summaryrefslogtreecommitdiff
path: root/Master/texmf-dist/source/latex/l3experimental/xcoffins/xcoffins.dtx
blob: e4a7b5b12ea6427c14330567b60b0133d8b7e900 (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
% \iffalse meta-comment
%
%% File: xcoffins.dtx Copyright(C) 2010-2012,2014,2016,2017 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}
\usepackage{xcoffins} % Not yet part of expl3, so not in l3doc
\usepackage{xcolor} % As coffins only loads basic color support
\NewCoffin \ExampleCoffin
\NewCoffin \SmallCoffin
\NewCoffin \OutputCoffin
\NewCoffin \RedCoffin
\NewCoffin \BlueCoffin
\NewCoffin \GreenCoffin
\NewCoffin \YellowCoffin
\NewCoffin \OrangeCoffin
\begin{document}
  \DocInput{\jobname.dtx}
\end{document}
%</driver>
% \fi
%
% \title{^^A
%   The \textsf{xcoffins} package\\ Design-level coffins^^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 2018/03/05}
%
% \maketitle
%
% \begin{documentation}
%
% \section{Introduction: the coffin concept}
%
% In \LaTeX3 terminology, a \enquote{coffin} is a box containing
% typeset material. Along with the box itself, the coffin structure
% includes information on the size and shape of the box, which makes
% it possible to align two or more coffins easily. This is achieved
% by providing a series of `poles' for each coffin. These
% are horizontal and vertical lines through the coffin at defined
% positions, for example the top or horizontal centre. The points
% where these poles intersect are called \enquote{handles}. Two
% coffins can then be aligned by describing the relationship between
% a handle on one coffin with a handle on the second. In words, an
% example might then read
% \begin{quote}
%   Align the top-left handle of coffin A with the bottom-right
%   handle of coffin B.
% \end{quote}
%
% The locations of coffin handles are much easier to understand
% visually. Figure~\ref{fgr:handles} shows the standard handle
% positions for a coffin typeset in horizontal mode (left) and in
% vertical mode (right). Notice that the later case results in a greater
% number of handles being available. As illustrated, each handle
% results from the intersection of two poles. For example, the centre
% of the coffin is marked |(hc,vc)|, \emph{i.e.}~it is the
% point of intersection of the horizontal centre pole with the
% vertical centre pole. New handles are generated automatically when
% poles are added to a coffin: handles are \enquote{dynamic} entities.
%
% \begin{figure}
%   \hfil
%   \begin{minipage}{0.4\textwidth}
%     \SetHorizontalCoffin\ExampleCoffin
%       {\color{black!10!white}\rule{1 in}{1 in}}
%     \DisplayCoffinHandles\ExampleCoffin{blue}
%   \end{minipage}
%   \hfil
%   \begin{minipage}{0.4\textwidth}
%     \SetVerticalCoffin\ExampleCoffin{1 in}
%       {\color{black!10!white}\rule{1 in}{1 in}}
%     \DisplayCoffinHandles\ExampleCoffin{blue}
%   \end{minipage}
%   \hfil
%   \caption{Standard coffin handles: left, horizontal coffin; right,
%     vertical coffin}
%   \label{fgr:handles}
% \end{figure}
%
%\section{Creating and setting coffins}
%
% Before any alignment can take place, coffins must be created and
% their contents must be created. All coffin operations are local
% to the current \TeX{} group with the exception of coffin creation.
% \begin{function}{\NewCoffin}
%   \begin{syntax}
%     \cs{NewCoffin} \meta{coffin}
%   \end{syntax}
%   Before a \meta{coffin} can be used, it must be allocated using
%   \cs{NewCoffin}. The name of the \meta{coffin} should be a
%   control sequence (starting with the escape character, usually
%   |\|), for example
%   \begin{verbatim}
%     \NewCoffin\MyCoffin
%   \end{verbatim}
%   Coffins are allocated globally, and an error will be raised if the
%   name of the \meta{coffin} is not globally-unique.
% \end{function}
%
% \begin{function}{\SetHorizontalCoffin}
%   \begin{syntax}
%     \cs{SetHorizontalCoffin} \meta{coffin} \Arg{material}
%   \end{syntax}
%   Typesets the \meta{material} in horizontal mode, storing the result
%   in the \meta{coffin}. The standard poles for the \meta{coffin} are
%   then set up based on the size of the typeset material.
% \end{function}
%
% \begin{function}{\SetVerticalCoffin}
%   \begin{syntax}
%     \cs{SetVerticalCoffin} \meta{coffin} \Arg{width} \Arg{material}
%   \end{syntax}
%   Typesets the \meta{material} in vertical mode constrained to the
%   given \meta{width} and stores the result in the \meta{coffin}. The
%   standard poles for the \meta{coffin} are then set up based on the
%   size of the typeset material.
% \end{function}
%
% \section{Controlling coffin poles}
%
% A number of standard poles are automatically generated when the coffin
% is set or an alignment takes place. The standard poles for all coffins
% are:
% \begin{itemize}[font = \ttfamily]
%   \item[l] a pole running along the left-hand edge of the bounding
%     box of the coffin;
%   \item[hc] a pole running vertically through the centre of the coffin
%     half-way between the left- and right-hand edges of the bounding
%       box (\emph{i.e.}~the \enquote{horizontal centre});
%   \item[r] a pole running along the right-hand edge of the bounding
%     box of the coffin;
%   \item[b] a pole running along the bottom edge of the bounding
%     box of the coffin;
%   \item[vc] a pole running horizontally through the centre of the
%     coffin half-way between the bottom and top edges of the bounding
%     box (\emph{i.e.}~the \enquote{vertical centre});
%   \item[t] a pole running along the top edge of the bounding
%     box of the coffin;
%   \item[H] a pole running along the baseline of the typeset material
%     contained in the coffin.
% \end{itemize}
% In addition, coffins containing vertical-mode material also
% feature poles which reflect the richer nature of these systems:
% \begin{itemize}
%   \item[B] a pole running along the baseline of the material at the
%     bottom of the coffin.
%   \item[T] a pole running along the baseline of the material at the top
%     of the coffin.
% \end{itemize}
%
% \begin{function}{\SetHorizontalPole}
%   \begin{syntax}
%     \cs{SetHorizontalPole} \meta{coffin} \Arg{pole} \Arg{offset}
%   \end{syntax}
%   Sets the \meta{pole} to run horizontally through the \meta{coffin}.
%   The \meta{pole} will be located at the \meta{offset} from the
%   bottom edge of the bounding box of the \meta{coffin}. The
%   \meta{offset} should be given as a dimension expression; this may
%   include the terms \cs{TotalHeight}, \cs{Height}, \cs{Depth} and
%   \cs{Width}, which will evaluate to the appropriate dimensions of
%   the \meta{coffin}. For example, to create a pole running
%   horizontally through the coffin at one third of the distance from
%   the base of the coffin to the top, the appropriate instruction would
%   be
%   \begin{verbatim}
%     \SetHorizontalPole \MyCoffin {height/3} {\TotalHeight/3}
%   \end{verbatim}
%   Note that poles which run \emph{horizontally} are described in terms
%   of their \emph{vertical} location in the coffin. Also notice that
%   the total height of the coffin is described by the sum of
%   \cs{Height} and \cs{Depth}: these are both measured from the
%   horizontal baseline of the material in the coffin.
% \end{function}
%
% \begin{function}{\SetVerticalPole}
%   \begin{syntax}
%     \cs{SetVerticalPole} \meta{coffin} \Arg{pole} \Arg{offset}
%   \end{syntax}
%   Sets the \meta{pole} to run vertically through the \meta{coffin}.
%   The \meta{pole} will be located at the \meta{offset} from the
%   left-hand edge of the bounding box of the \meta{coffin}. The
%   \meta{offset} should be given as a dimension expression; this may
%   include the terms \cs{TotalHeight}, \cs{Height}, \cs{Depth} and
%   \cs{Width}, which will evaluate to the appropriate dimensions of
%   the \meta{coffin}. For example, to create a pole running vertically
%   through the coffin at one third of the distance from the left-hand
%   edge, the appropriate instruction would be
%   \begin{verbatim}
%     \SetVerticalPole \MyCoffin {width/3} {\Width/3}
%   \end{verbatim}
%   Note that poles which run \emph{vertically} are described in terms
%   of their \emph{horizontal} location in the coffin.
% \end{function}
%
% \begin{function}{\TotalHeight}
%   \begin{syntax}
%     \cs{TotalHeight}
%   \end{syntax}
%   Within the \meta{offset} argument of \cs{SetHorizontalPole} and
%   \cs{SetVerticalPole}, \cs{TotalHeight} will give the distance from
%   the base to the top of the bounding box of the relevant coffin.
% \end{function}
%
% \begin{function}{\Height}
%   \begin{syntax}
%     \cs{Height}
%   \end{syntax}
%   Within the \meta{offset} argument of \cs{SetHorizontalPole} and
%   \cs{SetVerticalPole}, \cs{Height} will give the distance from the
%   baseline to the top of the bounding box of the relevant coffin.
% \end{function}
%
% \begin{function}{\Depth}
%   \begin{syntax}
%     \cs{Depth}
%   \end{syntax}
%   Within the \meta{offset} argument of \cs{SetHorizontalPole} and
%   \cs{SetVerticalPole}, \cs{Depth} will give the distance from the
%   baseline to the bottom of the bounding box of the relevant coffin.
% \end{function}
%
% \begin{function}{\Width}
%   \begin{syntax}
%     \cs{Width}
%   \end{syntax}
%   Within the \meta{offset} argument of \cs{SetHorizontalPole} and
%   \cs{SetVerticalPole}, \cs{Width} will give the distance from the
%   right edge to the left edge of the bounding box of the relevant
%   coffin.
% \end{function}
%
% \section{Rotating coffins}
%
% \begin{function}{\RotateCoffin}
%   \begin{syntax}
%     \cs{RotateCoffin} \meta{coffin} \Arg{angle}
%   \end{syntax}
%   Rotates the \meta{coffin} by the given \meta{angle} about its reference
%   point (given in degrees counter-clockwise) . This process will rotate both
%   the coffin content and poles. Multiple rotations will not result in
%   the bounding box of the coffin growing unnecessarily.
%
%   The effect of rotation on a coffin is illustrated in
%   Figure~\ref{fgr:rotation}. As is shown, the coffin handles will
%   remain correctly positioned relative to the content of the coffin.
%   The \enquote{top} of a rotated coffin may of course no longer be the
%   edge closest to the top of the physical page.
% \end{function}
%
%   \begin{figure}
%     \hfil
%     \SetHorizontalCoffin\ExampleCoffin
%       {^^A
%         \color{black!10!white}\rule{0.5 in}{1 in}^^A
%         \color{black!20!white}\rule{0.5 in}{1 in}^^A
%       }
%     \begin{minipage}{0.4\textwidth}
%       \DisplayCoffinHandles\ExampleCoffin{blue}
%     \end{minipage}
%     \hfil
%     \begin{minipage}{0.4\textwidth}
%       \RotateCoffin\ExampleCoffin{45}
%       \DisplayCoffinHandles\ExampleCoffin{blue}
%     \end{minipage}
%     \hfil
%     \caption{Coffin rotation: left, unrotated; right, rotated by
%       $45$\textdegree.}
%     \label{fgr:rotation}
%   \end{figure}
%
% \section{Resizing coffins}
%
% \begin{function}{\ResizeCoffin}
%   \begin{syntax}
%     \cs{ResizeCoffin} \meta{coffin} \Arg{width} \Arg{total-height}
%   \end{syntax}
%   Resized the \meta{coffin} to \meta{width} and \meta{total-height},
%   both of which should be given as dimension expressions.
% \end{function}
%
% \begin{function}{\ScaleCoffin}
%   \begin{syntax}
%     \cs{ScaleCoffin} \meta{coffin} \Arg{x-scale} \Arg{y-scale}
%   \end{syntax}
%   Scales the \meta{coffin} by a factors \meta{x-scale} and
%   \meta{y-scale} in the horizontal and vertical directions,
%   respectively. The two scale factors should be given as real numbers.
% \end{function}
%
% \cs{ResizeCoffin} and \cs{ScaleCoffin} can be used interchangeably:
% whether scale factors or absolute values are the best form for the
% resizing will depend upon the context (Figure~\ref{fgr:resizing}).
%
% \begin{figure}
%   \hfil
%   \SetHorizontalCoffin\ExampleCoffin
%     {^^A
%       \color{black!10!white}\rule{0.5 in}{1 in}^^A
%       \color{black!20!white}\rule{0.5 in}{1 in}^^A
%     }
%   \begin{minipage}{0.4\textwidth}
%     \ResizeCoffin \ExampleCoffin {4 cm} {3 cm}
%     \DisplayCoffinHandles \ExampleCoffin {blue}
%   \end{minipage}
%   \hfil
%   \begin{minipage}{0.4\textwidth}
%     \ScaleCoffin \ExampleCoffin {2.0} {0.5}
%     \DisplayCoffinHandles \ExampleCoffin {blue}
%   \end{minipage}
%   \hfil
%   \caption{Coffin resizing: left, resized to exactly $4$\,cm by
%   $6$\,cm; right, scaled a factors of $2$ and $0.5$ in
%   $x$ and $y$, respectively (example coffin as in
%   Figure~\ref{fgr:rotation}).}
%   \label{fgr:resizing}
% \end{figure}
%
% \section{Joining coffins}
%
% The key operation for coffins is joining coffins to each other. This
% is always carried out such that the first coffin is the
% \enquote{parent}, and is updated by the alignment. The second
% \enquote{child} coffin is not altered by the alignment process.
%
% \begin{function}{\JoinCoffins}
%   \begin{syntax}
%     \cs{JoinCoffins} *
%     ~~\meta{coffin1} [ \meta{coffin1-pole1} , \meta{coffin1-pole2} ]
%     ~~\meta{coffin2} [ \meta{coffin2-pole1} , \meta{coffin2-pole2} ]
%     ~~( \meta{x-offset} , \meta{y-offset} )
%   \end{syntax}
%   Joining of two coffins is carried out by the \cs{JoinCoffins}
%   function, which takes two mandatory arguments: the \enquote{parent}
%   \meta{coffin1} and the \enquote{child} \meta{coffin2}. All of the
%   other arguments shown are optional.
% \end{function}
%
%   The standard \cs{JoinCoffins} functions joins \meta{coffin2} to
%   \meta{coffin1} such that the bounding box of \meta{coffin1} after the
%   process will expand. The new bounding box will be the smallest
%   rectangle covering the bounding boxes of the two input coffins.
%   When the starred variant of \cs{JoinCoffins} is used, the bounding
%   box of \meta{coffin1} is not altered, \emph{i.e.}~\meta{coffin2} may
%   protrude outside of the bounding box of the updated \meta{coffin1}.
%   The difference between the two forms of alignment is best illustrated
%   using a visual example. In Figure~\ref{fgr:alignment}, the two
%   processes are contrasted. In both cases, the small red coffin has been
%   aligned with the large grey coffin. In the left-hand illustration,
%   the \cs{JoinCoffins} function was used, resulting in an expanded
%   bounding box. In contrast, on the right \cs{AttachCoffin} was used,
%   meaning that the bounding box does not include the area of the
%   smaller coffin.
%
%   \begin{figure}
%     \fboxsep 0 pt\relax
%     \SetHorizontalCoffin\ExampleCoffin
%       {\color{black!20!white}\rule{1 in}{1 in}}
%     \SetHorizontalCoffin \SmallCoffin
%       {\color{red!20!white}\rule{0.1 in}{0.1 in}}
%     \hfil
%     \begin{minipage}{0.4\textwidth}
%       \centering
%       \JoinCoffins\ExampleCoffin[vc,r]\SmallCoffin[vc,l]
%       \fbox{\TypesetCoffin\ExampleCoffin}
%     \end{minipage}
%     \hfil
%     \begin{minipage}{0.4\textwidth}
%       \centering
%        \JoinCoffins*\ExampleCoffin[vc,r]\SmallCoffin[vc,l]
%       \fbox{\TypesetCoffin\ExampleCoffin}%
%     \end{minipage}
%     \hfil
%     \caption{Contrast between \cs{JoinCoffins} (left) and
%       \cs{JoinCoffins*} (right); the bounding box of the coffin is show
%       in black.}
%     \label{fgr:alignment}
%   \end{figure}
%
%   The alignment is carried out by first calculating \meta{handle1}, the
%   point of intersection of \meta{coffin1-pole1} and
%   \meta{coffin1-pole2}, and \meta{handle2}, the point of intersection
%   of \meta{coffin2-pole1} and \meta{coffin2-pole2}. If the two
%   \meta{poles} are not specified, \cs{JoinCoffins} will use the
%   default value |(H,l)|, \emph{i.e.}~the reference point used by \TeX\
%   for the underlying box. Once the two \meta{handles} have been
%   located, \meta{coffin2} is then attached to \meta{coffin1} such that
%   the relationship between \meta{handle1} and \meta{handle2} is
%   described by the \meta{x-offset} and \meta{y-offset}. This
%   \meta{offset} is an optional argument, and if it is not given then
%   |(0 pt, 0 pt)| is used.
%
% Notice that when \cs{JoinCoffins} is used the new bounding box is
% the smallest rectangle containing the bounding boxes of the two input
% coffins. As a result, it will include additional white space unless
% one coffin entirely overlaps the other (Figure~\ref{fgr:bounding},
% left). Rotation of coffins will take account of the extent of the
% material after rotation when re-calculating the bounding box. This
% means that no \emph{unnecessary} white space will be added on
% rotation (Figure~\ref{fgr:bounding}, right).
%
% \begin{figure}
%   \fboxsep 0 pt\relax
%   \SetHorizontalCoffin\ExampleCoffin
%     {\color{black!20!white}\rule{1 in}{1 in}}
%   \SetHorizontalCoffin\SmallCoffin
%     {\color{red!20!white}\rule{0.1 in}{0.1 in}}
%   \JoinCoffins\ExampleCoffin[vc,r]\SmallCoffin[vc,l]
%   \hfil
%   \begin{minipage}{0.4\textwidth}
%     \centering
%     \fbox{\copy\ExampleCoffin}
%   \end{minipage}
%   \hfil
%   \begin{minipage}{0.4\textwidth}
%     \centering
%     \RotateCoffin\ExampleCoffin{135}
%     \fbox{\copy\ExampleCoffin}
%   \end{minipage}
%   \hfil
%   \caption{The effect of rotation of a joined coffin: the black line
%     shows the coffin bounding box.}
%   \label{fgr:bounding}
% \end{figure}
%
% As part of the joining procedure, the poles of the two input coffins
% are preserved within the structure of the updated coffin. In this way
% it is possible to carry out complex alignment procedures. The poles of
% a coffin after alignment may therefore be divided into three groups:
% \begin{enumerate}
%   \item The \enquote{native} poles of the updated coffin, such as
%     \texttt{l}, \texttt{r}, \texttt{hc}, \emph{etc}.
%   \item Poles derived from \meta{coffin1}, such as
%     \texttt{\meta{coffin1}-l},  \texttt{\meta{coffin1}-r},
%      \texttt{\meta{coffin1}-hc}, \emph{etc.}
%   \item Poles derived from \meta{coffin2}, such as
%     \texttt{\meta{coffin2}-l},  \texttt{\meta{coffin2}-r},
%      \texttt{\meta{coffin2}-hc}, \emph{etc.}
% \end{enumerate}
%
% Applying this ability allows a series of joining operations to
% take place, as illustrated in Figure~\ref{fgr:nested}. In this
% example, the scheme used for alignment was as follows:
% \begin{verbatim}
%   \SetHorizontalCoffin\OutputCoffin{}
%   \SetHorizontalCoffin\RedCoffin
%     {\color{red!20!white}\rule{0.2 in}{0.2 in}}
%   \JoinCoffins\OutputCoffin[vc,hc]\RedCoffin[vc,hc]
%   \SetHorizontalCoffin\BlueCoffin
%     {\color{blue!20!white}\rule{0.2 in}{0.2 in}}
%   \JoinCoffins\OutputCoffin[\RedCoffin-vc,\RedCoffin-hc]
%     \BlueCoffin[b,l]
%   \SetHorizontalCoffin\GreenCoffin
%     {\color{green!20!white}\rule{0.2 in}{0.2 in}}
%   \JoinCoffins\OutputCoffin[\BlueCoffin-vc,\BlueCoffin-hc]
%     \GreenCoffin[b,l]
%   \SetHorizontalCoffin\YellowCoffin
%     {\color{yellow!20!white}\rule{0.2 in}{0.2 in}}
%   \JoinCoffins\OutputCoffin[\GreenCoffin-vc,\GreenCoffin-hc]
%     \YellowCoffin[b,l]
%   \SetHorizontalCoffin \OrangeCoffin
%     {\color{orange!20!white}\rule{0.2 in}{0.2 in}}
%   \JoinCoffins\OutputCoffin[\BlueCoffin-t,\BlueCoffin-l]
%     \OrangeCoffin[b,r]
%   \TypesetCoffin\OutputCoffin
% \end{verbatim}
% This process begins by setting up \cs{OutputCoffin} to hold the joined
% output. Each join then takes place placing the new addition relative
% to the previous one. As each coffin joined has a unique name it is
% possible to align relative to each one of the component parts of the
% assembly. This is illustrated by the addition of the final
% \cs{OrangeCoffin} based on the earlier placement of the
% \cs{BlueCoffin}.
%
% \begin{figure}
%   \centering
%   \SetHorizontalCoffin\OutputCoffin{}
%   \SetHorizontalCoffin\RedCoffin
%     {\color{red!20!white}\rule{0.2 in}{0.2 in}}
%   \JoinCoffins\OutputCoffin[vc,hc]\RedCoffin[vc,hc]
%   \SetHorizontalCoffin\BlueCoffin
%     {\color{blue!20!white}\rule{0.2 in}{0.2 in}}
%   \JoinCoffins\OutputCoffin[\RedCoffin-vc,\RedCoffin-hc]
%     \BlueCoffin[b,l]
%   \SetHorizontalCoffin\GreenCoffin
%     {\color{green!20!white}\rule{0.2 in}{0.2 in}}
%   \JoinCoffins\OutputCoffin[\BlueCoffin-vc,\BlueCoffin-hc]
%     \GreenCoffin[b,l]
%   \SetHorizontalCoffin\YellowCoffin
%     {\color{yellow!20!white}\rule{0.2 in}{0.2 in}}
%   \JoinCoffins\OutputCoffin[\GreenCoffin-vc,\GreenCoffin-hc]
%     \YellowCoffin[b,l]
%   \SetHorizontalCoffin \OrangeCoffin
%     {\color{orange!20!white}\rule{0.2 in}{0.2 in}}
%   \JoinCoffins\OutputCoffin[\BlueCoffin-t,\BlueCoffin-l]
%     \OrangeCoffin[b,r]
%   \TypesetCoffin\OutputCoffin
%   \caption{Aligning coffins using poles from previous operations.}
%   \label{fgr:nested}
% \end{figure}
%
% \section{Typesetting coffins}
%
% \begin{function}{\TypesetCoffin}
%   \begin{syntax}
%     \cs{TypesetCoffin}
%     ~~\meta{coffin} [ \meta{pole1} , \meta{pole2} ]
%     ~~( \meta{x-offset} , \meta{y-offset} )
%   \end{syntax}
%   Typesetting is carried out by first calculating \meta{handle}, the
%   point of intersection of \meta{pole1} and \meta{pole2}. This is an
%   optional argument, and if not given then |(H,l)|, the \TeX{}
%   reference point of the underlying box, is used. The coffin
%   is then typeset such that the relationship between the current
%   reference point in the document and the \meta{handle} is described
%   by the \meta{x-offset} and \meta{y-offset}. This \meta{offset} is
%   optional, and if not given |(0 pt, 0 pt)| is used. Typesetting a
%   coffin is therefore analogous to carrying out an alignment where the
%   \enquote{parent} coffin is the current insertion point.
% \end{function}
%
% \section{Measuring coffins}
%
% There are places in the design process where it is useful to be able to
% measure coffins outside of pole-setting procedures.
%
% \begin{function}{\CoffinDepth}
%   \begin{syntax}
%     \cs{CoffinDepth} \meta{coffin}
%   \end{syntax}
%   Calculates the depth (below the baseline) of the \meta{coffin}
%   in a form suitable for use in a \meta{dimension expression}, for example
%   |\setlength{\mylength}{\CoffinDepth\ExampleCoffin}|.
% \end{function}
%
% \begin{function}{\CoffinHeight}
%   \begin{syntax}
%     \cs{CoffinHeight} \meta{coffin}
%   \end{syntax}
%   Calculates the height (above the baseline) of the \meta{coffin}
%   in a form suitable for use in a \meta{dimension expression}, for example
%   |\setlength{\mylength}{\CoffinHeight\ExampleCoffin}|.
% \end{function}
%
% \begin{function}{\CoffinTotalHeight}
%   \begin{syntax}
%     \cs{CoffinTotalHeight} \meta{coffin}
%   \end{syntax}
%   Calculates the total height of the \meta{coffin}
%   in a form suitable for use in a \meta{dimension expression}, for example
%   |\setlength{\mylength}{\CoffinTotalHeight\ExampleCoffin}|.
% \end{function}
%
% \begin{function}{\CoffinWidth}
%   \begin{syntax}
%     \cs{CoffinWidth} \meta{coffin}
%   \end{syntax}
%   Calculates the width of the \meta{coffin} in a form
%   suitable for use in a \meta{dimension expression}, for example
%   |\setlength{\mylength}{\CoffinWidth\ExampleCoffin}|.
% \end{function}
%
% \section{Diagnostic functions}
%
% Diagnostic data for following the coffin-building process is
% available both graphically and at the terminal. This reflects the
% fact that coffins are visual constructs.
%
% \begin{function}{\DisplayCoffinHandles}
%   \begin{syntax}
%     \cs{DisplayCoffinHandles} \meta{coffin} \Arg{color}
%   \end{syntax}
%   This function first calculates the intersections between all of
%   the \meta{poles} of the \meta{coffin} to give a set of
%   \meta{handles}. It then prints the \meta{coffin} at the current
%   location in the source, with the  position of the \meta{handles}
%   marked on the coffin. The \meta{handles} will be labelled as part
%   of this process: the locations of the \meta{handles} and the labels
%   are both printed in the \meta{color} specified.
% \end{function}
%
% \begin{function}{\MarkCoffinHandle}
%   \begin{syntax}
%     \cs{MarkCoffinHandle} \meta{coffin}
%     ~~[ \meta{pole1} , \meta{pole2} ] \Arg{color}
%   \end{syntax}
%   This function first calculates the \meta{handle} for the
%   \meta{coffin} as defined by the intersection of \meta{pole1} and
%   \meta{pole2}. It then marks the position of the \meta{handle}
%   on the \meta{coffin}. The \meta{handle} will be labelled as part of
%   this process: the location of the \meta{handle} and the label are
%   both printed in the \meta{color} specified. If no \meta{poles} are
%   give, the default |(H,l)| is used.
% \end{function}
%
% \begin{function}{\ShowCoffinStructure}
%   \begin{syntax}
%     \cs{ShowCoffinStructure} \meta{coffin}
%   \end{syntax}
%   This function shows the structural information about the
%   \meta{coffin} in the terminal. The width, height and depth of the
%   typeset material are given, along with the location of all of the
%   poles of the coffin. For example, for the rotated coffin in
%   Figure~\ref{fgr:rotation}, the output of \cs{ShowCoffinStructure}
%   is:
%   \begin{verbatim}
%     Size of coffin \ExampleCoffin:
%     > ht = 72.26999pt
%     > dp = 0.0pt
%     > wd = 72.26999pt
%     Poles of coffin \ExampleCoffin:
%     >  l  =>  {0pt}{0pt}{0pt}{1000pt}
%     >  B  =>  {0pt}{0pt}{1000pt}{0pt}
%     >  H  =>  {0pt}{0pt}{1000pt}{0pt}
%     >  T  =>  {0pt}{0pt}{1000pt}{0pt}
%     >  hc  =>  {36.135pt}{0pt}{0pt}{1000pt}
%     >  r  =>  {72.26999pt}{0pt}{0pt}{1000pt}
%     >  vc  =>  {0pt}{36.135pt}{1000pt}{0pt}
%     >  t  =>  {0pt}{72.26999pt}{1000pt}{0pt}
%     >  b  =>  {0pt}{0.0pt}{1000pt}{0pt}.
%     <recently read> }
%   \end{verbatim}
%   Notice that the poles of a coffin are defined by four values:
%   the $x$ and $y$ co-ordinates of a point that the pole
%   passes through and the $x$- and $y$-components of a
%   vector denoting the direction of the pole. It is the ratio between
%   the later, rather than the absolute values, which determines the
%   direction of the pole.
% \end{function}
%
% \end{documentation}
%
% \begin{implementation}
%
% \section{Implementation}
%
%    \begin{macrocode}
%<*package>
%    \end{macrocode}
%
%    \begin{macrocode}
%<@@=coffin>
%    \end{macrocode}
%
%    \begin{macrocode}
\ProvidesExplPackage{xcoffins}{2018/03/05}{}
  {L3 Experimental design level coffins}
%    \end{macrocode}
%
% \begin{variable}
%   {
%     \l_@@_A_hpole_tl          ,
%     \l_@@_A_vpole_tl          ,
%     \l_@@_B_hpole_tl          ,
%     \l_@@_B_vpole_tl          ,
%     \l_@@_bound_box_grow_bool ,
%     \l_@@_hoffset_dim         ,
%     \l_@@_voffset_dim
%   }
%   Key--value definitions for the alignment system. With the exception
%   of \texttt{grow-bounding-box}, all of these have to be given with a
%   value.
%    \begin{macrocode}
\keys_define:nn { coffin }
  {
    coffin1-hpole     .tl_set:N         = \l_@@_A_hpole_tl          ,
    coffin1-hpole     .value_required:n = true                      ,
    coffin1-vpole     .tl_set:N         = \l_@@_A_vpole_tl          ,
    coffin1-vpole     .value_required:n = true                      ,
    coffin2-hpole     .tl_set:N         = \l_@@_B_hpole_tl          ,
    coffin2-hpole     .value_required:n = true                      ,
    coffin2-vpole     .tl_set:N         = \l_@@_B_vpole_tl          ,
    coffin2-vpole     .value_required:n = true                      ,
    grow-bounding-box .bool_set:N       = \l_@@_bound_box_grow_bool ,
    grow-bounding-box .default:n        = true                      ,
    hoffset           .dim_set:N        = \l_@@_hoffset_dim         ,
    hoffset           .value_required:n = true                      ,
    voffset           .dim_set:N        = \l_@@_voffset_dim         ,
    voffset           .value_required:n = true
  }
\keys_set:nn { coffin }
  {
    coffin1-hpole     = H    ,
    coffin1-vpole     = l    ,
    coffin2-hpole     = H    ,
    coffin2-vpole     = l    ,
    grow-bounding-box = true ,
    hoffset           = 0 pt ,
    voffset           = 0 pt
  }
%    \end{macrocode}
% \end{variable}
%
% \begin{macro}{\@@_design_names:N}
% \begin{variable}{\Height, \Depth, \Width, \TotalHeight}
% \begin{variable}
%   {\l_@@_height_dim, \l_@@_depth_dim, \l_@@_width_dim, \l_@@_totalheight_dim}
%   Sets up design-level names for the various coffin dimensions. These are
%   not defined outside of this scope, and are dimensions so that they work
%   correctly inside for example \cs{fp_eval:n}.
%    \begin{macrocode}
\cs_new_protected:Npn \@@_design_names:N #1
  {
    \dim_set:Nn \l_@@_height_dim { \coffin_ht:N #1 }
    \dim_set:Nn \l_@@_depth_dim  { \coffin_dp:N #1 }
    \dim_set:Nn \l_@@_width_dim  { \coffin_wd:N #1 }
    \dim_set:Nn \l_@@_totalheight_dim
      { \l_@@_height_dim + \l_@@_depth_dim }
    \cs_set_eq:NN \Height \l_@@_height_dim
    \cs_set_eq:NN \Depth \l_@@_depth_dim
    \cs_set_eq:NN \Width \l_@@_width_dim
    \cs_set_eq:NN \TotalHeight \l_@@_totalheight_dim
  }
\dim_new:N \l_@@_height_dim
\dim_new:N \l_@@_depth_dim
\dim_new:N \l_@@_width_dim
\dim_new:N \l_@@_totalheight_dim
%    \end{macrocode}
% \end{variable}
% \end{variable}
% \end{macro}
%
% A lot of this is more-or-less just passing data straight through.
%
% \begin{macro}{\NewCoffin}
% This is a very easy conversion.
%    \begin{macrocode}
\NewDocumentCommand \NewCoffin { m }
  { \coffin_new:N #1 }
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\SetHorizontalCoffin}
% \begin{macro}{\SetVerticalCoffin}
%   These are again straight-forward translations.
%    \begin{macrocode}
\NewDocumentCommand \SetHorizontalCoffin { m +m }
  { \hcoffin_set:Nn #1 {#2} }
\NewDocumentCommand \SetVerticalCoffin { m m +m }
  { \vcoffin_set:Nnn #1 {#2} {#3} }
%    \end{macrocode}
% \end{macro}
% \end{macro}
%
% \begin{macro}{\SetHorizontalPole}
% \begin{macro}{\SetVerticalPole}
%   Here, there is a need to set up the design-level names for coffin
%   dimensions. This requires grouping, but the coffin work has to occur
%   outside of the group. Hence there is a bit of expansion trickery.
%    \begin{macrocode}
\NewDocumentCommand \SetHorizontalPole { m m m }
  {
    \group_begin:
      \@@_design_names:N #1
    \use:x
      {
        \group_end:
        \coffin_set_horizontal_pole:Nnn #1
          { \exp_not:n {#2} } { \dim_eval:n {#3} }
      }
  }
\NewDocumentCommand \SetVerticalPole { m m m }
  {
    \group_begin:
      \@@_design_names:N #1
    \use:x
      {
        \group_end:
        \coffin_set_vertical_pole:Nnn #1
          { \exp_not:n {#2} } { \dim_eval:n {#3} }
      }
  }
%    \end{macrocode}
% \end{macro}
% \end{macro}
%
% \begin{macro}{\JoinCoffins}
%   The \cs{JoinCoffins} function needs to do a bit of work on the input
%   syntax, as there are a number of optional arguments to worry about.
%   The idea here is that \cs{JoinCoffins} can be used to either expand
%   the bounding box of \meta{coffin1} or add \meta{coffin2} without any
%   expansion of the bounding box. There are also the two handle positions
%   and the offset to sort out.
%    \begin{macrocode}
\NewDocumentCommand \JoinCoffins
  {
    o
    s
    m
    > { \SplitArgument { 1 } { , } } O { H , l }
    m
    > { \SplitArgument { 1 } { , } } O { H , l }
    > { \SplitArgument { 1 } { , } } D ( ) { 0 pt , 0 pt }
  }
  {
    \IfNoValueTF {#1}
      {
        \IfBooleanTF #2
          { \coffin_attach:NnnNnnnn #3 #4 #5 #6 #7 }
          { \coffin_join:NnnNnnnn #3 #4 #5 #6 #7 }
      }
      {
        \group_begin:
          \keys_set:nn { coffin } {#1}
          \tl_set:Nx \l_@@_tmp_tl
            {
              \group_end:
              \bool_if:NTF \l_@@_bound_box_grow_bool
                { \coffin_join:NnnNnnnn }
                { \coffin_attach:NnnNnnnn }
              \exp_not:N #3
              { \exp_not:o { \l_@@_A_hpole_tl } }
              { \exp_not:o { \l_@@_A_vpole_tl } }
              \exp_not:N #5
              { \exp_not:o { \l_@@_B_hpole_tl } }
              { \exp_not:o { \l_@@_B_vpole_tl } }
              { \dim_use:N \l_@@_hoffset_dim }
              { \dim_use:N \l_@@_voffset_dim }
            }
        \l_@@_tmp_tl
      }
  }
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\TypesetCoffin}
%   For typesetting coffins there are two optional arguments, both of
%   which need to be split. This is a simpler case of the code needed for
%   \cs{JoinCoffins}.
%    \begin{macrocode}
\NewDocumentCommand \TypesetCoffin
  {
     m
     > { \SplitArgument { 1 } { , } } O { H , l }
     > { \SplitArgument { 1 } { , } } D ( ) { 0 pt , 0 pt }
  }
  { \coffin_typeset:Nnnnn #1 #2 #3 }
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\RotateCoffin}
% \begin{macro}{\ResizeCoffin}
% \begin{macro}{\ScaleCoffin}
%   Mores straight-forward copies.
%    \begin{macrocode}
\NewDocumentCommand \RotateCoffin  { m m }
  { \coffin_rotate:Nn #1 {#2} }
\NewDocumentCommand \ResizeCoffin  { m m m }
  { \coffin_resize:Nnn #1 {#2} {#3} }
\NewDocumentCommand \ScaleCoffin  { m m m }
  { \coffin_scale:Nnn #1 {#2} {#3} }
%    \end{macrocode}
% \end{macro}
% \end{macro}
% \end{macro}
%
% \begin{macro}{\CoffinDepth, \CoffinHeight, \CoffinTotalHeigth, \CoffinWidth}
%   Nothing too complex, except that the total height is set up as an
%   expression so that it will act correctly if prefixed with a negative
%   sign, \emph{etc.}
%    \begin{macrocode}
\NewDocumentCommand \CoffinDepth { m }
  { \coffin_dp:N #1 }
\NewDocumentCommand \CoffinHeight { m }
  { \coffin_ht:N #1 }
\NewDocumentCommand \CoffinTotalHeight { m }
  { \__dim_eval:n { \coffin_ht:N #1 + \coffin_dp:N #1 } }
\NewDocumentCommand \CoffinWidth { m }
  { \coffin_wd:N #1 }
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\DisplayCoffinHandles}
%   Displaying all of the handles is a bit easier, as there is no need
%   to worry about the handle.
%    \begin{macrocode}
\NewDocumentCommand \DisplayCoffinHandles { m m }
  { \coffin_if_exist:NT #1 { \coffin_display_handles:Nn #1 {#2} } }
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\MarkCoffinHandle}
%   Marking a handle requires a bit of work with the input, so that
%   the design-level interface is \enquote{nice}.
%    \begin{macrocode}
\NewDocumentCommand \MarkCoffinHandle
  { m > { \SplitArgument { 1 } { , } } O { H , l } m }
  {  \coffin_if_exist:NT #1 { \coffin_mark_handle:Nnnn #1 #2 {#3} } }
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\ShowCoffinStructure}
%   Back again to easy-to-implement functions.
%    \begin{macrocode}
\NewDocumentCommand \ShowCoffinStructure { m }
  { \coffin_show_structure:N #1 }
%    \end{macrocode}
% \end{macro}
%
%    \begin{macrocode}
%</package>
%    \end{macrocode}
%
% \end{implementation}
%
% \PrintIndex