeX{} to report an
%        underfull vertical box.^^A
%      }
%      {\meta{none}}
%   \TemplateKey{broken-penalty}{integer}
%      {Penalty for page breaking after a hyphenated line.}
%      {\meta{none}}
%   \TemplateKey{club-penalty}{integer}
%      {Penalty for generating a club line when page breaking.}
%      {\meta{none}}
%   \TemplateKey{display-club-penalty}{integer}
%      {^^A
%        Penalty for breaking between to leave a club line after display
%        math.^^A
%      }
%      {\meta{none}}
%   \TemplateKey{display-widow-penalty}{integer}
%      {^^A
%        Penalty for breaking between to leave a widow line before display
%        math.^^A
%      }
%      {\meta{none}}
%   \TemplateKey{fuzz}{length}
%      {Boundary below which overfull vertical boxes are not reported.}
%      {\meta{none}}
%   \TemplateKey{interline-penalty}{integer}
%      {Penalty for breaking between lines in a paragraph.}
%      {\meta{none}}
%   \TemplateKey{pre-display-penalty}{integer}
%      {Penalty for breaking between immediately before display math material.}
%      {\meta{none}}
%   \TemplateKey{post-display-penalty}{integer}
%      {Penalty for breaking between immediately after display math material.}
%      {\meta{none}}
%   \TemplateKey{widow-penalty}{integer}
%      {Penalty for generating a widow line when page breaking.}
%      {\meta{none}}
%   \TemplateSemantics
%   This template provides an interface to the underlying \TeX{} mechanism for
%   controlling page breaking. The template applies only to the next paragraph,
%   and can thus be used to achieve effects such as non-breaking paragraphs.
% \end{TemplateDescription}
%
% \begin{InstanceDescription}{paragraph-breaking}{single-std}{single}
%   \InstanceSemantics
%   Sets the next paragraph such that it can break with widows and orphans
%   discouraged but not prevented. Breaks are possible after display math
%   material but no immediately before it.
% \end{InstanceDescription}
%
% \begin{InstanceDescription}[post-display-penalty-xxx]{paragraph-breaking}{single-nobreak}{single}
%   \InstanceKey{interline-penalty}{10000}
%   \InstanceKey{post-display-penalty}{10000}
%   \InstanceSemantics
%   Sets the next paragraph such that it cannot be broken at all (as far as is
%   possible in \TeX{}).
% \end{InstanceDescription}
%
% \begin{InstanceDescription}[display-club-penalty-xxx]{paragraph-breaking}{single-noclub}{single}
%   \InstanceKey{club-penalty}{10000}
%   \InstanceKey{display-club-penalty}{10000}
%   \InstanceSemantics
%   Sets the next paragraph such that it cannot be broken to leave a club
%   line (as far as is possible in \TeX{}).
% \end{InstanceDescription}
%
% \begin{InstanceDescription}[display-widow-penalty-xxx]{paragraph-breaking}{single-nolone}{single}
%   \InstanceKey{club-penalty}{10000}
%   \InstanceKey{display-club-penalty}{10000}
%   \InstanceKey{display-widow-penalty}{10000}
%   \InstanceKey{widow-penalty}{10000}
%   \InstanceSemantics
%   Sets the next paragraph such that it cannot be broken to leave a club or
%   widow line (as far as is possible in \TeX{}).
% \end{InstanceDescription}
%
% \begin{InstanceDescription}[display-widow-penalty-xxx]{paragraph-breaking}{single-nowidow}{single}
%   \InstanceKey{display-widow-penalty}{10000}
%   \InstanceKey{widow-penalty}{10000}
%   \InstanceSemantics
%   Sets the next paragraph such that it cannot be broken to leave a
%   widow line (as far as is possible in \TeX{}).
% \end{InstanceDescription}
%
% \end{documentation}
%
% \begin{implementation}
%
% \section{\pkg{xgalley} Implementation}
%
% This module provided a template-level interface for the \LaTeX3 galley. As
% such, the code here is intended for design-level changes which apply to
% large blocks. The variables provided are therefore used only for supporting
% the templates, while any documented interfaces are in \pkg{l3galley}.
%
%    \begin{macrocode}
%<*package>
%    \end{macrocode}
%
%    \begin{macrocode}
%<@@=galley>
%    \end{macrocode}
%
%    \begin{macrocode}
\ProvidesExplPackage{xgalley}{2018-11-19}{}
  {L3 Experimental galley}
\RequirePackage{xparse,xtemplate,l3galley}
%    \end{macrocode}
%
% \subsection{Variables}
%
% \begin{variable}{\l_@@_tmpa_clist, \l_@@_tmpb_clist}
%   Scratch space.
%    \begin{macrocode}
\clist_new:N \l_@@_tmpa_clist
\clist_new:N \l_@@_tmpb_clist
%    \end{macrocode}
% \end{variable}
%
% \subsection{Layer two: internal dimensions}
%
% There is a single object type for level two, the \texttt{measure} for
% the text in the galley. There are no arguments, as the measure is a design
% concept.
%    \begin{macrocode}
\DeclareObjectType { measure } { 0 }
%    \end{macrocode}
%
% There are two templates for galley measures: absolute and relative.
% Both use the same interface.
%    \begin{macrocode}
\DeclareTemplateInterface { measure } { absolute } { 0 }
  {
    left-margin  : length = 0pt ,
    right-margin : length = 0pt
  }
\DeclareTemplateInterface { measure } { relative } { 0 }
  {
    left-margin  : length = 0pt ,
    right-margin : length = 0pt
  }
%    \end{macrocode}
%
% \begin{variable}{\l_@@_left_margin_dim, \l_@@_right_margin_dim}
%   In the \texttt{absolute} template, the two margin values are relative
%   to the edges of the galley. This means that any existing offset or
%   line-length adjustment are ignored.
%    \begin{macrocode}
%<*package>
\cs_new_eq:NN \l_@@_left_margin_dim \leftmargin
%</package>
%<*package>
\cs_new_eq:NN \l_@@_right_margin_dim \rightmargin
%</package>
\DeclareTemplateCode { measure } { absolute } { 0 }
  {
    left-margin  = \l_@@_left_margin_dim  ,
    right-margin = \l_@@_right_margin_dim
  }
  {
    \AssignTemplateKeys
    \galley_margins_set_absolute:nn \l_@@_left_margin_dim
      \l_@@_right_margin_dim
  }
%    \end{macrocode}
% On the other hand, the \texttt{relative} template works relative to
% the current indentation at both sides.
%    \begin{macrocode}
\DeclareTemplateCode { measure } { relative } { 0 }
  {
    left-margin  = \l_@@_left_margin_dim  ,
    right-margin = \l_@@_right_margin_dim
  }
  {
    \AssignTemplateKeys
    \galley_margins_set_relative:nn \l_@@_left_margin_dim
      \l_@@_right_margin_dim
  }
%    \end{macrocode}
% \end{variable}
%
% \subsection{Layer three: paragraph shape}
%
% The object type \texttt{parshape} is a somewhat extended interface
% to the \TeX{} \cs{tex_parshape:D} primitive. As with the \texttt{measure},
% the \texttt{parshape} template has no arguments as it is essentially a
% design-oriented concept.
%    \begin{macrocode}
\DeclareObjectType { parshape } { 0 }
%    \end{macrocode}
%
% There are two standard templates for paragraph shapes which do
% something, both with the same interface. The \texttt{hang} template
% provides one or more standard lines followed by a hanging paragraph,
% while the \texttt{initial} template cuts out a space at the start of
% the paragraph.
%    \begin{macrocode}
\DeclareTemplateInterface { parshape } { hang } { 0 }
  {
    indent       : length  = 0pt  ,
    on-left-side : boolean = true ,
    lines        : integer = 1
  }
\DeclareTemplateInterface { parshape } { initial } { 0 }
 {
    indent       : length  = 0pt  ,
    on-left-side : boolean = true ,
    lines        : integer = 2
  }
%    \end{macrocode}
% \begin{variable}{\l_@@_parshape_indent_dim}
% \begin{variable}{\l_@@_parshape_on_left_bool}
% \begin{variable}{\l_@@_parshape_lines_int}
%   Both of the templates are implemented as special cases of the more
%   general function defined earlier.
%    \begin{macrocode}
\DeclareTemplateCode { parshape } { hang } { 0 }
  {
    indent       = \l_@@_parshape_indent_dim   ,
    on-left-side = \l_@@_parshape_on_left_bool ,
    lines        = \l_@@_parshape_lines_int
  }
  {
    \AssignTemplateKeys
    \bool_if:NTF \l_@@_parshape_on_left_bool
      {
        \galley_parshape_set_single:nVVN
          \l_@@_parshape_lines_int
          \l_@@_parshape_indent_dim
          \c_zero_dim
          \c_false_bool
      }
      {
        \galley_parshape_set_single:nVVN
          \l_@@_parshape_lines_int
          \c_zero_dim
          \l_@@_parshape_indent_dim
          \c_false_bool
      }
  }
\DeclareTemplateCode { parshape } { initial } { 0 }
  {
    indent       = \l_@@_parshape_indent_dim   ,
    on-left-side = \l_@@_parshape_on_left_bool ,
    lines        = \l_@@_parshape_lines_int
  }
  {
    \AssignTemplateKeys
    \clist_clear:N \l_@@_tmpa_clist
    \clist_clear:N \l_@@_tmpb_clist
    \prg_replicate:nn { \l_@@_parshape_lines_int }
      {
        \clist_put_right:Nn \l_@@_tmpa_clist
          { \l_@@_parshape_indent_dim }
        \clist_put_right:Nn \l_@@_tmpb_clist
          { \c_zero_dim }
      }
    \bool_if:NTF \l_@@_parshape_on_left_bool
      {
        \galley_parshape_set_single:nVVN
          { 0 }
          \l_@@_tmpa_clist
          \l_@@_tmpb_clist
          \c_true_bool
      }
      {
        \galley_parshape_set_single:nVVN
          { 0 }
          \l_@@_tmpb_clist
          \l_@@_tmpa_clist
          \c_true_bool
      }
  }
%    \end{macrocode}
% \end{variable}
% \end{variable}
% \end{variable}
%
% There is also a \enquote{do nothing} paragraph shape for cases where
% a template is needed but no action is desirable.
%    \begin{macrocode}
\DeclareTemplateInterface { parshape } { std } { 0 } { }
\DeclareTemplateCode { parshape } { std } { 0 } { } { }
%    \end{macrocode}
%
% \subsection{Layer four: formatting inside the paragraph}
%
% The first type of object within a paragraph is the hyphenation. This
% object needs no arguments.
%    \begin{macrocode}
\DeclareObjectType { hyphenation } { 0 }
%    \end{macrocode}
%
% There is only hyphenation template as standard. This provides a
% semi-flexible interface to the underlying \TeX{} methods. (The detail
% is therefore hidden within the implementation phase.)
%    \begin{macrocode}
\DeclareTemplateInterface { hyphenation } { std } { 0 }
  {
    enable            : boolean                        = true ,
    enable-upper-case : boolean                        = true ,
    penalty           : choice { low , medium , high } = low
  }
%    \end{macrocode}
% The implementation for hyphenation mainly sets low-level values.
% The minimum number of characters after a hyphen is set directly,
% whereas the number before is not. This is so that
% \cs{tex_lefthyphenmin:D} can also be used to completely prevent
% hyphenation.
%    \begin{macrocode}
\DeclareTemplateCode { hyphenation } { std } { 0 }
  {
    enable            = \l_galley_hyphen_enable_bool    ,
    enable-upper-case = \l_galley_hyphen_uppercase_bool ,
    penalty           =
      {
        low    =
          {
            \int_set:Nn \tex_hyphenpenalty:D   { 51 }
            \int_set:Nn \tex_exhyphenpenalty:D { 51 }
          } ,
        medium =
          {
            \int_set:Nn \tex_hyphenpenalty:D   { 151 }
            \int_set:Nn \tex_exhyphenpenalty:D { 151 }
          } ,
        high   =
          {
            \int_set:Nn \tex_hyphenpenalty:D   { 301 }
            \int_set:Nn \tex_exhyphenpenalty:D { 301 }
          } ,
      }
  }
  {
    \AssignTemplateKeys
    \int_set:Nn \tex_lefthyphenmin:D
      {
        \bool_if:NTF \l_galley_hyphen_enable_bool
          { \l_galley_hyphen_left_int  }
          { 63 }
      }
    \int_set:Nn \tex_uchyph:D
      {
        \bool_if:NTF \l_galley_hyphen_uppercase_bool
          { 1 }
          { 0 }
      }
  }
%    \end{macrocode}
% At this stage, the default hyphenation character should be set and
% hyphenation should be enabled.
%    \begin{macrocode}
\UseTemplate { hyphenation } { std } { }
\tex_defaulthyphenchar:D 45 \scan_stop:
%    \end{macrocode}
%
% \begin{variable}{\l_@@_justification_other_tl}
%   Used for the reset system for justification: using this token list means
%   that there is no need to remove anything from
%   \cs{g_galley_restore_running_tl}.
%    \begin{macrocode}
\tl_new:N \l_@@_justification_other_tl
%    \end{macrocode}
% \end{variable}
%
% The second level four object is the justification, which again
% takes no arguments.
%    \begin{macrocode}
\DeclareObjectType { justification } { 0 }
%    \end{macrocode}
% There are two templates here with the same interface: the standard one
% to apply from this point onward, and one which applies only to a single
% paragraph.
%    \begin{macrocode}
\DeclareTemplateInterface { justification } { std } { 0 }
  {
    end-skip           : skip    = 0pt plus 1fil ,
    fixed-word-spacing : boolean = false         ,
    indent-width       : length                  ,
    left-skip          : skip    = 0pt           ,
    right-skip         : skip    = 0pt           ,
    start-skip         : skip    = 0pt           ,
    stretch-last-line  : boolean = false
  }
\DeclareTemplateInterface { justification } { single } { 0 }
  {
    end-skip           : skip    = 0pt plus 1fil ,
    fixed-word-spacing : boolean = false         ,
    indent-width       : length                  ,
    left-skip          : skip    = 0pt           ,
    right-skip         : skip    = 0pt           ,
    start-skip         : skip    = 0pt           ,
    stretch-last-line  : boolean = false
  }
%    \end{macrocode}
% \begin{variable}{\l_galley_fixed_spacing_bool}
%   The implementation here is pretty simple as almost everything that
%   goes on is a simple case of saving the settings, which are then
%   applied either by \TeX{} itself or the rest of the galley system.
%    \begin{macrocode}
\DeclareTemplateCode { justification } { std } { 0 }
  {
    end-skip           = \l_galley_par_end_skip          ,
    fixed-word-spacing = \l_galley_fixed_spacing_bool    ,
    indent-width       = \l_galley_par_indent_dim        ,
    left-skip          = \l_galley_line_left_skip        ,
    right-skip         = \l_galley_line_right_skip       ,
    start-skip         = \l_galley_par_begin_skip        ,
    stretch-last-line  = \l_galley_par_stretch_last_bool
  }
  {
    \AssignTemplateKeys
    \tl_clear:N \l_@@_justification_other_tl
    \galley_interword_spacing_set:N \l_galley_fixed_spacing_bool
    \bool_if:NTF \l_galley_par_stretch_last_bool
      { \int_set:Nn \l_galley_last_line_fit_int { 1000 } }
      { \int_zero:N \l_galley_last_line_fit_int }
    \skip_set:Nn \@rightskip { \l_galley_line_right_skip }
  }
%    \end{macrocode}
% \end{variable}
% To deal with a single paragraph, the approach used is to save the current
% settings to the paragraph-reset code, then to assign the template in the
% same way as for the |std| template.
%    \begin{macrocode}
\DeclareTemplateCode { justification } { single } { 0 }
  {
    end-skip           = \l_galley_par_end_skip         ,
    fixed-word-spacing = \l_galley_fixed_spacing_bool   ,
    indent-width       = \l_galley_par_indent_dim       ,
    left-skip          = \l_galley_line_left_skip       ,
    right-skip         = \l_galley_line_right_skip      ,
    start-skip         = \l_galley_par_begin_skip       ,
    stretch-last-line  = \l_galley_par_stretch_last_bool
  }
  {
    \tl_put_left:Nx \l_@@_justification_other_tl
      {
        \skip_set:Nn \exp_not:N \l_galley_par_end_skip
          { \skip_use:N \l_galley_par_end_skip }
        \bool_if:NTF \l_galley_fixed_spacing_bool
          { \bool_set_true:N  \exp_not:N \l_galley_fixed_spacing_bool }
          { \bool_set_false:N \exp_not:N \l_galley_fixed_spacing_bool }
        \galley_interword_spacing_set:N
          \exp_not:N \l_galley_fixed_spacing_bool
        \dim_set:Nn \exp_not:N \l_galley_par_indent_dim
          { \dim_use:N \l_galley_par_indent_dim  }
        \skip_set:Nn \l_galley_line_left_skip
          { \skip_use:N \l_galley_line_left_skip }
        \skip_set:Nn \exp_not:N \l_galley_line_right_skip
          { \skip_use:N \l_galley_line_right_skip }
        \skip_set:Nn \exp_not:N \l_galley_par_begin_skip
          { \skip_use:N \l_galley_par_begin_skip }
        \int_set:Nn \exp_not:N \l_galley_last_line_fit_int
          { \int_use:N \l_galley_last_line_fit_int }
        \skip_set:Nn \exp_not:N \@rightskip
          { \skip_use:N \l_galley_line_right_skip }
      }
    \tl_gput_right:Nn \g_galley_restore_running_tl
      { \l_@@_justification_other_tl }
    \AssignTemplateKeys
    \galley_interword_spacing_set:N \l_galley_fixed_spacing_bool
    \bool_if:NTF \l_galley_par_stretch_last_bool
      { \int_set:Nn \l_galley_last_line_fit_int { 1000 } }
      { \int_zero:N \l_galley_last_line_fit_int }
    \skip_set:Nn \@rightskip { \l_galley_line_right_skip }
  }
%    \end{macrocode}
% The standard instance for justification is very simple to set up as
% the default values for the template are set up for exactly this case.
% The advantage of this scheme is that at a design level altering the
% indent used for justified paragraphs is very easy to do. As this is
% the standard template for all \LaTeX3 documents, it is applied here.
%    \begin{macrocode}
\DeclareInstance { justification } { justified } { std }
  { indent-width = 15pt }
\UseInstance { justification } { justified }
%    \end{macrocode}
% The instance for no indentation at all but with justified text is
% intended for layouts which leave white space between paragraphs. With
% no indentation, some space has to be included at the end of each
% paragraph. This is set up to mirror the indent that has been removed.
%    \begin{macrocode}
\DeclareInstance { justification } { noindent } { std }
  {
    end-skip     = 15pt plus 1fil ,
    indent-width = 0pt
  }
%    \end{macrocode}
% The other standard justification schemes are for text which ragged.
% The settings here are taken from the \LaTeXe{}
% \pkg{ragged2e} package, as they maintain a reasonable appearance by
% ensuring that \TeX{} will not be too tolerant of very short lines.
% To keep the design clear here, no default values are relied on even
% though this would make the instance declarations shorter.
%    \begin{macrocode}
\DeclareInstance { justification } { ragged-left } { std }
  {
    end-skip           = 0pt           ,
    fixed-word-spacing = true          ,
    indent-width       = 0pt           ,
    left-skip          = 0pt plus 2em  ,
    right-skip         = 0pt
  }
\DeclareInstance { justification } { ragged-right } { std }
  {
    end-skip           = 0pt plus 1fil ,
    fixed-word-spacing = true          ,
    indent-width       = 0pt           ,
    left-skip          = 0pt           ,
    right-skip         = 0pt plus 2em
  }
%    \end{macrocode}
% The \texttt{center} instance is used to center material with minimal
% hyphenation.
%    \begin{macrocode}
\DeclareInstance { justification } { center } { std }
  {
    end-skip           = 0pt           ,
    fixed-word-spacing = true          ,
    indent-width       = 0pt           ,
    left-skip          = 0pt plus 1fil ,
    right-skip         = 0pt plus 1fil
  }
%    \end{macrocode}
%
% \begin{macro}{\@@_justification_first:, \@@_justification_other:}
%   A second form of justification template is the case where the first
%   paragraph is different from all of the others. This is set up by
%   getting the justification to reset itself after the first paragraph.
%   The code built into the \texttt{std} version will ensure that any
%   subsequent template use will over-ride the setting here correctly.
%    \begin{macrocode}
\DeclareTemplateInterface { justification } { compound } { 0 }
  {
    first-paragraph  : instance { justification } ,
    other-paragraphs : instance { justification }
  }
\DeclareTemplateCode { justification } { compound } { 0 }
  {
    first-paragraph  = \@@_justification_first: ,
    other-paragraphs = \@@_justification_other:
  }
  {
    \AssignTemplateKeys
    \@@_justification_first:
    \tl_set:Nn \l_@@_justification_other_tl
      { \@@_justification_other: }
    \tl_gput_right:Nn \g_galley_restore_running_tl
      { \l_@@_justification_other_tl }
  }
%    \end{macrocode}
% \end{macro}
%
% How \TeX{} breaks text into lines is influences by a number of
% parameters, most of which are not actually likely to change. These
% work with the \texttt{hyphenation} but are independent of whether
% any hyphenation is actually active. The math values here could be
% set up as a separate template, but in practice this seems likely to
% be overkill.
%    \begin{macrocode}
\DeclareObjectType { line-breaking } { 0 }
%    \end{macrocode}
% The only template provided for line breaking is a simple interface to
% \TeX{}'s parameters. There is not really much that can be added to this:
% after all, the way that penalties work is more or less arbitrary but
% works well! The default values given here are intended to be sensible
% for a lot of cases.
%    \begin{macrocode}
\DeclareTemplateInterface { line-breaking } { std } { 0 }
  {
    badness                : integer = 1000  ,
    binop-penalty          : integer = 700   ,
    double-hyphen-demerits : integer = 10000 ,
    emergency-stretch      : skip    = 0pt   ,
    final-hyphen-demerits  : integer = 5000  ,
    fuzz                   : length  = 0.1pt ,
    line-penalty           : integer = 10    ,
    mismatch-demerits      : integer = 10000 ,
    pretolerance           : integer = 100   ,
    relation-penalty       : integer = 500   ,
    tolerance              : integer = 200
  }
\DeclareTemplateCode{ line-breaking } { std } { 0 }
  {
    badness                = \l_galley_linebreak_badness_int      ,
    binop-penalty          = \l_@@_binop_penalty_int          ,
    double-hyphen-demerits = \l_galley_double_hyphen_demerits_int ,
    emergency-stretch      = \l_galley_emergency_stretch_skip     ,
    final-hyphen-demerits  = \l_galley_final_hyphen_demerits_int  ,
    fuzz                   = \l_galley_linebreak_fuzz_dim         ,
    line-penalty           = \l_@@_linebreak_penalty_int      ,
    mismatch-demerits      = \l_galley_mismatch_demerits_int      ,
    pretolerance           = \l_galley_linebreak_pretolerance_int ,
    relation-penalty       = \l_@@_relation_penalty_int       ,
    tolerance              = \l_galley_linebreak_tolerance_int
  }
  { \AssignTemplateKeys }
%    \end{macrocode}
% The default values are set such that they are suitable for good
% quality typesetting. So the standard template changes nothing at
% all from the template. This instance should also be applied now,
% as it will then apply to the entire document unless changed
% deliberately.
%    \begin{macrocode}
\DeclareInstance { line-breaking } { std } { std } { }
\UseInstance { line-breaking } { std }
%    \end{macrocode}
%
% \subsection{Between paragraphs}
%
% \begin{variable}
%   {
%     \l_@@_club_penalty_int          ,
%     \l_@@_display_club_penalty_int  ,
%     \l_@@_display_widow_penalty_int ,
%     \l_@@_interline_penalty_int     ,
%     \l_@@_widow_penalty_int
%   }
%   The second object here sets up how \TeX{} acts to break paragraphs at
%   page boundaries. As with the \texttt{line-breaking} object, there is not
%   much to do except provide an interface to the \TeX{} internals. The
%   \texttt{std} template does \emph{not} make the \eTeX{} array nature of
%   various penalties available.
%    \begin{macrocode}
\DeclareObjectType { paragraph-breaking } { 0 }
\DeclareTemplateInterface { paragraph-breaking } { std } { 0 }
  {
    badness               : integer = 1000  ,
    broken-penalty        : integer = 100   ,
    club-penalty          : integer = 150   ,
    display-club-penalty  : integer = 150   ,
    display-widow-penalty : integer = 150   ,
    fuzz                  : length  = 0.1pt ,
    interline-penalty     : integer = 0     ,
    post-display-penalty  : integer = 0     ,
    pre-display-penalty   : integer = 10000 ,
    widow-penalty         : integer = 150
  }
\DeclareTemplateCode { paragraph-breaking } { std } { 0 }
  {
    badness               = \l_galley_parbreak_badness_int      ,
    broken-penalty        = \l_@@_broken_penalty_int        ,
    club-penalty          = \l_@@_club_penalty_int          ,
    display-club-penalty  = \l_@@_display_club_penalty_int  ,
    display-widow-penalty = \l_@@_display_widow_penalty_int ,
    fuzz                  = \l_galley_parbreak_fuzz_dim         ,
    interline-penalty     = \l_@@_interline_penalty_int     ,
    post-display-penalty  = \l_@@_post_display_penalty_int  ,
    pre-display-penalty   = \l_@@_pre_display_penalty_int   ,
    widow-penalty         = \l_@@_widow_penalty_int
  }
  {
    \AssignTemplateKeys
    \galley_club_penalties_set:V          \l_@@_club_penalty_int
    \galley_display_club_penalties_set:V  \l_@@_display_club_penalty_int
    \galley_display_widow_penalties_set:V \l_@@_display_widow_penalty_int
    \galley_interline_penalty_set:n       \l_@@_interline_penalty_int
    \galley_widow_penalties_set:V         \l_@@_widow_penalty_int
  }
%    \end{macrocode}
% \end{variable}
% The standard instance of the \texttt{paragraph-breaking} object simply
% applies the defaults: this is used.
%    \begin{macrocode}
\DeclareInstance { paragraph-breaking } { std } { std } { }
\UseInstance { paragraph-breaking } { std }
%    \end{macrocode}
% Two additional instances are provided: one to prevent any breaks
% at all, and a second to prevent any widow or club lines.
%    \begin{macrocode}
\DeclareInstance { paragraph-breaking } { nobreak } { std }
  {
    interline-penalty    = 10 000 ,
    post-display-penalty = 10 000
  }
\DeclareInstance { paragraph-breaking } { nolone } { std }
  {
    club-penalty          = 10 000 ,
    display-club-penalty  = 10 000 ,
    display-widow-penalty = 10 000 ,
    widow-penalty         = 10 000
  }
%    \end{macrocode}
% \begin{variable}
%   {
%     \l_@@_parbreak_badness_tl        ,
%     \l_@@_broken_penalty_tl          ,
%     \l_@@_club_penalties_tl          ,
%     \l_@@_display_club_penalties_tl  ,
%     \l_@@_display_widow_penalties_tl ,
%     \l_@@_parbreak_fuzz_tl           ,
%     \l_@@_interline_penalty_tl       ,
%     \l_@@_post_display_penalty_tl    ,
%     \l_@@_pre_display_penalty_tl     ,
%     \l_@@_widow_penalties_tl         ,
%     \c_@@_parbreak_multi_seq         ,
%     \c_@@_parbreak_single_seq
%   }
%   There is also a version of this code which applies only to one
%   paragraph. This is done by storing the input in token list variables
%   with no default: only explicit settings will be picked up.
%    \begin{macrocode}
\DeclareTemplateInterface { paragraph-breaking } { single } { 0 }
  {
    badness               : tokenlist ,
    broken-penalty        : tokenlist ,
    club-penalty          : tokenlist ,
    display-club-penalty  : tokenlist ,
    display-widow-penalty : tokenlist ,
    fuzz                  : tokenlist ,
    interline-penalty     : tokenlist ,
    post-display-penalty  : tokenlist ,
    pre-display-penalty   : tokenlist ,
    widow-penalty         : tokenlist
  }
\DeclareTemplateCode { paragraph-breaking } { single } { 0 }
  {
    badness               = \l_@@_parbreak_badness_tl        ,
    broken-penalty        = \l_@@_broken_penalty_tl          ,
    club-penalty          = \l_@@_club_penalties_tl          ,
    display-club-penalty  = \l_@@_display_club_penalties_tl  ,
    display-widow-penalty = \l_@@_display_widow_penalties_tl ,
    fuzz                  = \l_@@_parbreak_fuzz_tl           ,
    interline-penalty     = \l_@@_interline_penalty_tl       ,
    post-display-penalty  = \l_@@_post_display_penalty_tl    ,
    pre-display-penalty   = \l_@@_pre_display_penalty_tl     ,
    widow-penalty         = \l_@@_widow_penalties_tl
  }
  {
    \AssignTemplateKeys
%    \end{macrocode}
%   The fuzz and interline penalties are handled explicitly as they have
%   particular requirements.
%    \begin{macrocode}
    \tl_if_empty:NF \l_@@_interline_penalty_tl
      {
        \tl_gput_right:Nx \g_galley_par_reset_hook_tl
          {
            \int_set:Nn \exp_not:N \l_@@_interline_penalty_int
              { \galley_interline_penalty: }
          }
        \int_set:Nn \l_@@_interline_penalty_int
          { \l_@@_interline_penalty_tl }
      }
    \tl_if_empty:NF \l_@@_parbreak_fuzz_tl
      {
        \tl_gput_right:Nx \g_galley_par_reset_hook_tl
          {
            \dim_set:Nn \exp_not:N \l_galley_parbreak_fuzz_dim
              { \dim_use:N \l_galley_parbreak_fuzz_dim }
          }
        \dim_set:Nn \l_galley_parbreak_fuzz_dim { \l_@@_parbreak_fuzz_tl }
      }
%    \end{macrocode}
%  For the single integer penalties, a simple check is needed to save the
%  value.
%    \begin{macrocode}
    \seq_map_inline:Nn \c_@@_parbreak_single_seq
      {
        \tl_if_empty:cF { l_galley_ ##1 _tl }
          {
            \tl_gput_right:Nx \g_galley_par_reset_hook_tl
              {
                \int_set:Nn \exp_not:c { l_galley_ ##1 _int }
                  { \int_use:c { l_galley_ ##1 _int } }
              }
            \int_set:cn { l_galley_ ##1 _int }
              { \tl_use:c { l_galley_ ##1 _tl } }
          }
      }
%    \end{macrocode}
%   A bit more complex for the array penalties. Although the interface here
%   does not expose the arrays, it is necessary to correctly save them.
%   We suspend debugging to allow an assignment to a constant.
%    \begin{macrocode}
    \seq_map_inline:Nn \c_@@_parbreak_multi_seq
      {
        \tl_if_empty:cF { l_galley_ ##1 _tl }
          {
            \use:c { galley_save_ ##1 :N } \l_@@_tmpa_clist
            \tl_gput_right:Nx \g_galley_par_reset_hook_tl
              {
                \exp_not:c { galley_set_ ##1 :n }
                  { \exp_not:o \l_@@_tmpa_clist }
              }
            \use:c { galley_set_ ##1 :v } { l_galley_ ##1 _tl }
          }
      }
  }
\seq_const_from_clist:Nn \c_@@_parbreak_multi_seq
  {
    club_penalties ,
    display_club_penalties ,
    display_widow_penalties ,
    widow_penalties ,
  }
\seq_const_from_clist:Nn \c_@@_parbreak_single_seq
  {
    parbreak_badness ,
    broken_penalty ,
    post_display_penalty ,
    pre_display_penalty ,
  }
%    \end{macrocode}
% \end{variable}
%    \begin{macrocode}
\DeclareInstance { paragraph-breaking } { single-std } { single } { }
\DeclareInstance { paragraph-breaking } { single-nobreak } { single }
  {
    interline-penalty    = 10 000 ,
    post-display-penalty = 10 000
  }
\DeclareInstance { paragraph-breaking } { single-noclub } { single }
  {
    club-penalty         = 10 000 ,
    display-club-penalty = 10 000
  }
\DeclareInstance { paragraph-breaking } { single-nolone } { single }
  {
    club-penalty          = 10 000 ,
    display-club-penalty  = 10 000 ,
    display-widow-penalty = 10 000 ,
    widow-penalty         = 10 000
  }
\DeclareInstance { paragraph-breaking } { single-nowidow } { single }
  {
    display-widow-penalty = 10 000 ,
    widow-penalty         = 10 000
  }
%    \end{macrocode}
%
% \subsection{Templates for display material}
%
% To allow special handling of display-like material, templates are
% needed at the beginning and end of the block which set up any special
% space or breaks. These need to be optional, and so are stored as token
% lists: rather than \enquote{magic} values, empty lists indicate that
% standard settings are to be used. To ensure that the error checking
% needed takes place early, each token list is re-set with the
% appropriate evaluation.
%    \begin{macrocode}
\DeclareObjectType { display-begin } { 0 }
\DeclareObjectType { display-end }   { 0 }
\DeclareTemplateInterface { display-begin } { std } { 0 }
  {
    par-penalty : tokenlist ,
    par-space   : tokenlist ,
    penalty     : tokenlist ,
    space       : tokenlist
  }
\DeclareTemplateInterface { display-end } { std } { 0 }
  {
    par-penalty : tokenlist ,
    par-space   : tokenlist ,
    penalty     : tokenlist ,
    space       : tokenlist
  }
\DeclareTemplateCode { display-begin } { std } { 0 }
  {
    par-penalty = \l_galley_display_begin_par_vpenalty_tl ,
    par-space   = \l_galley_display_begin_par_vspace_tl   ,
    penalty     = \l_galley_display_begin_vpenalty_tl     ,
    space       = \l_galley_display_begin_vspace_tl
  }
  {
   \AssignTemplateKeys
    \tl_if_empty:NF \l_galley_display_begin_par_vpenalty_tl
      {
        \tl_set:Nx \l_galley_display_begin_par_vpenalty_tl
          { \int_eval:n { \l_galley_display_begin_par_vpenalty_tl } }
      }
    \tl_if_empty:NF \l_galley_display_begin_par_vspace_tl
      {
        \tl_set:Nx \l_galley_display_begin_par_vspace_tl
          { \skip_eval:n { \l_galley_display_begin_par_vspace_tl } }
      }
    \tl_if_empty:NF \l_galley_display_begin_vpenalty_tl
      {
        \tl_set:Nx \l_galley_display_begin_vpenalty_tl
          { \int_eval:n { \l_galley_display_begin_vpenalty_tl } }
      }
    \tl_if_empty:NF \l_galley_display_begin_vspace_tl
      {
        \tl_set:Nx \l_galley_display_begin_vspace_tl
          { \skip_eval:n { \l_galley_display_begin_vspace_tl } }
      }
  }
\DeclareTemplateCode { display-end } { std } { 0 }
  {
    par-penalty = \l_galley_display_end_par_vpenalty_tl ,
    par-space   = \l_galley_display_end_par_vspace_tl   ,
    penalty     = \l_galley_display_end_vpenalty_tl     ,
    space       = \l_galley_display_end_vspace_tl
  }
  {
    \AssignTemplateKeys
    \tl_if_empty:NF \l_galley_display_end_par_vpenalty_tl
      {
        \tl_set:Nx \l_galley_display_end_par_vpenalty_tl
          { \int_eval:n { \l_galley_display_end_par_vpenalty_tl } }
      }
    \tl_if_empty:NF \l_galley_display_end_par_vspace_tl
      {
        \tl_set:Nx \l_galley_display_end_par_vspace_tl
          { \skip_eval:n { \l_galley_display_end_par_vspace_tl } }
      }
    \tl_if_empty:NF \l_galley_display_end_vpenalty_tl
      {
        \tl_set:Nx \l_galley_display_end_vpenalty_tl
          { \int_eval:n { \l_galley_display_end_vpenalty_tl } }
      }
    \tl_if_empty:NF \l_galley_display_end_vspace_tl
      {
        \tl_set:Nx \l_galley_display_end_vspace_tl
          { \skip_eval:n { \l_galley_display_end_vspace_tl } }
      }
  }
%    \end{macrocode}
%
%    \begin{macrocode}
%</package>
%    \end{macrocode}
%
% \end{implementation}
%
% \PrintIndex