aboutsummaryrefslogtreecommitdiffhomepage
path: root/src/core/SkMatrix.cpp
blob: a05ae0a177670a298b4945e870a534d7c584183f (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
/*
 * Copyright 2006 The Android Open Source Project
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#include "SkFloatBits.h"
#include "SkMatrix.h"
#include "SkNx.h"
#include "SkPaint.h"
#include "SkRSXform.h"
#include "SkString.h"
#include <stddef.h>

static void normalize_perspective(SkScalar mat[9]) {
    // If it was interesting to never store the last element, we could divide all 8 other
    // elements here by the 9th, making it 1.0...
    //
    // When SkScalar was SkFixed, we would sometimes rescale the entire matrix to keep its
    // component values from getting too large. This is not a concern when using floats/doubles,
    // so we do nothing now.

    // Disable this for now, but it could be enabled.
#if 0
    if (0 == mat[SkMatrix::kMPersp0] && 0 == mat[SkMatrix::kMPersp1]) {
        SkScalar p2 = mat[SkMatrix::kMPersp2];
        if (p2 != 0 && p2 != 1) {
            double inv = 1.0 / p2;
            for (int i = 0; i < 6; ++i) {
                mat[i] = SkDoubleToScalar(mat[i] * inv);
            }
            mat[SkMatrix::kMPersp2] = 1;
        }
    }
#endif
}

// In a few places, we performed the following
//      a * b + c * d + e
// as
//      a * b + (c * d + e)
//
// sdot and scross are indended to capture these compound operations into a
// function, with an eye toward considering upscaling the intermediates to
// doubles for more precision (as we do in concat and invert).
//
// However, these few lines that performed the last add before the "dot", cause
// tiny image differences, so we guard that change until we see the impact on
// chrome's layouttests.
//
#define SK_LEGACY_MATRIX_MATH_ORDER

static inline float SkDoubleToFloat(double x) {
    return static_cast<float>(x);
}

/*      [scale-x    skew-x      trans-x]   [X]   [X']
        [skew-y     scale-y     trans-y] * [Y] = [Y']
        [persp-0    persp-1     persp-2]   [1]   [1 ]
*/

void SkMatrix::reset() {
    fMat[kMScaleX] = fMat[kMScaleY] = fMat[kMPersp2] = 1;
    fMat[kMSkewX]  = fMat[kMSkewY] =
    fMat[kMTransX] = fMat[kMTransY] =
    fMat[kMPersp0] = fMat[kMPersp1] = 0;
    this->setTypeMask(kIdentity_Mask | kRectStaysRect_Mask);
}

void SkMatrix::set9(const SkScalar buffer[]) {
    memcpy(fMat, buffer, 9 * sizeof(SkScalar));
    normalize_perspective(fMat);
    this->setTypeMask(kUnknown_Mask);
}

void SkMatrix::setAffine(const SkScalar buffer[]) {
    fMat[kMScaleX] = buffer[kAScaleX];
    fMat[kMSkewX]  = buffer[kASkewX];
    fMat[kMTransX] = buffer[kATransX];
    fMat[kMSkewY]  = buffer[kASkewY];
    fMat[kMScaleY] = buffer[kAScaleY];
    fMat[kMTransY] = buffer[kATransY];
    fMat[kMPersp0] = 0;
    fMat[kMPersp1] = 0;
    fMat[kMPersp2] = 1;
    this->setTypeMask(kUnknown_Mask);
}

// this guy aligns with the masks, so we can compute a mask from a varaible 0/1
enum {
    kTranslate_Shift,
    kScale_Shift,
    kAffine_Shift,
    kPerspective_Shift,
    kRectStaysRect_Shift
};

static const int32_t kScalar1Int = 0x3f800000;

uint8_t SkMatrix::computePerspectiveTypeMask() const {
    // Benchmarking suggests that replacing this set of SkScalarAs2sCompliment
    // is a win, but replacing those below is not. We don't yet understand
    // that result.
    if (fMat[kMPersp0] != 0 || fMat[kMPersp1] != 0 || fMat[kMPersp2] != 1) {
        // If this is a perspective transform, we return true for all other
        // transform flags - this does not disable any optimizations, respects
        // the rule that the type mask must be conservative, and speeds up
        // type mask computation.
        return SkToU8(kORableMasks);
    }

    return SkToU8(kOnlyPerspectiveValid_Mask | kUnknown_Mask);
}

uint8_t SkMatrix::computeTypeMask() const {
    unsigned mask = 0;

    if (fMat[kMPersp0] != 0 || fMat[kMPersp1] != 0 || fMat[kMPersp2] != 1) {
        // Once it is determined that that this is a perspective transform,
        // all other flags are moot as far as optimizations are concerned.
        return SkToU8(kORableMasks);
    }

    if (fMat[kMTransX] != 0 || fMat[kMTransY] != 0) {
        mask |= kTranslate_Mask;
    }

    int m00 = SkScalarAs2sCompliment(fMat[SkMatrix::kMScaleX]);
    int m01 = SkScalarAs2sCompliment(fMat[SkMatrix::kMSkewX]);
    int m10 = SkScalarAs2sCompliment(fMat[SkMatrix::kMSkewY]);
    int m11 = SkScalarAs2sCompliment(fMat[SkMatrix::kMScaleY]);

    if (m01 | m10) {
        // The skew components may be scale-inducing, unless we are dealing
        // with a pure rotation.  Testing for a pure rotation is expensive,
        // so we opt for being conservative by always setting the scale bit.
        // along with affine.
        // By doing this, we are also ensuring that matrices have the same
        // type masks as their inverses.
        mask |= kAffine_Mask | kScale_Mask;

        // For rectStaysRect, in the affine case, we only need check that
        // the primary diagonal is all zeros and that the secondary diagonal
        // is all non-zero.

        // map non-zero to 1
        m01 = m01 != 0;
        m10 = m10 != 0;

        int dp0 = 0 == (m00 | m11) ;  // true if both are 0
        int ds1 = m01 & m10;        // true if both are 1

        mask |= (dp0 & ds1) << kRectStaysRect_Shift;
    } else {
        // Only test for scale explicitly if not affine, since affine sets the
        // scale bit.
        if ((m00 ^ kScalar1Int) | (m11 ^ kScalar1Int)) {
            mask |= kScale_Mask;
        }

        // Not affine, therefore we already know secondary diagonal is
        // all zeros, so we just need to check that primary diagonal is
        // all non-zero.

        // map non-zero to 1
        m00 = m00 != 0;
        m11 = m11 != 0;

        // record if the (p)rimary diagonal is all non-zero
        mask |= (m00 & m11) << kRectStaysRect_Shift;
    }

    return SkToU8(mask);
}

///////////////////////////////////////////////////////////////////////////////

bool operator==(const SkMatrix& a, const SkMatrix& b) {
    const SkScalar* SK_RESTRICT ma = a.fMat;
    const SkScalar* SK_RESTRICT mb = b.fMat;

    return  ma[0] == mb[0] && ma[1] == mb[1] && ma[2] == mb[2] &&
            ma[3] == mb[3] && ma[4] == mb[4] && ma[5] == mb[5] &&
            ma[6] == mb[6] && ma[7] == mb[7] && ma[8] == mb[8];
}

///////////////////////////////////////////////////////////////////////////////

// helper function to determine if upper-left 2x2 of matrix is degenerate
static inline bool is_degenerate_2x2(SkScalar scaleX, SkScalar skewX,
                                     SkScalar skewY,  SkScalar scaleY) {
    SkScalar perp_dot = scaleX*scaleY - skewX*skewY;
    return SkScalarNearlyZero(perp_dot, SK_ScalarNearlyZero*SK_ScalarNearlyZero);
}

///////////////////////////////////////////////////////////////////////////////

bool SkMatrix::isSimilarity(SkScalar tol) const {
    // if identity or translate matrix
    TypeMask mask = this->getType();
    if (mask <= kTranslate_Mask) {
        return true;
    }
    if (mask & kPerspective_Mask) {
        return false;
    }

    SkScalar mx = fMat[kMScaleX];
    SkScalar my = fMat[kMScaleY];
    // if no skew, can just compare scale factors
    if (!(mask & kAffine_Mask)) {
        return !SkScalarNearlyZero(mx) && SkScalarNearlyEqual(SkScalarAbs(mx), SkScalarAbs(my));
    }
    SkScalar sx = fMat[kMSkewX];
    SkScalar sy = fMat[kMSkewY];

    if (is_degenerate_2x2(mx, sx, sy, my)) {
        return false;
    }

    // upper 2x2 is rotation/reflection + uniform scale if basis vectors
    // are 90 degree rotations of each other
    return (SkScalarNearlyEqual(mx, my, tol) && SkScalarNearlyEqual(sx, -sy, tol))
        || (SkScalarNearlyEqual(mx, -my, tol) && SkScalarNearlyEqual(sx, sy, tol));
}

bool SkMatrix::preservesRightAngles(SkScalar tol) const {
    TypeMask mask = this->getType();

    if (mask <= kTranslate_Mask) {
        // identity, translate and/or scale
        return true;
    }
    if (mask & kPerspective_Mask) {
        return false;
    }

    SkASSERT(mask & (kAffine_Mask | kScale_Mask));

    SkScalar mx = fMat[kMScaleX];
    SkScalar my = fMat[kMScaleY];
    SkScalar sx = fMat[kMSkewX];
    SkScalar sy = fMat[kMSkewY];

    if (is_degenerate_2x2(mx, sx, sy, my)) {
        return false;
    }

    // upper 2x2 is scale + rotation/reflection if basis vectors are orthogonal
    SkVector vec[2];
    vec[0].set(mx, sy);
    vec[1].set(sx, my);

    return SkScalarNearlyZero(vec[0].dot(vec[1]), SkScalarSquare(tol));
}

///////////////////////////////////////////////////////////////////////////////

static inline SkScalar sdot(SkScalar a, SkScalar b, SkScalar c, SkScalar d) {
    return a * b + c * d;
}

static inline SkScalar sdot(SkScalar a, SkScalar b, SkScalar c, SkScalar d,
                             SkScalar e, SkScalar f) {
    return a * b + c * d + e * f;
}

static inline SkScalar scross(SkScalar a, SkScalar b, SkScalar c, SkScalar d) {
    return a * b - c * d;
}

void SkMatrix::setTranslate(SkScalar dx, SkScalar dy) {
    if (dx || dy) {
        fMat[kMTransX] = dx;
        fMat[kMTransY] = dy;

        fMat[kMScaleX] = fMat[kMScaleY] = fMat[kMPersp2] = 1;
        fMat[kMSkewX]  = fMat[kMSkewY] =
        fMat[kMPersp0] = fMat[kMPersp1] = 0;

        this->setTypeMask(kTranslate_Mask | kRectStaysRect_Mask);
    } else {
        this->reset();
    }
}

void SkMatrix::preTranslate(SkScalar dx, SkScalar dy) {
    if (!dx && !dy) {
        return;
    }

    if (fTypeMask <= kTranslate_Mask) {
        fMat[kMTransX] += dx;
        fMat[kMTransY] += dy;
        this->setTypeMask((fMat[kMTransX] != 0 || fMat[kMTransY] != 0) ? kTranslate_Mask
                                                                       : kIdentity_Mask);
    } else if (this->hasPerspective()) {
        SkMatrix    m;
        m.setTranslate(dx, dy);
        this->preConcat(m);
    } else {
        fMat[kMTransX] += sdot(fMat[kMScaleX], dx, fMat[kMSkewX], dy);
        fMat[kMTransY] += sdot(fMat[kMSkewY], dx, fMat[kMScaleY], dy);
        this->setTypeMask(kUnknown_Mask | kOnlyPerspectiveValid_Mask);
    }
}

void SkMatrix::postTranslate(SkScalar dx, SkScalar dy) {
    if (!dx && !dy) {
        return;
    }

    if (this->hasPerspective()) {
        SkMatrix    m;
        m.setTranslate(dx, dy);
        this->postConcat(m);
    } else {
        fMat[kMTransX] += dx;
        fMat[kMTransY] += dy;
        this->setTypeMask(kUnknown_Mask | kOnlyPerspectiveValid_Mask);
    }
}

///////////////////////////////////////////////////////////////////////////////

void SkMatrix::setScale(SkScalar sx, SkScalar sy, SkScalar px, SkScalar py) {
    if (1 == sx && 1 == sy) {
        this->reset();
    } else {
        this->setScaleTranslate(sx, sy, px - sx * px, py - sy * py);
    }
}

void SkMatrix::setScale(SkScalar sx, SkScalar sy) {
    if (1 == sx && 1 == sy) {
        this->reset();
    } else {
        fMat[kMScaleX] = sx;
        fMat[kMScaleY] = sy;
        fMat[kMPersp2] = 1;

        fMat[kMTransX] = fMat[kMTransY] =
        fMat[kMSkewX]  = fMat[kMSkewY] =
        fMat[kMPersp0] = fMat[kMPersp1] = 0;

        this->setTypeMask(kScale_Mask | kRectStaysRect_Mask);
    }
}

bool SkMatrix::setIDiv(int divx, int divy) {
    if (!divx || !divy) {
        return false;
    }
    this->setScale(SkScalarInvert(divx), SkScalarInvert(divy));
    return true;
}

void SkMatrix::preScale(SkScalar sx, SkScalar sy, SkScalar px, SkScalar py) {
    if (1 == sx && 1 == sy) {
        return;
    }

    SkMatrix    m;
    m.setScale(sx, sy, px, py);
    this->preConcat(m);
}

void SkMatrix::preScale(SkScalar sx, SkScalar sy) {
    if (1 == sx && 1 == sy) {
        return;
    }

    // the assumption is that these multiplies are very cheap, and that
    // a full concat and/or just computing the matrix type is more expensive.
    // Also, the fixed-point case checks for overflow, but the float doesn't,
    // so we can get away with these blind multiplies.

    fMat[kMScaleX] *= sx;
    fMat[kMSkewY]  *= sx;
    fMat[kMPersp0] *= sx;

    fMat[kMSkewX]  *= sy;
    fMat[kMScaleY] *= sy;
    fMat[kMPersp1] *= sy;

    // Attempt to simplify our type when applying an inverse scale.
    // TODO: The persp/affine preconditions are in place to keep the mask consistent with
    //       what computeTypeMask() would produce (persp/skew always implies kScale).
    //       We should investigate whether these flag dependencies are truly needed.
    if (fMat[kMScaleX] == 1 && fMat[kMScaleY] == 1
        && !(fTypeMask & (kPerspective_Mask | kAffine_Mask))) {
        this->clearTypeMask(kScale_Mask);
    } else {
        this->orTypeMask(kScale_Mask);
    }
}

void SkMatrix::postScale(SkScalar sx, SkScalar sy, SkScalar px, SkScalar py) {
    if (1 == sx && 1 == sy) {
        return;
    }
    SkMatrix    m;
    m.setScale(sx, sy, px, py);
    this->postConcat(m);
}

void SkMatrix::postScale(SkScalar sx, SkScalar sy) {
    if (1 == sx && 1 == sy) {
        return;
    }
    SkMatrix    m;
    m.setScale(sx, sy);
    this->postConcat(m);
}

// this guy perhaps can go away, if we have a fract/high-precision way to
// scale matrices
bool SkMatrix::postIDiv(int divx, int divy) {
    if (divx == 0 || divy == 0) {
        return false;
    }

    const float invX = 1.f / divx;
    const float invY = 1.f / divy;

    fMat[kMScaleX] *= invX;
    fMat[kMSkewX]  *= invX;
    fMat[kMTransX] *= invX;

    fMat[kMScaleY] *= invY;
    fMat[kMSkewY]  *= invY;
    fMat[kMTransY] *= invY;

    this->setTypeMask(kUnknown_Mask);
    return true;
}

////////////////////////////////////////////////////////////////////////////////////

void SkMatrix::setSinCos(SkScalar sinV, SkScalar cosV, SkScalar px, SkScalar py) {
    const SkScalar oneMinusCosV = 1 - cosV;

    fMat[kMScaleX]  = cosV;
    fMat[kMSkewX]   = -sinV;
    fMat[kMTransX]  = sdot(sinV, py, oneMinusCosV, px);

    fMat[kMSkewY]   = sinV;
    fMat[kMScaleY]  = cosV;
    fMat[kMTransY]  = sdot(-sinV, px, oneMinusCosV, py);

    fMat[kMPersp0] = fMat[kMPersp1] = 0;
    fMat[kMPersp2] = 1;

    this->setTypeMask(kUnknown_Mask | kOnlyPerspectiveValid_Mask);
}

SkMatrix& SkMatrix::setRSXform(const SkRSXform& xform) {
    fMat[kMScaleX]  = xform.fSCos;
    fMat[kMSkewX]   = -xform.fSSin;
    fMat[kMTransX]  = xform.fTx;

    fMat[kMSkewY]   = xform.fSSin;
    fMat[kMScaleY]  = xform.fSCos;
    fMat[kMTransY]  = xform.fTy;

    fMat[kMPersp0] = fMat[kMPersp1] = 0;
    fMat[kMPersp2] = 1;

    this->setTypeMask(kUnknown_Mask | kOnlyPerspectiveValid_Mask);
    return *this;
}

void SkMatrix::setSinCos(SkScalar sinV, SkScalar cosV) {
    fMat[kMScaleX]  = cosV;
    fMat[kMSkewX]   = -sinV;
    fMat[kMTransX]  = 0;

    fMat[kMSkewY]   = sinV;
    fMat[kMScaleY]  = cosV;
    fMat[kMTransY]  = 0;

    fMat[kMPersp0] = fMat[kMPersp1] = 0;
    fMat[kMPersp2] = 1;

    this->setTypeMask(kUnknown_Mask | kOnlyPerspectiveValid_Mask);
}

void SkMatrix::setRotate(SkScalar degrees, SkScalar px, SkScalar py) {
    SkScalar sinV, cosV;
    sinV = SkScalarSinCos(SkDegreesToRadians(degrees), &cosV);
    this->setSinCos(sinV, cosV, px, py);
}

void SkMatrix::setRotate(SkScalar degrees) {
    SkScalar sinV, cosV;
    sinV = SkScalarSinCos(SkDegreesToRadians(degrees), &cosV);
    this->setSinCos(sinV, cosV);
}

void SkMatrix::preRotate(SkScalar degrees, SkScalar px, SkScalar py) {
    SkMatrix    m;
    m.setRotate(degrees, px, py);
    this->preConcat(m);
}

void SkMatrix::preRotate(SkScalar degrees) {
    SkMatrix    m;
    m.setRotate(degrees);
    this->preConcat(m);
}

void SkMatrix::postRotate(SkScalar degrees, SkScalar px, SkScalar py) {
    SkMatrix    m;
    m.setRotate(degrees, px, py);
    this->postConcat(m);
}

void SkMatrix::postRotate(SkScalar degrees) {
    SkMatrix    m;
    m.setRotate(degrees);
    this->postConcat(m);
}

////////////////////////////////////////////////////////////////////////////////////

void SkMatrix::setSkew(SkScalar sx, SkScalar sy, SkScalar px, SkScalar py) {
    fMat[kMScaleX]  = 1;
    fMat[kMSkewX]   = sx;
    fMat[kMTransX]  = -sx * py;

    fMat[kMSkewY]   = sy;
    fMat[kMScaleY]  = 1;
    fMat[kMTransY]  = -sy * px;

    fMat[kMPersp0] = fMat[kMPersp1] = 0;
    fMat[kMPersp2] = 1;

    this->setTypeMask(kUnknown_Mask | kOnlyPerspectiveValid_Mask);
}

void SkMatrix::setSkew(SkScalar sx, SkScalar sy) {
    fMat[kMScaleX]  = 1;
    fMat[kMSkewX]   = sx;
    fMat[kMTransX]  = 0;

    fMat[kMSkewY]   = sy;
    fMat[kMScaleY]  = 1;
    fMat[kMTransY]  = 0;

    fMat[kMPersp0] = fMat[kMPersp1] = 0;
    fMat[kMPersp2] = 1;

    this->setTypeMask(kUnknown_Mask | kOnlyPerspectiveValid_Mask);
}

void SkMatrix::preSkew(SkScalar sx, SkScalar sy, SkScalar px, SkScalar py) {
    SkMatrix    m;
    m.setSkew(sx, sy, px, py);
    this->preConcat(m);
}

void SkMatrix::preSkew(SkScalar sx, SkScalar sy) {
    SkMatrix    m;
    m.setSkew(sx, sy);
    this->preConcat(m);
}

void SkMatrix::postSkew(SkScalar sx, SkScalar sy, SkScalar px, SkScalar py) {
    SkMatrix    m;
    m.setSkew(sx, sy, px, py);
    this->postConcat(m);
}

void SkMatrix::postSkew(SkScalar sx, SkScalar sy) {
    SkMatrix    m;
    m.setSkew(sx, sy);
    this->postConcat(m);
}

///////////////////////////////////////////////////////////////////////////////

bool SkMatrix::setRectToRect(const SkRect& src, const SkRect& dst, ScaleToFit align) {
    if (src.isEmpty()) {
        this->reset();
        return false;
    }

    if (dst.isEmpty()) {
        sk_bzero(fMat, 8 * sizeof(SkScalar));
        fMat[kMPersp2] = 1;
        this->setTypeMask(kScale_Mask | kRectStaysRect_Mask);
    } else {
        SkScalar    tx, sx = dst.width() / src.width();
        SkScalar    ty, sy = dst.height() / src.height();
        bool        xLarger = false;

        if (align != kFill_ScaleToFit) {
            if (sx > sy) {
                xLarger = true;
                sx = sy;
            } else {
                sy = sx;
            }
        }

        tx = dst.fLeft - src.fLeft * sx;
        ty = dst.fTop - src.fTop * sy;
        if (align == kCenter_ScaleToFit || align == kEnd_ScaleToFit) {
            SkScalar diff;

            if (xLarger) {
                diff = dst.width() - src.width() * sy;
            } else {
                diff = dst.height() - src.height() * sy;
            }

            if (align == kCenter_ScaleToFit) {
                diff = SkScalarHalf(diff);
            }

            if (xLarger) {
                tx += diff;
            } else {
                ty += diff;
            }
        }

        this->setScaleTranslate(sx, sy, tx, ty);
    }
    return true;
}

///////////////////////////////////////////////////////////////////////////////

static inline float muladdmul(float a, float b, float c, float d) {
    return SkDoubleToFloat((double)a * b + (double)c * d);
}

static inline float rowcol3(const float row[], const float col[]) {
    return row[0] * col[0] + row[1] * col[3] + row[2] * col[6];
}

static bool only_scale_and_translate(unsigned mask) {
    return 0 == (mask & (SkMatrix::kAffine_Mask | SkMatrix::kPerspective_Mask));
}

void SkMatrix::setConcat(const SkMatrix& a, const SkMatrix& b) {
    TypeMask aType = a.getType();
    TypeMask bType = b.getType();

    if (a.isTriviallyIdentity()) {
        *this = b;
    } else if (b.isTriviallyIdentity()) {
        *this = a;
    } else if (only_scale_and_translate(aType | bType)) {
        this->setScaleTranslate(a.fMat[kMScaleX] * b.fMat[kMScaleX],
                                a.fMat[kMScaleY] * b.fMat[kMScaleY],
                                a.fMat[kMScaleX] * b.fMat[kMTransX] + a.fMat[kMTransX],
                                a.fMat[kMScaleY] * b.fMat[kMTransY] + a.fMat[kMTransY]);
    } else {
        SkMatrix tmp;

        if ((aType | bType) & kPerspective_Mask) {
            tmp.fMat[kMScaleX] = rowcol3(&a.fMat[0], &b.fMat[0]);
            tmp.fMat[kMSkewX]  = rowcol3(&a.fMat[0], &b.fMat[1]);
            tmp.fMat[kMTransX] = rowcol3(&a.fMat[0], &b.fMat[2]);
            tmp.fMat[kMSkewY]  = rowcol3(&a.fMat[3], &b.fMat[0]);
            tmp.fMat[kMScaleY] = rowcol3(&a.fMat[3], &b.fMat[1]);
            tmp.fMat[kMTransY] = rowcol3(&a.fMat[3], &b.fMat[2]);
            tmp.fMat[kMPersp0] = rowcol3(&a.fMat[6], &b.fMat[0]);
            tmp.fMat[kMPersp1] = rowcol3(&a.fMat[6], &b.fMat[1]);
            tmp.fMat[kMPersp2] = rowcol3(&a.fMat[6], &b.fMat[2]);

            normalize_perspective(tmp.fMat);
            tmp.setTypeMask(kUnknown_Mask);
        } else {
            tmp.fMat[kMScaleX] = muladdmul(a.fMat[kMScaleX],
                                           b.fMat[kMScaleX],
                                           a.fMat[kMSkewX],
                                           b.fMat[kMSkewY]);

            tmp.fMat[kMSkewX]  = muladdmul(a.fMat[kMScaleX],
                                           b.fMat[kMSkewX],
                                           a.fMat[kMSkewX],
                                           b.fMat[kMScaleY]);

            tmp.fMat[kMTransX] = muladdmul(a.fMat[kMScaleX],
                                           b.fMat[kMTransX],
                                           a.fMat[kMSkewX],
                                           b.fMat[kMTransY]) + a.fMat[kMTransX];

            tmp.fMat[kMSkewY]  = muladdmul(a.fMat[kMSkewY],
                                           b.fMat[kMScaleX],
                                           a.fMat[kMScaleY],
                                           b.fMat[kMSkewY]);

            tmp.fMat[kMScaleY] = muladdmul(a.fMat[kMSkewY],
                                           b.fMat[kMSkewX],
                                           a.fMat[kMScaleY],
                                           b.fMat[kMScaleY]);

            tmp.fMat[kMTransY] = muladdmul(a.fMat[kMSkewY],
                                           b.fMat[kMTransX],
                                           a.fMat[kMScaleY],
                                           b.fMat[kMTransY]) + a.fMat[kMTransY];

            tmp.fMat[kMPersp0] = 0;
            tmp.fMat[kMPersp1] = 0;
            tmp.fMat[kMPersp2] = 1;
            //SkDebugf("Concat mat non-persp type: %d\n", tmp.getType());
            //SkASSERT(!(tmp.getType() & kPerspective_Mask));
            tmp.setTypeMask(kUnknown_Mask | kOnlyPerspectiveValid_Mask);
        }
        *this = tmp;
    }
}

void SkMatrix::preConcat(const SkMatrix& mat) {
    // check for identity first, so we don't do a needless copy of ourselves
    // to ourselves inside setConcat()
    if(!mat.isIdentity()) {
        this->setConcat(*this, mat);
    }
}

void SkMatrix::postConcat(const SkMatrix& mat) {
    // check for identity first, so we don't do a needless copy of ourselves
    // to ourselves inside setConcat()
    if (!mat.isIdentity()) {
        this->setConcat(mat, *this);
    }
}

///////////////////////////////////////////////////////////////////////////////

/*  Matrix inversion is very expensive, but also the place where keeping
    precision may be most important (here and matrix concat). Hence to avoid
    bitmap blitting artifacts when walking the inverse, we use doubles for
    the intermediate math, even though we know that is more expensive.
 */

static inline SkScalar scross_dscale(SkScalar a, SkScalar b,
                                     SkScalar c, SkScalar d, double scale) {
    return SkDoubleToScalar(scross(a, b, c, d) * scale);
}

static inline double dcross(double a, double b, double c, double d) {
    return a * b - c * d;
}

static inline SkScalar dcross_dscale(double a, double b,
                                     double c, double d, double scale) {
    return SkDoubleToScalar(dcross(a, b, c, d) * scale);
}

static double sk_inv_determinant(const float mat[9], int isPerspective) {
    double det;

    if (isPerspective) {
        det = mat[SkMatrix::kMScaleX] *
              dcross(mat[SkMatrix::kMScaleY], mat[SkMatrix::kMPersp2],
                     mat[SkMatrix::kMTransY], mat[SkMatrix::kMPersp1])
              +
              mat[SkMatrix::kMSkewX]  *
              dcross(mat[SkMatrix::kMTransY], mat[SkMatrix::kMPersp0],
                     mat[SkMatrix::kMSkewY],  mat[SkMatrix::kMPersp2])
              +
              mat[SkMatrix::kMTransX] *
              dcross(mat[SkMatrix::kMSkewY],  mat[SkMatrix::kMPersp1],
                     mat[SkMatrix::kMScaleY], mat[SkMatrix::kMPersp0]);
    } else {
        det = dcross(mat[SkMatrix::kMScaleX], mat[SkMatrix::kMScaleY],
                     mat[SkMatrix::kMSkewX], mat[SkMatrix::kMSkewY]);
    }

    // Since the determinant is on the order of the cube of the matrix members,
    // compare to the cube of the default nearly-zero constant (although an
    // estimate of the condition number would be better if it wasn't so expensive).
    if (SkScalarNearlyZero((float)det, SK_ScalarNearlyZero * SK_ScalarNearlyZero * SK_ScalarNearlyZero)) {
        return 0;
    }
    return 1.0 / det;
}

void SkMatrix::SetAffineIdentity(SkScalar affine[6]) {
    affine[kAScaleX] = 1;
    affine[kASkewY] = 0;
    affine[kASkewX] = 0;
    affine[kAScaleY] = 1;
    affine[kATransX] = 0;
    affine[kATransY] = 0;
}

bool SkMatrix::asAffine(SkScalar affine[6]) const {
    if (this->hasPerspective()) {
        return false;
    }
    if (affine) {
        affine[kAScaleX] = this->fMat[kMScaleX];
        affine[kASkewY] = this->fMat[kMSkewY];
        affine[kASkewX] = this->fMat[kMSkewX];
        affine[kAScaleY] = this->fMat[kMScaleY];
        affine[kATransX] = this->fMat[kMTransX];
        affine[kATransY] = this->fMat[kMTransY];
    }
    return true;
}

void SkMatrix::ComputeInv(SkScalar dst[9], const SkScalar src[9], double invDet, bool isPersp) {
    SkASSERT(src != dst);
    SkASSERT(src && dst);

    if (isPersp) {
        dst[kMScaleX] = scross_dscale(src[kMScaleY], src[kMPersp2], src[kMTransY], src[kMPersp1], invDet);
        dst[kMSkewX]  = scross_dscale(src[kMTransX], src[kMPersp1], src[kMSkewX],  src[kMPersp2], invDet);
        dst[kMTransX] = scross_dscale(src[kMSkewX],  src[kMTransY], src[kMTransX], src[kMScaleY], invDet);

        dst[kMSkewY]  = scross_dscale(src[kMTransY], src[kMPersp0], src[kMSkewY],  src[kMPersp2], invDet);
        dst[kMScaleY] = scross_dscale(src[kMScaleX], src[kMPersp2], src[kMTransX], src[kMPersp0], invDet);
        dst[kMTransY] = scross_dscale(src[kMTransX], src[kMSkewY],  src[kMScaleX], src[kMTransY], invDet);

        dst[kMPersp0] = scross_dscale(src[kMSkewY],  src[kMPersp1], src[kMScaleY], src[kMPersp0], invDet);
        dst[kMPersp1] = scross_dscale(src[kMSkewX],  src[kMPersp0], src[kMScaleX], src[kMPersp1], invDet);
        dst[kMPersp2] = scross_dscale(src[kMScaleX], src[kMScaleY], src[kMSkewX],  src[kMSkewY],  invDet);
    } else {   // not perspective
        dst[kMScaleX] = SkDoubleToScalar(src[kMScaleY] * invDet);
        dst[kMSkewX]  = SkDoubleToScalar(-src[kMSkewX] * invDet);
        dst[kMTransX] = dcross_dscale(src[kMSkewX], src[kMTransY], src[kMScaleY], src[kMTransX], invDet);

        dst[kMSkewY]  = SkDoubleToScalar(-src[kMSkewY] * invDet);
        dst[kMScaleY] = SkDoubleToScalar(src[kMScaleX] * invDet);
        dst[kMTransY] = dcross_dscale(src[kMSkewY], src[kMTransX], src[kMScaleX], src[kMTransY], invDet);

        dst[kMPersp0] = 0;
        dst[kMPersp1] = 0;
        dst[kMPersp2] = 1;
    }
}

bool SkMatrix::invertNonIdentity(SkMatrix* inv) const {
    SkASSERT(!this->isIdentity());

    TypeMask mask = this->getType();

    if (0 == (mask & ~(kScale_Mask | kTranslate_Mask))) {
        bool invertible = true;
        if (inv) {
            if (mask & kScale_Mask) {
                SkScalar invX = fMat[kMScaleX];
                SkScalar invY = fMat[kMScaleY];
                if (0 == invX || 0 == invY) {
                    return false;
                }
                invX = SkScalarInvert(invX);
                invY = SkScalarInvert(invY);

                // Must be careful when writing to inv, since it may be the
                // same memory as this.

                inv->fMat[kMSkewX] = inv->fMat[kMSkewY] =
                inv->fMat[kMPersp0] = inv->fMat[kMPersp1] = 0;

                inv->fMat[kMScaleX] = invX;
                inv->fMat[kMScaleY] = invY;
                inv->fMat[kMPersp2] = 1;
                inv->fMat[kMTransX] = -fMat[kMTransX] * invX;
                inv->fMat[kMTransY] = -fMat[kMTransY] * invY;

                inv->setTypeMask(mask | kRectStaysRect_Mask);
            } else {
                // translate only
                inv->setTranslate(-fMat[kMTransX], -fMat[kMTransY]);
            }
        } else {    // inv is nullptr, just check if we're invertible
            if (!fMat[kMScaleX] || !fMat[kMScaleY]) {
                invertible = false;
            }
        }
        return invertible;
    }

    int    isPersp = mask & kPerspective_Mask;
    double invDet = sk_inv_determinant(fMat, isPersp);

    if (invDet == 0) { // underflow
        return false;
    }

    bool applyingInPlace = (inv == this);

    SkMatrix* tmp = inv;

    SkMatrix storage;
    if (applyingInPlace || nullptr == tmp) {
        tmp = &storage;     // we either need to avoid trampling memory or have no memory
    }

    ComputeInv(tmp->fMat, fMat, invDet, isPersp);
    if (!tmp->isFinite()) {
        return false;
    }

    tmp->setTypeMask(fTypeMask);

    if (applyingInPlace) {
        *inv = storage; // need to copy answer back
    }

    return true;
}

///////////////////////////////////////////////////////////////////////////////

void SkMatrix::Identity_pts(const SkMatrix& m, SkPoint dst[], const SkPoint src[], int count) {
    SkASSERT(m.getType() == 0);

    if (dst != src && count > 0) {
        memcpy(dst, src, count * sizeof(SkPoint));
    }
}

void SkMatrix::Trans_pts(const SkMatrix& m, SkPoint dst[], const SkPoint src[], int count) {
    SkASSERT(m.getType() <= SkMatrix::kTranslate_Mask);
    if (count > 0) {
        SkScalar tx = m.getTranslateX();
        SkScalar ty = m.getTranslateY();
        if (count & 1) {
            dst->fX = src->fX + tx;
            dst->fY = src->fY + ty;
            src += 1;
            dst += 1;
        }
        Sk4s trans4(tx, ty, tx, ty);
        count >>= 1;
        if (count & 1) {
            (Sk4s::Load(src) + trans4).store(dst);
            src += 2;
            dst += 2;
        }
        count >>= 1;
        for (int i = 0; i < count; ++i) {
            (Sk4s::Load(src+0) + trans4).store(dst+0);
            (Sk4s::Load(src+2) + trans4).store(dst+2);
            src += 4;
            dst += 4;
        }
    }
}

void SkMatrix::Scale_pts(const SkMatrix& m, SkPoint dst[], const SkPoint src[], int count) {
    SkASSERT(m.getType() <= (SkMatrix::kScale_Mask | SkMatrix::kTranslate_Mask));
    if (count > 0) {
        SkScalar tx = m.getTranslateX();
        SkScalar ty = m.getTranslateY();
        SkScalar sx = m.getScaleX();
        SkScalar sy = m.getScaleY();
        if (count & 1) {
            dst->fX = src->fX * sx + tx;
            dst->fY = src->fY * sy + ty;
            src += 1;
            dst += 1;
        }
        Sk4s trans4(tx, ty, tx, ty);
        Sk4s scale4(sx, sy, sx, sy);
        count >>= 1;
        if (count & 1) {
            (Sk4s::Load(src) * scale4 + trans4).store(dst);
            src += 2;
            dst += 2;
        }
        count >>= 1;
        for (int i = 0; i < count; ++i) {
            (Sk4s::Load(src+0) * scale4 + trans4).store(dst+0);
            (Sk4s::Load(src+2) * scale4 + trans4).store(dst+2);
            src += 4;
            dst += 4;
        }
    }
}

void SkMatrix::Persp_pts(const SkMatrix& m, SkPoint dst[],
                         const SkPoint src[], int count) {
    SkASSERT(m.hasPerspective());

    if (count > 0) {
        do {
            SkScalar sy = src->fY;
            SkScalar sx = src->fX;
            src += 1;

            SkScalar x = sdot(sx, m.fMat[kMScaleX], sy, m.fMat[kMSkewX])  + m.fMat[kMTransX];
            SkScalar y = sdot(sx, m.fMat[kMSkewY],  sy, m.fMat[kMScaleY]) + m.fMat[kMTransY];
#ifdef SK_LEGACY_MATRIX_MATH_ORDER
            SkScalar z = sx * m.fMat[kMPersp0] + (sy * m.fMat[kMPersp1] + m.fMat[kMPersp2]);
#else
            SkScalar z = sdot(sx, m.fMat[kMPersp0], sy, m.fMat[kMPersp1]) + m.fMat[kMPersp2];
#endif
            if (z) {
                z = SkScalarFastInvert(z);
            }

            dst->fY = y * z;
            dst->fX = x * z;
            dst += 1;
        } while (--count);
    }
}

void SkMatrix::Affine_vpts(const SkMatrix& m, SkPoint dst[], const SkPoint src[], int count) {
    SkASSERT(m.getType() != SkMatrix::kPerspective_Mask);
    if (count > 0) {
        SkScalar tx = m.getTranslateX();
        SkScalar ty = m.getTranslateY();
        SkScalar sx = m.getScaleX();
        SkScalar sy = m.getScaleY();
        SkScalar kx = m.getSkewX();
        SkScalar ky = m.getSkewY();
        if (count & 1) {
            dst->set(src->fX * sx + src->fY * kx + tx,
                     src->fX * ky + src->fY * sy + ty);
            src += 1;
            dst += 1;
        }
        Sk4s trans4(tx, ty, tx, ty);
        Sk4s scale4(sx, sy, sx, sy);
        Sk4s  skew4(kx, ky, kx, ky);    // applied to swizzle of src4
        count >>= 1;
        for (int i = 0; i < count; ++i) {
            Sk4s src4 = Sk4s::Load(src);
            Sk4s swz4 = SkNx_shuffle<1,0,3,2>(src4);  // y0 x0, y1 x1
            (src4 * scale4 + swz4 * skew4 + trans4).store(dst);
            src += 2;
            dst += 2;
        }
    }
}

const SkMatrix::MapPtsProc SkMatrix::gMapPtsProcs[] = {
    SkMatrix::Identity_pts, SkMatrix::Trans_pts,
    SkMatrix::Scale_pts,   SkMatrix::Scale_pts,
    SkMatrix::Affine_vpts,  SkMatrix::Affine_vpts,
    SkMatrix::Affine_vpts,  SkMatrix::Affine_vpts,
    // repeat the persp proc 8 times
    SkMatrix::Persp_pts,    SkMatrix::Persp_pts,
    SkMatrix::Persp_pts,    SkMatrix::Persp_pts,
    SkMatrix::Persp_pts,    SkMatrix::Persp_pts,
    SkMatrix::Persp_pts,    SkMatrix::Persp_pts
};

///////////////////////////////////////////////////////////////////////////////

void SkMatrix::mapHomogeneousPoints(SkScalar dst[], const SkScalar src[], int count) const {
    SkASSERT((dst && src && count > 0) || 0 == count);
    // no partial overlap
    SkASSERT(src == dst || &dst[3*count] <= &src[0] || &src[3*count] <= &dst[0]);

    if (count > 0) {
        if (this->isIdentity()) {
            memcpy(dst, src, 3*count*sizeof(SkScalar));
            return;
        }
        do {
            SkScalar sx = src[0];
            SkScalar sy = src[1];
            SkScalar sw = src[2];
            src += 3;

            SkScalar x = sdot(sx, fMat[kMScaleX], sy, fMat[kMSkewX],  sw, fMat[kMTransX]);
            SkScalar y = sdot(sx, fMat[kMSkewY],  sy, fMat[kMScaleY], sw, fMat[kMTransY]);
            SkScalar w = sdot(sx, fMat[kMPersp0], sy, fMat[kMPersp1], sw, fMat[kMPersp2]);

            dst[0] = x;
            dst[1] = y;
            dst[2] = w;
            dst += 3;
        } while (--count);
    }
}

///////////////////////////////////////////////////////////////////////////////

void SkMatrix::mapVectors(SkPoint dst[], const SkPoint src[], int count) const {
    if (this->hasPerspective()) {
        SkPoint origin;

        MapXYProc proc = this->getMapXYProc();
        proc(*this, 0, 0, &origin);

        for (int i = count - 1; i >= 0; --i) {
            SkPoint tmp;

            proc(*this, src[i].fX, src[i].fY, &tmp);
            dst[i].set(tmp.fX - origin.fX, tmp.fY - origin.fY);
        }
    } else {
        SkMatrix tmp = *this;

        tmp.fMat[kMTransX] = tmp.fMat[kMTransY] = 0;
        tmp.clearTypeMask(kTranslate_Mask);
        tmp.mapPoints(dst, src, count);
    }
}

static Sk4f sort_as_rect(const Sk4f& ltrb) {
    Sk4f rblt(ltrb[2], ltrb[3], ltrb[0], ltrb[1]);
    Sk4f min = Sk4f::Min(ltrb, rblt);
    Sk4f max = Sk4f::Max(ltrb, rblt);
    // We can extract either pair [0,1] or [2,3] from min and max and be correct, but on
    // ARM this sequence generates the fastest (a single instruction).
    return Sk4f(min[2], min[3], max[0], max[1]);
}

void SkMatrix::mapRectScaleTranslate(SkRect* dst, const SkRect& src) const {
    SkASSERT(dst);
    SkASSERT(this->isScaleTranslate());

    SkScalar sx = fMat[kMScaleX];
    SkScalar sy = fMat[kMScaleY];
    SkScalar tx = fMat[kMTransX];
    SkScalar ty = fMat[kMTransY];
    Sk4f scale(sx, sy, sx, sy);
    Sk4f trans(tx, ty, tx, ty);
    sort_as_rect(Sk4f::Load(&src.fLeft) * scale + trans).store(&dst->fLeft);
}

bool SkMatrix::mapRect(SkRect* dst, const SkRect& src) const {
    SkASSERT(dst);

    if (this->getType() <= kTranslate_Mask) {
        SkScalar tx = fMat[kMTransX];
        SkScalar ty = fMat[kMTransY];
        Sk4f trans(tx, ty, tx, ty);
        sort_as_rect(Sk4f::Load(&src.fLeft) + trans).store(&dst->fLeft);
        return true;
    }
    if (this->isScaleTranslate()) {
        this->mapRectScaleTranslate(dst, src);
        return true;
    } else {
        SkPoint quad[4];

        src.toQuad(quad);
        this->mapPoints(quad, quad, 4);
        dst->set(quad, 4);
        return false;
    }
}

SkScalar SkMatrix::mapRadius(SkScalar radius) const {
    SkVector    vec[2];

    vec[0].set(radius, 0);
    vec[1].set(0, radius);
    this->mapVectors(vec, 2);

    SkScalar d0 = vec[0].length();
    SkScalar d1 = vec[1].length();

    // return geometric mean
    return SkScalarSqrt(d0 * d1);
}

///////////////////////////////////////////////////////////////////////////////

void SkMatrix::Persp_xy(const SkMatrix& m, SkScalar sx, SkScalar sy,
                        SkPoint* pt) {
    SkASSERT(m.hasPerspective());

    SkScalar x = sdot(sx, m.fMat[kMScaleX], sy, m.fMat[kMSkewX])  + m.fMat[kMTransX];
    SkScalar y = sdot(sx, m.fMat[kMSkewY],  sy, m.fMat[kMScaleY]) + m.fMat[kMTransY];
    SkScalar z = sdot(sx, m.fMat[kMPersp0], sy, m.fMat[kMPersp1]) + m.fMat[kMPersp2];
    if (z) {
        z = SkScalarFastInvert(z);
    }
    pt->fX = x * z;
    pt->fY = y * z;
}

void SkMatrix::RotTrans_xy(const SkMatrix& m, SkScalar sx, SkScalar sy,
                           SkPoint* pt) {
    SkASSERT((m.getType() & (kAffine_Mask | kPerspective_Mask)) == kAffine_Mask);

#ifdef SK_LEGACY_MATRIX_MATH_ORDER
    pt->fX = sx * m.fMat[kMScaleX] + (sy * m.fMat[kMSkewX]  +  m.fMat[kMTransX]);
    pt->fY = sx * m.fMat[kMSkewY]  + (sy * m.fMat[kMScaleY] + m.fMat[kMTransY]);
#else
    pt->fX = sdot(sx, m.fMat[kMScaleX], sy, m.fMat[kMSkewX])  + m.fMat[kMTransX];
    pt->fY = sdot(sx, m.fMat[kMSkewY],  sy, m.fMat[kMScaleY]) + m.fMat[kMTransY];
#endif
}

void SkMatrix::Rot_xy(const SkMatrix& m, SkScalar sx, SkScalar sy,
                      SkPoint* pt) {
    SkASSERT((m.getType() & (kAffine_Mask | kPerspective_Mask))== kAffine_Mask);
    SkASSERT(0 == m.fMat[kMTransX]);
    SkASSERT(0 == m.fMat[kMTransY]);

#ifdef SK_LEGACY_MATRIX_MATH_ORDER
    pt->fX = sx * m.fMat[kMScaleX] + (sy * m.fMat[kMSkewX]  + m.fMat[kMTransX]);
    pt->fY = sx * m.fMat[kMSkewY]  + (sy * m.fMat[kMScaleY] + m.fMat[kMTransY]);
#else
    pt->fX = sdot(sx, m.fMat[kMScaleX], sy, m.fMat[kMSkewX])  + m.fMat[kMTransX];
    pt->fY = sdot(sx, m.fMat[kMSkewY],  sy, m.fMat[kMScaleY]) + m.fMat[kMTransY];
#endif
}

void SkMatrix::ScaleTrans_xy(const SkMatrix& m, SkScalar sx, SkScalar sy,
                             SkPoint* pt) {
    SkASSERT((m.getType() & (kScale_Mask | kAffine_Mask | kPerspective_Mask))
             == kScale_Mask);

    pt->fX = sx * m.fMat[kMScaleX] + m.fMat[kMTransX];
    pt->fY = sy * m.fMat[kMScaleY] + m.fMat[kMTransY];
}

void SkMatrix::Scale_xy(const SkMatrix& m, SkScalar sx, SkScalar sy,
                        SkPoint* pt) {
    SkASSERT((m.getType() & (kScale_Mask | kAffine_Mask | kPerspective_Mask))
             == kScale_Mask);
    SkASSERT(0 == m.fMat[kMTransX]);
    SkASSERT(0 == m.fMat[kMTransY]);

    pt->fX = sx * m.fMat[kMScaleX];
    pt->fY = sy * m.fMat[kMScaleY];
}

void SkMatrix::Trans_xy(const SkMatrix& m, SkScalar sx, SkScalar sy,
                        SkPoint* pt) {
    SkASSERT(m.getType() == kTranslate_Mask);

    pt->fX = sx + m.fMat[kMTransX];
    pt->fY = sy + m.fMat[kMTransY];
}

void SkMatrix::Identity_xy(const SkMatrix& m, SkScalar sx, SkScalar sy,
                           SkPoint* pt) {
    SkASSERT(0 == m.getType());

    pt->fX = sx;
    pt->fY = sy;
}

const SkMatrix::MapXYProc SkMatrix::gMapXYProcs[] = {
    SkMatrix::Identity_xy, SkMatrix::Trans_xy,
    SkMatrix::Scale_xy,    SkMatrix::ScaleTrans_xy,
    SkMatrix::Rot_xy,      SkMatrix::RotTrans_xy,
    SkMatrix::Rot_xy,      SkMatrix::RotTrans_xy,
    // repeat the persp proc 8 times
    SkMatrix::Persp_xy,    SkMatrix::Persp_xy,
    SkMatrix::Persp_xy,    SkMatrix::Persp_xy,
    SkMatrix::Persp_xy,    SkMatrix::Persp_xy,
    SkMatrix::Persp_xy,    SkMatrix::Persp_xy
};

///////////////////////////////////////////////////////////////////////////////

// if its nearly zero (just made up 26, perhaps it should be bigger or smaller)
#define PerspNearlyZero(x)  SkScalarNearlyZero(x, (1.0f / (1 << 26)))

bool SkMatrix::isFixedStepInX() const {
  return PerspNearlyZero(fMat[kMPersp0]);
}

SkVector SkMatrix::fixedStepInX(SkScalar y) const {
    SkASSERT(PerspNearlyZero(fMat[kMPersp0]));
    if (PerspNearlyZero(fMat[kMPersp1]) &&
        PerspNearlyZero(fMat[kMPersp2] - 1)) {
        return SkVector::Make(fMat[kMScaleX], fMat[kMSkewY]);
    } else {
        SkScalar z = y * fMat[kMPersp1] + fMat[kMPersp2];
        return SkVector::Make(fMat[kMScaleX] / z, fMat[kMSkewY] / z);
    }
}

///////////////////////////////////////////////////////////////////////////////

#include "SkPerspIter.h"

SkPerspIter::SkPerspIter(const SkMatrix& m, SkScalar x0, SkScalar y0, int count)
        : fMatrix(m), fSX(x0), fSY(y0), fCount(count) {
    SkPoint pt;

    SkMatrix::Persp_xy(m, x0, y0, &pt);
    fX = SkScalarToFixed(pt.fX);
    fY = SkScalarToFixed(pt.fY);
}

int SkPerspIter::next() {
    int n = fCount;

    if (0 == n) {
        return 0;
    }
    SkPoint pt;
    SkFixed x = fX;
    SkFixed y = fY;
    SkFixed dx, dy;

    if (n >= kCount) {
        n = kCount;
        fSX += SkIntToScalar(kCount);
        SkMatrix::Persp_xy(fMatrix, fSX, fSY, &pt);
        fX = SkScalarToFixed(pt.fX);
        fY = SkScalarToFixed(pt.fY);
        dx = (fX - x) >> kShift;
        dy = (fY - y) >> kShift;
    } else {
        fSX += SkIntToScalar(n);
        SkMatrix::Persp_xy(fMatrix, fSX, fSY, &pt);
        fX = SkScalarToFixed(pt.fX);
        fY = SkScalarToFixed(pt.fY);
        dx = (fX - x) / n;
        dy = (fY - y) / n;
    }

    SkFixed* p = fStorage;
    for (int i = 0; i < n; i++) {
        *p++ = x; x += dx;
        *p++ = y; y += dy;
    }

    fCount -= n;
    return n;
}

///////////////////////////////////////////////////////////////////////////////

static inline bool checkForZero(float x) {
    return x*x == 0;
}

static inline bool poly_to_point(SkPoint* pt, const SkPoint poly[], int count) {
    float   x = 1, y = 1;
    SkPoint pt1, pt2;

    if (count > 1) {
        pt1.fX = poly[1].fX - poly[0].fX;
        pt1.fY = poly[1].fY - poly[0].fY;
        y = SkPoint::Length(pt1.fX, pt1.fY);
        if (checkForZero(y)) {
            return false;
        }
        switch (count) {
            case 2:
                break;
            case 3:
                pt2.fX = poly[0].fY - poly[2].fY;
                pt2.fY = poly[2].fX - poly[0].fX;
                goto CALC_X;
            default:
                pt2.fX = poly[0].fY - poly[3].fY;
                pt2.fY = poly[3].fX - poly[0].fX;
            CALC_X:
                x = sdot(pt1.fX, pt2.fX, pt1.fY, pt2.fY) / y;
                break;
        }
    }
    pt->set(x, y);
    return true;
}

bool SkMatrix::Poly2Proc(const SkPoint srcPt[], SkMatrix* dst,
                         const SkPoint& scale) {
    float invScale = 1 / scale.fY;

    dst->fMat[kMScaleX] = (srcPt[1].fY - srcPt[0].fY) * invScale;
    dst->fMat[kMSkewY] = (srcPt[0].fX - srcPt[1].fX) * invScale;
    dst->fMat[kMPersp0] = 0;
    dst->fMat[kMSkewX] = (srcPt[1].fX - srcPt[0].fX) * invScale;
    dst->fMat[kMScaleY] = (srcPt[1].fY - srcPt[0].fY) * invScale;
    dst->fMat[kMPersp1] = 0;
    dst->fMat[kMTransX] = srcPt[0].fX;
    dst->fMat[kMTransY] = srcPt[0].fY;
    dst->fMat[kMPersp2] = 1;
    dst->setTypeMask(kUnknown_Mask);
    return true;
}

bool SkMatrix::Poly3Proc(const SkPoint srcPt[], SkMatrix* dst,
                         const SkPoint& scale) {
    float invScale = 1 / scale.fX;
    dst->fMat[kMScaleX] = (srcPt[2].fX - srcPt[0].fX) * invScale;
    dst->fMat[kMSkewY] = (srcPt[2].fY - srcPt[0].fY) * invScale;
    dst->fMat[kMPersp0] = 0;

    invScale = 1 / scale.fY;
    dst->fMat[kMSkewX] = (srcPt[1].fX - srcPt[0].fX) * invScale;
    dst->fMat[kMScaleY] = (srcPt[1].fY - srcPt[0].fY) * invScale;
    dst->fMat[kMPersp1] = 0;

    dst->fMat[kMTransX] = srcPt[0].fX;
    dst->fMat[kMTransY] = srcPt[0].fY;
    dst->fMat[kMPersp2] = 1;
    dst->setTypeMask(kUnknown_Mask);
    return true;
}

bool SkMatrix::Poly4Proc(const SkPoint srcPt[], SkMatrix* dst,
                         const SkPoint& scale) {
    float   a1, a2;
    float   x0, y0, x1, y1, x2, y2;

    x0 = srcPt[2].fX - srcPt[0].fX;
    y0 = srcPt[2].fY - srcPt[0].fY;
    x1 = srcPt[2].fX - srcPt[1].fX;
    y1 = srcPt[2].fY - srcPt[1].fY;
    x2 = srcPt[2].fX - srcPt[3].fX;
    y2 = srcPt[2].fY - srcPt[3].fY;

    /* check if abs(x2) > abs(y2) */
    if ( x2 > 0 ? y2 > 0 ? x2 > y2 : x2 > -y2 : y2 > 0 ? -x2 > y2 : x2 < y2) {
        float denom = SkScalarMulDiv(x1, y2, x2) - y1;
        if (checkForZero(denom)) {
            return false;
        }
        a1 = (SkScalarMulDiv(x0 - x1, y2, x2) - y0 + y1) / denom;
    } else {
        float denom = x1 - SkScalarMulDiv(y1, x2, y2);
        if (checkForZero(denom)) {
            return false;
        }
        a1 = (x0 - x1 - SkScalarMulDiv(y0 - y1, x2, y2)) / denom;
    }

    /* check if abs(x1) > abs(y1) */
    if ( x1 > 0 ? y1 > 0 ? x1 > y1 : x1 > -y1 : y1 > 0 ? -x1 > y1 : x1 < y1) {
        float denom = y2 - SkScalarMulDiv(x2, y1, x1);
        if (checkForZero(denom)) {
            return false;
        }
        a2 = (y0 - y2 - SkScalarMulDiv(x0 - x2, y1, x1)) / denom;
    } else {
        float denom = SkScalarMulDiv(y2, x1, y1) - x2;
        if (checkForZero(denom)) {
            return false;
        }
        a2 = (SkScalarMulDiv(y0 - y2, x1, y1) - x0 + x2) / denom;
    }

    float invScale = SkScalarInvert(scale.fX);
    dst->fMat[kMScaleX] = (a2 * srcPt[3].fX + srcPt[3].fX - srcPt[0].fX) * invScale;
    dst->fMat[kMSkewY]  = (a2 * srcPt[3].fY + srcPt[3].fY - srcPt[0].fY) * invScale;
    dst->fMat[kMPersp0] = a2 * invScale;

    invScale = SkScalarInvert(scale.fY);
    dst->fMat[kMSkewX]  = (a1 * srcPt[1].fX + srcPt[1].fX - srcPt[0].fX) * invScale;
    dst->fMat[kMScaleY] = (a1 * srcPt[1].fY + srcPt[1].fY - srcPt[0].fY) * invScale;
    dst->fMat[kMPersp1] = a1 * invScale;

    dst->fMat[kMTransX] = srcPt[0].fX;
    dst->fMat[kMTransY] = srcPt[0].fY;
    dst->fMat[kMPersp2] = 1;
    dst->setTypeMask(kUnknown_Mask);
    return true;
}

typedef bool (*PolyMapProc)(const SkPoint[], SkMatrix*, const SkPoint&);

/*  Taken from Rob Johnson's original sample code in QuickDraw GX
*/
bool SkMatrix::setPolyToPoly(const SkPoint src[], const SkPoint dst[],
                             int count) {
    if ((unsigned)count > 4) {
        SkDebugf("--- SkMatrix::setPolyToPoly count out of range %d\n", count);
        return false;
    }

    if (0 == count) {
        this->reset();
        return true;
    }
    if (1 == count) {
        this->setTranslate(dst[0].fX - src[0].fX, dst[0].fY - src[0].fY);
        return true;
    }

    SkPoint scale;
    if (!poly_to_point(&scale, src, count) ||
            SkScalarNearlyZero(scale.fX) ||
            SkScalarNearlyZero(scale.fY)) {
        return false;
    }

    static const PolyMapProc gPolyMapProcs[] = {
        SkMatrix::Poly2Proc, SkMatrix::Poly3Proc, SkMatrix::Poly4Proc
    };
    PolyMapProc proc = gPolyMapProcs[count - 2];

    SkMatrix tempMap, result;
    tempMap.setTypeMask(kUnknown_Mask);

    if (!proc(src, &tempMap, scale)) {
        return false;
    }
    if (!tempMap.invert(&result)) {
        return false;
    }
    if (!proc(dst, &tempMap, scale)) {
        return false;
    }
    this->setConcat(tempMap, result);
    return true;
}

///////////////////////////////////////////////////////////////////////////////

enum MinMaxOrBoth {
    kMin_MinMaxOrBoth,
    kMax_MinMaxOrBoth,
    kBoth_MinMaxOrBoth
};

template <MinMaxOrBoth MIN_MAX_OR_BOTH> bool get_scale_factor(SkMatrix::TypeMask typeMask,
                                                              const SkScalar m[9],
                                                              SkScalar results[/*1 or 2*/]) {
    if (typeMask & SkMatrix::kPerspective_Mask) {
        return false;
    }
    if (SkMatrix::kIdentity_Mask == typeMask) {
        results[0] = SK_Scalar1;
        if (kBoth_MinMaxOrBoth == MIN_MAX_OR_BOTH) {
            results[1] = SK_Scalar1;
        }
        return true;
    }
    if (!(typeMask & SkMatrix::kAffine_Mask)) {
        if (kMin_MinMaxOrBoth == MIN_MAX_OR_BOTH) {
             results[0] = SkMinScalar(SkScalarAbs(m[SkMatrix::kMScaleX]),
                                      SkScalarAbs(m[SkMatrix::kMScaleY]));
        } else if (kMax_MinMaxOrBoth == MIN_MAX_OR_BOTH) {
             results[0] = SkMaxScalar(SkScalarAbs(m[SkMatrix::kMScaleX]),
                                      SkScalarAbs(m[SkMatrix::kMScaleY]));
        } else {
            results[0] = SkScalarAbs(m[SkMatrix::kMScaleX]);
            results[1] = SkScalarAbs(m[SkMatrix::kMScaleY]);
             if (results[0] > results[1]) {
                 SkTSwap(results[0], results[1]);
             }
        }
        return true;
    }
    // ignore the translation part of the matrix, just look at 2x2 portion.
    // compute singular values, take largest or smallest abs value.
    // [a b; b c] = A^T*A
    SkScalar a = sdot(m[SkMatrix::kMScaleX], m[SkMatrix::kMScaleX],
                      m[SkMatrix::kMSkewY],  m[SkMatrix::kMSkewY]);
    SkScalar b = sdot(m[SkMatrix::kMScaleX], m[SkMatrix::kMSkewX],
                      m[SkMatrix::kMScaleY], m[SkMatrix::kMSkewY]);
    SkScalar c = sdot(m[SkMatrix::kMSkewX],  m[SkMatrix::kMSkewX],
                      m[SkMatrix::kMScaleY], m[SkMatrix::kMScaleY]);
    // eigenvalues of A^T*A are the squared singular values of A.
    // characteristic equation is det((A^T*A) - l*I) = 0
    // l^2 - (a + c)l + (ac-b^2)
    // solve using quadratic equation (divisor is non-zero since l^2 has 1 coeff
    // and roots are guaranteed to be pos and real).
    SkScalar bSqd = b * b;
    // if upper left 2x2 is orthogonal save some math
    if (bSqd <= SK_ScalarNearlyZero*SK_ScalarNearlyZero) {
        if (kMin_MinMaxOrBoth == MIN_MAX_OR_BOTH) {
            results[0] = SkMinScalar(a, c);
        } else if (kMax_MinMaxOrBoth == MIN_MAX_OR_BOTH) {
            results[0] = SkMaxScalar(a, c);
        } else {
            results[0] = a;
            results[1] = c;
            if (results[0] > results[1]) {
                SkTSwap(results[0], results[1]);
            }
        }
    } else {
        SkScalar aminusc = a - c;
        SkScalar apluscdiv2 = SkScalarHalf(a + c);
        SkScalar x = SkScalarHalf(SkScalarSqrt(aminusc * aminusc + 4 * bSqd));
        if (kMin_MinMaxOrBoth == MIN_MAX_OR_BOTH) {
            results[0] = apluscdiv2 - x;
        } else if (kMax_MinMaxOrBoth == MIN_MAX_OR_BOTH) {
            results[0] = apluscdiv2 + x;
        } else {
            results[0] = apluscdiv2 - x;
            results[1] = apluscdiv2 + x;
        }
    }
    if (!SkScalarIsFinite(results[0])) {
        return false;
    }
    // Due to the floating point inaccuracy, there might be an error in a, b, c
    // calculated by sdot, further deepened by subsequent arithmetic operations
    // on them. Therefore, we allow and cap the nearly-zero negative values.
    SkASSERT(results[0] >= -SK_ScalarNearlyZero);
    if (results[0] < 0) {
        results[0] = 0;
    }
    results[0] = SkScalarSqrt(results[0]);
    if (kBoth_MinMaxOrBoth == MIN_MAX_OR_BOTH) {
        if (!SkScalarIsFinite(results[1])) {
            return false;
        }
        SkASSERT(results[1] >= -SK_ScalarNearlyZero);
        if (results[1] < 0) {
            results[1] = 0;
        }
        results[1] = SkScalarSqrt(results[1]);
    }
    return true;
}

SkScalar SkMatrix::getMinScale() const {
    SkScalar factor;
    if (get_scale_factor<kMin_MinMaxOrBoth>(this->getType(), fMat, &factor)) {
        return factor;
    } else {
        return -1;
    }
}

SkScalar SkMatrix::getMaxScale() const {
    SkScalar factor;
    if (get_scale_factor<kMax_MinMaxOrBoth>(this->getType(), fMat, &factor)) {
        return factor;
    } else {
        return -1;
    }
}

bool SkMatrix::getMinMaxScales(SkScalar scaleFactors[2]) const {
    return get_scale_factor<kBoth_MinMaxOrBoth>(this->getType(), fMat, scaleFactors);
}

namespace {

// SkMatrix is C++11 POD (trivial and standard-layout), but not aggregate (it has private fields).
struct AggregateMatrix {
    SkScalar matrix[9];
    uint32_t typemask;

    const SkMatrix& asSkMatrix() const { return *reinterpret_cast<const SkMatrix*>(this); }
};
static_assert(sizeof(AggregateMatrix) == sizeof(SkMatrix), "AggregateMatrix size mismatch.");

}  // namespace

const SkMatrix& SkMatrix::I() {
    static_assert(offsetof(SkMatrix,fMat)      == offsetof(AggregateMatrix,matrix),   "fMat");
    static_assert(offsetof(SkMatrix,fTypeMask) == offsetof(AggregateMatrix,typemask), "fTypeMask");

    static const AggregateMatrix identity = { {SK_Scalar1, 0, 0,
                                               0, SK_Scalar1, 0,
                                               0, 0, SK_Scalar1 },
                                             kIdentity_Mask | kRectStaysRect_Mask};
    SkASSERT(identity.asSkMatrix().isIdentity());
    return identity.asSkMatrix();
}

const SkMatrix& SkMatrix::InvalidMatrix() {
    static_assert(offsetof(SkMatrix,fMat)      == offsetof(AggregateMatrix,matrix),   "fMat");
    static_assert(offsetof(SkMatrix,fTypeMask) == offsetof(AggregateMatrix,typemask), "fTypeMask");

    static const AggregateMatrix invalid =
        { {SK_ScalarMax, SK_ScalarMax, SK_ScalarMax,
           SK_ScalarMax, SK_ScalarMax, SK_ScalarMax,
           SK_ScalarMax, SK_ScalarMax, SK_ScalarMax },
         kTranslate_Mask | kScale_Mask | kAffine_Mask | kPerspective_Mask };
    return invalid.asSkMatrix();
}

bool SkMatrix::decomposeScale(SkSize* scale, SkMatrix* remaining) const {
    if (this->hasPerspective()) {
        return false;
    }

    const SkScalar sx = SkVector::Length(this->getScaleX(), this->getSkewY());
    const SkScalar sy = SkVector::Length(this->getSkewX(), this->getScaleY());
    if (!SkScalarIsFinite(sx) || !SkScalarIsFinite(sy) ||
        SkScalarNearlyZero(sx) || SkScalarNearlyZero(sy)) {
        return false;
    }

    if (scale) {
        scale->set(sx, sy);
    }
    if (remaining) {
        *remaining = *this;
        remaining->postScale(SkScalarInvert(sx), SkScalarInvert(sy));
    }
    return true;
}

///////////////////////////////////////////////////////////////////////////////

size_t SkMatrix::writeToMemory(void* buffer) const {
    // TODO write less for simple matrices
    static const size_t sizeInMemory = 9 * sizeof(SkScalar);
    if (buffer) {
        memcpy(buffer, fMat, sizeInMemory);
    }
    return sizeInMemory;
}

size_t SkMatrix::readFromMemory(const void* buffer, size_t length) {
    static const size_t sizeInMemory = 9 * sizeof(SkScalar);
    if (length < sizeInMemory) {
        return 0;
    }
    if (buffer) {
        memcpy(fMat, buffer, sizeInMemory);
        this->setTypeMask(kUnknown_Mask);
    }
    return sizeInMemory;
}

void SkMatrix::dump() const {
    SkString str;
    this->toString(&str);
    SkDebugf("%s\n", str.c_str());
}

void SkMatrix::toString(SkString* str) const {
    str->appendf("[%8.4f %8.4f %8.4f][%8.4f %8.4f %8.4f][%8.4f %8.4f %8.4f]",
             fMat[0], fMat[1], fMat[2], fMat[3], fMat[4], fMat[5],
             fMat[6], fMat[7], fMat[8]);
}

///////////////////////////////////////////////////////////////////////////////

#include "SkMatrixUtils.h"

bool SkTreatAsSprite(const SkMatrix& mat, const SkISize& size, const SkPaint& paint) {
    // Our path aa is 2-bits, and our rect aa is 8, so we could use 8,
    // but in practice 4 seems enough (still looks smooth) and allows
    // more slightly fractional cases to fall into the fast (sprite) case.
    static const unsigned kAntiAliasSubpixelBits = 4;

    const unsigned subpixelBits = paint.isAntiAlias() ? kAntiAliasSubpixelBits : 0;

    // quick reject on affine or perspective
    if (mat.getType() & ~(SkMatrix::kScale_Mask | SkMatrix::kTranslate_Mask)) {
        return false;
    }

    // quick success check
    if (!subpixelBits && !(mat.getType() & ~SkMatrix::kTranslate_Mask)) {
        return true;
    }

    // mapRect supports negative scales, so we eliminate those first
    if (mat.getScaleX() < 0 || mat.getScaleY() < 0) {
        return false;
    }

    SkRect dst;
    SkIRect isrc = SkIRect::MakeSize(size);

    {
        SkRect src;
        src.set(isrc);
        mat.mapRect(&dst, src);
    }

    // just apply the translate to isrc
    isrc.offset(SkScalarRoundToInt(mat.getTranslateX()),
                SkScalarRoundToInt(mat.getTranslateY()));

    if (subpixelBits) {
        isrc.fLeft = SkLeftShift(isrc.fLeft, subpixelBits);
        isrc.fTop = SkLeftShift(isrc.fTop, subpixelBits);
        isrc.fRight = SkLeftShift(isrc.fRight, subpixelBits);
        isrc.fBottom = SkLeftShift(isrc.fBottom, subpixelBits);

        const float scale = 1 << subpixelBits;
        dst.fLeft *= scale;
        dst.fTop *= scale;
        dst.fRight *= scale;
        dst.fBottom *= scale;
    }

    SkIRect idst;
    dst.round(&idst);
    return isrc == idst;
}

// A square matrix M can be decomposed (via polar decomposition) into two matrices --
// an orthogonal matrix Q and a symmetric matrix S. In turn we can decompose S into U*W*U^T,
// where U is another orthogonal matrix and W is a scale matrix. These can be recombined
// to give M = (Q*U)*W*U^T, i.e., the product of two orthogonal matrices and a scale matrix.
//
// The one wrinkle is that traditionally Q may contain a reflection -- the
// calculation has been rejiggered to put that reflection into W.
bool SkDecomposeUpper2x2(const SkMatrix& matrix,
                         SkPoint* rotation1,
                         SkPoint* scale,
                         SkPoint* rotation2) {

    SkScalar A = matrix[SkMatrix::kMScaleX];
    SkScalar B = matrix[SkMatrix::kMSkewX];
    SkScalar C = matrix[SkMatrix::kMSkewY];
    SkScalar D = matrix[SkMatrix::kMScaleY];

    if (is_degenerate_2x2(A, B, C, D)) {
        return false;
    }

    double w1, w2;
    SkScalar cos1, sin1;
    SkScalar cos2, sin2;

    // do polar decomposition (M = Q*S)
    SkScalar cosQ, sinQ;
    double Sa, Sb, Sd;
    // if M is already symmetric (i.e., M = I*S)
    if (SkScalarNearlyEqual(B, C)) {
        cosQ = 1;
        sinQ = 0;

        Sa = A;
        Sb = B;
        Sd = D;
    } else {
        cosQ = A + D;
        sinQ = C - B;
        SkScalar reciplen = SkScalarInvert(SkScalarSqrt(cosQ*cosQ + sinQ*sinQ));
        cosQ *= reciplen;
        sinQ *= reciplen;

        // S = Q^-1*M
        // we don't calc Sc since it's symmetric
        Sa = A*cosQ + C*sinQ;
        Sb = B*cosQ + D*sinQ;
        Sd = -B*sinQ + D*cosQ;
    }

    // Now we need to compute eigenvalues of S (our scale factors)
    // and eigenvectors (bases for our rotation)
    // From this, should be able to reconstruct S as U*W*U^T
    if (SkScalarNearlyZero(SkDoubleToScalar(Sb))) {
        // already diagonalized
        cos1 = 1;
        sin1 = 0;
        w1 = Sa;
        w2 = Sd;
        cos2 = cosQ;
        sin2 = sinQ;
    } else {
        double diff = Sa - Sd;
        double discriminant = sqrt(diff*diff + 4.0*Sb*Sb);
        double trace = Sa + Sd;
        if (diff > 0) {
            w1 = 0.5*(trace + discriminant);
            w2 = 0.5*(trace - discriminant);
        } else {
            w1 = 0.5*(trace - discriminant);
            w2 = 0.5*(trace + discriminant);
        }

        cos1 = SkDoubleToScalar(Sb); sin1 = SkDoubleToScalar(w1 - Sa);
        SkScalar reciplen = SkScalarInvert(SkScalarSqrt(cos1*cos1 + sin1*sin1));
        cos1 *= reciplen;
        sin1 *= reciplen;

        // rotation 2 is composition of Q and U
        cos2 = cos1*cosQ - sin1*sinQ;
        sin2 = sin1*cosQ + cos1*sinQ;

        // rotation 1 is U^T
        sin1 = -sin1;
    }

    if (scale) {
        scale->fX = SkDoubleToScalar(w1);
        scale->fY = SkDoubleToScalar(w2);
    }
    if (rotation1) {
        rotation1->fX = cos1;
        rotation1->fY = sin1;
    }
    if (rotation2) {
        rotation2->fX = cos2;
        rotation2->fY = sin2;
    }

    return true;
}

//////////////////////////////////////////////////////////////////////////////////////////////////

void SkRSXform::toQuad(SkScalar width, SkScalar height, SkPoint quad[4]) const {
#if 0
    // This is the slow way, but it documents what we're doing
    quad[0].set(0, 0);
    quad[1].set(width, 0);
    quad[2].set(width, height);
    quad[3].set(0, height);
    SkMatrix m;
    m.setRSXform(*this).mapPoints(quad, quad, 4);
#else
    const SkScalar m00 = fSCos;
    const SkScalar m01 = -fSSin;
    const SkScalar m02 = fTx;
    const SkScalar m10 = -m01;
    const SkScalar m11 = m00;
    const SkScalar m12 = fTy;

    quad[0].set(m02, m12);
    quad[1].set(m00 * width + m02, m10 * width + m12);
    quad[2].set(m00 * width + m01 * height + m02, m10 * width + m11 * height + m12);
    quad[3].set(m01 * height + m02, m11 * height + m12);
#endif
}