summaryrefslogtreecommitdiff
path: root/src/Type1/paths.c
blob: 0b5b4ea9369a74e13222aad52682e2958d79b204 (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
/* $Xorg: paths.c,v 1.3 2000/08/17 19:46:31 cpqbld Exp $ */
/* Copyright International Business Machines, Corp. 1991
 * All Rights Reserved
 * Copyright Lexmark International, Inc. 1991
 * All Rights Reserved
 *
 * License to use, copy, modify, and distribute this software and its
 * documentation for any purpose and without fee is hereby granted,
 * provided that the above copyright notice appear in all copies and that
 * both that copyright notice and this permission notice appear in
 * supporting documentation, and that the name of IBM or Lexmark not be
 * used in advertising or publicity pertaining to distribution of the
 * software without specific, written prior permission.
 *
 * IBM AND LEXMARK PROVIDE THIS SOFTWARE "AS IS", WITHOUT ANY WARRANTIES OF
 * ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING, BUT NOT LIMITED TO ANY
 * IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE,
 * AND NONINFRINGEMENT OF THIRD PARTY RIGHTS.  THE ENTIRE RISK AS TO THE
 * QUALITY AND PERFORMANCE OF THE SOFTWARE, INCLUDING ANY DUTY TO SUPPORT
 * OR MAINTAIN, BELONGS TO THE LICENSEE.  SHOULD ANY PORTION OF THE
 * SOFTWARE PROVE DEFECTIVE, THE LICENSEE (NOT IBM OR LEXMARK) ASSUMES THE
 * ENTIRE COST OF ALL SERVICING, REPAIR AND CORRECTION.  IN NO EVENT SHALL
 * IBM OR LEXMARK BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL
 * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
 * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
 * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF
 * THIS SOFTWARE.
 */
/* $XFree86$ */

 /* PATHS    CWEB         V0021 ********                             */
/*
:h1 id=paths.PATHS Module - Path Operator Handler
 
This is the module that is responsible for building and transforming
path lists.
 
&author. Jeffrey B. Lotspiech (lotspiech@almaden.ibm.com)
 
 
:h3.Include Files
 
The included files are:
*/
 
                             /*   after the system includes  (dsr)           */
#include  "os.h"
#include  "objects.h"
#include  "spaces.h"
#include  "paths.h"
#include  "regions.h"      /* understands about Union                      */
#include  "fonts.h"        /* understands about TEXTTYPEs                  */
#include  "pictures.h"     /* understands about handles                    */
#include  "strokes.h"      /* understands how to coerce stroke paths       */
#include  "trig.h"


/*
:h3.Routines Available to the TYPE1IMAGER User
 
The PATHS routines that are made available to the outside user are:
*/
 
/*SHARED LINE(S) ORIGINATED HERE*/
/*
:h3.Functions Provided to Other Modules
 
The path routines that are made available to other TYPE1IMAGER modules
are defined here:
*/
 
/*SHARED LINE(S) ORIGINATED HERE*/
/*
NOTE:  because of the casts put in the macros for Loc, ArcCA, Conic,
RoundConic, PathSegment, and JoinSegment, we cannot use the macro names
when the functions are actually defined.  We have to use the unique
names with their unique first two characters.  Thus, if anyone in the
future ever decided to change the first two characters, it would not be
enough just to change the macro (as it would for most other functions).
He would have to also change the function definition.
*/
/*
:h3.Macros Provided to Other Modules
 
The CONCAT macro is defined here and used in the STROKES module.  See
:hdref refid=pathmac..
*/
 
/*SHARED LINE(S) ORIGINATED HERE*/
 
/*
:h2.Path Segment Structures
 
A path is represented as a linked list of the following structure:
*/
 
/*SHARED LINE(S) ORIGINATED HERE*/
/*
When 'link' is NULL, we are at the last segment in the path (surprise!).
 
'last' is only non-NULL on the first segment of a path,
for all the other segments 'last' == NULL.  We test for a non-NULL
'last' (ISPATHANCHOR predicate) when we are given an alleged path
to make sure the user is not trying to pull a fast one on us.
 
A path may be a collection of disjoint paths.  Every break in the
disjoint path is represented by a MOVETYPE segment.
 
Closed paths are discussed in :hdref refid=close..
 
:h3.CopyPath() - Physically Duplicating a Path
 
This simple function illustrates moving through the path linked list.
Duplicating a segment just involves making a copy of it, except for
text, which has some auxilliary things involved.  We don't feel
competent to duplicate text in this module, so we call someone who
knows how (in the FONTS module).
*/
struct segment *
CopyPath(struct segment *p0)         /* path to duplicate                    */
{
       register struct segment *p,*n = NULL,*last = NULL,*anchor;
 
       for (p = p0, anchor = NULL; p != NULL; p = p->link) {
 
               ARGCHECK((!ISPATHTYPE(p->type) || (p != p0 && p->last != NULL)),
                       "CopyPath: invalid segment", p, NULL, (0), struct segment *);
 
               if (p->type == TEXTTYPE)
                       n = (struct segment *) CopyText(p);
               else
                       n = (struct segment *)Allocate(p->size, p, 0);
               n->last = NULL;
               if (anchor == NULL)
                       anchor = n;
               else
                       last->link = n;
               last = n;
       }
/*
At this point we have a chain of newly allocated segments hanging off
'anchor'.  We need to make sure the first segment points to the last:
*/
       if (anchor != NULL) {
               n->link = NULL;
               anchor->last = n;
       }
 
       return(anchor);
}
/*
:h3.KillPath() - Destroying a Path
 
Destroying a path is simply a matter of freeing each segment in the
linked list.  Again, we let the experts handle text.
*/
void 
KillPath(struct segment *p)         /* path to destroy                       */
{
       register struct segment *linkp;  /* temp register holding next segment*/
 
       /* return conditional based on reference count 3-26-91 PNM */
       if ( (--(p->references) > 1) ||
          ( (p->references == 1) && !ISPERMANENT(p->flag) ) )
           return;
 
       while (p != NULL) {
               if (!ISPATHTYPE(p->type)) {
                       ArgErr("KillPath: bad segment", p, NULL);
                       return;
               }
               linkp = p->link;
               if (p->type == TEXTTYPE)
                       KillText(p);
               else
                       Free(p);
               p = linkp;
       }
}
 
/*
:h2 id=location."location" Objects
 
The TYPE1IMAGER user creates and destroys objects of type "location".  These
objects locate points for the primitive path operators.  We play a trick
here and store these objects in the same "segment" structure used for
paths, with a type field == MOVETYPE.
 
This allows the Line() operator, for example, to be very trivial:
It merely stamps its input structure as a LINETYPE and returns it to the
caller--assuming, of course, the input structure was not permanent (as
it usually isn't).
 
:h3.The "movesegment" Template Structure
 
This template is used as a generic segment structure for Allocate:
*/
 
/* added reference field 1 to temporary template below 3-26-91 PNM */
static struct segment movetemplate = { MOVETYPE, 0, 1, sizeof(struct segment), 0,
                NULL, NULL, {0, 0} };
/*
:h3.Loc() - Create an "Invisible Line" Between (0,0) and a Point
 
*/
 
struct segment *
t1_Loc(struct XYspace *S,    /* coordinate space to interpret X,Y            */
       double x, double y)   /* destination point                            */
{
       register struct segment *r;
 
 
       r = (struct segment *)Allocate(sizeof(struct segment), &movetemplate, 0);
       TYPECHECK("Loc", S, SPACETYPE, r, (0), struct segment *);
 
       r->last = r;
       r->context = S->context;
       (*S->convert)(&r->dest, S, x, y);
       ConsumeSpace(S);
       return(r);
}
/*
:h3.ILoc() - Loc() With Integer Arguments
 
*/
struct segment *
ILoc(struct XYspace *S,         /* coordinate space to interpret X,Y         */
     int x, int y)              /* destination point                         */
{
       register struct segment *r;
 
       r = (struct segment *)Allocate(sizeof(struct segment), &movetemplate, 0);
       TYPECHECK("Loc", S, SPACETYPE, r, (0), struct segment *);
 
       r->last = r;
       r->context = S->context;
       (*S->iconvert)(&r->dest, S, (long) x, (long) y);
       ConsumeSpace(S);
       return(r);
}
 
/*
:h3.SubLoc() - Vector Subtraction of Two Locition Objects
 
This user operator subtracts two location objects, yielding a new
location object that is the result.
 
The symmetrical function AddLoc() is totally redundent with Join(),
so it is not provided.
*/
 
struct segment *
SubLoc(struct segment *p1, struct segment *p2)
{
       ARGCHECK(!ISLOCATION(p1), "SubLoc: bad first arg", p1, NULL, (0), struct segment *);
       ARGCHECK(!ISLOCATION(p2), "SubLoc: bad second arg", p2, NULL, (0), struct segment *);
       p1 = UniquePath(p1);
       p1->dest.x -= p2->dest.x;
       p1->dest.y -= p2->dest.y;
       ConsumePath(p2);
       return(p1);
}
 
/*
:h2.Straight Line Segments
 
:h3.PathSegment() - Create a Generic Path Segment
 
Many routines need a LINETYPE or MOVETYPE path segment, but do not
want to go through the external user's interface, because, for example,
they already know the "fractpel" destination of the segment and the
conversion is unnecessary.  PathSegment() is an internal routine
provided to the rest of TYPE1IMAGER for handling these cases.
*/
 
struct segment *
t1_PathSegment(int type,     /* LINETYPE or MOVETYPE                         */
	       fractpel x, fractpel y) /* where to go to, if known           */
{
       register struct segment *r;  /* newly created segment                 */
 
       r = (struct segment *)Allocate(sizeof(struct segment), &movetemplate, 0);
       r->type = type;
       r->last = r;          /* last points to itself for singleton          */
       r->dest.x = x;
       r->dest.y = y;
       return(r);
}
/*
:h3.Line() - Create a Line Segment Between (0,0) and a Point P
 
This involves just creating and filling out a segment structure:
*/
struct segment *
Line(struct segment *P)      /* relevant coordinate space                    */
{
       ARGCHECK(!ISLOCATION(P), "Line: arg not a location", P, NULL, (0), struct segment *);
 
       P = UniquePath(P);
       P->type = LINETYPE;
       return(P);
}
/*
:h2.Curved Path Segments
 
We need more points to describe curves.  So, the structures for curved
path segments are slightly different.  The first part is identical;
the curved structures are larger with the extra points on the end.
 
:h3.Bezier Segment Structure
 
We support third order Bezier curves.  They are specified with four
control points A, B, C, and D.  The curve starts at A with slope AB
and ends at D with slope CD.  The curvature at the point A is inversely
related to the length |AB|, and the curvature at the point D is
inversely related to the length |CD|.  Point A is always point (0,0).
 
*/
 
/*SHARED LINE(S) ORIGINATED HERE*/
/*
:h3.Bezier() - Generate a Bezier Segment
 
This is just a simple matter of filling out a 'beziersegment' structure:
*/
 
struct beziersegment *
Bezier(struct segment *B,           /* second control point                  */
       struct segment *C,           /* third control point                   */
       struct segment *D)           /* fourth control point (ending point)   */
{
/* added reference field of 1 to temporary template below 3-26-91  PNM */
       static struct beziersegment template =
                    { BEZIERTYPE, 0, 1, sizeof(struct beziersegment), 0,
                      NULL, NULL, { 0, 0 }, { 0, 0 }, { 0, 0 } };
 
       register struct beziersegment *r;  /* output segment                  */
 
       ARGCHECK(!ISLOCATION(B), "Bezier: bad B", B, NULL, (2,C,D), struct beziersegment *);
       ARGCHECK(!ISLOCATION(C), "Bezier: bad C", C, NULL, (2,B,D), struct beziersegment *);
       ARGCHECK(!ISLOCATION(D), "Bezier: bad D", D, NULL, (2,B,C), struct beziersegment *);
 
       r = (struct beziersegment *)Allocate(sizeof(struct beziersegment), &template, 0);
       r->last = (struct segment *) r;
       r->dest.x = D->dest.x;
       r->dest.y = D->dest.y;
       r->B.x = B->dest.x;
       r->B.y = B->dest.y;
       r->C.x = C->dest.x;
       r->C.y = C->dest.y;
 
       ConsumePath(B);
       ConsumePath(C);
       ConsumePath(D);
       return(r);
}
 
/*
:h2.Font "Hint" Segments
 
:h3.Hint() - A Font 'Hint' Segment
 
This is temporary code while we experiment with hints.
*/
 
/*SHARED LINE(S) ORIGINATED HERE*/
struct hintsegment *
Hint(struct XYspace *S, float ref, float width, 
     char orientation, char hinttype, char adjusttype, char direction, 
     int label)
{
/* added reference field of 1 to hintsegment template below 3-26-91 PNM */
       static struct hintsegment template = { HINTTYPE, 0, 1, sizeof(struct hintsegment), 0,
                                          NULL, NULL, { 0, 0 }, { 0, 0 }, { 0, 0 },
                                          ' ', ' ', ' ', ' ', 0};
 
       register struct hintsegment *r;
 
       r = (struct hintsegment *)Allocate(sizeof(struct hintsegment), &template, 0);
 
       r->orientation = orientation;
       if (width == 0.0)  width = 1.0;
 
       if (orientation == 'h') {
               (*S->convert)(&r->ref, S, 0.0, ref);
               (*S->convert)(&r->width, S, 0.0, width);
       }
       else if (orientation == 'v') {
               (*S->convert)(&r->ref, S, ref, 0.0);
               (*S->convert)(&r->width, S, width, 0.0);
       }
       else
               return((struct hintsegment *)ArgErr("Hint: orient not 'h' or 'v'", NULL, NULL));
       if (r->width.x < 0)  r->width.x = - r->width.x;
       if (r->width.y < 0)  r->width.y = - r->width.y;
       r->hinttype = hinttype;
       r->adjusttype = adjusttype;
       r->direction = direction;
       r->label = label;
       r->last = (struct segment *) r;
       ConsumeSpace(S);
       return(r);
}
 
/*
*/
 
/*SHARED LINE(S) ORIGINATED HERE*/
 
/*
POP removes the first segment in a path 'p' and Frees it.  'p' is left
pointing to the end of the path:
*/
#define POP(p) \
     { register struct segment *linkp; \
       linkp = p->link; \
       if (linkp != NULL) \
               linkp->last = p->last; \
       Free(p); \
       p = linkp; }
/*
INSERT inserts a single segment in the middle of a chain.  'b' is
the segment before, 'p' the segment to be inserted, and 'a' the
segment after.
*/
#define INSERT(b,p,a)  b->link=p; p->link=a; p->last=NULL
 
/*
:h3.Join() - Join Two Objects Together
 
If these are paths, this operator simply invokes the CONCAT macro.
Why so much code then, you ask?  Well we have to check for object
types other than paths, and also check for certain path consistency
rules.
*/
 
struct segment *
Join(struct segment *p1, struct segment *p2)
{
/*
We start with a whole bunch of very straightforward argument tests:
*/
       if (p2 != NULL) {
               if (!ISPATHTYPE(p2->type)) {
 
                       if (p1 == NULL)
                               return((struct segment *)Unique(p2));
 
                       switch (p1->type) {
 
                           case REGIONTYPE:
 
                           case STROKEPATHTYPE:
                               p1 = CoercePath(p1);
                               break;
 
                           default:
                               return((struct segment *)BegHandle(p1, p2));
                       }
               }
 
               ARGCHECK((p2->last == NULL), "Join: right arg not anchor", p2, NULL, (1,p1), struct segment *);
               p2 = UniquePath(p2);
 
/*
In certain circumstances, we don't have to duplicate a permanent
location.  (We would just end up destroying it anyway).  These cases
are when 'p2' begins with a move-type segment:
*/
               if (p2->type == TEXTTYPE || p2->type == MOVETYPE) {
                       if (p1 == NULL)
                               return(p2);
                       if (ISLOCATION(p1)) {
                               p2->dest.x += p1->dest.x;
                               p2->dest.y += p1->dest.y;
                               ConsumePath(p1);
                               return(p2);
                       }
               }
       }
       else
               return((struct segment *)Unique(p1));
 
       if (p1 != NULL) {
               if (!ISPATHTYPE(p1->type))
 
                       switch (p2->type) {
 
                           case REGIONTYPE:
 
                           case STROKEPATHTYPE:
                               p2 = CoercePath(p2);
                               break;
 
                           default:
                               return((struct segment *)EndHandle(p1, p2));
                       }
 
               ARGCHECK((p1->last == NULL), "Join: left arg not anchor", p1, NULL, (1,p2), struct segment *);
               p1 = UniquePath(p1);
       }
       else
               return(p2);
 
/*
At this point all the checking is done.  We have two temporary non-null
path types in 'p1' and 'p2'.  If p1 ends with a MOVE, and p2 begins with
a MOVE, we collapse the two MOVEs into one.  We enforce the rule that
there may not be two MOVEs in a row:
*/
 
       if (p1->last->type == MOVETYPE && p2->type == MOVETYPE) {
               p1->last->flag |= p2->flag;
               p1->last->dest.x += p2->dest.x;
               p1->last->dest.y += p2->dest.y;
               POP(p2);
               if (p2 == NULL)
                       return(p1);
       }
/*
Now we check for another silly rule.  If a path has any TEXTTYPEs,
then it must have only TEXTTYPEs and MOVETYPEs, and furthermore,
it must begin with a TEXTTYPE.  This rule makes it easy to check
for the special case of text.  If necessary, we will coerce
TEXTTYPEs into paths so we don't mix TEXTTYPEs with normal paths.
*/
       if (p1->type == TEXTTYPE) {
               if (p2->type != TEXTTYPE && !ISLOCATION(p2))
                       p1 = CoerceText(p1);
       }
       else {
               if (p2->type == TEXTTYPE) {
                       if (ISLOCATION(p1)) {
                               p2->dest.x += p1->dest.x;
                               p2->dest.y += p1->dest.y;
                               Free(p1);
                               return(p2);
                       }
                       else
                               p2 = CoerceText(p2);
               }
       }
/*
Thank God!  Finally!  It's hard to believe, but we are now able to
actually do the join.  This is just invoking the CONCAT macro:
*/
       CONCAT(p1, p2);
 
       return(p1);
}
 
/*
:h3.JoinSegment() - Create a Path Segment and Join It to a Known Path
 
This internal function is quicker than a full-fledged join because
it can do much less checking.
*/
 
struct segment *
t1_JoinSegment(struct segment *before, /* path to join before new segment    */
	       int type,     /* type of new segment (MOVETYPE or LINETYPE)   */
	       fractpel x, fractpel y, /* x,y of new segment                 */
	       struct segment *after) /* path to join after new segment      */
{
       register struct segment *r;  /* returned path built here              */
 
       r = PathSegment(type, x, y);
       if (before != NULL) {
               CONCAT(before, r);
               r = before;
       }
       else
               r->context = after->context;
       if (after != NULL)
               CONCAT(r, after);
       return(r);
}
 
/*
:h2.Other Path Functions
 
*/
 
 
struct segment *
t1_ClosePath(struct segment *p0, /* path to close                            */
	     int lastonly)     /*  flag deciding to close all subpaths or... */
{
       register struct segment *p,*last = NULL,*start;  /* used in looping through path */
       register fractpel x,y;  /* current position in path                   */
       register fractpel firstx = 0,firsty = 0;  /* start position of sub path       */
       register struct segment *lastnonhint = NULL;  /* last non-hint segment in path */
 
       if (p0 != NULL && p0->type == TEXTTYPE)
               return(UniquePath(p0));
       if (p0->type == STROKEPATHTYPE)
               return((struct segment *)Unique(p0));
       /*
       * NOTE: a null closed path is different from a null open path
       * and is denoted by a closed (0,0) move segment.  We make
       * sure this path begins and ends with a MOVETYPE:
       */
       if (p0 == NULL || p0->type != MOVETYPE)
               p0 = JoinSegment(NULL, MOVETYPE, 0, 0, p0);
       TYPECHECK("ClosePath", p0, MOVETYPE, NULL, (0), struct segment *);
       if (p0->last->type != MOVETYPE)
               p0 = JoinSegment(p0, MOVETYPE, 0, 0, NULL);
 
       p0 = UniquePath(p0);
 
/*
We now begin a loop through the path,
incrementing current 'x' and 'y'.  We are searching
for MOVETYPE segments (breaks in the path) that are not already closed.
At each break, we insert a close segment.
*/
       for (p = p0, x = y = 0, start = NULL;
            p != NULL;
            x += p->dest.x, y += p->dest.y, last = p, p = p->link)
       {
 
               if (p->type == MOVETYPE) {
                       if (start != NULL && (lastonly?p->link==NULL:TRUE) &&
                             !(ISCLOSED(start->flag) && LASTCLOSED(last->flag))) {
                               register struct segment *r;  /* newly created */
 
                               start->flag |= ISCLOSED(ON);
                               r = PathSegment(LINETYPE, firstx - x,
                                                         firsty - y);
                               INSERT(last, r, p);
                               r->flag |= LASTCLOSED(ON);
                               /*< adjust 'last' if possible for a 0,0 close >*/
{
 
#define   CLOSEFUDGE    3    /* if we are this close, let's change last segment */
 
       if (r->dest.x != 0 || r->dest.y != 0) {
               if (r->dest.x <= CLOSEFUDGE && r->dest.x >= -CLOSEFUDGE
                    && r->dest.y <= CLOSEFUDGE && r->dest.y >= -CLOSEFUDGE) {
                       lastnonhint->dest.x += r->dest.x;
                       lastnonhint->dest.y += r->dest.y;
                       r->dest.x = r->dest.y = 0;
               }
       }
}
                               if (p->link != NULL) {
                                       p->dest.x += x - firstx;
                                       p->dest.y += y - firsty;
                                       x = firstx;
                                       y = firsty;
                               }
                       }
                       start = p;
                       firstx = x + p->dest.x;
                       firsty = y + p->dest.y;
               }
               else if (p->type != HINTTYPE)
                       lastnonhint = p;
       }
       return(p0);
}
/*
*/
/*
:h2.Reversing the Direction of a Path
 
This turned out to be more difficult than I thought at first.  The
trickiness was due to the fact that closed paths must remain closed,
etc.
 
We need three subroutines:
*/
 
/* break a path at any point             */
static struct segment *SplitPath ( struct segment *anchor, 
					  struct segment *before );
/* breaks a path after first sub-path */
static struct segment *DropSubPath ( struct segment *p0 );
/* reverses a single sub-path      */
static struct segment *ReverseSubPath ( struct segment *p );

/*
:h3.Reverse() - User Operator to Reverse a Path
 
This operator reverses the entire path.
*/
 
struct segment *
Reverse(struct segment *p)            /* full path to reverse                */
{
       register struct segment *r;    /* output path built here              */
       register struct segment *nextp;  /* contains next sub-path            */
 
       if (p == NULL)
               return(NULL);
 
       ARGCHECK(!ISPATHANCHOR(p), "Reverse: invalid path", p, NULL, (0), struct segment *);
 
       if (p->type == TEXTTYPE)
               p = CoerceText(p);
       p = UniquePath(p);
 
       r = NULL;
 
       do {
               nextp = DropSubPath(p);
               p = ReverseSubPath(p);
               r = Join(p, r);
               p = nextp;
 
       } while (p != NULL);
 
       return(r);
}
 
/*
:h4.ReverseSubPath() - Subroutine to Reverse a Single Sub-Path
*/
 
static struct segment *
ReverseSubPath(struct segment *p)   /* input path                            */
{
       register struct segment *r;  /* reversed path will be created here    */
       register struct segment *nextp;  /* temporary variable used in loop   */
       register int wasclosed;  /* flag, path was closed                     */
 
       if (p == NULL)
               return(NULL);
 
       wasclosed = ISCLOSED(p->flag);
       r = NULL;
 
       do {
/*
First we reverse the direction of this segment and clean up its flags:
*/
               p->dest.x = - p->dest.x;  p->dest.y = - p->dest.y;
               p->flag &= ~(ISCLOSED(ON) | LASTCLOSED(ON));
 
               switch (p->type) {
 
                   case LINETYPE:
                   case MOVETYPE:
                       break;
 
                   case CONICTYPE:
                   {
/*
The logic of this is that the new M point (stored relative to the new
beginning) is (M - C).  However, C ("dest") has already been reversed
So, we add "dest" instead of subtracting it:
*/
                       register struct conicsegment *cp = (struct conicsegment *) p;
 
                       cp->M.x += cp->dest.x;  cp->M.y += cp->dest.y;
                   }
                       break;
 
                   case BEZIERTYPE:
                   {
                       register struct beziersegment *bp = (struct beziersegment *) p;
 
                       bp->B.x += bp->dest.x;  bp->B.y += bp->dest.y;
                       bp->C.x += bp->dest.x;  bp->C.y += bp->dest.y;
                   }
                       break;
 
                   case HINTTYPE:
                   {
                       register struct hintsegment *hp = (struct hintsegment *) p;
 
                       hp->ref.x = -hp->ref.x;  hp->ref.y = -hp->ref.y;
                   }
                       break;
 
                   default:
                       Abort("Reverse: bad path segment");
               }
/*
We need to reverse the order of segments too, so we break this segment
off of the input path, and tack it on the front of the growing path
in 'r':
*/
               nextp = p->link;
               p->link = NULL;
               p->last = p;
               if (r != NULL)
                       CONCAT(p,r);  /* leaves result in 'p'... not what we want */
               r = p;
               p = nextp;    /* advance to next segment in input path        */
 
       } while (p != NULL);
 
       if (wasclosed)
               r = ClosePath(r);
 
       return(r);
}
 
/*
:h4.DropSubPath() - Drops the First Sub-Path Off a Path
 
This subroutine returns the remaining sub-path(s).  While doing so, it
breaks the input path after the first sub-path so that a pointer to
the original path now contains the first sub-path only.
*/
 
static struct segment *
DropSubPath(struct segment *p0)     /* original path                         */
{
       register struct segment *p;  /* returned remainder here               */
 
       for (p = p0; p->link != NULL; p = p->link) {
               if (p->link->type == MOVETYPE)
                       break;
       }
 
       return(SplitPath(p0, p));
}
 
static struct segment *
SplitPath(struct segment *anchor, struct segment *before)
{
       register struct segment *r;
 
       if (before == anchor->last)
               return(NULL);
 
       r = before->link;
       r->last = anchor->last;
       anchor->last = before;
       before->link = NULL;
 
       return(r);
}
 
static void
UnClose(struct segment *p0)
{
       register struct segment *p;
 
       for (p=p0; p->link->link != NULL; p=p->link) { ; }
 
       if (!LASTCLOSED(p->link->flag))
               Abort("UnClose:  no LASTCLOSED");
 
       Free(SplitPath(p0, p));
       p0->flag &= ~ISCLOSED(ON);
}
 
/*
:h3.ReverseSubPaths() - Reverse the Direction of Sub-paths Within a Path
 
This user operator reverses the sub-paths in a path, but leaves the
'move' segments unchanged.  It builds on top of the subroutines
already established.
*/
 
struct segment *
ReverseSubPaths(struct segment *p)  /* input path                            */
{
       register struct segment *r;  /* reversed path will be created here    */
       register struct segment *nextp;  /* temporary variable used in loop   */
       int wasclosed;        /* flag; subpath was closed                     */
       register struct segment *nomove;  /* the part of sub-path without move segment */
       struct fractpoint delta;
 
       if (p == NULL)
               return(NULL);
 
       ARGCHECK(!ISPATHANCHOR(p), "ReverseSubPaths: invalid path", p, NULL, (0), struct segment *);
 
       if (p->type == TEXTTYPE)
               p = CoerceText(p);
       if (p->type != MOVETYPE)
               p = JoinSegment(NULL, MOVETYPE, 0, 0, p);
 
       p = UniquePath(p);
 
       r = NULL;
 
       for (; p != NULL;) {
               nextp = DropSubPath(p);
               wasclosed = ISCLOSED(p->flag);
               if (wasclosed)
                       UnClose(p);
 
               nomove = SplitPath(p, p);
               r = Join(r, p);
 
               PathDelta(nomove, &delta);
 
               nomove = ReverseSubPath(nomove);
               p->dest.x += delta.x;
               p->dest.y += delta.y;
               if (nextp != NULL) {
                       nextp->dest.x += delta.x;
                       nextp->dest.y += delta.y;
               }
               if (wasclosed) {
                       nomove = ClosePath(nomove);
                       nextp->dest.x -= delta.x;
                       nextp->dest.y -= delta.y;
               }
               r = Join(r, nomove);
               p = nextp;
 
       }
 
       return(r);
}
 
/*
:h2.Transforming and Putting Handles on Paths
 
:h3.PathTransform() - Transform a Path
 
Transforming a path involves transforming all the points.  In order
that closed paths do not become "unclosed" when their relative
positions are slightly changed due to loss of arithmetic precision,
all point transformations are in absolute coordinates.
 
(It might be better to reset the "absolute" coordinates every time a
move segment is encountered.  This would mean that we could accumulate
error from subpath to subpath, but we would be less likely to make
the "big error" where our fixed point arithmetic "wraps".  However, I
think I'll keep it this way until something happens to convince me
otherwise.)
 
The transform is described as a "space", that way we can use our
old friend the "iconvert" function, which should be very efficient.
*/
 
struct segment *
PathTransform(struct segment *p0,      /* path to transform                  */
	      struct XYspace *S)       /* pseudo space to transform in       */
{
       register struct segment *p;   /* to loop through path with            */
       register fractpel newx,newy;  /* current transformed position in path */
       register fractpel oldx,oldy;  /* current untransformed position in path */
       register fractpel savex,savey;  /* save path delta x,y                */
 
       p0 = UniquePath(p0);
 
       newx = newy = oldx = oldy = 0;
 
       for (p=p0; p != NULL; p=p->link) {
 
               savex = p->dest.x;   savey = p->dest.y;
 
               (*S->iconvert)(&p->dest, S, p->dest.x + oldx, p->dest.y + oldy);
               p->dest.x -= newx;
               p->dest.y -= newy;
 
               switch (p->type) {
 
                   case LINETYPE:
                   case MOVETYPE:
                       break;
 
                   case CONICTYPE:
                   {
                       register struct conicsegment *cp = (struct conicsegment *) p;
 
                       (*S->iconvert)(&cp->M, S, cp->M.x + oldx, cp->M.y + oldy);
                       cp->M.x -= newx;
                       cp->M.y -= newy;
                       /*
                       * Note roundness doesn't change... linear transform
                       */
                       break;
                   }
 
 
                   case BEZIERTYPE:
                   {
                       register struct beziersegment *bp = (struct beziersegment *) p;
 
                       (*S->iconvert)(&bp->B, S, bp->B.x + oldx, bp->B.y + oldy);
                       bp->B.x -= newx;
                       bp->B.y -= newy;
                       (*S->iconvert)(&bp->C, S, bp->C.x + oldx, bp->C.y + oldy);
                       bp->C.x -= newx;
                       bp->C.y -= newy;
                       break;
                   }
 
                   case HINTTYPE:
                   {
                       register struct hintsegment *hp = (struct hintsegment *) p;
 
                       (*S->iconvert)(&hp->ref, S, hp->ref.x + oldx, hp->ref.y + oldy);
                       hp->ref.x -= newx;
                       hp->ref.y -= newy;
                       (*S->iconvert)(&hp->width, S, hp->width.x, hp->width.y);
                       /* Note: width is not relative to origin */
                       break;
                   }
 
                   case TEXTTYPE:
                   {
                        XformText(p,S);
                        break;
                   }
 
                   default:
                       Abort("PathTransform:  invalid segment");
               }
               oldx += savex;
               oldy += savey;
               newx += p->dest.x;
               newy += p->dest.y;
       }
       return(p0);
}
 
/*
:h3.PathDelta() - Return a Path's Ending Point
*/
 
void 
PathDelta(struct segment *p,       /* input path                             */
	  struct fractpoint *pt)   /* pointer to x,y to set                  */
{
       struct fractpoint mypoint;  /* I pass this to TextDelta               */
       register fractpel x,y;  /* working variables for path current point   */
 
       for (x=y=0; p != NULL; p=p->link) {
               x += p->dest.x;
               y += p->dest.y;
               if (p->type == TEXTTYPE) {
                       TextDelta(p, &mypoint);
                       x += mypoint.x;
                       y += mypoint.y;
               }
       }
 
       pt->x = x;
       pt->y = y;
}
 
/*
:h3.BoundingBox() - Produce a Bounding Box Path
 
This function is called by image code, when we know the size of the
image in pels, and need to get a bounding box path that surrounds it.
The starting/ending handle is in the lower right hand corner.
*/
struct segment *
BoundingBox(pel h, pel w)    /* size of box                                  */
{
       register struct segment *path;
 
       path = PathSegment(LINETYPE, -TOFRACTPEL(w), 0);
       path = JoinSegment(NULL, LINETYPE, 0, -TOFRACTPEL(h), path);
       path = JoinSegment(NULL, LINETYPE, TOFRACTPEL(w), 0, path);
       path = ClosePath(path);
 
       return(path);
}
 
/*
:h2.Querying Locations and Paths
 
:h3.QueryLoc() - Return the X,Y of a Locition
*/
 
void 
QueryLoc(struct segment *P,      /* location to query, not consumed          */
	 struct XYspace *S,      /* XY space to return coordinates in        */
	 double *xP, double *yP) /* coordinates returned here                */
{
       if (!ISLOCATION(P)) {
               ArgErr("QueryLoc: first arg not a location", P, NULL);
               return;
       }
       if (S->type != SPACETYPE) {
               ArgErr("QueryLoc: second arg not a space", S, NULL);
               return;
       }
       UnConvert(S, &P->dest, xP, yP);
}
/*
:h3.QueryPath() - Find Out the Type of Segment at the Head of a Path
 
This is a very simple routine that looks at the first segment of a
path and tells the caller what it is, as well as returning the control
point(s) of the path segment.  Different path segments have different
number of control points.  If the caller knows that the segment is
a move segment, for example, he only needs to pass pointers to return
one control point.
*/
 
void 
QueryPath(struct segment *path, /* path to check                             */
	  int *typeP,        /* return the type of path here                 */
	  struct segment **Bp,  /* return location of first point            */
	  struct segment **Cp,  /* return location of second point           */
	  struct segment **Dp,  /* return location of third point            */
	  double *fP)           /* return Conic sharpness                    */
{
       register int coerced = FALSE;  /* did I coerce a text path?           */
 
       if (path == NULL) {
               *typeP = -1;
               return;
       }
       if (!ISPATHANCHOR(path)) {
               ArgErr("QueryPath: arg not a valid path", path, NULL);
       }
       if (path->type == TEXTTYPE) {
               path = CoerceText(path);
               coerced = TRUE;
       }
 
       switch (path->type) {
 
           case MOVETYPE:
               *typeP = 0;
               *Bp = PathSegment(MOVETYPE, path->dest.x, path->dest.y);
               break;
 
           case LINETYPE:
               *typeP = (LASTCLOSED(path->flag)) ? 4 : 1;
               *Bp = PathSegment(MOVETYPE, path->dest.x, path->dest.y);
               break;
 
           case CONICTYPE:
           {
               register struct conicsegment *cp = (struct conicsegment *) path;
 
               *typeP = 2;
               *Bp = PathSegment(MOVETYPE, cp->M.x, cp->M.y);
               *Cp = PathSegment(MOVETYPE, cp->dest.x, cp->dest.y);
               *fP = cp->roundness;
           }
               break;
 
           case BEZIERTYPE:
           {
               register struct beziersegment *bp = (struct beziersegment *) path;
 
               *typeP = 3;
               *Bp = PathSegment(MOVETYPE, bp->B.x, bp->B.y);
               *Cp = PathSegment(MOVETYPE, bp->C.x, bp->C.y);
               *Dp = PathSegment(MOVETYPE, bp->dest.x, bp->dest.y);
           }
               break;
 
           case HINTTYPE:
               *typeP = 5;
               break;
 
           default:
               Abort("QueryPath: unknown segment");
       }
       if (coerced)
               KillPath(path);
}
/*
:h3.QueryBounds() - Return the Bounding Box of a Path
 
Returns the bounding box by setting the user's variables.
*/
 
void 
QueryBounds(struct segment *p0, /* object to check for bound                 */
	    struct XYspace *S, /* coordinate space of returned values        */
	    double *xminP,   /* lower left hand corner (set by routine)      */
	    double *yminP,
	    double *xmaxP,   /* upper right hand corner (set by routine)     */
	    double *ymaxP)
{
       register struct segment *path;  /* loop variable for path segments    */
       register fractpel lastx,lasty;  /* loop variables:  previous endingpoint */
       register fractpel x,y;  /* loop variables:  current ending point      */
       struct fractpoint min;  /* registers to keep lower left hand corner   */
       struct fractpoint max;  /* registers to keep upper right hand corner  */
       int coerced = FALSE;  /* we have coerced the path from another object */
       double x1,y1,x2,y2,x3,y3,x4,y4;  /* corners of rectangle in space X   */
 
       if (S->type != SPACETYPE) {
               ArgErr("QueryBounds:  bad XYspace", S, NULL);
               return;
       }
 
       min.x = min.y = max.x = max.y = 0;
       if (p0 != NULL) {
               if (!ISPATHANCHOR(p0)) {
                       switch(p0->type) {
                           case STROKEPATHTYPE:
      /* replaced DupStrokePath() with Dup() 3-26-91 PNM */
                               p0 = (struct segment *) DoStroke(Dup(p0));
                               /* no break here, we have a region in p0 */
                           case REGIONTYPE:
                               p0 = RegionBounds((struct region *)p0);
                               break;
 
                           case PICTURETYPE:
                               p0 = PictureBounds(p0);
                               break;
 
                           default:
                               ArgErr("QueryBounds:  bad object", p0, NULL);
                               return;
                       }
                       coerced = TRUE;
               }
               if (p0->type == TEXTTYPE) {
    /* replaced CopyPath() with Dup() 3-26-91 PNM */
                       p0 = (struct segment *)CoerceText(Dup(p0));  /* there are faster ways */
                       coerced = TRUE;
               }
               if (p0->type == MOVETYPE) {
                       min.x = max.x = p0->dest.x;
                       min.y = max.y = p0->dest.y;
               }
       }
       lastx = lasty = 0;
 
       for (path = p0; path != NULL; path = path->link) {
 
               x = lastx + path->dest.x;
               y = lasty + path->dest.y;
 
               switch (path->type) {
 
                   case LINETYPE:
                       break;
 
                   case CONICTYPE:
                   {
                       register struct conicsegment *cp = (struct conicsegment *) path;
                       register fractpel Mx = lastx + cp->M.x;
                       register fractpel My = lasty + cp->M.y;
                       register fractpel deltax = 0.5 * cp->roundness * cp->dest.x;
                       register fractpel deltay = 0.5 * cp->roundness * cp->dest.y;
                       register fractpel Px = Mx - deltax;
                       register fractpel Py = My - deltay;
                       register fractpel Qx = Mx + deltax;
                       register fractpel Qy = My + deltay;
 
 
                       if (Mx < min.x) min.x = Mx;
                       else if (Mx > max.x) max.x = Mx;
                       if (My < min.y) min.y = My;
                       else if (My > max.y) max.y = My;
 
                       if (Px < min.x) min.x = Px;
                       else if (Px > max.x) max.x = Px;
                       if (Py < min.y) min.y = Py;
                       else if (Py > max.y) max.y = Py;
 
                       if (Qx < min.x) min.x = Qx;
                       else if (Qx > max.x) max.x = Qx;
                       if (Qy < min.y) min.y = Qy;
                       else if (Qy > max.y) max.y = Qy;
                   }
                       break;
 
 
                   case MOVETYPE:
                       /*
                       * We can't risk adding trailing Moves to the
                       * bounding box:
                       */
                       if (path->link == NULL)
                               goto done;  /* God forgive me                 */
                       break;
 
                   case BEZIERTYPE:
                   {
                       register struct beziersegment *bp = (struct beziersegment *) path;
                       register fractpel Bx = lastx + bp->B.x;
                       register fractpel By = lasty + bp->B.y;
                       register fractpel Cx = lastx + bp->C.x;
                       register fractpel Cy = lasty + bp->C.y;
 
                       if (Bx < min.x) min.x = Bx;
                       else if (Bx > max.x) max.x = Bx;
                       if (By < min.y) min.y = By;
                       else if (By > max.y) max.y = By;
 
                       if (Cx < min.x) min.x = Cx;
                       else if (Cx > max.x) max.x = Cx;
                       if (Cy < min.y) min.y = Cy;
                       else if (Cy > max.y) max.y = Cy;
                   }
                       break;
 
                   case HINTTYPE:
                       break;
                   default:
                       Abort("QueryBounds: unknown type");
               }
 
               if (x < min.x) min.x = x;
               else if (x > max.x) max.x = x;
               if (y < min.y) min.y = y;
               else if (y > max.y) max.y = y;
 
               lastx = x;   lasty = y;
       }
done:
       UnConvert(S, &min, &x1, &y1);
       UnConvert(S, &max, &x4, &y4);
       x = min.x;  min.x = max.x; max.x = x;
       UnConvert(S, &min, &x2, &y2);
       UnConvert(S, &max, &x3, &y3);
 
       *xminP = *xmaxP = x1;
       if (x2 < *xminP)  *xminP = x2;
       else if (x2 > *xmaxP)  *xmaxP = x2;
       if (x3 < *xminP)  *xminP = x3;
       else if (x3 > *xmaxP)  *xmaxP = x3;
       if (x4 < *xminP)  *xminP = x4;
       else if (x4 > *xmaxP)  *xmaxP = x4;
 
       *yminP = *ymaxP = y1;
       if (y2 < *yminP)  *yminP = y2;
       else if (y2 > *ymaxP)  *ymaxP = y2;
       if (y3 < *yminP)  *yminP = y3;
       else if (y3 > *ymaxP)  *ymaxP = y3;
       if (y4 < *yminP)  *yminP = y4;
       else if (y4 > *ymaxP)  *ymaxP = y4;
 
       if (coerced)
               Destroy(p0);
}
/*
:h3.BoxPath()
*/
struct segment *
BoxPath(struct XYspace *S, int h, int w)
{
       struct segment *path;
 
       path = Join( Line(ILoc(S, w, 0)), Line(ILoc(S, 0, h)) );
       path = JoinSegment(path, LINETYPE, -path->dest.x, -path->dest.y, NULL);
       return(ClosePath(path));
}
 
/*
:h3.DropSegment() - Drop the First Segment in a Path
 
This routine takes the path and returns a new path that is one segment
shorter.  It can be used in conjunction with QueryPath(), for example,
to ask about an entire path.
*/
 
struct segment *
DropSegment(struct segment *path)
{
       if (path != NULL && path->type == STROKEPATHTYPE)
               path = CoercePath(path);
       ARGCHECK((path == NULL || !ISPATHANCHOR(path)),
                 "DropSegment: arg not a non-null path", path, path, (0), struct segment *);
       if (path->type == TEXTTYPE)
               path = CoerceText(path);
       path = UniquePath(path);
 
       POP(path);
       return(path);
}
/*
:h3.HeadSegment() - Return the First Segment in a Path
 
This routine takes the path and returns a new path consists of the
first segment only.
*/
 
struct segment *
HeadSegment(struct segment *path)     /* input path                         */
{
       if (path == NULL)
               return(NULL);
       if (path->type == STROKEPATHTYPE)
               path = CoercePath(path);
       ARGCHECK(!ISPATHANCHOR(path), "HeadSegment: arg not a path", path, path, (0), struct segment *);
       if (path->type == TEXTTYPE)
               path = CoerceText(path);
       path = UniquePath(path);
 
       if (path->link != NULL)
               KillPath(path->link);
       path->link = NULL;
       path->last = path;
       return(path);
}
 
/*
:h2.Path Debug Routines
 
:h3.DumpPath() - Display a Path on the Trace File
*/
 
void 
DumpPath(struct segment *p)
{
}