summaryrefslogtreecommitdiff
path: root/src/constraints.c
blob: cd686e62362d6d8cb6c9cdc676a1e3185892366b (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
/* Metacity size/position constraints */

/*
 * Copyright (C) 2002, 2003 Red Hat, Inc.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
 * 02111-1307, USA.
 */

#include <config.h>
#include "constraints.h"
#include "place.h"

/* The way this code works was suggested by Owen Taylor.
 *
 * For any move_resize, we determine which variables are "free
 * variables" and apply constraints in terms of those. During the move
 * resize, we only want to modify those variables; otherwise the
 * constraint process can have peculiar side effects when the size and
 * position constraints interact. For example, resizing a window from
 * the top might go wrong when position constraints apply to the top
 * edge, and result in the bottom edge moving downward while the top
 * stays fixed.
 *
 * After selecting the variables we plan to vary, we define
 * each constraint on the window in terms of those variables.
 *
 * Trivial example, say we are resizing vertically from the top of the
 * window. In that case we are applying the user's mouse motion delta
 * to an original size and position, note that dy is positive to
 * resize downward:
 *
 *   new_height = orig_height - dy;
 *   new_y      = orig_y + dy;
 *
 * A constraint that the position can't go above the top panel would
 * look like this:
 *
 *   new_y >= screen_top_bound
 *
 * Substitute:
 *
 *   orig_y + dy >= screen_top_bound
 *
 * Find the "boundary point" by changing to an equality:
 *
 *   orig_y + dy = screen_top_bound
 *
 * Solve:
 *
 *   dy = screen_top_bound - orig_y
 *
 * This dy is now the _maximum_ dy and you constrain dy with that
 * value, applying it to both the move and the resize:
 *
 *   new_height = orig_height - dy;
 *   new_y      = orig_y + dy;
 *
 * This way the constraint is applied simultaneously to size/position,
 * so you aren't running the risk of constraining one but still
 * changing the other. i.e. we've converted an operation that may
 * modify both the Y position and the height of the window into an
 * operation that modifies a single variable, dy.  That variable is
 * then constrained, rather than the constraining the Y pos and height
 * separately. This is a rather complicated fix for an obscure bug
 * that happened when resizing a window and encountering a constraint
 * such as the top edge of the screen.
 *
 */


/* To adjust for window gravity, such as a client moving itself to the
 * southeast corner, we want to compute the gravity reference point
 * - (screen_width,screen_height) in the SE corner case - using the
 * size the client had in its configure request. But then we want
 * to compute the actual position we intend to land on using
 * the real constrained dimensions of the window.
 *
 * So for a window being placed in the SE corner and simultaneously
 * resized, we get the gravity reference point, then compute where the
 * window should go to maintain that ref. point at its current size
 * instead of at the requested size, and conceptually move the window
 * to the requested ref. point but at its current size, without
 * applying any constraints. Then we constrain it with the top and
 * left edges as the edges that vary, with a dx/dy that are the delta
 * from the current size to the requested size.
 *
 * This method applies to any ConfigureRequest that does a simultaneous
 * move/resize.
 *
 * We use the same method to e.g. maximize a window; if the window is
 * maximized, we want to MOVE_VERTICAL/MOVE_HORIZONTAL to the top
 * center of the screen, then RESIZE_BOTTOM and
 * RESIZE_HORIZONTAL_CENTER. i.e. essentially NorthGravity.
 *
 */

#define FLOOR(value, base)	( ((int) ((value) / (base))) * (base) )

typedef struct
{
  MetaWindow *window;
  MetaFrameGeometry fgeom;
  const MetaXineramaScreenInfo *xinerama;
  MetaRectangle work_area_xinerama;
  MetaRectangle work_area_screen;
  int nw_x, nw_y, se_x, se_y; /* these are whole-screen not xinerama */
} ConstraintInfo;

/* (FIXME instead of TITLEBAR_LENGTH_ONSCREEN, get the actual
 * size of the menu control?).
 */

#define TITLEBAR_LENGTH_ONSCREEN 36

typedef gboolean (* MetaConstraintAppliesFunc) (MetaWindow *window);

/* There's a function for each case with a different "free variable" */
typedef void (* MetaConstrainTopFunc)     (MetaWindow           *window,
                                           const ConstraintInfo *info,
                                           const MetaRectangle  *orig,
                                           int                  *y_delta);
typedef void (* MetaConstrainBottomFunc)  (MetaWindow           *window,
                                           const ConstraintInfo *info,
                                           const MetaRectangle  *orig,
                                           int                  *y_delta);
typedef void (* MetaConstrainVCenterFunc) (MetaWindow           *window,
                                           const ConstraintInfo *info,
                                           const MetaRectangle  *orig,
                                           int                  *y_delta);
typedef void (* MetaConstrainLeftFunc)    (MetaWindow           *window,
                                           const ConstraintInfo *info,
                                           const MetaRectangle  *orig,
                                           int                  *x_delta);
typedef void (* MetaConstrainRightFunc)   (MetaWindow           *window,
                                           const ConstraintInfo *info,
                                           const MetaRectangle  *orig,
                                           int                  *x_delta);
typedef void (* MetaConstrainHCenterFunc) (MetaWindow           *window,
                                           const ConstraintInfo *info,
                                           const MetaRectangle  *orig,
                                           int                  *x_delta);
typedef void (* MetaConstrainMoveFunc)    (MetaWindow           *window,
                                           const ConstraintInfo *info,
                                           const MetaRectangle  *orig,
                                           int                  *x_delta,
                                           int                  *y_delta);

typedef struct
{
  const char               *name;
  MetaConstraintAppliesFunc applies_func;
  MetaConstrainTopFunc      top_func;
  MetaConstrainBottomFunc   bottom_func;
  MetaConstrainVCenterFunc  vcenter_func;
  MetaConstrainLeftFunc     left_func;
  MetaConstrainRightFunc    right_func;
  MetaConstrainHCenterFunc  hcenter_func;
  MetaConstrainMoveFunc     move_func;
} Constraint;

/* "Is the desktop window" constraint:
 *
 *  new_x = 0;
 *  new_y = 0;
 *  new_w = orig_width;
 *  new_h = orig_height;
 *
 * Note that if we are applying a resize constraint,
 * e.g. constraint_desktop_top_func, this is kind of broken since we
 * end up resizing the window in order to get its position right. But
 * that case shouldn't happen in practice.
 */
static gboolean
constraint_desktop_applies_func (MetaWindow *window)
{
  return window->type == META_WINDOW_DESKTOP;
}

static void
constraint_desktop_top_func     (MetaWindow           *window,
                                 const ConstraintInfo *info,
                                 const MetaRectangle  *orig,
                                 int                  *y_delta)
{
  *y_delta = 0 - orig->y;
}

static void
constraint_desktop_bottom_func  (MetaWindow           *window,
                                 const ConstraintInfo *info,
                                 const MetaRectangle  *orig,
                                 int                  *y_delta)
{
  /* nothing */
}

static void
constraint_desktop_vcenter_func (MetaWindow           *window,
                                 const ConstraintInfo *info,
                                 const MetaRectangle  *orig,
                                 int                  *y_delta)
{
  *y_delta = 0 - orig->y;
}

static void
constraint_desktop_left_func    (MetaWindow           *window,
                                 const ConstraintInfo *info,
                                 const MetaRectangle  *orig,
                                 int                  *x_delta)
{
  *x_delta = 0 - orig->x;
}

static void
constraint_desktop_right_func   (MetaWindow           *window,
                                 const ConstraintInfo *info,
                                 const MetaRectangle  *orig,
                                 int                  *x_delta)
{
  /* nothing */
}

static void
constraint_desktop_hcenter_func (MetaWindow           *window,
                                 const ConstraintInfo *info,
                                 const MetaRectangle  *orig,
                                 int                  *x_delta)
{
  *x_delta = 0 - orig->x;
}

static void
constraint_desktop_move_func    (MetaWindow           *window,
                                 const ConstraintInfo *info,
                                 const MetaRectangle  *orig,
                                 int                  *x_delta,
                                 int                  *y_delta)
{
  *x_delta = 0 - orig->x;
  *y_delta = 0 - orig->y;
}

static const Constraint constraint_desktop = {
  "Desktop",
  constraint_desktop_applies_func,
  constraint_desktop_top_func,
  constraint_desktop_bottom_func,
  constraint_desktop_vcenter_func,
  constraint_desktop_left_func,
  constraint_desktop_right_func,
  constraint_desktop_hcenter_func,
  constraint_desktop_move_func
};

/* Titlebar is onscreen constraint:
 *
 * Constants:
 *  titlebar_width_onscreen = amount of titlebar width that has to be onscreen
 *  nw_x, nw_y = left/top edges that titlebar can't go outside
 *  se_x, se_y = right/bottom edges
 *
 * NW limit has priority over SE, since titlebar is on NW
 *
 * Left resize
 * ===
 *
 *   new_width = orig_width - dx
 *   new_x = orig_x + dx
 *
 * Amount of window+frame that doesn't fit in the work area:
 *
 *   offscreen_width = left_width + new_width + right_width - (se_x - nw_x)
 *
 * If we keep the old metacity rule where a window can be offscreen by
 * offscreen_width, then the math works out that left/top resizes are not
 * constrained. If we instead have a rule where the window can never be offscreen,
 * you get the following:
 *
 *  new_x >= nw_x + left_width + titlebar_width_offscreen
 *  orig_x + dx >= nw_x + left_width + titlebar_width_onscreen
 *  dx >= nw_x + left_width + titlebar_width_onscreen - orig_x
 *
 * i.e. the minimum dx is: nw_x + left_width + titlebar_width_onscreen - orig_x
 *
 * We could have a more complicated rule that constrains only if the current
 * offscreen width is positive, thus allowing something more like the old
 * behavior, but not doing that for now.
 *
 * Top resize works the same as left resize. Right/bottom resize don't have a limit
 * because the constraint is designed to keep the top right corner of the
 * window or its titlebar on the screen, and right/bottom resize will never move that
 * area. Center resize is almost like left/top but dx has the opposite sign
 * and new_width = orig_width + 2dx.
 *
 * For right/bottom we can try to handle windows that aren't in a valid
 * location to begin with:
 *
 *  new_x <= se_x - titlebar_width_onscreen
 *  dx <= se_x - titlebar_width_onscreen - orig_x
 *
 * but in principle this constraint is never triggered.
 *
 * Vertical move
 * ===
 *
 *  new_height = orig_height
 *  new_y = orig_y + dy
 *
 *  new_y >= nw_y + top_height
 *
 *  Min negative dy (nw_y + top_height - orig_y) just as with top resize.
 *  Max positive dy has to be computed from se_y and given less priority than the
 *  min negative:
 *
 *   new_y < se_y
 *   orig_y + dy = se_y
 *   so max dy is (se_y - orig_y)
 *
 * Horizontal move is equivalent to vertical.
 *
 */

static gboolean
constraint_onscreen_applies_func (MetaWindow *window)
{
  return
    window->type != META_WINDOW_DESKTOP &&
    window->type != META_WINDOW_DOCK;
}

static void
get_outermost_onscreen_positions (MetaWindow           *window,
                                  const ConstraintInfo *info,
                                  const MetaRectangle  *orig,
                                  int                  *leftmost_x,
                                  int                  *rightmost_x,
                                  int                  *topmost_y,
                                  int                  *bottommost_y)
{
  if (leftmost_x)
    *leftmost_x = info->nw_x + TITLEBAR_LENGTH_ONSCREEN - orig->width;

  if (rightmost_x)
    *rightmost_x = info->se_x - TITLEBAR_LENGTH_ONSCREEN;

  if (topmost_y)
    *topmost_y = info->nw_y + info->fgeom.top_height;

  if (bottommost_y)
    {
      /* If no frame, keep random TITLEBAR_LENGTH_ONSCREEN pixels on the
       * screen.
       */
      if (window->frame)
        *bottommost_y = info->se_y;
      else
        *bottommost_y = info->se_y - TITLEBAR_LENGTH_ONSCREEN;
    }
}

static void
constraint_onscreen_top_func     (MetaWindow           *window,
                                  const ConstraintInfo *info,
                                  const MetaRectangle  *orig,
                                  int                  *y_delta)
{
  int min_dy;
  int topmost_y;

  get_outermost_onscreen_positions (window, info, orig,
                                    NULL, NULL, &topmost_y, NULL);

  min_dy = topmost_y - orig->y;

  if (*y_delta < min_dy)
    *y_delta = min_dy;
}

static void
constraint_onscreen_bottom_func  (MetaWindow           *window,
                                  const ConstraintInfo *info,
                                  const MetaRectangle  *orig,
                                  int                  *y_delta)
{
  int max_dy;
  int bottommost_y;

  get_outermost_onscreen_positions (window, info, orig,
                                    NULL, NULL, NULL, &bottommost_y);

  max_dy = bottommost_y - orig->y;

  if (*y_delta > max_dy)
    *y_delta = max_dy;
}

static void
constraint_onscreen_vcenter_func (MetaWindow           *window,
                                  const ConstraintInfo *info,
                                  const MetaRectangle  *orig,
                                  int                  *y_delta)
{
  int max_dy;
  int topmost_y;

  get_outermost_onscreen_positions (window, info, orig,
                                    NULL, NULL, &topmost_y, NULL);

  max_dy = orig->y - topmost_y;

  if (*y_delta > max_dy)
    *y_delta = max_dy;
}

static void
constraint_onscreen_left_func    (MetaWindow           *window,
                                  const ConstraintInfo *info,
                                  const MetaRectangle  *orig,
                                  int                  *x_delta)
{
  int min_dx;
  int leftmost_x;

  get_outermost_onscreen_positions (window, info, orig,
                                    &leftmost_x, NULL, NULL, NULL);

  min_dx = leftmost_x - orig->x;

  if (*x_delta < min_dx)
    *x_delta = min_dx;
}

static void
constraint_onscreen_right_func   (MetaWindow           *window,
                                  const ConstraintInfo *info,
                                  const MetaRectangle  *orig,
                                  int                  *x_delta)
{
  int max_dx;
  int rightmost_x;

  get_outermost_onscreen_positions (window, info, orig,
                                    NULL, &rightmost_x, NULL, NULL);

  max_dx = rightmost_x - orig->x;

  if (*x_delta > max_dx)
    *x_delta = max_dx;
}

static void
constraint_onscreen_hcenter_func (MetaWindow           *window,
                                  const ConstraintInfo *info,
                                  const MetaRectangle  *orig,
                                  int                  *x_delta)
{
  int max_dx;
  int leftmost_x;
  
  get_outermost_onscreen_positions (window, info, orig,
                                    &leftmost_x, NULL, NULL, NULL);

  max_dx = orig->x - leftmost_x;

  if (*x_delta > max_dx)
    *x_delta = max_dx;
}

static void
constraint_onscreen_move_func    (MetaWindow           *window,
                                  const ConstraintInfo *info,
                                  const MetaRectangle  *orig,
                                  int                  *x_delta,
                                  int                  *y_delta)
{
  int min_delta;
  int max_delta;
  int leftmost_x, rightmost_x, topmost_y, bottommost_y;

  get_outermost_onscreen_positions (window, info, orig,
                                    &leftmost_x, &rightmost_x,
                                    &topmost_y, &bottommost_y);

  min_delta = topmost_y - orig->y;
  max_delta = bottommost_y - orig->y;

  /* Note that min delta (top left) has priority over
   * max delta (bottom right) to facilitate keeping
   * titlebar on the screen
   */
  if (*y_delta > max_delta)
    *y_delta = max_delta;
  if (*y_delta < min_delta)
    *y_delta = min_delta;

  min_delta = leftmost_x - orig->x;
  max_delta = rightmost_x - orig->x;

  if (*x_delta > max_delta)
    *x_delta = max_delta;
  if (*x_delta < min_delta)
    *x_delta = min_delta;
}

static const Constraint constraint_onscreen = {
  "Onscreen",
  constraint_onscreen_applies_func,
  constraint_onscreen_top_func,
  constraint_onscreen_bottom_func,
  constraint_onscreen_vcenter_func,
  constraint_onscreen_left_func,
  constraint_onscreen_right_func,
  constraint_onscreen_hcenter_func,
  constraint_onscreen_move_func
};


/* Size hints constraints:
 *
 * For min/max size we just clamp to those, and for resize increment
 * we clamp to the one at or below the requested place.
 *
 * For aspect ratio, we special-case it at the end of
 * meta_window_constrain, because it involves both dimensions, and
 * thus messes up our generic framework.
 *
 * Left resize can be solved for dx like this:
 *   new_width = orig_width - dx
 *   new_x = orig_x + dx
 *
 *   new_width >= min_width
 *   orig_width - dx >= min_width
 *   - dx >= min_width - orig_width
 *   dx <= orig_width - min_width
 *
 *   new_width <= max_width
 *   orig_width - dx <= max_width
 *   - dx <= max_width - orig_width
 *   dx >= orig_width - max_width
 *
 */

static gboolean
constraint_hints_applies_func (MetaWindow *window)
{
  return TRUE;
}

static void
constraint_hints_top_func     (MetaWindow           *window,
                               const ConstraintInfo *info,
                               const MetaRectangle  *orig,
                               int                  *y_delta)
{
  int min_dy;
  int max_dy;
  int height;

  max_dy = orig->height - window->size_hints.min_height;
  min_dy = orig->height - window->size_hints.max_height;

  g_assert (max_dy >= min_dy);

  if (*y_delta > max_dy)
    *y_delta = max_dy;
  if (*y_delta < min_dy)
    *y_delta = min_dy;

  /* shrink to base + N * inc
   */
  height = orig->height - *y_delta;
  height = window->size_hints.base_height +
    FLOOR (height - window->size_hints.base_height, window->size_hints.height_inc);

  *y_delta = orig->height - height;
}

static void
constraint_hints_bottom_func  (MetaWindow           *window,
                               const ConstraintInfo *info,
                               const MetaRectangle  *orig,
                               int                  *y_delta)
{
  int min_dy;
  int max_dy;
  int height;

  min_dy = window->size_hints.min_height - orig->height;
  max_dy = window->size_hints.max_height - orig->height;

  g_assert (max_dy >= min_dy);

  if (*y_delta > max_dy)
    *y_delta = max_dy;
  if (*y_delta < min_dy)
    *y_delta = min_dy;

  /* shrink to base + N * inc
   */
  height = orig->height + *y_delta;
  height = window->size_hints.base_height +
    FLOOR (height - window->size_hints.base_height, window->size_hints.height_inc);

  *y_delta = height - orig->height;
}

static void
constraint_hints_vcenter_func (MetaWindow           *window,
                               const ConstraintInfo *info,
                               const MetaRectangle  *orig,
                               int                  *y_delta)
{
  int min_dy;
  int max_dy;
  int height;

  /* Remember our delta is negative to shrink window, positive to
   * grow it, and the actual resize is y_delta * 2 (which is broken,
   * but that's how it currently is)
   */

  min_dy = (window->size_hints.min_height - orig->height) / 2;
  max_dy = (window->size_hints.max_height - orig->height) / 2;

  g_assert (max_dy >= min_dy);

  if (*y_delta > max_dy)
    *y_delta = max_dy;
  if (*y_delta < min_dy)
    *y_delta = min_dy;

  /* shrink to base + N * inc
   */
  height = orig->height + *y_delta * 2;
  height = window->size_hints.base_height +
    FLOOR (height - window->size_hints.base_height, window->size_hints.height_inc);

  *y_delta = (height - orig->height) / 2;
}

static void
constraint_hints_left_func    (MetaWindow           *window,
                               const ConstraintInfo *info,
                               const MetaRectangle  *orig,
                               int                  *x_delta)
{
  int min_dx;
  int max_dx;
  int width;

  max_dx = orig->width - window->size_hints.min_width;
  min_dx = orig->width - window->size_hints.max_width;

  g_assert (max_dx >= min_dx);

  if (*x_delta > max_dx)
    *x_delta = max_dx;
  if (*x_delta < min_dx)
    *x_delta = min_dx;

  /* shrink to base + N * inc
   */
  width = orig->width - *x_delta;
  width = window->size_hints.base_width +
    FLOOR (width - window->size_hints.base_width, window->size_hints.width_inc);

  *x_delta = orig->width - width;
}

static void
constraint_hints_right_func   (MetaWindow           *window,
                               const ConstraintInfo *info,
                               const MetaRectangle  *orig,
                               int                  *x_delta)
{
  int min_dx;
  int max_dx;
  int width;

  min_dx = window->size_hints.min_width - orig->width;
  max_dx = window->size_hints.max_width - orig->width;

  g_assert (max_dx >= min_dx);

  if (*x_delta > max_dx)
    *x_delta = max_dx;
  if (*x_delta < min_dx)
    *x_delta = min_dx;

  /* shrink to base + N * inc
   */
  width = orig->width + *x_delta;
  width = window->size_hints.base_width +
    FLOOR (width - window->size_hints.base_width, window->size_hints.width_inc);

  *x_delta = width - orig->width;
}

static void
constraint_hints_hcenter_func (MetaWindow           *window,
                               const ConstraintInfo *info,
                               const MetaRectangle  *orig,
                               int                  *x_delta)
{
  int min_dx;
  int max_dx;
  int width;
  
  /* Remember our delta is negative to shrink window, positive to
   * grow it, and the actual resize is x_delta * 2 (which is broken,
   * but that's how it currently is)
   */

  min_dx = (window->size_hints.min_width - orig->width) / 2;
  max_dx = (window->size_hints.max_width - orig->width) / 2;

  g_assert (max_dx >= min_dx);

  if (*x_delta > max_dx)
    *x_delta = max_dx;
  if (*x_delta < min_dx)
    *x_delta = min_dx;

  /* shrink to base + N * inc
   */
  width = orig->width + *x_delta * 2;
  width = window->size_hints.base_width +
    FLOOR (width - window->size_hints.base_width, window->size_hints.width_inc);

  *x_delta = (width - orig->width) / 2;
}

static void
constraint_hints_move_func    (MetaWindow           *window,
                               const ConstraintInfo *info,
                               const MetaRectangle  *orig,
                               int                  *x_delta,
                               int                  *y_delta)
{
  /* nothing */
}

static const Constraint constraint_hints = {
  "Hints",
  constraint_hints_applies_func,
  constraint_hints_top_func,
  constraint_hints_bottom_func,
  constraint_hints_vcenter_func,
  constraint_hints_left_func,
  constraint_hints_right_func,
  constraint_hints_hcenter_func,
  constraint_hints_move_func
};

/* Array of all constraints at once */
static const Constraint *all_constraints[] = {
  &constraint_desktop,
  &constraint_onscreen,
  &constraint_hints,
  NULL
};

/* Move with no accompanying change to window size */
static void
constrain_move (MetaWindow           *window,
                const ConstraintInfo *info,
                const MetaRectangle  *orig,
                int                   x_delta,
                int                   y_delta,
                MetaRectangle        *new)
{
  const Constraint **cp;

  cp = &all_constraints[0];

  while (*cp)
    {
      meta_topic (META_DEBUG_GEOMETRY,
                  "Before: %d %d (Move constraint '%s')\n",
                  x_delta, y_delta, (*cp)->name);
                  
      if ((* (*cp)->applies_func) (window))
        (* (*cp)->move_func) (window, info, orig,
                              &x_delta, &y_delta);

      meta_topic (META_DEBUG_GEOMETRY,
                  "After:  %d %d (Move constraint '%s')\n",
                  x_delta, y_delta, (*cp)->name);
      
      ++cp;
    }

  new->x = orig->x + x_delta;
  new->y = orig->y + y_delta;
}

static void
constrain_resize_left (MetaWindow           *window,
                       const ConstraintInfo *info,
                       const MetaRectangle  *orig,
                       int                   x_delta,
                       MetaRectangle        *new)
{
  const Constraint **cp;

  cp = &all_constraints[0];

  while (*cp)
    {
      meta_topic (META_DEBUG_GEOMETRY,
                  "Before: %d (Left constraint '%s')\n",
                  x_delta, (*cp)->name);
      
      if ((* (*cp)->applies_func) (window))
        (* (*cp)->left_func) (window, info, orig,
                              &x_delta);

      meta_topic (META_DEBUG_GEOMETRY,
                  "After:  %d (Left constraint '%s')\n",
                  x_delta, (*cp)->name);
      
      ++cp;
    }

  /* Moving mouse from 10 to 5 means current - orig means 5 - 10 means
   * a delta of -5
   */
  new->x = orig->x + x_delta;
  new->width = orig->width - x_delta;
}

static void
constrain_resize_hcenter (MetaWindow           *window,
                          const ConstraintInfo *info,
                          const MetaRectangle  *orig,
                          int                   x_delta,
                          MetaRectangle        *new)
{
  const Constraint **cp;
  
  cp = &all_constraints[0];

  while (*cp)
    {
      meta_topic (META_DEBUG_GEOMETRY,
                  "Before: %d (HCenter constraint '%s')\n",
                  x_delta, (*cp)->name);
      
      if ((* (*cp)->applies_func) (window))
        (* (*cp)->hcenter_func) (window, info, orig,
                                 &x_delta);

      meta_topic (META_DEBUG_GEOMETRY,
                  "After:  %d (HCenter constraint '%s')\n",
                  x_delta, (*cp)->name);
      
      ++cp;
    }
  
  /* center deltas are positive to grow the window and negative to
   * shrink it.
   */
  new->x = orig->x - x_delta;
  new->width = orig->width + x_delta * 2;
  /* FIXME above implies that with center gravity you have to grow
   * in increments of two
   */
}

static void
constrain_resize_right (MetaWindow           *window,
                        const ConstraintInfo *info,
                        const MetaRectangle  *orig,
                        int                   x_delta,
                        MetaRectangle        *new)
{
  const Constraint **cp;

  cp = &all_constraints[0];

  while (*cp)
    {
      meta_topic (META_DEBUG_GEOMETRY,
                  "Before: %d (Right constraint '%s')\n",
                  x_delta, (*cp)->name);
      
      if ((* (*cp)->applies_func) (window))
        (* (*cp)->right_func) (window, info, orig,
                               &x_delta);

      meta_topic (META_DEBUG_GEOMETRY,
                  "After:  %d (Right constraint '%s')\n",
                  x_delta, (*cp)->name);
      
      ++cp;
    }

  new->width = orig->width + x_delta;
}

static void
constrain_resize_top (MetaWindow           *window,
                      const ConstraintInfo *info,
                      const MetaRectangle  *orig,
                      int                   y_delta,
                      MetaRectangle        *new)
{
  const Constraint **cp;

  cp = &all_constraints[0];

  while (*cp)
    {
      meta_topic (META_DEBUG_GEOMETRY,
                  "Before: %d (Top constraint '%s')\n",
                  y_delta, (*cp)->name);
      
      if ((* (*cp)->applies_func) (window))
        (* (*cp)->top_func) (window, info, orig,
                             &y_delta);

      meta_topic (META_DEBUG_GEOMETRY,
                  "After:  %d (Top constraint '%s')\n",
                  y_delta, (*cp)->name);
      
      ++cp;
    }

  new->y = orig->y + y_delta;
  new->height = orig->height - y_delta;
}

static void
constrain_resize_vcenter (MetaWindow           *window,
                          const ConstraintInfo *info,
                          const MetaRectangle  *orig,
                          int                   y_delta,
                          MetaRectangle        *new)
{
  const Constraint **cp;

  cp = &all_constraints[0];

  while (*cp)
    {
      meta_topic (META_DEBUG_GEOMETRY,
                  "Before: %d (VCenter constraint '%s')\n",
                  y_delta, (*cp)->name);
      
      if ((* (*cp)->applies_func) (window))
        (* (*cp)->vcenter_func) (window, info, orig,
                                 &y_delta);

      meta_topic (META_DEBUG_GEOMETRY,
                  "After:  %d (VCenter constraint '%s')\n",
                  y_delta, (*cp)->name);
      
      ++cp;
    }

  /* center deltas are positive to grow the window and negative to
   * shrink it.
   */
  new->y = orig->y - y_delta;
  new->height = orig->height + y_delta * 2;
  /* FIXME above implies that with center gravity you have to grow
   * in increments of two
   */
}

static void
constrain_resize_bottom (MetaWindow           *window,
                         const ConstraintInfo *info,
                         const MetaRectangle  *orig,
                         int                   y_delta,
                         MetaRectangle        *new)
{
  const Constraint **cp;

  cp = &all_constraints[0];

  while (*cp)
    {
      meta_topic (META_DEBUG_GEOMETRY,
                  "Before: %d (Bottom constraint '%s')\n",
                  y_delta, (*cp)->name);
      
      if ((* (*cp)->applies_func) (window))
        (* (*cp)->bottom_func) (window, info, orig,
                                &y_delta);

      meta_topic (META_DEBUG_GEOMETRY,
                  "After:  %d (Bottom constraint '%s')\n",
                  y_delta, (*cp)->name);
      
      ++cp;
    }

  new->height = orig->height + y_delta;
}

static void
update_position_limits (MetaWindow          *window,
                        ConstraintInfo      *info)
{
  int nw_x, nw_y;
  int se_x, se_y;

  nw_x = info->work_area_screen.x;
  nw_y = info->work_area_screen.y;

  /* find bottom-right corner of workarea */
  se_x = info->work_area_screen.x + info->work_area_screen.width;
  se_y = info->work_area_screen.y + info->work_area_screen.height;

  /* If we have a micro-screen or huge frames maybe nw/se got
   * swapped
   */
  if (nw_x > se_x)
    {
      int tmp = nw_x;
      nw_x = se_x;
      se_x = tmp;
    }

  if (nw_y > se_y)
    {
      int tmp = nw_y;
      nw_y = se_y;
      se_y = tmp;
    }

  info->nw_x = nw_x;
  info->nw_y = nw_y;
  info->se_x = se_x;
  info->se_y = se_y;
}

/* The delta values are the mouse motion distance deltas,
 * i.e. mouse_current_pos - mouse_orig_pos, for resizing on
 * the sides, or moving. For center resize, the delta
 * value is positive to grow the window and negative to
 * shrink it (while the sign of the mouse delta
 * depends on which side of the window you are center resizing
 * from)
 */
void
meta_window_constrain (MetaWindow          *window,
                       MetaFrameGeometry   *orig_fgeom,
                       const MetaRectangle *orig,
                       int                  x_move_delta,
                       int                  y_move_delta,
                       MetaResizeDirection  x_direction,
                       int                  x_delta,
                       MetaResizeDirection  y_direction,
                       int                  y_delta,
                       MetaRectangle       *new)
{
  ConstraintInfo info;
  MetaRectangle current;

#define OUTER_WIDTH(rect) ((rect).width + info.fgeom.left_width + info.fgeom.right_width)
#define OUTER_HEIGHT(rect) ((rect).height + info.fgeom.top_height + info.fgeom.bottom_height)
  
  meta_topic (META_DEBUG_GEOMETRY,
              "Constraining %s x_move_delta = %d y_move_delta = %d x_direction = %d y_direction = %d x_delta = %d y_delta = %d orig %d,%d %dx%d\n",
              window->desc, x_move_delta, y_move_delta,
              x_direction, y_direction, x_delta, y_delta,
              orig->x, orig->y, orig->width, orig->height);

  /* Create a fake frame geometry if none really exists */
  if (orig_fgeom && !window->fullscreen)
    info.fgeom = *orig_fgeom;
  else
    {
      info.fgeom.top_height = 0;
      info.fgeom.bottom_height = 0;
      info.fgeom.left_width = 0;
      info.fgeom.right_width = 0;
    }

  meta_window_get_work_area_current_xinerama (window, &info.work_area_xinerama);
  meta_window_get_work_area_all_xineramas (window, &info.work_area_screen);

  info.window = window;
  info.xinerama = meta_screen_get_xinerama_for_window (window->screen,
                                                       window);

  /* Init info->nw_x etc. */
  update_position_limits (window, &info);

  current = *orig;
  *new = current;

  /* Do placement if any, so we go ahead and apply position
   * constraints in a move-only context. Don't place
   * maximized/fullscreen windows until they are unmaximized
   * and unfullscreened
   */
  if (!window->placed &&
      window->calc_placement &&
      !window->maximized &&
      !window->fullscreen)
    {
      int x, y;

      meta_window_place (window, orig_fgeom, current.x, current.y,
                         &x, &y);

      constrain_move (window, &info, &current,
                      x - current.x,
                      y - current.y,
                      new);
      current = *new;

      /* Ignore any non-placement movement */
      x_move_delta = 0;
      y_move_delta = 0;
    }

  /* Maximization, fullscreen, etc. are defined as a move followed by
   * a resize, as explained in one of the big comments at the top of
   * this file.
   */
  if (window->fullscreen)
    {
      int center_x;

      center_x = info.xinerama->x_origin + (info.xinerama->width / 2);
      center_x -= OUTER_WIDTH (current) / 2;

      constrain_move (window, &info, &current,
                      center_x - current.x,
                      info.xinerama->y_origin - current.y + info.fgeom.top_height,
                      new);

      current = *new;

      constrain_resize_bottom (window, &info, &current,
                               (info.xinerama->height - OUTER_HEIGHT (current)),
                               new);

      current = *new;

      constrain_resize_hcenter (window, &info, &current,
                                (info.xinerama->width - OUTER_WIDTH (current)) / 2,
                                new);
      current = *new;
    }
  else if (window->maximized)
    {
      int center_x;

      center_x = info.work_area_xinerama.x + (info.work_area_xinerama.width / 2);
      center_x -= OUTER_WIDTH (current) / 2;

      constrain_move (window, &info, &current,
                      center_x - current.x,
                      info.work_area_xinerama.y - current.y + info.fgeom.top_height,
                      new);

      current = *new;

      constrain_resize_bottom (window, &info, &current,
                               (info.work_area_xinerama.height - OUTER_HEIGHT (current)),
                               new);

      current = *new;

      constrain_resize_hcenter (window, &info, &current,
                                (info.work_area_xinerama.width - OUTER_WIDTH (current)) / 2,
                                new);
      current = *new;
    }
  else
    {
      constrain_move (window, &info, &current,
                      x_move_delta, y_move_delta,
                      new);

      current = *new;

      switch (x_direction)
        {
        case META_RESIZE_LEFT_OR_TOP:
          constrain_resize_left (window, &info, &current,
                                 x_delta, new);
          break;
        case META_RESIZE_CENTER:
          constrain_resize_hcenter (window, &info, &current,
                                    x_delta, new);
          break;
        case META_RESIZE_RIGHT_OR_BOTTOM:
          constrain_resize_right (window, &info, &current,
                                  x_delta, new);
          break;
        }

      switch (y_direction)
        {
        case META_RESIZE_LEFT_OR_TOP:
          constrain_resize_top (window, &info, &current,
                                y_delta, new);
          break;
        case META_RESIZE_CENTER:
          constrain_resize_vcenter (window, &info, &current,
                                    y_delta, new);
          break;
        case META_RESIZE_RIGHT_OR_BOTTOM:
          constrain_resize_bottom (window, &info, &current,
                                   y_delta, new);
          break;
        }

      current = *new;
    }

#if 0
  /* Now we have to sort out the aspect ratio */
  {
    /*
     *                width
     * min_aspect <= -------- <= max_aspect
     *                height
     */
    double min_aspect, max_aspect;
    int width, height;

    min_aspect = window->size_hints.min_aspect.x / (double) window->size_hints.min_aspect.y;
    max_aspect = window->size_hints.max_aspect.x / (double) window->size_hints.max_aspect.y;

    width = current.width;
    height = current.height;

    /* Use the standard cut-and-pasted-between-every-WM code: */
    if (min_aspect * height > width)
      {
        int delta;

        delta = FLOOR (height - width / min_aspect, window->size_hints.height_inc);
        if (height - delta >= window->size_hints.min_height)
          height -= delta;
        else
          {
            delta = FLOOR (height * min_aspect - width, window->size_hints.width_inc);
            if (width + delta <= window->size_hints.max_width)
              width += delta;
          }
      }

    if (max_aspect * height < width)
      {
        int delta;

        delta = FLOOR (width - height * max_aspect, window->size_hints.width_inc);
        if (width - delta >= window->size_hints.min_width)
          width -= delta;
        else
          {
            delta = FLOOR (width / max_aspect - height, window->size_hints.height_inc);
            if (height + delta <= window->size_hints.max_height)
              height += delta;
          }
      }

    /* Convert into terms of the direction of resize and reapply the
     * earlier constraints; this means aspect ratio becomes the
     * least-important of the constraints. If we wanted aspect to be
     * the most important, we could just not do this next bit.
     */

    if (current.width != width)
      {
        x_delta = width - current.width; /* positive delta to increase width */
        switch (x_direction)
          {
          case META_RESIZE_LEFT_OR_TOP:
            constrain_resize_left (window, &info, &current,
                                   - x_delta, new);
            break;
          case META_RESIZE_CENTER:
            constrain_resize_hcenter (window, &info, &current,
                                      x_delta, new);
            break;
          case META_RESIZE_RIGHT_OR_BOTTOM:
            constrain_resize_right (window, &info, &current,
                                    x_delta, new);
            break;
          }
      }

    if (current.height != height)
      {
        y_delta = height - current.height; /* positive to increase height */

        switch (y_direction)
          {
          case META_RESIZE_LEFT_OR_TOP:
            constrain_resize_top (window, &info, &current,
                                  - y_delta, new);
            break;
          case META_RESIZE_CENTER:
            constrain_resize_vcenter (window, &info, &current,
                                      y_delta, new);
            break;
          case META_RESIZE_RIGHT_OR_BOTTOM:
            constrain_resize_bottom (window, &info, &current,
                                     y_delta, new);
            break;
          }
      }

    current = *new;
  }


  g_print ("3 x_delta = %d y_delta = %d pos = %d,%d size = %dx%d\n",
           x_delta, y_delta,
           current.x, current.y, current.width, current.height);
#endif

  meta_topic (META_DEBUG_GEOMETRY,
              "Constrained %s new %d,%d %dx%d old %d,%d %dx%d\n",
              window->desc,
              new->x, new->y, new->width, new->height,
              orig->x, orig->y, orig->width, orig->height);
}

MetaResizeDirection
meta_x_direction_from_gravity (int gravity)
{
  switch (gravity)
    {
    case EastGravity:
    case NorthEastGravity:
    case SouthEastGravity:
      return META_RESIZE_LEFT_OR_TOP;
      break;

    case WestGravity:
    case NorthWestGravity:
    case SouthWestGravity:
    case StaticGravity:
      return META_RESIZE_RIGHT_OR_BOTTOM;
      break;

    default:
      return META_RESIZE_CENTER;
      break;
    }
}

MetaResizeDirection
meta_y_direction_from_gravity (int gravity)
{
  switch (gravity)
    {
    case SouthGravity:
    case SouthWestGravity:
    case SouthEastGravity:
      return META_RESIZE_LEFT_OR_TOP;
      break;

    case NorthGravity:
    case NorthWestGravity:
    case NorthEastGravity:
    case StaticGravity:
      return META_RESIZE_RIGHT_OR_BOTTOM;
      break;

    default:
      return META_RESIZE_CENTER;
    }
}