summaryrefslogtreecommitdiff
path: root/macros/latex/contrib/l3experimental/l3draw-softpath.dtx
blob: ca1f161df56291d6df543f9a2134d1ffb162cd3c (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
% \iffalse meta-comment
%
%% File: l3draw-softpath.dtx
%
% Copyright (C) 2018-2020 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
%
%    http://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>
\RequirePackage{expl3}
\documentclass[full]{l3doc}
\begin{document}
  \DocInput{\jobname.dtx}
\end{document}
%</driver>
% \fi
%
% \title{^^A
%   The \pkg{l3draw-softpath} package\\ Soft paths^^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 2020-05-18}
%
% \maketitle
%
% \begin{implementation}
%
% \section{\pkg{l3draw-softpath} implementation}
%
%    \begin{macrocode}
%<*initex|package>
%    \end{macrocode}
%
%    \begin{macrocode}
%<@@=draw>
%    \end{macrocode}
%
% \subsection{Managing soft paths}
%
% There are two linked aims in the code here. The most significant is to
% provide a way to modify paths, for example to shorten the ends or round
% the corners.  This means that the path cannot be written piecemeal as
% specials, but rather needs to be held in macros. The second aspect that
% follows from this is performance: simply adding to a single macro a piece
% at a time will have poor performance as the list gets long so we use
% \cs[no-index]{tl_build_\ldots{}} functions.
%
% Each marker (operation) token takes two arguments, which makes processing
% more straight-forward. As such, some operations have dummy arguments, whilst
% others have to be split over several tokens. As the code here is at a low
% level, all dimension arguments are assumed to be explicit and fully-expanded.
%
% \begin{variable}{\g_@@_softpath_main_tl}
%   The soft path itself.
%    \begin{macrocode}
\tl_new:N \g_@@_softpath_main_tl
%    \end{macrocode}
% \end{variable}
%
% \begin{variable}{\l_@@_softpath_internal_tl}
%   The soft path itself.
%    \begin{macrocode}
\tl_new:N \l_@@_softpath_internal_tl
%    \end{macrocode}
% \end{variable}
%
% \begin{variable}{\g_@@_softpath_corners_bool}
%   Allow for optimised path use.
%    \begin{macrocode}
\bool_new:N \g_@@_softpath_corners_bool
%    \end{macrocode}
% \end{variable}
%
% \begin{macro}{\@@_softpath_add:n, \@@_softpath_add:o, \@@_softpath_add:x}
%    \begin{macrocode}
\cs_new_protected:Npn \@@_softpath_add:n
  { \tl_build_gput_right:Nn \g_@@_softpath_main_tl }
\cs_generate_variant:Nn \@@_softpath_add:n { o, x }
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}
%   {\@@_softpath_use:, \@@_softpath_clear:}
%   Using and clearing is trivial.
%    \begin{macrocode}
\cs_new_protected:Npn \@@_softpath_use:
  {
    \tl_build_get:NN \g_@@_softpath_main_tl \l_@@_softpath_internal_tl
    \l_@@_softpath_internal_tl
  }
\cs_new_protected:Npn \@@_softpath_clear:
  {
    \tl_build_gclear:N \g_@@_softpath_main_tl
    \bool_gset_false:N \g_@@_softpath_corners_bool
  }
%    \end{macrocode}
% \end{macro}
%
% \begin{variable}{\g_@@_softpath_lastx_dim, \g_@@_softpath_lasty_dim}
%   For tracking the end of the path (to close it).
%    \begin{macrocode}
\dim_new:N \g_@@_softpath_lastx_dim
\dim_new:N \g_@@_softpath_lasty_dim
%    \end{macrocode}
% \end{variable}
%
% \begin{variable}{\g_@@_softpath_move_bool}
%   Track if moving a point should update the close position.
%    \begin{macrocode}
\bool_new:N \g_@@_softpath_move_bool
\bool_gset_true:N \g_@@_softpath_move_bool
%    \end{macrocode}
% \end{variable}
%
% \begin{macro}{\@@_softpath_curveto:nnnnnn}
% \begin{macro}
%   {
%     \@@_softpath_lineto:nn,
%     \@@_softpath_moveto:nn
%   }
% \begin{macro}{\@@_softpath_rectangle:nnnn}
% \begin{macro}{\@@_softpath_roundpoint:nn, \@@_softpath_roundpoint:VV}
%   The various parts of a path expressed as the appropriate soft path
%   functions.
%    \begin{macrocode}
\cs_new_protected:Npn \@@_softpath_closepath:
  {
    \@@_softpath_add:x
      {
        \@@_softpath_close_op:nn
          { \dim_use:N \g_@@_softpath_lastx_dim }
          { \dim_use:N \g_@@_softpath_lasty_dim }
      }
  }
\cs_new_protected:Npn \@@_softpath_curveto:nnnnnn #1#2#3#4#5#6
  {
    \@@_softpath_add:n
      {
        \@@_softpath_curveto_opi:nn {#1} {#2}
        \@@_softpath_curveto_opii:nn {#3} {#4}
        \@@_softpath_curveto_opiii:nn {#5} {#6}
      }
  }
\cs_new_protected:Npn \@@_softpath_lineto:nn #1#2
  {
    \@@_softpath_add:n
      { \@@_softpath_lineto_op:nn {#1} {#2} }
  }
\cs_new_protected:Npn \@@_softpath_moveto:nn #1#2
  {
    \@@_softpath_add:n
      { \@@_softpath_moveto_op:nn {#1} {#2} }
    \bool_if:NT \g_@@_softpath_move_bool
      {
        \dim_gset:Nn \g_@@_softpath_lastx_dim {#1}
        \dim_gset:Nn \g_@@_softpath_lasty_dim {#2}
      }
  }
\cs_new_protected:Npn \@@_softpath_rectangle:nnnn #1#2#3#4
  {
    \@@_softpath_add:n
      {
        \@@_softpath_rectangle_opi:nn {#1} {#2}
        \@@_softpath_rectangle_opii:nn {#3} {#4}
      }
  }
\cs_new_protected:Npn \@@_softpath_roundpoint:nn #1#2
  {
    \@@_softpath_add:n
      { \@@_softpath_roundpoint_op:nn {#1} {#2} }
    \bool_gset_true:N \g_@@_softpath_corners_bool
  }
\cs_generate_variant:Nn \@@_softpath_roundpoint:nn { VV }
%    \end{macrocode}
% \end{macro}
% \end{macro}
% \end{macro}
% \end{macro}
%
% \begin{macro}
%   {
%     \@@_softpath_close_op:nn      ,
%     \@@_softpath_curveto_opi:nn   ,
%     \@@_softpath_curveto_opii:nn  ,
%     \@@_softpath_curveto_opiii:nn ,
%     \@@_softpath_lineto_op:nn     ,
%     \@@_softpath_moveto_op:nn     ,
%     \@@_softpath_roundpoint_op:nn ,
%     \@@_softpath_rectangle_opi:nn ,
%     \@@_softpath_rectangle_opii:nn
%   }
% \begin{macro}{\@@_softpath_curveto_opi:nnNnnNnn}
% \begin{macro}{\@@_softpath_rectangle_opi:nnNnn}
%   The markers for operations: all the top-level ones take two arguments.
%   The support tokens for curves have to be different in meaning to a
%   round point, hence being quark-like.
%    \begin{macrocode}
\cs_new_protected:Npn \@@_softpath_close_op:nn #1#2
  { \@@_backend_closepath: }
\cs_new_protected:Npn \@@_softpath_curveto_opi:nn #1#2 
  { \@@_softpath_curveto_opi:nnNnnNnn {#1} {#2} }
\cs_new_protected:Npn \@@_softpath_curveto_opi:nnNnnNnn #1#2#3#4#5#6#7#8
  { \@@_backend_curveto:nnnnnn {#1} {#2} {#4} {#5} {#7} {#8} }
\cs_new_protected:Npn \@@_softpath_curveto_opii:nn #1#2
  { \@@_softpath_curveto_opii:nn }
\cs_new_protected:Npn \@@_softpath_curveto_opiii:nn #1#2
  { \@@_softpath_curveto_opiii:nn }
\cs_new_protected:Npn \@@_softpath_lineto_op:nn #1#2
  { \@@_backend_lineto:nn {#1} {#2} }
\cs_new_protected:Npn \@@_softpath_moveto_op:nn #1#2
  { \@@_backend_moveto:nn {#1} {#2} }
\cs_new_protected:Npn \@@_softpath_roundpoint_op:nn #1#2 { }
\cs_new_protected:Npn \@@_softpath_rectangle_opi:nn #1#2 
  { \@@_softpath_rectangle_opi:nnNnn {#1} {#2} }
\cs_new_protected:Npn \@@_softpath_rectangle_opi:nnNnn #1#2#3#4#5
  { \@@_backend_rectangle:nnnn {#1} {#2} {#4} {#5} }
  \cs_new_protected:Npn \@@_softpath_rectangle_opii:nn #1#2 { }
%    \end{macrocode}
% \end{macro}
% \end{macro}
% \end{macro}
%
% \subsection{Rounding soft path corners}
%
% The aim here is to find corner rounding points and to replace them with
% arcs of appropriate length. The approach is exactly that in \pkg{pgf}:
% step through, find the corners, find the supporting data, do the rounding.
%
% \begin{variable}{\l_@@_softpath_main_tl}
%   For constructing the updated path.
%    \begin{macrocode}
\tl_new:N \l_@@_softpath_main_tl
%    \end{macrocode}
% \end{variable}
%
% \begin{variable}{\l_@@_softpath_part_tl}
%   Data structures.
%    \begin{macrocode}
\tl_new:N \l_@@_softpath_part_tl
\tl_new:N \l_@@_softpath_curve_end_tl
%    \end{macrocode}
% \end{variable}
%
% \begin{variable}
%   {\l_@@_softpath_lastx_fp, \l_@@_softpath_lasty_fp}
% \begin{variable}
%   {\l_@@_softpath_corneri_dim, \l_@@_softpath_cornerii_dim}
% \begin{variable}{\l_@@_softpath_first_tl, \l_@@_softpath_move_tl}
%   Position tracking: the token list data may be entirely empty or set to
%   a co-ordinate.
%    \begin{macrocode}
\fp_new:N \l_@@_softpath_lastx_fp
\fp_new:N \l_@@_softpath_lasty_fp
\dim_new:N \l_@@_softpath_corneri_dim
\dim_new:N \l_@@_softpath_cornerii_dim
\tl_new:N \l_@@_softpath_first_tl
\tl_new:N \l_@@_softpath_move_tl
%    \end{macrocode}
% \end{variable}
% \end{variable}
% \end{variable}
%
% \begin{variable}{\c_@@_softpath_arc_fp}
%   The magic constant.
%    \begin{macrocode}
\fp_const:Nn \c_@@_softpath_arc_fp { 4/3 * (sqrt(2) - 1) }
%    \end{macrocode}
% \end{variable}
%
% \begin{macro}{\@@_softpath_round_corners:}
% \begin{macro}{\@@_softpath_round_loop:Nnn}
% \begin{macro}{\@@_softpath_round_action:nn}
% \begin{macro}{\@@_softpath_round_action:Nnn}
% \begin{macro}{\@@_softpath_round_action_curveto:NnnNnn}
% \begin{macro}{\@@_softpath_round_action_close:}
% \begin{macro}{\@@_softpath_round_lookahead:NnnNnn}
% \begin{macro}{\@@_softpath_round_roundpoint:NnnNnnNnn}
% \begin{macro}{\@@_softpath_round_calc:NnnNnn}
% \begin{macro}[EXP]
%   {\@@_softpath_round_calc:nnnnnn, \@@_softpath_round_calc:fVnnnn}
% \begin{macro}[EXP]{\@@_softpath_round_calc:nnnnw}
% \begin{macro}{\@@_softpath_round_close:nn}
% \begin{macro}[EXP]{\@@_softpath_round_close:w}
% \begin{macro}{\@@_softpath_round_end:}
%   Rounding corners on a path means going through the entire path and
%   adjusting it. As such, we avoid this entirely if we know there are no
%   corners to deal with. Assuming there is work to do, we recover the existing
%   path and start a loop.
%    \begin{macrocode}
\cs_new_protected:Npn \@@_softpath_round_corners:
  {
    \bool_if:NT \g_@@_softpath_corners_bool
      {
        \group_begin:
          \tl_clear:N \l_@@_softpath_main_tl
          \tl_clear:N \l_@@_softpath_part_tl
          \fp_zero:N \l_@@_softpath_lastx_fp
          \fp_zero:N \l_@@_softpath_lasty_fp
          \tl_clear:N \l_@@_softpath_first_tl
          \tl_clear:N \l_@@_softpath_move_tl
          \tl_build_get:NN \g_@@_softpath_main_tl \l_@@_softpath_internal_tl
          \exp_after:wN \@@_softpath_round_loop:Nnn
            \l_@@_softpath_internal_tl
            \q_@@_recursion_tail ? ?
            \q_@@_recursion_stop
        \group_end:
      }
    \bool_gset_false:N \g_@@_softpath_corners_bool
  }
%    \end{macrocode}
%   The loop can take advantage of the fact that all soft path operations are
%   made up of a token followed by two arguments. At this stage, there is
%   a simple split: have we round a round point. If so, is there any actual
%   rounding to be done: if the arcs have come through zero, just ignore it.
%   In cases where we are not at a corner, we simply move along the path,
%   allowing for any new part starting due to a \texttt{moveto}.
%    \begin{macrocode}
\cs_new_protected:Npn \@@_softpath_round_loop:Nnn #1#2#3
  {
    \@@_if_recursion_tail_stop_do:Nn #1 { \@@_softpath_round_end: }
    \token_if_eq_meaning:NNTF #1 \@@_softpath_roundpoint_op:nn
      { \@@_softpath_round_action:nn {#2} {#3} }
      {
        \tl_if_empty:NT \l_@@_softpath_first_tl
          { \tl_set:Nn \l_@@_softpath_first_tl { {#2} {#3} } }
        \fp_set:Nn \l_@@_softpath_lastx_fp {#2}
        \fp_set:Nn \l_@@_softpath_lasty_fp {#3}
        \token_if_eq_meaning:NNTF #1 \@@_softpath_moveto_op:nn
          {
            \tl_put_right:No \l_@@_softpath_main_tl
              \l_@@_softpath_move_tl
            \tl_put_right:No \l_@@_softpath_main_tl
              \l_@@_softpath_part_tl
            \tl_set:Nn \l_@@_softpath_move_tl { #1 {#2} {#3} }
            \tl_clear:N \l_@@_softpath_first_tl
            \tl_clear:N \l_@@_softpath_part_tl
          }
          { \tl_put_right:Nn \l_@@_softpath_part_tl { #1 {#2} {#3} } }
        \@@_softpath_round_loop:Nnn
      }
  }
\cs_new_protected:Npn \@@_softpath_round_action:nn #1#2
  {
    \dim_set:Nn \l_@@_softpath_corneri_dim {#1}
    \dim_set:Nn \l_@@_softpath_cornerii_dim {#2}
    \bool_lazy_and:nnTF
      { \dim_compare_p:nNn \l_@@_softpath_corneri_dim = { 0pt } }
      { \dim_compare_p:nNn \l_@@_softpath_cornerii_dim = { 0pt } }
      { \@@_softpath_round_loop:Nnn }
      { \@@_softpath_round_action:Nnn } 
  }
%    \end{macrocode}
%   We now have a round point to work on and have grabbed the next item in
%   the path. There are only a few cases where we have to do anything. Each of
%   them is picked up by looking for the appropriate action.
%    \begin{macrocode}
\cs_new_protected:Npn \@@_softpath_round_action:Nnn #1#2#3
  {
    \tl_if_empty:NT \l_@@_softpath_first_tl
      { \tl_set:Nn \l_@@_softpath_first_tl { {#2} {#3} } }
    \token_if_eq_meaning:NNTF #1 \@@_softpath_curveto_opi:nn
      { \@@_softpath_round_action_curveto:NnnNnn }
      {
        \token_if_eq_meaning:NNTF #1 \@@_softpath_close_op:nn
          { \@@_softpath_round_action_close: }
          {
            \token_if_eq_meaning:NNTF #1 \@@_softpath_lineto_op:nn
              { \@@_softpath_round_lookahead:NnnNnn }
              { \@@_softpath_round_loop:Nnn }
          }
      }
      #1 {#2} {#3}
  }
%    \end{macrocode}
%   For a curve, we collect the two control points then move on to grab the
%   end point and add the curve there: the second control point becomes our
%   starter.
%    \begin{macrocode}
\cs_new_protected:Npn \@@_softpath_round_action_curveto:NnnNnn
  #1#2#3#4#5#6
  {
    \tl_put_right:Nn \l_@@_softpath_part_tl
      { #1 {#2} {#3} #4 {#5} {#6} }
    \fp_set:Nn \l_@@_softpath_lastx_fp {#5}
    \fp_set:Nn \l_@@_softpath_lasty_fp {#6}
    \@@_softpath_round_lookahead:NnnNnn
  }
\cs_new_protected:Npn \@@_softpath_round_action_close:
  {
    \bool_lazy_and:nnTF
      { ! \tl_if_empty_p:N \l_@@_softpath_first_tl }
      { ! \tl_if_empty_p:N \l_@@_softpath_move_tl }
      {
        \exp_after:wN \@@_softpath_round_close:nn
          \l_@@_softpath_first_tl
      }
      { \@@_softpath_round_loop:Nnn }
  }
%    \end{macrocode}
%   At this stage we have a current (sub)operation (|#1|) and the next
%   operation (|#4|), and can therefore decide whether to round or not.
%   In the case of yet another rounding marker, we have to look a bit
%   further ahead.
%    \begin{macrocode}
\cs_new_protected:Npn \@@_softpath_round_lookahead:NnnNnn #1#2#3#4#5#6
  {
    \bool_lazy_any:nTF
      {
        { \token_if_eq_meaning_p:NN #4 \@@_softpath_lineto_op:nn }
        { \token_if_eq_meaning_p:NN #4 \@@_softpath_curveto_opi:nn }
        { \token_if_eq_meaning_p:NN #4 \@@_softpath_close_op:nn }
      }
      {
        \@@_softpath_round_calc:NnnNnn
          \@@_softpath_round_loop:Nnn
          {#5} {#6}
      }
      {
        \token_if_eq_meaning:NNTF #4 \@@_softpath_roundpoint_op:nn
          { \@@_softpath_round_roundpoint:NnnNnnNnn }
          { \@@_softpath_round_loop:Nnn }
      }
    #1 {#2} {#3}
    #4 {#5} {#6}
  }
\cs_new_protected:Npn \@@_softpath_round_roundpoint:NnnNnnNnn
  #1#2#3#4#5#6#7#8#9
  {
    \@@_softpath_round_calc:NnnNnn
      \@@_softpath_round_loop:Nnn
      {#8} {#9}
      #1 {#2} {#3}
    #4 {#5} {#6} #7 {#8} {#9}
  }
%    \end{macrocode}
%   We now have all of the data needed to construct a rounded corner: all that
%   is left to do is to work out the detail! At this stage, we have details
%   of where the corner itself is (|#5|, |#6|), and where the next point is
%   (|#2|, |#3|). There are two types of calculations to do. First, we
%   need to interpolate from those two points in the direction of the
%   corner, in order to work out where the curve we are adding will start
%   and end. From those, plus the points we already have, we work out where
%   the control points will lie.  All of this is done in an expansion to
%   avoid multiple calls to |\tl_put_right:Nx|. The end point of the line
%   is worked out up-front and saved: we need that if dealing with a
%   close-path operation.
%    \begin{macrocode}
\cs_new_protected:Npn \@@_softpath_round_calc:NnnNnn #1#2#3#4#5#6
  {
    \tl_set:Nx \l_@@_softpath_curve_end_tl
      {
        \draw_point_interpolate_distance:nnn
          \l_@@_softpath_cornerii_dim
          { #5 , #6 } { #2 , #3 }
      }
    \tl_put_right:Nx \l_@@_softpath_part_tl
      {
        \exp_not:N #4
        \@@_softpath_round_calc:fVnnnn
          {
            \draw_point_interpolate_distance:nnn
              \l_@@_softpath_corneri_dim
              { #5 , #6 }
              {
                \l_@@_softpath_lastx_fp ,
                \l_@@_softpath_lasty_fp
              }
          }
          \l_@@_softpath_curve_end_tl
          {#5} {#6} {#2} {#3}
      }
    \fp_set:Nn \l_@@_softpath_lastx_fp {#5}
    \fp_set:Nn \l_@@_softpath_lasty_fp {#6}
    #1
  }
%    \end{macrocode}
%   At this stage we have the two curve end points, but they are in
%   co-ordinate form. So we split them up (with some more reordering).
%    \begin{macrocode}
\cs_new:Npn \@@_softpath_round_calc:nnnnnn #1#2#3#4#5#6
  {
    \@@_softpath_round_calc:nnnnw {#3} {#4} {#5} {#6}
      #1 \s_@@_mark #2 \s_@@_stop
  }
\cs_generate_variant:Nn \@@_softpath_round_calc:nnnnnn { fV }
%    \end{macrocode}
%   The calculations themselves are relatively straight-forward, as we use a
%   quadratic Bézier curve.
%    \begin{macrocode}
\cs_new:Npn \@@_softpath_round_calc:nnnnw
  #1#2#3#4 #5 , #6 \s_@@_mark #7 , #8 \s_@@_stop
  {
    {#5} {#6}
    \exp_not:N \@@_softpath_curveto_opi:nn
      {
        \fp_to_dim:n
          { #5 + \c_@@_softpath_arc_fp * ( #1 - #5 ) }
      }
      {
        \fp_to_dim:n
          { #6 + \c_@@_softpath_arc_fp * ( #2 - #6 ) }
      }
    \exp_not:N \@@_softpath_curveto_opii:nn
      {
        \fp_to_dim:n
          { #7 + \c_@@_softpath_arc_fp * ( #1 - #7 ) }
      }
      {
        \fp_to_dim:n
          { #8 + \c_@@_softpath_arc_fp* ( #2 - #8 ) }
      }
    \exp_not:N \@@_softpath_curveto_opiii:nn
      {#7} {#8}
  }
%    \end{macrocode}
%   To deal with a close-path operation, we need to do some manipulation.
%   It needs to be treated as a line operation for rounding, and then
%   have the close path operation re-added at the point where the curve
%   ends. That means saving the end point in the calculation step (see
%   earlier), and shuffling a lot.
%    \begin{macrocode}
\cs_new_protected:Npn \@@_softpath_round_close:nn #1#2
  {
    \use:x
      {
        \@@_softpath_round_calc:NnnNnn
          {
            \tl_set:Nx \exp_not:N \l_@@_softpath_move_tl
              {
                \@@_softpath_moveto_op:nn
                \exp_not:N \exp_after:wN
                  \exp_not:N \@@_softpath_round_close:w
                  \exp_not:N \l_@@_softpath_curve_end_tl
                    \s_@@_stop
              }
            \use:x
              {
                \exp_not:N \exp_not:N \exp_not:N \use_i:nnnn
                  {
                    \@@_softpath_round_loop:Nnn
                      \@@_softpath_close_op:nn
                      \exp_not:N \exp_after:wN
                        \exp_not:N \@@_softpath_round_close:w
                        \exp_not:N \l_@@_softpath_curve_end_tl
                          \s_@@_stop
                  }
              }
          }
          {#1} {#2}
          \@@_softpath_lineto_op:nn
          \exp_after:wN \use_none:n \l_@@_softpath_move_tl
      }
  }
\cs_new:Npn \@@_softpath_round_close:w #1 , #2 \s_@@_stop { {#1} {#2} }
%    \end{macrocode}
%   Tidy up the parts of the path, complete the built token list and put
%   it back into action. 
%    \begin{macrocode}
\cs_new_protected:Npn \@@_softpath_round_end:
  {
    \tl_put_right:No \l_@@_softpath_main_tl
      \l_@@_softpath_move_tl
    \tl_put_right:No \l_@@_softpath_main_tl
      \l_@@_softpath_part_tl
    \tl_build_gclear:N \g_@@_softpath_main_tl
    \@@_softpath_add:o \l_@@_softpath_main_tl
  }
%    \end{macrocode}
% \end{macro}
% \end{macro}
% \end{macro}
% \end{macro}
% \end{macro}
% \end{macro}
% \end{macro}
% \end{macro}
% \end{macro}
% \end{macro}
% \end{macro}
% \end{macro}
% \end{macro}
% \end{macro}
%
%    \begin{macrocode}
%</initex|package>
%    \end{macrocode}
%
% \end{implementation}
%
% \PrintIndex