summaryrefslogtreecommitdiffstats
path: root/mozglue/misc/PreXULSkeletonUI.cpp
blob: 1b17837fc171da982d1bb99a7188224a3e9e4bcd (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
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
2075
2076
2077
2078
2079
2080
2081
2082
2083
2084
2085
2086
2087
2088
2089
2090
2091
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
2108
2109
2110
2111
2112
2113
2114
2115
2116
2117
2118
2119
2120
2121
2122
2123
2124
2125
2126
2127
2128
2129
2130
2131
2132
2133
2134
2135
2136
2137
2138
2139
2140
2141
2142
2143
2144
2145
2146
2147
2148
2149
2150
2151
2152
2153
2154
2155
2156
2157
2158
2159
2160
2161
2162
2163
2164
2165
2166
2167
2168
2169
2170
2171
2172
2173
2174
2175
2176
2177
2178
2179
2180
2181
2182
2183
2184
2185
2186
2187
2188
2189
2190
2191
2192
2193
2194
2195
2196
2197
2198
2199
2200
2201
2202
2203
2204
2205
2206
2207
2208
2209
2210
2211
2212
2213
2214
2215
2216
2217
2218
2219
2220
2221
2222
2223
2224
2225
2226
2227
2228
2229
2230
2231
2232
2233
2234
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "PreXULSkeletonUI.h"

#include <algorithm>
#include <math.h>
#include <limits.h>
#include <cmath>
#include <locale>
#include <string>
#include <objbase.h>
#include <shlobj.h>

#include "mozilla/Assertions.h"
#include "mozilla/Attributes.h"
#include "mozilla/BaseProfilerMarkers.h"
#include "mozilla/CacheNtDllThunk.h"
#include "mozilla/FStream.h"
#include "mozilla/GetKnownFolderPath.h"
#include "mozilla/HashFunctions.h"
#include "mozilla/HelperMacros.h"
#include "mozilla/glue/Debug.h"
#include "mozilla/Maybe.h"
#include "mozilla/mscom/ProcessRuntime.h"
#include "mozilla/ResultVariant.h"
#include "mozilla/ScopeExit.h"
#include "mozilla/Try.h"
#include "mozilla/UniquePtr.h"
#include "mozilla/UniquePtrExtensions.h"
#include "mozilla/Unused.h"
#include "mozilla/WindowsDpiAwareness.h"
#include "mozilla/WindowsProcessMitigations.h"

namespace mozilla {

// ColorRect defines an optionally-rounded, optionally-bordered rectangle of a
// particular color that we will draw.
struct ColorRect {
  uint32_t color;
  uint32_t borderColor;
  int x;
  int y;
  int width;
  int height;
  int borderWidth;
  int borderRadius;
  bool flipIfRTL;
};

// DrawRect is mostly the same as ColorRect, but exists as an implementation
// detail to simplify drawing borders. We draw borders as a strokeOnly rect
// underneath an inner rect of a particular color. We also need to keep
// track of the backgroundColor for rounding rects, in order to correctly
// anti-alias.
struct DrawRect {
  uint32_t color;
  uint32_t backgroundColor;
  int x;
  int y;
  int width;
  int height;
  int borderRadius;
  int borderWidth;
  bool strokeOnly;
};

struct NormalizedRGB {
  double r;
  double g;
  double b;
};

NormalizedRGB UintToRGB(uint32_t color) {
  double r = static_cast<double>(color >> 16 & 0xff) / 255.0;
  double g = static_cast<double>(color >> 8 & 0xff) / 255.0;
  double b = static_cast<double>(color >> 0 & 0xff) / 255.0;
  return NormalizedRGB{r, g, b};
}

uint32_t RGBToUint(const NormalizedRGB& rgb) {
  return (static_cast<uint32_t>(rgb.r * 255.0) << 16) |
         (static_cast<uint32_t>(rgb.g * 255.0) << 8) |
         (static_cast<uint32_t>(rgb.b * 255.0) << 0);
}

double Lerp(double a, double b, double x) { return a + x * (b - a); }

NormalizedRGB Lerp(const NormalizedRGB& a, const NormalizedRGB& b, double x) {
  return NormalizedRGB{Lerp(a.r, b.r, x), Lerp(a.g, b.g, x), Lerp(a.b, b.b, x)};
}

// Produces a smooth curve in [0,1] based on a linear input in [0,1]
double SmoothStep3(double x) { return x * x * (3.0 - 2.0 * x); }

static const wchar_t kPreXULSkeletonUIKeyPath[] =
    L"SOFTWARE"
    L"\\" MOZ_APP_VENDOR L"\\" MOZ_APP_BASENAME L"\\PreXULSkeletonUISettings";

static bool sPreXULSkeletonUIShown = false;
static bool sPreXULSkeletonUIEnabled = false;
static HWND sPreXULSkeletonUIWindow;
static LPWSTR const gStockApplicationIcon = MAKEINTRESOURCEW(32512);
static LPWSTR const gIDCWait = MAKEINTRESOURCEW(32514);
static HANDLE sPreXULSKeletonUIAnimationThread;
static HANDLE sPreXULSKeletonUILockFile = INVALID_HANDLE_VALUE;

static mozilla::mscom::ProcessRuntime* sProcessRuntime;
static uint32_t* sPixelBuffer = nullptr;
static Vector<ColorRect>* sAnimatedRects = nullptr;
static int sTotalChromeHeight = 0;
static volatile LONG sAnimationControlFlag = 0;
static bool sMaximized = false;
static int sNonClientVerticalMargins = 0;
static int sNonClientHorizontalMargins = 0;
static uint32_t sDpi = 0;

// Color values needed by the animation loop
static uint32_t sAnimationColor;
static uint32_t sToolbarForegroundColor;

static ThemeMode sTheme = ThemeMode::Invalid;

typedef BOOL(WINAPI* EnableNonClientDpiScalingProc)(HWND);
static EnableNonClientDpiScalingProc sEnableNonClientDpiScaling = NULL;
typedef int(WINAPI* GetSystemMetricsForDpiProc)(int, UINT);
GetSystemMetricsForDpiProc sGetSystemMetricsForDpi = NULL;
typedef UINT(WINAPI* GetDpiForWindowProc)(HWND);
GetDpiForWindowProc sGetDpiForWindow = NULL;
typedef ATOM(WINAPI* RegisterClassWProc)(const WNDCLASSW*);
RegisterClassWProc sRegisterClassW = NULL;
typedef HICON(WINAPI* LoadIconWProc)(HINSTANCE, LPCWSTR);
LoadIconWProc sLoadIconW = NULL;
typedef HICON(WINAPI* LoadCursorWProc)(HINSTANCE, LPCWSTR);
LoadCursorWProc sLoadCursorW = NULL;
typedef HWND(WINAPI* CreateWindowExWProc)(DWORD, LPCWSTR, LPCWSTR, DWORD, int,
                                          int, int, int, HWND, HMENU, HINSTANCE,
                                          LPVOID);
CreateWindowExWProc sCreateWindowExW = NULL;
typedef BOOL(WINAPI* ShowWindowProc)(HWND, int);
ShowWindowProc sShowWindow = NULL;
typedef BOOL(WINAPI* SetWindowPosProc)(HWND, HWND, int, int, int, int, UINT);
SetWindowPosProc sSetWindowPos = NULL;
typedef HDC(WINAPI* GetWindowDCProc)(HWND);
GetWindowDCProc sGetWindowDC = NULL;
typedef int(WINAPI* FillRectProc)(HDC, const RECT*, HBRUSH);
FillRectProc sFillRect = NULL;
typedef BOOL(WINAPI* DeleteObjectProc)(HGDIOBJ);
DeleteObjectProc sDeleteObject = NULL;
typedef int(WINAPI* ReleaseDCProc)(HWND, HDC);
ReleaseDCProc sReleaseDC = NULL;
typedef HMONITOR(WINAPI* MonitorFromWindowProc)(HWND, DWORD);
MonitorFromWindowProc sMonitorFromWindow = NULL;
typedef BOOL(WINAPI* GetMonitorInfoWProc)(HMONITOR, LPMONITORINFO);
GetMonitorInfoWProc sGetMonitorInfoW = NULL;
typedef LONG_PTR(WINAPI* SetWindowLongPtrWProc)(HWND, int, LONG_PTR);
SetWindowLongPtrWProc sSetWindowLongPtrW = NULL;
typedef int(WINAPI* StretchDIBitsProc)(HDC, int, int, int, int, int, int, int,
                                       int, const VOID*, const BITMAPINFO*,
                                       UINT, DWORD);
StretchDIBitsProc sStretchDIBits = NULL;
typedef HBRUSH(WINAPI* CreateSolidBrushProc)(COLORREF);
CreateSolidBrushProc sCreateSolidBrush = NULL;

static int sWindowWidth;
static int sWindowHeight;
static double sCSSToDevPixelScaling;

static Maybe<PreXULSkeletonUIError> sErrorReason;

static const int kAnimationCSSPixelsPerFrame = 11;
static const int kAnimationCSSExtraWindowSize = 300;

// NOTE: these values were pulled out of thin air as round numbers that are
// likely to be too big to be seen in practice. If we legitimately see windows
// this big, we probably don't want to be drawing them on the CPU anyway.
static const uint32_t kMaxWindowWidth = 1 << 16;
static const uint32_t kMaxWindowHeight = 1 << 16;

static const wchar_t* sEnabledRegSuffix = L"|Enabled";
static const wchar_t* sScreenXRegSuffix = L"|ScreenX";
static const wchar_t* sScreenYRegSuffix = L"|ScreenY";
static const wchar_t* sWidthRegSuffix = L"|Width";
static const wchar_t* sHeightRegSuffix = L"|Height";
static const wchar_t* sMaximizedRegSuffix = L"|Maximized";
static const wchar_t* sUrlbarCSSRegSuffix = L"|UrlbarCSSSpan";
static const wchar_t* sCssToDevPixelScalingRegSuffix = L"|CssToDevPixelScaling";
static const wchar_t* sSearchbarRegSuffix = L"|SearchbarCSSSpan";
static const wchar_t* sSpringsCSSRegSuffix = L"|SpringsCSSSpan";
static const wchar_t* sThemeRegSuffix = L"|Theme";
static const wchar_t* sFlagsRegSuffix = L"|Flags";
static const wchar_t* sProgressSuffix = L"|Progress";

std::wstring GetRegValueName(const wchar_t* prefix, const wchar_t* suffix) {
  std::wstring result(prefix);
  result.append(suffix);
  return result;
}

// This is paraphrased from WinHeaderOnlyUtils.h. The fact that this file is
// included in standalone SpiderMonkey builds prohibits us from including that
// file directly, and it hardly warrants its own header. Bug 1674920 tracks
// only including this file for gecko-related builds.
Result<UniquePtr<wchar_t[]>, PreXULSkeletonUIError> GetBinaryPath() {
  DWORD bufLen = MAX_PATH;
  UniquePtr<wchar_t[]> buf;
  while (true) {
    buf = MakeUnique<wchar_t[]>(bufLen);
    DWORD retLen = ::GetModuleFileNameW(nullptr, buf.get(), bufLen);
    if (!retLen) {
      return Err(PreXULSkeletonUIError::FilesystemFailure);
    }

    if (retLen == bufLen && ::GetLastError() == ERROR_INSUFFICIENT_BUFFER) {
      bufLen *= 2;
      continue;
    }

    break;
  }

  return buf;
}

// PreXULSkeletonUIDisallowed means that we don't even have the capacity to
// enable the skeleton UI, whether because we're on a platform that doesn't
// support it or because we launched with command line arguments that we don't
// support. Some of these situations are transient, so we want to make sure we
// don't mess with registry values in these scenarios that we may use in
// other scenarios in which the skeleton UI is actually enabled.
static bool PreXULSkeletonUIDisallowed() {
  return sErrorReason.isSome() &&
         (*sErrorReason == PreXULSkeletonUIError::Cmdline ||
          *sErrorReason == PreXULSkeletonUIError::EnvVars);
}

// Note: this is specifically *not* a robust, multi-locale lowercasing
// operation. It is not intended to be such. It is simply intended to match the
// way in which we look for other instances of firefox to remote into.
// See
// https://searchfox.org/mozilla-central/rev/71621bfa47a371f2b1ccfd33c704913124afb933/toolkit/components/remote/nsRemoteService.cpp#56
static void MutateStringToLowercase(wchar_t* ptr) {
  while (*ptr) {
    wchar_t ch = *ptr;
    if (ch >= L'A' && ch <= L'Z') {
      *ptr = ch + (L'a' - L'A');
    }
    ++ptr;
  }
}

static Result<Ok, PreXULSkeletonUIError> GetSkeletonUILock() {
  auto localAppDataPath = GetKnownFolderPath(FOLDERID_LocalAppData);
  if (!localAppDataPath) {
    return Err(PreXULSkeletonUIError::FilesystemFailure);
  }

  if (sPreXULSKeletonUILockFile != INVALID_HANDLE_VALUE) {
    return Ok();
  }

  // Note: because we're in mozglue, we cannot easily access things from
  // toolkit, like `GetInstallHash`. We could move `GetInstallHash` into
  // mozglue, and rip out all of its usage of types defined in toolkit headers.
  // However, it seems cleaner to just hash the bin path ourselves. We don't
  // get quite the same robustness that `GetInstallHash` might provide, but
  // we already don't have that with how we key our registry values, so it
  // probably makes sense to just match those.
  UniquePtr<wchar_t[]> binPath;
  MOZ_TRY_VAR(binPath, GetBinaryPath());

  // Lowercase the binpath to match how we look for remote instances.
  MutateStringToLowercase(binPath.get());

  // The number of bytes * 2 characters per byte + 1 for the null terminator
  uint32_t hexHashSize = sizeof(uint32_t) * 2 + 1;
  UniquePtr<wchar_t[]> installHash = MakeUnique<wchar_t[]>(hexHashSize);
  // This isn't perfect - it's a 32-bit hash of the path to our executable. It
  // could reasonably collide, or casing could potentially affect things, but
  // the theory is that that should be uncommon enough and the failure case
  // mild enough that this is fine.
  uint32_t binPathHash = HashString(binPath.get());
  swprintf(installHash.get(), hexHashSize, L"%08x", binPathHash);

  std::wstring lockFilePath;
  lockFilePath.append(localAppDataPath.get());
  lockFilePath.append(
      L"\\" MOZ_APP_VENDOR L"\\" MOZ_APP_BASENAME L"\\SkeletonUILock-");
  lockFilePath.append(installHash.get());

  // We intentionally leak this file - that is okay, and (kind of) the point.
  // We want to hold onto this handle until the application exits, and hold
  // onto it with exclusive rights. If this check fails, then we assume that
  // another instance of the executable is holding it, and thus return false.
  sPreXULSKeletonUILockFile =
      ::CreateFileW(lockFilePath.c_str(), GENERIC_READ | GENERIC_WRITE,
                    0,  // No sharing - this is how the lock works
                    nullptr, CREATE_ALWAYS,
                    FILE_FLAG_DELETE_ON_CLOSE,  // Don't leave this lying around
                    nullptr);
  if (sPreXULSKeletonUILockFile == INVALID_HANDLE_VALUE) {
    return Err(PreXULSkeletonUIError::FailedGettingLock);
  }

  return Ok();
}

const char kGeneralSection[] = "[General]";
const char kStartWithLastProfile[] = "StartWithLastProfile=";

static bool ProfileDbHasStartWithLastProfile(IFStream& iniContents) {
  bool inGeneral = false;
  std::string line;
  while (std::getline(iniContents, line)) {
    size_t whitespace = 0;
    while (line.length() > whitespace &&
           (line[whitespace] == ' ' || line[whitespace] == '\t')) {
      whitespace++;
    }
    line.erase(0, whitespace);

    if (line.compare(kGeneralSection) == 0) {
      inGeneral = true;
    } else if (inGeneral) {
      if (line[0] == '[') {
        inGeneral = false;
      } else {
        if (line.find(kStartWithLastProfile) == 0) {
          char val = line.c_str()[sizeof(kStartWithLastProfile) - 1];
          if (val == '0') {
            return false;
          } else if (val == '1') {
            return true;
          }
        }
      }
    }
  }

  // If we don't find it in the .ini file, we interpret that as true
  return true;
}

static Result<Ok, PreXULSkeletonUIError> CheckForStartWithLastProfile() {
  auto roamingAppData = GetKnownFolderPath(FOLDERID_RoamingAppData);
  if (!roamingAppData) {
    return Err(PreXULSkeletonUIError::FilesystemFailure);
  }
  std::wstring profileDbPath(roamingAppData.get());
  profileDbPath.append(
      L"\\" MOZ_APP_VENDOR L"\\" MOZ_APP_BASENAME L"\\profiles.ini");
  IFStream profileDb(profileDbPath.c_str());
  if (profileDb.fail()) {
    return Err(PreXULSkeletonUIError::FilesystemFailure);
  }

  if (!ProfileDbHasStartWithLastProfile(profileDb)) {
    return Err(PreXULSkeletonUIError::NoStartWithLastProfile);
  }

  return Ok();
}

// We could use nsAutoRegKey, but including nsWindowsHelpers.h causes build
// failures in random places because we're in mozglue. Overall it should be
// simpler and cleaner to just step around that issue with this class:
class MOZ_RAII AutoCloseRegKey {
 public:
  explicit AutoCloseRegKey(HKEY key) : mKey(key) {}
  ~AutoCloseRegKey() { ::RegCloseKey(mKey); }

 private:
  HKEY mKey;
};

int CSSToDevPixels(double cssPixels, double scaling) {
  return floor(cssPixels * scaling + 0.5);
}

int CSSToDevPixels(int cssPixels, double scaling) {
  return CSSToDevPixels((double)cssPixels, scaling);
}

int CSSToDevPixelsFloor(double cssPixels, double scaling) {
  return floor(cssPixels * scaling);
}

// Some things appear to floor to device pixels rather than rounding. A good
// example of this is border widths.
int CSSToDevPixelsFloor(int cssPixels, double scaling) {
  return CSSToDevPixelsFloor((double)cssPixels, scaling);
}

double SignedDistanceToCircle(double x, double y, double radius) {
  return sqrt(x * x + y * y) - radius;
}

// For more details, see
// https://searchfox.org/mozilla-central/rev/a5d9abfda1e26b1207db9549549ab0bdd73f735d/gfx/wr/webrender/res/shared.glsl#141-187
// which was a reference for this function.
double DistanceAntiAlias(double signedDistance) {
  // Distance assumed to be in device pixels. We use an aa range of 0.5 for
  // reasons detailed in the linked code above.
  const double aaRange = 0.5;
  double dist = 0.5 * signedDistance / aaRange;
  if (dist <= -0.5 + std::numeric_limits<double>::epsilon()) return 1.0;
  if (dist >= 0.5 - std::numeric_limits<double>::epsilon()) return 0.0;
  return 0.5 + dist * (0.8431027 * dist * dist - 1.14453603);
}

void RasterizeRoundedRectTopAndBottom(const DrawRect& rect) {
  if (rect.height <= 2 * rect.borderRadius) {
    MOZ_ASSERT(false, "Skeleton UI rect height too small for border radius.");
    return;
  }
  if (rect.width <= 2 * rect.borderRadius) {
    MOZ_ASSERT(false, "Skeleton UI rect width too small for border radius.");
    return;
  }

  NormalizedRGB rgbBase = UintToRGB(rect.backgroundColor);
  NormalizedRGB rgbBlend = UintToRGB(rect.color);

  for (int rowIndex = 0; rowIndex < rect.borderRadius; ++rowIndex) {
    int yTop = rect.y + rect.borderRadius - 1 - rowIndex;
    int yBottom = rect.y + rect.height - rect.borderRadius + rowIndex;

    uint32_t* lineStartTop = &sPixelBuffer[yTop * sWindowWidth];
    uint32_t* innermostPixelTopLeft =
        lineStartTop + rect.x + rect.borderRadius - 1;
    uint32_t* innermostPixelTopRight =
        lineStartTop + rect.x + rect.width - rect.borderRadius;
    uint32_t* lineStartBottom = &sPixelBuffer[yBottom * sWindowWidth];
    uint32_t* innermostPixelBottomLeft =
        lineStartBottom + rect.x + rect.borderRadius - 1;
    uint32_t* innermostPixelBottomRight =
        lineStartBottom + rect.x + rect.width - rect.borderRadius;

    // Add 0.5 to x and y to get the pixel center.
    double pixelY = (double)rowIndex + 0.5;
    for (int columnIndex = 0; columnIndex < rect.borderRadius; ++columnIndex) {
      double pixelX = (double)columnIndex + 0.5;
      double distance =
          SignedDistanceToCircle(pixelX, pixelY, (double)rect.borderRadius);
      double alpha = DistanceAntiAlias(distance);
      NormalizedRGB rgb = Lerp(rgbBase, rgbBlend, alpha);
      uint32_t color = RGBToUint(rgb);

      innermostPixelTopLeft[-columnIndex] = color;
      innermostPixelTopRight[columnIndex] = color;
      innermostPixelBottomLeft[-columnIndex] = color;
      innermostPixelBottomRight[columnIndex] = color;
    }

    std::fill(innermostPixelTopLeft + 1, innermostPixelTopRight, rect.color);
    std::fill(innermostPixelBottomLeft + 1, innermostPixelBottomRight,
              rect.color);
  }
}

void RasterizeAnimatedRoundedRectTopAndBottom(
    const ColorRect& colorRect, const uint32_t* animationLookup,
    int priorUpdateAreaMin, int priorUpdateAreaMax, int currentUpdateAreaMin,
    int currentUpdateAreaMax, int animationMin) {
  // We iterate through logical pixel rows here, from inside to outside, which
  // for the top of the rounded rect means from bottom to top, and for the
  // bottom of the rect means top to bottom. We paint pixels from left to
  // right on the top and bottom rows at the same time for the entire animation
  // window. (If the animation window does not overlap any rounded corners,
  // however, we won't be called at all)
  for (int rowIndex = 0; rowIndex < colorRect.borderRadius; ++rowIndex) {
    int yTop = colorRect.y + colorRect.borderRadius - 1 - rowIndex;
    int yBottom =
        colorRect.y + colorRect.height - colorRect.borderRadius + rowIndex;

    uint32_t* lineStartTop = &sPixelBuffer[yTop * sWindowWidth];
    uint32_t* lineStartBottom = &sPixelBuffer[yBottom * sWindowWidth];

    // Add 0.5 to x and y to get the pixel center.
    double pixelY = (double)rowIndex + 0.5;
    for (int x = priorUpdateAreaMin; x < currentUpdateAreaMax; ++x) {
      // The column index is the distance from the innermost pixel, which
      // is different depending on whether we're on the left or right
      // side of the rect. It will always be the max here, and if it's
      // negative that just means we're outside the rounded area.
      int columnIndex =
          std::max((int)colorRect.x + (int)colorRect.borderRadius - x - 1,
                   x - ((int)colorRect.x + (int)colorRect.width -
                        (int)colorRect.borderRadius));

      double alpha = 1.0;
      if (columnIndex >= 0) {
        double pixelX = (double)columnIndex + 0.5;
        double distance = SignedDistanceToCircle(
            pixelX, pixelY, (double)colorRect.borderRadius);
        alpha = DistanceAntiAlias(distance);
      }
      // We don't do alpha blending for the antialiased pixels at the
      // shape's border. It is not noticeable in the animation.
      if (alpha > 1.0 - std::numeric_limits<double>::epsilon()) {
        // Overwrite the tail end of last frame's animation with the
        // rect's normal, unanimated color.
        uint32_t color = x < priorUpdateAreaMax
                             ? colorRect.color
                             : animationLookup[x - animationMin];
        lineStartTop[x] = color;
        lineStartBottom[x] = color;
      }
    }
  }
}

void RasterizeColorRect(const ColorRect& colorRect) {
  // We sometimes split our rect into two, to simplify drawing borders. If we
  // have a border, we draw a stroke-only rect first, and then draw the smaller
  // inner rect on top of it.
  Vector<DrawRect, 2> drawRects;
  Unused << drawRects.reserve(2);
  if (colorRect.borderWidth == 0) {
    DrawRect rect = {};
    rect.color = colorRect.color;
    rect.backgroundColor =
        sPixelBuffer[colorRect.y * sWindowWidth + colorRect.x];
    rect.x = colorRect.x;
    rect.y = colorRect.y;
    rect.width = colorRect.width;
    rect.height = colorRect.height;
    rect.borderRadius = colorRect.borderRadius;
    rect.strokeOnly = false;
    drawRects.infallibleAppend(rect);
  } else {
    DrawRect borderRect = {};
    borderRect.color = colorRect.borderColor;
    borderRect.backgroundColor =
        sPixelBuffer[colorRect.y * sWindowWidth + colorRect.x];
    borderRect.x = colorRect.x;
    borderRect.y = colorRect.y;
    borderRect.width = colorRect.width;
    borderRect.height = colorRect.height;
    borderRect.borderRadius = colorRect.borderRadius;
    borderRect.borderWidth = colorRect.borderWidth;
    borderRect.strokeOnly = true;
    drawRects.infallibleAppend(borderRect);

    DrawRect baseRect = {};
    baseRect.color = colorRect.color;
    baseRect.backgroundColor = borderRect.color;
    baseRect.x = colorRect.x + colorRect.borderWidth;
    baseRect.y = colorRect.y + colorRect.borderWidth;
    baseRect.width = colorRect.width - 2 * colorRect.borderWidth;
    baseRect.height = colorRect.height - 2 * colorRect.borderWidth;
    baseRect.borderRadius =
        std::max(0, (int)colorRect.borderRadius - (int)colorRect.borderWidth);
    baseRect.borderWidth = 0;
    baseRect.strokeOnly = false;
    drawRects.infallibleAppend(baseRect);
  }

  for (const DrawRect& rect : drawRects) {
    if (rect.height <= 0 || rect.width <= 0) {
      continue;
    }

    // For rounded rectangles, the first thing we do is draw the top and
    // bottom of the rectangle, with the more complicated logic below. After
    // that we can just draw the vertically centered part of the rect like
    // normal.
    RasterizeRoundedRectTopAndBottom(rect);

    // We then draw the flat, central portion of the rect (which in the case of
    // non-rounded rects, is just the entire thing.)
    int solidRectStartY =
        std::clamp(rect.y + rect.borderRadius, 0, sTotalChromeHeight);
    int solidRectEndY = std::clamp(rect.y + rect.height - rect.borderRadius, 0,
                                   sTotalChromeHeight);
    for (int y = solidRectStartY; y < solidRectEndY; ++y) {
      // For strokeOnly rects (used to draw borders), we just draw the left
      // and right side here. Looping down a column of pixels is not the most
      // cache-friendly thing, but it shouldn't be a big deal given the height
      // of the urlbar.
      // Also, if borderRadius is less than borderWidth, we need to ensure
      // that we fully draw the top and bottom lines, so we make sure to check
      // that we're inside the middle range range before excluding pixels.
      if (rect.strokeOnly && y - rect.y > rect.borderWidth &&
          rect.y + rect.height - y > rect.borderWidth) {
        int startXLeft = std::clamp(rect.x, 0, sWindowWidth);
        int endXLeft = std::clamp(rect.x + rect.borderWidth, 0, sWindowWidth);
        int startXRight =
            std::clamp(rect.x + rect.width - rect.borderWidth, 0, sWindowWidth);
        int endXRight = std::clamp(rect.x + rect.width, 0, sWindowWidth);

        uint32_t* lineStart = &sPixelBuffer[y * sWindowWidth];
        uint32_t* dataStartLeft = lineStart + startXLeft;
        uint32_t* dataEndLeft = lineStart + endXLeft;
        uint32_t* dataStartRight = lineStart + startXRight;
        uint32_t* dataEndRight = lineStart + endXRight;
        std::fill(dataStartLeft, dataEndLeft, rect.color);
        std::fill(dataStartRight, dataEndRight, rect.color);
      } else {
        int startX = std::clamp(rect.x, 0, sWindowWidth);
        int endX = std::clamp(rect.x + rect.width, 0, sWindowWidth);
        uint32_t* lineStart = &sPixelBuffer[y * sWindowWidth];
        uint32_t* dataStart = lineStart + startX;
        uint32_t* dataEnd = lineStart + endX;
        std::fill(dataStart, dataEnd, rect.color);
      }
    }
  }
}

// Paints the pixels to sPixelBuffer for the skeleton UI animation (a light
// gradient which moves from left to right across the grey placeholder rects).
// Takes in the rect to draw, together with a lookup table for the gradient,
// and the bounds of the previous and current frame of the animation.
bool RasterizeAnimatedRect(const ColorRect& colorRect,
                           const uint32_t* animationLookup,
                           int priorAnimationMin, int animationMin,
                           int animationMax) {
  int rectMin = colorRect.x;
  int rectMax = colorRect.x + colorRect.width;
  bool animationWindowOverlaps =
      rectMax >= priorAnimationMin && rectMin < animationMax;

  int priorUpdateAreaMin = std::max(rectMin, priorAnimationMin);
  int priorUpdateAreaMax = std::min(rectMax, animationMin);
  int currentUpdateAreaMin = std::max(rectMin, animationMin);
  int currentUpdateAreaMax = std::min(rectMax, animationMax);

  if (!animationWindowOverlaps) {
    return false;
  }

  bool animationWindowOverlapsBorderRadius =
      rectMin + colorRect.borderRadius > priorAnimationMin ||
      rectMax - colorRect.borderRadius <= animationMax;

  // If we don't overlap the left or right side of the rounded rectangle,
  // just pretend it's not rounded. This is a small optimization but
  // there's no point in doing all of this rounded rectangle checking if
  // we aren't even overlapping
  int borderRadius =
      animationWindowOverlapsBorderRadius ? colorRect.borderRadius : 0;

  if (borderRadius > 0) {
    // Similarly to how we draw the rounded rects in DrawSkeletonUI, we
    // first draw the rounded top and bottom, and then we draw the center
    // rect.
    RasterizeAnimatedRoundedRectTopAndBottom(
        colorRect, animationLookup, priorUpdateAreaMin, priorUpdateAreaMax,
        currentUpdateAreaMin, currentUpdateAreaMax, animationMin);
  }

  for (int y = colorRect.y + borderRadius;
       y < colorRect.y + colorRect.height - borderRadius; ++y) {
    uint32_t* lineStart = &sPixelBuffer[y * sWindowWidth];
    // Overwrite the tail end of last frame's animation with the rect's
    // normal, unanimated color.
    for (int x = priorUpdateAreaMin; x < priorUpdateAreaMax; ++x) {
      lineStart[x] = colorRect.color;
    }
    // Then apply the animated color
    for (int x = currentUpdateAreaMin; x < currentUpdateAreaMax; ++x) {
      lineStart[x] = animationLookup[x - animationMin];
    }
  }

  return true;
}

Result<Ok, PreXULSkeletonUIError> DrawSkeletonUI(
    HWND hWnd, CSSPixelSpan urlbarCSSSpan, CSSPixelSpan searchbarCSSSpan,
    Vector<CSSPixelSpan>& springs, const ThemeColors& currentTheme,
    const EnumSet<SkeletonUIFlag, uint32_t>& flags) {
  // NOTE: we opt here to paint a pixel buffer for the application chrome by
  // hand, without using native UI library methods. Why do we do this?
  //
  // 1) It gives us a little bit more control, especially if we want to animate
  //    any of this.
  // 2) It's actually more portable. We can do this on any platform where we
  //    can blit a pixel buffer to the screen, and it only has to change
  //    insofar as the UI is different on those platforms (and thus would have
  //    to change anyway.)
  //
  // The performance impact of this ought to be negligible. As far as has been
  // observed, on slow reference hardware this might take up to a millisecond,
  // for a startup which otherwise takes 30 seconds.
  //
  // The readability and maintainability are a greater concern. When the
  // silhouette of Firefox's core UI changes, this code will likely need to
  // change. However, for the foreseeable future, our skeleton UI will be mostly
  // axis-aligned geometric shapes, and the thought is that any code which is
  // manipulating raw pixels should not be *too* hard to maintain and
  // understand so long as it is only painting such simple shapes.

  sAnimationColor = currentTheme.animationColor;
  sToolbarForegroundColor = currentTheme.toolbarForegroundColor;

  bool menubarShown = flags.contains(SkeletonUIFlag::MenubarShown);
  bool bookmarksToolbarShown =
      flags.contains(SkeletonUIFlag::BookmarksToolbarShown);
  bool rtlEnabled = flags.contains(SkeletonUIFlag::RtlEnabled);

  int chromeHorMargin = CSSToDevPixels(2, sCSSToDevPixelScaling);
  int verticalOffset = sMaximized ? sNonClientVerticalMargins : 0;
  int horizontalOffset =
      sNonClientHorizontalMargins - (sMaximized ? 0 : chromeHorMargin);

  // found in tabs.inc.css, "--tab-min-height" + 2 * "--tab-block-margin"
  int tabBarHeight = CSSToDevPixels(44, sCSSToDevPixelScaling);
  int selectedTabBorderWidth = CSSToDevPixels(2, sCSSToDevPixelScaling);
  // found in tabs.inc.css, "--tab-block-margin"
  int titlebarSpacerWidth = horizontalOffset +
                            CSSToDevPixels(2, sCSSToDevPixelScaling) -
                            selectedTabBorderWidth;
  if (!sMaximized && !menubarShown) {
    // found in tabs.inc.css, ".titlebar-spacer"
    titlebarSpacerWidth += CSSToDevPixels(40, sCSSToDevPixelScaling);
  }
  // found in tabs.inc.css, "--tab-block-margin"
  int selectedTabMarginTop =
      CSSToDevPixels(4, sCSSToDevPixelScaling) - selectedTabBorderWidth;
  int selectedTabMarginBottom =
      CSSToDevPixels(4, sCSSToDevPixelScaling) - selectedTabBorderWidth;
  int selectedTabBorderRadius = CSSToDevPixels(4, sCSSToDevPixelScaling);
  int selectedTabWidth =
      CSSToDevPixels(221, sCSSToDevPixelScaling) + 2 * selectedTabBorderWidth;
  int toolbarHeight = CSSToDevPixels(40, sCSSToDevPixelScaling);
  // found in browser.css, "#PersonalToolbar"
  int bookmarkToolbarHeight = CSSToDevPixels(28, sCSSToDevPixelScaling);
  if (bookmarksToolbarShown) {
    toolbarHeight += bookmarkToolbarHeight;
  }
  // found in urlbar-searchbar.inc.css, "#urlbar[breakout]"
  int urlbarTopOffset = CSSToDevPixels(4, sCSSToDevPixelScaling);
  int urlbarHeight = CSSToDevPixels(32, sCSSToDevPixelScaling);
  // found in browser-aero.css, "#navigator-toolbox::after" border-bottom
  int chromeContentDividerHeight = CSSToDevPixels(1, sCSSToDevPixelScaling);

  int tabPlaceholderBarMarginTop = CSSToDevPixels(14, sCSSToDevPixelScaling);
  int tabPlaceholderBarMarginLeft = CSSToDevPixels(10, sCSSToDevPixelScaling);
  int tabPlaceholderBarHeight = CSSToDevPixels(10, sCSSToDevPixelScaling);
  int tabPlaceholderBarWidth = CSSToDevPixels(120, sCSSToDevPixelScaling);

  int toolbarPlaceholderHeight = CSSToDevPixels(10, sCSSToDevPixelScaling);
  int toolbarPlaceholderMarginRight =
      rtlEnabled ? CSSToDevPixels(11, sCSSToDevPixelScaling)
                 : CSSToDevPixels(9, sCSSToDevPixelScaling);
  int toolbarPlaceholderMarginLeft =
      rtlEnabled ? CSSToDevPixels(9, sCSSToDevPixelScaling)
                 : CSSToDevPixels(11, sCSSToDevPixelScaling);
  int placeholderMargin = CSSToDevPixels(8, sCSSToDevPixelScaling);

  int menubarHeightDevPixels =
      menubarShown ? CSSToDevPixels(28, sCSSToDevPixelScaling) : 0;

  // defined in urlbar-searchbar.inc.css as --urlbar-margin-inline: 5px
  int urlbarMargin =
      CSSToDevPixels(5, sCSSToDevPixelScaling) + horizontalOffset;

  int urlbarTextPlaceholderMarginTop =
      CSSToDevPixels(12, sCSSToDevPixelScaling);
  int urlbarTextPlaceholderMarginLeft =
      CSSToDevPixels(12, sCSSToDevPixelScaling);
  int urlbarTextPlaceHolderWidth = CSSToDevPixels(
      std::clamp(urlbarCSSSpan.end - urlbarCSSSpan.start - 10.0, 0.0, 260.0),
      sCSSToDevPixelScaling);
  int urlbarTextPlaceholderHeight = CSSToDevPixels(10, sCSSToDevPixelScaling);

  int searchbarTextPlaceholderWidth = CSSToDevPixels(62, sCSSToDevPixelScaling);

  auto scopeExit = MakeScopeExit([&] {
    delete sAnimatedRects;
    sAnimatedRects = nullptr;
  });

  Vector<ColorRect> rects;

  ColorRect menubar = {};
  menubar.color = currentTheme.tabBarColor;
  menubar.x = 0;
  menubar.y = verticalOffset;
  menubar.width = sWindowWidth;
  menubar.height = menubarHeightDevPixels;
  menubar.flipIfRTL = false;
  if (!rects.append(menubar)) {
    return Err(PreXULSkeletonUIError::OOM);
  }

  int placeholderBorderRadius = CSSToDevPixels(4, sCSSToDevPixelScaling);
  // found in browser.css "--toolbarbutton-border-radius"
  int urlbarBorderRadius = CSSToDevPixels(4, sCSSToDevPixelScaling);

  // The (traditionally dark blue on Windows) background of the tab bar.
  ColorRect tabBar = {};
  tabBar.color = currentTheme.tabBarColor;
  tabBar.x = 0;
  tabBar.y = menubar.y + menubar.height;
  tabBar.width = sWindowWidth;
  tabBar.height = tabBarHeight;
  tabBar.flipIfRTL = false;
  if (!rects.append(tabBar)) {
    return Err(PreXULSkeletonUIError::OOM);
  }

  // The initial selected tab
  ColorRect selectedTab = {};
  selectedTab.color = currentTheme.tabColor;
  selectedTab.x = titlebarSpacerWidth;
  selectedTab.y = menubar.y + menubar.height + selectedTabMarginTop;
  selectedTab.width = selectedTabWidth;
  selectedTab.height =
      tabBar.y + tabBar.height - selectedTab.y - selectedTabMarginBottom;
  selectedTab.borderColor = currentTheme.tabOutlineColor;
  selectedTab.borderWidth = selectedTabBorderWidth;
  selectedTab.borderRadius = selectedTabBorderRadius;
  selectedTab.flipIfRTL = true;
  if (!rects.append(selectedTab)) {
    return Err(PreXULSkeletonUIError::OOM);
  }

  // A placeholder rect representing text that will fill the selected tab title
  ColorRect tabTextPlaceholder = {};
  tabTextPlaceholder.color = currentTheme.toolbarForegroundColor;
  tabTextPlaceholder.x = selectedTab.x + tabPlaceholderBarMarginLeft;
  tabTextPlaceholder.y = selectedTab.y + tabPlaceholderBarMarginTop;
  tabTextPlaceholder.width = tabPlaceholderBarWidth;
  tabTextPlaceholder.height = tabPlaceholderBarHeight;
  tabTextPlaceholder.borderRadius = placeholderBorderRadius;
  tabTextPlaceholder.flipIfRTL = true;
  if (!rects.append(tabTextPlaceholder)) {
    return Err(PreXULSkeletonUIError::OOM);
  }

  // The toolbar background
  ColorRect toolbar = {};
  toolbar.color = currentTheme.backgroundColor;
  toolbar.x = 0;
  toolbar.y = tabBar.y + tabBarHeight;
  toolbar.width = sWindowWidth;
  toolbar.height = toolbarHeight;
  toolbar.flipIfRTL = false;
  if (!rects.append(toolbar)) {
    return Err(PreXULSkeletonUIError::OOM);
  }

  // The single-pixel divider line below the toolbar
  ColorRect chromeContentDivider = {};
  chromeContentDivider.color = currentTheme.chromeContentDividerColor;
  chromeContentDivider.x = 0;
  chromeContentDivider.y = toolbar.y + toolbar.height;
  chromeContentDivider.width = sWindowWidth;
  chromeContentDivider.height = chromeContentDividerHeight;
  chromeContentDivider.flipIfRTL = false;
  if (!rects.append(chromeContentDivider)) {
    return Err(PreXULSkeletonUIError::OOM);
  }

  // The urlbar
  ColorRect urlbar = {};
  urlbar.color = currentTheme.urlbarColor;
  urlbar.x = CSSToDevPixels(urlbarCSSSpan.start, sCSSToDevPixelScaling) +
             horizontalOffset;
  urlbar.y = tabBar.y + tabBarHeight + urlbarTopOffset;
  urlbar.width = CSSToDevPixels((urlbarCSSSpan.end - urlbarCSSSpan.start),
                                sCSSToDevPixelScaling);
  urlbar.height = urlbarHeight;
  urlbar.borderColor = currentTheme.urlbarBorderColor;
  urlbar.borderWidth = CSSToDevPixels(1, sCSSToDevPixelScaling);
  urlbar.borderRadius = urlbarBorderRadius;
  urlbar.flipIfRTL = false;
  if (!rects.append(urlbar)) {
    return Err(PreXULSkeletonUIError::OOM);
  }

  // The urlbar placeholder rect representating text that will fill the urlbar
  // If rtl is enabled, it is flipped relative to the the urlbar rectangle, not
  // sWindowWidth.
  ColorRect urlbarTextPlaceholder = {};
  urlbarTextPlaceholder.color = currentTheme.toolbarForegroundColor;
  urlbarTextPlaceholder.x =
      rtlEnabled
          ? ((urlbar.x + urlbar.width) - urlbarTextPlaceholderMarginLeft -
             urlbarTextPlaceHolderWidth)
          : (urlbar.x + urlbarTextPlaceholderMarginLeft);
  urlbarTextPlaceholder.y = urlbar.y + urlbarTextPlaceholderMarginTop;
  urlbarTextPlaceholder.width = urlbarTextPlaceHolderWidth;
  urlbarTextPlaceholder.height = urlbarTextPlaceholderHeight;
  urlbarTextPlaceholder.borderRadius = placeholderBorderRadius;
  urlbarTextPlaceholder.flipIfRTL = false;
  if (!rects.append(urlbarTextPlaceholder)) {
    return Err(PreXULSkeletonUIError::OOM);
  }

  // The searchbar and placeholder text, if present
  // This is y-aligned with the urlbar
  bool hasSearchbar = searchbarCSSSpan.start != 0 && searchbarCSSSpan.end != 0;
  ColorRect searchbarRect = {};
  if (hasSearchbar == true) {
    searchbarRect.color = currentTheme.urlbarColor;
    searchbarRect.x =
        CSSToDevPixels(searchbarCSSSpan.start, sCSSToDevPixelScaling) +
        horizontalOffset;
    searchbarRect.y = urlbar.y;
    searchbarRect.width = CSSToDevPixels(
        searchbarCSSSpan.end - searchbarCSSSpan.start, sCSSToDevPixelScaling);
    searchbarRect.height = urlbarHeight;
    searchbarRect.borderRadius = urlbarBorderRadius;
    searchbarRect.borderColor = currentTheme.urlbarBorderColor;
    searchbarRect.borderWidth = CSSToDevPixels(1, sCSSToDevPixelScaling);
    searchbarRect.flipIfRTL = false;
    if (!rects.append(searchbarRect)) {
      return Err(PreXULSkeletonUIError::OOM);
    }

    // The placeholder rect representating text that will fill the searchbar
    // This uses the same margins as the urlbarTextPlaceholder
    // If rtl is enabled, it is flipped relative to the the searchbar rectangle,
    // not sWindowWidth.
    ColorRect searchbarTextPlaceholder = {};
    searchbarTextPlaceholder.color = currentTheme.toolbarForegroundColor;
    searchbarTextPlaceholder.x =
        rtlEnabled
            ? ((searchbarRect.x + searchbarRect.width) -
               urlbarTextPlaceholderMarginLeft - searchbarTextPlaceholderWidth)
            : (searchbarRect.x + urlbarTextPlaceholderMarginLeft);
    searchbarTextPlaceholder.y =
        searchbarRect.y + urlbarTextPlaceholderMarginTop;
    searchbarTextPlaceholder.width = searchbarTextPlaceholderWidth;
    searchbarTextPlaceholder.height = urlbarTextPlaceholderHeight;
    searchbarTextPlaceholder.flipIfRTL = false;
    if (!rects.append(searchbarTextPlaceholder) ||
        !sAnimatedRects->append(searchbarTextPlaceholder)) {
      return Err(PreXULSkeletonUIError::OOM);
    }
  }

  // Determine where the placeholder rectangles should not go. This is
  // anywhere occupied by a spring, urlbar, or searchbar
  Vector<DevPixelSpan> noPlaceholderSpans;

  DevPixelSpan urlbarSpan;
  urlbarSpan.start = urlbar.x - urlbarMargin;
  urlbarSpan.end = urlbar.width + urlbar.x + urlbarMargin;

  DevPixelSpan searchbarSpan;
  if (hasSearchbar) {
    searchbarSpan.start = searchbarRect.x - urlbarMargin;
    searchbarSpan.end = searchbarRect.width + searchbarRect.x + urlbarMargin;
  }

  DevPixelSpan marginLeftPlaceholder;
  marginLeftPlaceholder.start = toolbarPlaceholderMarginLeft;
  marginLeftPlaceholder.end = toolbarPlaceholderMarginLeft;
  if (!noPlaceholderSpans.append(marginLeftPlaceholder)) {
    return Err(PreXULSkeletonUIError::OOM);
  }

  if (rtlEnabled) {
    // If we're RTL, then the springs as ordered in the DOM will be from right
    // to left, which will break our comparison logic below
    springs.reverse();
  }

  for (auto spring : springs) {
    DevPixelSpan springDevPixels;
    springDevPixels.start =
        CSSToDevPixels(spring.start, sCSSToDevPixelScaling) + horizontalOffset;
    springDevPixels.end =
        CSSToDevPixels(spring.end, sCSSToDevPixelScaling) + horizontalOffset;
    if (!noPlaceholderSpans.append(springDevPixels)) {
      return Err(PreXULSkeletonUIError::OOM);
    }
  }

  DevPixelSpan marginRightPlaceholder;
  marginRightPlaceholder.start = sWindowWidth - toolbarPlaceholderMarginRight;
  marginRightPlaceholder.end = sWindowWidth - toolbarPlaceholderMarginRight;
  if (!noPlaceholderSpans.append(marginRightPlaceholder)) {
    return Err(PreXULSkeletonUIError::OOM);
  }

  Vector<DevPixelSpan, 2> spansToAdd;
  Unused << spansToAdd.reserve(2);
  spansToAdd.infallibleAppend(urlbarSpan);
  if (hasSearchbar) {
    spansToAdd.infallibleAppend(searchbarSpan);
  }

  for (auto& toAdd : spansToAdd) {
    for (auto& span : noPlaceholderSpans) {
      if (span.start > toAdd.start) {
        if (!noPlaceholderSpans.insert(&span, toAdd)) {
          return Err(PreXULSkeletonUIError::OOM);
        }
        break;
      }
    }
  }

  for (size_t i = 1; i < noPlaceholderSpans.length(); i++) {
    int start = noPlaceholderSpans[i - 1].end + placeholderMargin;
    int end = noPlaceholderSpans[i].start - placeholderMargin;
    if (start + 2 * placeholderBorderRadius >= end) {
      continue;
    }

    // The placeholder rects should all be y-aligned.
    ColorRect placeholderRect = {};
    placeholderRect.color = currentTheme.toolbarForegroundColor;
    placeholderRect.x = start;
    placeholderRect.y = urlbarTextPlaceholder.y;
    placeholderRect.width = end - start;
    placeholderRect.height = toolbarPlaceholderHeight;
    placeholderRect.borderRadius = placeholderBorderRadius;
    placeholderRect.flipIfRTL = false;
    if (!rects.append(placeholderRect) ||
        !sAnimatedRects->append(placeholderRect)) {
      return Err(PreXULSkeletonUIError::OOM);
    }
  }

  sTotalChromeHeight = chromeContentDivider.y + chromeContentDivider.height;
  if (sTotalChromeHeight > sWindowHeight) {
    return Err(PreXULSkeletonUIError::BadWindowDimensions);
  }

  if (!sAnimatedRects->append(tabTextPlaceholder) ||
      !sAnimatedRects->append(urlbarTextPlaceholder)) {
    return Err(PreXULSkeletonUIError::OOM);
  }

  sPixelBuffer =
      (uint32_t*)calloc(sWindowWidth * sTotalChromeHeight, sizeof(uint32_t));

  for (auto& rect : *sAnimatedRects) {
    if (rtlEnabled && rect.flipIfRTL) {
      rect.x = sWindowWidth - rect.x - rect.width;
    }
    rect.x = std::clamp(rect.x, 0, sWindowWidth);
    rect.width = std::clamp(rect.width, 0, sWindowWidth - rect.x);
    rect.y = std::clamp(rect.y, 0, sTotalChromeHeight);
    rect.height = std::clamp(rect.height, 0, sTotalChromeHeight - rect.y);
  }

  for (auto& rect : rects) {
    if (rtlEnabled && rect.flipIfRTL) {
      rect.x = sWindowWidth - rect.x - rect.width;
    }
    rect.x = std::clamp(rect.x, 0, sWindowWidth);
    rect.width = std::clamp(rect.width, 0, sWindowWidth - rect.x);
    rect.y = std::clamp(rect.y, 0, sTotalChromeHeight);
    rect.height = std::clamp(rect.height, 0, sTotalChromeHeight - rect.y);
    RasterizeColorRect(rect);
  }

  HDC hdc = sGetWindowDC(hWnd);
  if (!hdc) {
    return Err(PreXULSkeletonUIError::FailedGettingDC);
  }
  auto cleanupDC = MakeScopeExit([=] { sReleaseDC(hWnd, hdc); });

  BITMAPINFO chromeBMI = {};
  chromeBMI.bmiHeader.biSize = sizeof(chromeBMI.bmiHeader);
  chromeBMI.bmiHeader.biWidth = sWindowWidth;
  chromeBMI.bmiHeader.biHeight = -sTotalChromeHeight;
  chromeBMI.bmiHeader.biPlanes = 1;
  chromeBMI.bmiHeader.biBitCount = 32;
  chromeBMI.bmiHeader.biCompression = BI_RGB;

  // First, we just paint the chrome area with our pixel buffer
  int scanLinesCopied = sStretchDIBits(
      hdc, 0, 0, sWindowWidth, sTotalChromeHeight, 0, 0, sWindowWidth,
      sTotalChromeHeight, sPixelBuffer, &chromeBMI, DIB_RGB_COLORS, SRCCOPY);
  if (scanLinesCopied == 0) {
    return Err(PreXULSkeletonUIError::FailedBlitting);
  }

  // Then, we just fill the rest with FillRect
  RECT rect = {0, sTotalChromeHeight, sWindowWidth, sWindowHeight};
  HBRUSH brush =
      sCreateSolidBrush(RGB((currentTheme.backgroundColor & 0xff0000) >> 16,
                            (currentTheme.backgroundColor & 0x00ff00) >> 8,
                            (currentTheme.backgroundColor & 0x0000ff) >> 0));
  int fillRectResult = sFillRect(hdc, &rect, brush);

  sDeleteObject(brush);

  if (fillRectResult == 0) {
    return Err(PreXULSkeletonUIError::FailedFillingBottomRect);
  }

  scopeExit.release();
  return Ok();
}

DWORD WINAPI AnimateSkeletonUI(void* aUnused) {
  if (!sPixelBuffer || sAnimatedRects->empty()) {
    return 0;
  }

  // See the comments above the InterlockedIncrement calls below here - we
  // atomically flip this up and down around sleep so the main thread doesn't
  // have to wait for us if we're just sleeping.
  if (InterlockedIncrement(&sAnimationControlFlag) != 1) {
    return 0;
  }
  // Sleep for two seconds - startups faster than this don't really benefit
  // from an animation, and we don't want to take away cycles from them.
  // Startups longer than this, however, are more likely to be blocked on IO,
  // and thus animating does not substantially impact startup times for them.
  ::Sleep(2000);
  if (InterlockedDecrement(&sAnimationControlFlag) != 0) {
    return 0;
  }

  // On each of the animated rects (which happen to all be placeholder UI
  // rects sharing the same color), we want to animate a gradient moving across
  // the screen from left to right. The gradient starts as the rect's color on,
  // the left side, changes to the background color of the window by the middle
  // of the gradient, and then goes back down to the rect's color. To make this
  // faster than interpolating between the two colors for each pixel for each
  // frame, we simply create a lookup buffer in which we can look up the color
  // for a particular offset into the gradient.
  //
  // To do this we just interpolate between the two values, and to give the
  // gradient a smoother transition between colors, we transform the linear
  // blend amount via the cubic smooth step function (SmoothStep3) to produce
  // a smooth start and stop for the gradient. We do this for the first half
  // of the gradient, and then simply copy that backwards for the second half.
  //
  // The CSS width of 80 chosen here is effectively is just to match the size
  // of the animation provided in the design mockup. We define it in CSS pixels
  // simply because the rest of our UI is based off of CSS scalings.
  int animationWidth = CSSToDevPixels(80, sCSSToDevPixelScaling);
  UniquePtr<uint32_t[]> animationLookup =
      MakeUnique<uint32_t[]>(animationWidth);
  uint32_t animationColor = sAnimationColor;
  NormalizedRGB rgbBlend = UintToRGB(animationColor);

  // Build the first half of the lookup table
  for (int i = 0; i < animationWidth / 2; ++i) {
    uint32_t baseColor = sToolbarForegroundColor;
    double blendAmountLinear =
        static_cast<double>(i) / (static_cast<double>(animationWidth / 2));
    double blendAmount = SmoothStep3(blendAmountLinear);

    NormalizedRGB rgbBase = UintToRGB(baseColor);
    NormalizedRGB rgb = Lerp(rgbBase, rgbBlend, blendAmount);
    animationLookup[i] = RGBToUint(rgb);
  }

  // Copy the first half of the lookup table into the second half backwards
  for (int i = animationWidth / 2; i < animationWidth; ++i) {
    int j = animationWidth - 1 - i;
    if (j == animationWidth / 2) {
      // If animationWidth is odd, we'll be left with one pixel at the center.
      // Just color that as the animation color.
      animationLookup[i] = animationColor;
    } else {
      animationLookup[i] = animationLookup[j];
    }
  }

  // The bitmap info remains unchanged throughout the animation - this just
  // effectively describes the contents of sPixelBuffer
  BITMAPINFO chromeBMI = {};
  chromeBMI.bmiHeader.biSize = sizeof(chromeBMI.bmiHeader);
  chromeBMI.bmiHeader.biWidth = sWindowWidth;
  chromeBMI.bmiHeader.biHeight = -sTotalChromeHeight;
  chromeBMI.bmiHeader.biPlanes = 1;
  chromeBMI.bmiHeader.biBitCount = 32;
  chromeBMI.bmiHeader.biCompression = BI_RGB;

  uint32_t animationIteration = 0;

  int devPixelsPerFrame =
      CSSToDevPixels(kAnimationCSSPixelsPerFrame, sCSSToDevPixelScaling);
  int devPixelsExtraWindowSize =
      CSSToDevPixels(kAnimationCSSExtraWindowSize, sCSSToDevPixelScaling);

  if (::InterlockedCompareExchange(&sAnimationControlFlag, 0, 0)) {
    // The window got consumed before we were able to draw anything.
    return 0;
  }

  while (true) {
    // The gradient will move across the screen at devPixelsPerFrame at
    // 60fps, and then loop back to the beginning. However, we add a buffer of
    // devPixelsExtraWindowSize around the edges so it doesn't immediately
    // jump back, giving it a more pulsing feel.
    int animationMin = ((animationIteration * devPixelsPerFrame) %
                        (sWindowWidth + devPixelsExtraWindowSize)) -
                       devPixelsExtraWindowSize / 2;
    int animationMax = animationMin + animationWidth;
    // The priorAnimationMin is the beginning of the previous frame's animation.
    // Since we only want to draw the bits of the image that we updated, we need
    // to overwrite the left bit of the animation we drew last frame with the
    // default color.
    int priorAnimationMin = animationMin - devPixelsPerFrame;
    animationMin = std::max(0, animationMin);
    priorAnimationMin = std::max(0, priorAnimationMin);
    animationMax = std::min((int)sWindowWidth, animationMax);

    // The gradient only affects the specific rects that we put into
    // sAnimatedRects. So we simply update those rects, and maintain a flag
    // to avoid drawing when we don't need to.
    bool updatedAnything = false;
    for (ColorRect rect : *sAnimatedRects) {
      bool hadUpdates =
          RasterizeAnimatedRect(rect, animationLookup.get(), priorAnimationMin,
                                animationMin, animationMax);
      updatedAnything = updatedAnything || hadUpdates;
    }

    if (updatedAnything) {
      HDC hdc = sGetWindowDC(sPreXULSkeletonUIWindow);
      if (!hdc) {
        return 0;
      }

      sStretchDIBits(hdc, priorAnimationMin, 0,
                     animationMax - priorAnimationMin, sTotalChromeHeight,
                     priorAnimationMin, 0, animationMax - priorAnimationMin,
                     sTotalChromeHeight, sPixelBuffer, &chromeBMI,
                     DIB_RGB_COLORS, SRCCOPY);

      sReleaseDC(sPreXULSkeletonUIWindow, hdc);
    }

    animationIteration++;

    // We coordinate around our sleep here to ensure that the main thread does
    // not wait on us if we're sleeping. If we don't get 1 here, it means the
    // window has been consumed and we don't need to sleep. If in
    // ConsumePreXULSkeletonUIHandle we get a value other than 1 after
    // incrementing, it means we're sleeping, and that function can assume that
    // we will safely exit after the sleep because of the observed value of
    // sAnimationControlFlag.
    if (InterlockedIncrement(&sAnimationControlFlag) != 1) {
      return 0;
    }

    // Note: Sleep does not guarantee an exact time interval. If the system is
    // busy, for instance, we could easily end up taking several frames longer,
    // and really we could be left unscheduled for an arbitrarily long time.
    // This is fine, and we don't really care. We could track how much time this
    // actually took and jump the animation forward the appropriate amount, but
    // its not even clear that that's a better user experience. So we leave this
    // as simple as we can.
    ::Sleep(16);

    // Here we bring sAnimationControlFlag back down - again, if we don't get a
    // 0 here it means we consumed the skeleton UI window in the mean time, so
    // we can simply exit.
    if (InterlockedDecrement(&sAnimationControlFlag) != 0) {
      return 0;
    }
  }
}

LRESULT WINAPI PreXULSkeletonUIProc(HWND hWnd, UINT msg, WPARAM wParam,
                                    LPARAM lParam) {
  // Exposing a generic oleacc proxy for the skeleton isn't useful and may cause
  // screen readers to report spurious information when the skeleton appears.
  if (msg == WM_GETOBJECT && sPreXULSkeletonUIWindow) {
    return E_FAIL;
  }

  // NOTE: this block was copied from WinUtils.cpp, and needs to be kept in
  // sync.
  if (msg == WM_NCCREATE && sEnableNonClientDpiScaling) {
    sEnableNonClientDpiScaling(hWnd);
  }

  // NOTE: this block was paraphrased from the WM_NCCALCSIZE handler in
  // nsWindow.cpp, and will need to be kept in sync.
  if (msg == WM_NCCALCSIZE) {
    RECT* clientRect =
        wParam ? &(reinterpret_cast<NCCALCSIZE_PARAMS*>(lParam))->rgrc[0]
               : (reinterpret_cast<RECT*>(lParam));

    // These match the margins set in browser-tabsintitlebar.js with
    // default prefs on Windows. Bug 1673092 tracks lining this up with
    // that more correctly instead of hard-coding it.
    int horizontalOffset =
        sNonClientHorizontalMargins -
        (sMaximized ? 0 : CSSToDevPixels(2, sCSSToDevPixelScaling));
    int verticalOffset =
        sNonClientHorizontalMargins -
        (sMaximized ? 0 : CSSToDevPixels(2, sCSSToDevPixelScaling));
    clientRect->top = clientRect->top;
    clientRect->left += horizontalOffset;
    clientRect->right -= horizontalOffset;
    clientRect->bottom -= verticalOffset;
    return 0;
  }

  return ::DefWindowProcW(hWnd, msg, wParam, lParam);
}

bool IsSystemDarkThemeEnabled() {
  DWORD result;
  HKEY themeKey;
  DWORD dataLen = sizeof(uint32_t);
  LPCWSTR keyName =
      L"SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Themes\\Personalize";

  result = ::RegOpenKeyExW(HKEY_CURRENT_USER, keyName, 0, KEY_READ, &themeKey);
  if (result != ERROR_SUCCESS) {
    return false;
  }
  AutoCloseRegKey closeKey(themeKey);

  uint32_t lightThemeEnabled;
  result = ::RegGetValueW(
      themeKey, nullptr, L"AppsUseLightTheme", RRF_RT_REG_DWORD, nullptr,
      reinterpret_cast<PBYTE>(&lightThemeEnabled), &dataLen);
  if (result != ERROR_SUCCESS) {
    return false;
  }
  return !lightThemeEnabled;
}

ThemeColors GetTheme(ThemeMode themeId) {
  ThemeColors theme = {};
  switch (themeId) {
    case ThemeMode::Dark:
      // Dark theme or default theme when in dark mode

      // controlled by css variable --toolbar-bgcolor
      theme.backgroundColor = 0x2b2a33;
      theme.tabColor = 0x42414d;
      theme.toolbarForegroundColor = 0x6a6a6d;
      theme.tabOutlineColor = 0x1c1b22;
      // controlled by css variable --lwt-accent-color
      theme.tabBarColor = 0x1c1b22;
      // controlled by --toolbar-non-lwt-textcolor in browser.css
      theme.chromeContentDividerColor = 0x0c0c0d;
      // controlled by css variable --toolbar-field-background-color
      theme.urlbarColor = 0x42414d;
      theme.urlbarBorderColor = 0x42414d;
      theme.animationColor = theme.urlbarColor;
      return theme;
    case ThemeMode::Light:
    case ThemeMode::Default:
    default:
      // --toolbar-non-lwt-bgcolor in browser.css
      theme.backgroundColor = 0xf9f9fb;
      theme.tabColor = 0xf9f9fb;
      theme.toolbarForegroundColor = 0xdddde1;
      theme.tabOutlineColor = 0xdddde1;
      // found in browser-aero.css ":root[tabsintitlebar]:not(:-moz-lwtheme)"
      // (set to "hsl(235,33%,19%)")
      theme.tabBarColor = 0xf0f0f4;
      // --chrome-content-separator-color in browser.css
      theme.chromeContentDividerColor = 0xe1e1e2;
      // controlled by css variable --toolbar-color
      theme.urlbarColor = 0xffffff;
      theme.urlbarBorderColor = 0xdddde1;
      theme.animationColor = theme.backgroundColor;
      return theme;
  }
}

Result<HKEY, PreXULSkeletonUIError> OpenPreXULSkeletonUIRegKey() {
  HKEY key;
  DWORD disposition;
  LSTATUS result =
      ::RegCreateKeyExW(HKEY_CURRENT_USER, kPreXULSkeletonUIKeyPath, 0, nullptr,
                        0, KEY_ALL_ACCESS, nullptr, &key, &disposition);

  if (result != ERROR_SUCCESS) {
    return Err(PreXULSkeletonUIError::FailedToOpenRegistryKey);
  }

  if (disposition == REG_CREATED_NEW_KEY ||
      disposition == REG_OPENED_EXISTING_KEY) {
    return key;
  }

  ::RegCloseKey(key);
  return Err(PreXULSkeletonUIError::FailedToOpenRegistryKey);
}

Result<Ok, PreXULSkeletonUIError> LoadGdi32AndUser32Procedures() {
  HMODULE user32Dll = ::LoadLibraryW(L"user32");
  HMODULE gdi32Dll = ::LoadLibraryW(L"gdi32");

  if (!user32Dll || !gdi32Dll) {
    return Err(PreXULSkeletonUIError::FailedLoadingDynamicProcs);
  }

  auto getThreadDpiAwarenessContext =
      (decltype(GetThreadDpiAwarenessContext)*)::GetProcAddress(
          user32Dll, "GetThreadDpiAwarenessContext");
  auto areDpiAwarenessContextsEqual =
      (decltype(AreDpiAwarenessContextsEqual)*)::GetProcAddress(
          user32Dll, "AreDpiAwarenessContextsEqual");
  if (getThreadDpiAwarenessContext && areDpiAwarenessContextsEqual &&
      areDpiAwarenessContextsEqual(getThreadDpiAwarenessContext(),
                                   DPI_AWARENESS_CONTEXT_PER_MONITOR_AWARE)) {
    // EnableNonClientDpiScaling is optional - we can handle not having it.
    sEnableNonClientDpiScaling =
        (EnableNonClientDpiScalingProc)::GetProcAddress(
            user32Dll, "EnableNonClientDpiScaling");
  }

  sGetSystemMetricsForDpi = (GetSystemMetricsForDpiProc)::GetProcAddress(
      user32Dll, "GetSystemMetricsForDpi");
  if (!sGetSystemMetricsForDpi) {
    return Err(PreXULSkeletonUIError::FailedLoadingDynamicProcs);
  }
  sGetDpiForWindow =
      (GetDpiForWindowProc)::GetProcAddress(user32Dll, "GetDpiForWindow");
  if (!sGetDpiForWindow) {
    return Err(PreXULSkeletonUIError::FailedLoadingDynamicProcs);
  }
  sRegisterClassW =
      (RegisterClassWProc)::GetProcAddress(user32Dll, "RegisterClassW");
  if (!sRegisterClassW) {
    return Err(PreXULSkeletonUIError::FailedLoadingDynamicProcs);
  }
  sCreateWindowExW =
      (CreateWindowExWProc)::GetProcAddress(user32Dll, "CreateWindowExW");
  if (!sCreateWindowExW) {
    return Err(PreXULSkeletonUIError::FailedLoadingDynamicProcs);
  }
  sShowWindow = (ShowWindowProc)::GetProcAddress(user32Dll, "ShowWindow");
  if (!sShowWindow) {
    return Err(PreXULSkeletonUIError::FailedLoadingDynamicProcs);
  }
  sSetWindowPos = (SetWindowPosProc)::GetProcAddress(user32Dll, "SetWindowPos");
  if (!sSetWindowPos) {
    return Err(PreXULSkeletonUIError::FailedLoadingDynamicProcs);
  }
  sGetWindowDC = (GetWindowDCProc)::GetProcAddress(user32Dll, "GetWindowDC");
  if (!sGetWindowDC) {
    return Err(PreXULSkeletonUIError::FailedLoadingDynamicProcs);
  }
  sFillRect = (FillRectProc)::GetProcAddress(user32Dll, "FillRect");
  if (!sFillRect) {
    return Err(PreXULSkeletonUIError::FailedLoadingDynamicProcs);
  }
  sReleaseDC = (ReleaseDCProc)::GetProcAddress(user32Dll, "ReleaseDC");
  if (!sReleaseDC) {
    return Err(PreXULSkeletonUIError::FailedLoadingDynamicProcs);
  }
  sLoadIconW = (LoadIconWProc)::GetProcAddress(user32Dll, "LoadIconW");
  if (!sLoadIconW) {
    return Err(PreXULSkeletonUIError::FailedLoadingDynamicProcs);
  }
  sLoadCursorW = (LoadCursorWProc)::GetProcAddress(user32Dll, "LoadCursorW");
  if (!sLoadCursorW) {
    return Err(PreXULSkeletonUIError::FailedLoadingDynamicProcs);
  }
  sMonitorFromWindow =
      (MonitorFromWindowProc)::GetProcAddress(user32Dll, "MonitorFromWindow");
  if (!sMonitorFromWindow) {
    return Err(PreXULSkeletonUIError::FailedLoadingDynamicProcs);
  }
  sGetMonitorInfoW =
      (GetMonitorInfoWProc)::GetProcAddress(user32Dll, "GetMonitorInfoW");
  if (!sGetMonitorInfoW) {
    return Err(PreXULSkeletonUIError::FailedLoadingDynamicProcs);
  }
  sSetWindowLongPtrW =
      (SetWindowLongPtrWProc)::GetProcAddress(user32Dll, "SetWindowLongPtrW");
  if (!sSetWindowLongPtrW) {
    return Err(PreXULSkeletonUIError::FailedLoadingDynamicProcs);
  }
  sStretchDIBits =
      (StretchDIBitsProc)::GetProcAddress(gdi32Dll, "StretchDIBits");
  if (!sStretchDIBits) {
    return Err(PreXULSkeletonUIError::FailedLoadingDynamicProcs);
  }
  sCreateSolidBrush =
      (CreateSolidBrushProc)::GetProcAddress(gdi32Dll, "CreateSolidBrush");
  if (!sCreateSolidBrush) {
    return Err(PreXULSkeletonUIError::FailedLoadingDynamicProcs);
  }
  sDeleteObject = (DeleteObjectProc)::GetProcAddress(gdi32Dll, "DeleteObject");
  if (!sDeleteObject) {
    return Err(PreXULSkeletonUIError::FailedLoadingDynamicProcs);
  }

  return Ok();
}

// Strips "--", "-", and "/" from the front of the arg if one of those exists,
// returning `arg + 2`, `arg + 1`, and `arg + 1` respectively. If none of these
// prefixes are found, the argument is not a flag, and nullptr is returned.
const char* NormalizeFlag(const char* arg) {
  if (strstr(arg, "--") == arg) {
    return arg + 2;
  }

  if (arg[0] == '-') {
    return arg + 1;
  }

  if (arg[0] == '/') {
    return arg + 1;
  }

  return nullptr;
}

static bool EnvHasValue(const char* name) {
  const char* val = getenv(name);
  return (val && *val);
}

// Ensures that we only see arguments in the command line which are acceptable.
// This is based on manual inspection of the list of arguments listed in the MDN
// page for Gecko/Firefox commandline options:
// https://developer.mozilla.org/en-US/docs/Mozilla/Command_Line_Options
// Broadly speaking, we want to reject any argument which causes us to show
// something other than the default window at its normal size. Here is a non-
// exhaustive list of command line options we want to *exclude*:
//
//   -ProfileManager : This will display the profile manager window, which does
//                     not match the skeleton UI at all.
//
//   -CreateProfile  : This will display a firefox window with the default
//                     screen position and size, and not the position and size
//                     which we have recorded in the registry.
//
//   -P <profile>    : This could cause us to display firefox with a position
//                     and size of a different profile than that in which we
//                     were previously running.
//
//   -width, -height : This will cause the width and height values in the
//                     registry to be incorrect.
//
//   -kiosk          : See above.
//
//   -headless       : This one should be rather obvious.
//
//   -migration      : This will start with the import wizard, which of course
//                     does not match the skeleton UI.
//
//   -private-window : This is tricky, but the colors of the main content area
//                     make this not feel great with the white content of the
//                     default skeleton UI.
//
// NOTE: we generally want to skew towards erroneous rejections of the command
// line rather than erroneous approvals. The consequence of a bad rejection
// is that we don't show the skeleton UI, which is business as usual. The
// consequence of a bad approval is that we show it when we're not supposed to,
// which is visually jarring and can also be unpredictable - there's no
// guarantee that the code which handles the non-default window is set up to
// properly handle the transition from the skeleton UI window.
static Result<Ok, PreXULSkeletonUIError> ValidateCmdlineArguments(
    int argc, char** argv, bool* explicitProfile) {
  const char* approvedArgumentsArray[] = {
      // These won't cause the browser to be visualy different in any way
      "new-instance", "no-remote", "browser", "foreground", "setDefaultBrowser",
      "attach-console", "wait-for-browser", "osint",

      // These will cause the chrome to be a bit different or extra windows to
      // be created, but overall the skeleton UI should still be broadly
      // correct enough.
      "new-tab", "new-window",

      // To the extent possible, we want to ensure that existing tests cover
      // the skeleton UI, so we need to allow marionette
      "marionette",

      // These will cause the content area to appear different, but won't
      // meaningfully affect the chrome
      "preferences", "search", "url",

#ifndef MOZILLA_OFFICIAL
      // On local builds, we want to allow -profile, because it's how `mach run`
      // operates, and excluding that would create an unnecessary blind spot for
      // Firefox devs.
      "profile"
#endif

      // There are other arguments which are likely okay. However, they are
      // not included here because this list is not intended to be
      // exhaustive - it only intends to green-light some somewhat commonly
      // used arguments. We want to err on the side of an unnecessary
      // rejection of the command line.
  };

  int approvedArgumentsArraySize =
      sizeof(approvedArgumentsArray) / sizeof(approvedArgumentsArray[0]);
  Vector<const char*> approvedArguments;
  if (!approvedArguments.reserve(approvedArgumentsArraySize)) {
    return Err(PreXULSkeletonUIError::OOM);
  }

  for (int i = 0; i < approvedArgumentsArraySize; ++i) {
    approvedArguments.infallibleAppend(approvedArgumentsArray[i]);
  }

#ifdef MOZILLA_OFFICIAL
  int profileArgIndex = -1;
  // If we're running mochitests or direct marionette tests, those specify a
  // temporary profile, and we want to ensure that we get the added coverage
  // from those.
  for (int i = 1; i < argc; ++i) {
    const char* flag = NormalizeFlag(argv[i]);
    if (flag && !strcmp(flag, "marionette")) {
      if (!approvedArguments.append("profile")) {
        return Err(PreXULSkeletonUIError::OOM);
      }
      profileArgIndex = approvedArguments.length() - 1;

      break;
    }
  }
#else
  int profileArgIndex = approvedArguments.length() - 1;
#endif

  for (int i = 1; i < argc; ++i) {
    const char* flag = NormalizeFlag(argv[i]);
    if (!flag) {
      // If this is not a flag, then we interpret it as a URL, similar to
      // BrowserContentHandler.sys.mjs. Some command line options take
      // additional arguments, which may or may not be URLs. We don't need to
      // know this, because we don't need to parse them out; we just rely on the
      // assumption that if arg X is actually a parameter for the preceding
      // arg Y, then X must not look like a flag (starting with "--", "-",
      // or "/").
      //
      // The most important thing here is the assumption that if something is
      // going to meaningfully alter the appearance of the window itself, it
      // must be a flag.
      continue;
    }

    bool approved = false;
    for (const char* approvedArg : approvedArguments) {
      // We do a case-insensitive compare here with _stricmp. Even though some
      // of these arguments are *not* read as case-insensitive, others *are*.
      // Similar to the flag logic above, we don't really care about this
      // distinction, because we don't need to parse the arguments - we just
      // rely on the assumption that none of the listed flags in our
      // approvedArguments are overloaded in such a way that a different
      // casing would visually alter the firefox window.
      if (!_stricmp(flag, approvedArg)) {
        approved = true;

        if (i == profileArgIndex) {
          *explicitProfile = true;
        }
        break;
      }
    }

    if (!approved) {
      return Err(PreXULSkeletonUIError::Cmdline);
    }
  }

  return Ok();
}

static Result<Ok, PreXULSkeletonUIError> ValidateEnvVars() {
  if (EnvHasValue("MOZ_SAFE_MODE_RESTART") ||
      EnvHasValue("MOZ_APP_SILENT_START") ||
      EnvHasValue("MOZ_RESET_PROFILE_RESTART") || EnvHasValue("MOZ_HEADLESS") ||
      (EnvHasValue("XRE_PROFILE_PATH") &&
       !EnvHasValue("MOZ_SKELETON_UI_RESTARTING"))) {
    return Err(PreXULSkeletonUIError::EnvVars);
  }

  return Ok();
}

static bool VerifyWindowDimensions(uint32_t windowWidth,
                                   uint32_t windowHeight) {
  return windowWidth <= kMaxWindowWidth && windowHeight <= kMaxWindowHeight;
}

static Result<Vector<CSSPixelSpan>, PreXULSkeletonUIError> ReadRegCSSPixelSpans(
    HKEY regKey, const std::wstring& valueName) {
  DWORD dataLen = 0;
  LSTATUS result = ::RegQueryValueExW(regKey, valueName.c_str(), nullptr,
                                      nullptr, nullptr, &dataLen);
  if (result != ERROR_SUCCESS) {
    return Err(PreXULSkeletonUIError::RegistryError);
  }

  if (dataLen % (2 * sizeof(double)) != 0) {
    return Err(PreXULSkeletonUIError::CorruptData);
  }

  auto buffer = MakeUniqueFallible<wchar_t[]>(dataLen);
  if (!buffer) {
    return Err(PreXULSkeletonUIError::OOM);
  }
  result =
      ::RegGetValueW(regKey, nullptr, valueName.c_str(), RRF_RT_REG_BINARY,
                     nullptr, reinterpret_cast<PBYTE>(buffer.get()), &dataLen);
  if (result != ERROR_SUCCESS) {
    return Err(PreXULSkeletonUIError::RegistryError);
  }

  Vector<CSSPixelSpan> resultVector;
  double* asDoubles = reinterpret_cast<double*>(buffer.get());
  for (size_t i = 0; i < dataLen / (2 * sizeof(double)); i++) {
    CSSPixelSpan span = {};
    span.start = *(asDoubles++);
    span.end = *(asDoubles++);
    if (!resultVector.append(span)) {
      return Err(PreXULSkeletonUIError::OOM);
    }
  }

  return resultVector;
}

static Result<double, PreXULSkeletonUIError> ReadRegDouble(
    HKEY regKey, const std::wstring& valueName) {
  double value = 0;
  DWORD dataLen = sizeof(double);
  LSTATUS result =
      ::RegGetValueW(regKey, nullptr, valueName.c_str(), RRF_RT_REG_BINARY,
                     nullptr, reinterpret_cast<PBYTE>(&value), &dataLen);
  if (result != ERROR_SUCCESS || dataLen != sizeof(double)) {
    return Err(PreXULSkeletonUIError::RegistryError);
  }

  return value;
}

static Result<uint32_t, PreXULSkeletonUIError> ReadRegUint(
    HKEY regKey, const std::wstring& valueName) {
  DWORD value = 0;
  DWORD dataLen = sizeof(uint32_t);
  LSTATUS result =
      ::RegGetValueW(regKey, nullptr, valueName.c_str(), RRF_RT_REG_DWORD,
                     nullptr, reinterpret_cast<PBYTE>(&value), &dataLen);
  if (result != ERROR_SUCCESS) {
    return Err(PreXULSkeletonUIError::RegistryError);
  }

  return value;
}

static Result<bool, PreXULSkeletonUIError> ReadRegBool(
    HKEY regKey, const std::wstring& valueName) {
  uint32_t value;
  MOZ_TRY_VAR(value, ReadRegUint(regKey, valueName));
  return !!value;
}

static Result<Ok, PreXULSkeletonUIError> WriteRegCSSPixelSpans(
    HKEY regKey, const std::wstring& valueName, const CSSPixelSpan* spans,
    int spansLength) {
  // No guarantee on the packing of CSSPixelSpan. We could #pragma it, but it's
  // also trivial to just copy them into a buffer of doubles.
  auto doubles = MakeUnique<double[]>(spansLength * 2);
  for (int i = 0; i < spansLength; ++i) {
    doubles[i * 2] = spans[i].start;
    doubles[i * 2 + 1] = spans[i].end;
  }

  LSTATUS result =
      ::RegSetValueExW(regKey, valueName.c_str(), 0, REG_BINARY,
                       reinterpret_cast<const BYTE*>(doubles.get()),
                       spansLength * sizeof(double) * 2);
  if (result != ERROR_SUCCESS) {
    return Err(PreXULSkeletonUIError::RegistryError);
  }
  return Ok();
}

static Result<Ok, PreXULSkeletonUIError> WriteRegDouble(
    HKEY regKey, const std::wstring& valueName, double value) {
  LSTATUS result =
      ::RegSetValueExW(regKey, valueName.c_str(), 0, REG_BINARY,
                       reinterpret_cast<const BYTE*>(&value), sizeof(value));
  if (result != ERROR_SUCCESS) {
    return Err(PreXULSkeletonUIError::RegistryError);
  }

  return Ok();
}

static Result<Ok, PreXULSkeletonUIError> WriteRegUint(
    HKEY regKey, const std::wstring& valueName, uint32_t value) {
  LSTATUS result =
      ::RegSetValueExW(regKey, valueName.c_str(), 0, REG_DWORD,
                       reinterpret_cast<PBYTE>(&value), sizeof(value));
  if (result != ERROR_SUCCESS) {
    return Err(PreXULSkeletonUIError::RegistryError);
  }

  return Ok();
}

static Result<Ok, PreXULSkeletonUIError> WriteRegBool(
    HKEY regKey, const std::wstring& valueName, bool value) {
  return WriteRegUint(regKey, valueName, value ? 1 : 0);
}

static Result<Ok, PreXULSkeletonUIError> CreateAndStorePreXULSkeletonUIImpl(
    HINSTANCE hInstance, int argc, char** argv) {
  // Initializing COM below may load modules via SetWindowHookEx, some of
  // which may modify the executable's IAT for ntdll.dll.  If that happens,
  // this browser process fails to launch sandbox processes because we cannot
  // copy a modified IAT into a remote process (See SandboxBroker::LaunchApp).
  // To prevent that, we cache the intact IAT before COM initialization.
  // If EAF+ is enabled, CacheNtDllThunk() causes a crash, but EAF+ will
  // also prevent an injected module from parsing the PE headers and modifying
  // the IAT.  Therefore, we can skip CacheNtDllThunk().
  if (!mozilla::IsEafPlusEnabled()) {
    CacheNtDllThunk();
  }

  // NOTE: it's important that we initialize sProcessRuntime before showing a
  // window. Historically we ran into issues where showing the window would
  // cause an accessibility win event to fire, which could cause in-process
  // system or third party components to initialize COM and prevent us from
  // initializing it with important settings we need.

  // Some COM settings are global to the process and must be set before any non-
  // trivial COM is run in the application. Since these settings may affect
  // stability, we should instantiate COM ASAP so that we can ensure that these
  // global settings are configured before anything can interfere.
  sProcessRuntime = new mscom::ProcessRuntime(
      mscom::ProcessRuntime::ProcessCategory::GeckoBrowserParent);

  const TimeStamp skeletonStart = TimeStamp::Now();

  HKEY regKey;
  MOZ_TRY_VAR(regKey, OpenPreXULSkeletonUIRegKey());
  AutoCloseRegKey closeKey(regKey);

  UniquePtr<wchar_t[]> binPath;
  MOZ_TRY_VAR(binPath, GetBinaryPath());

  std::wstring regProgressName =
      GetRegValueName(binPath.get(), sProgressSuffix);
  auto progressResult = ReadRegUint(regKey, regProgressName);
  if (!progressResult.isErr() &&
      progressResult.unwrap() !=
          static_cast<uint32_t>(PreXULSkeletonUIProgress::Completed)) {
    return Err(PreXULSkeletonUIError::CrashedOnce);
  }

  MOZ_TRY(
      WriteRegUint(regKey, regProgressName,
                   static_cast<uint32_t>(PreXULSkeletonUIProgress::Started)));
  auto writeCompletion = MakeScopeExit([&] {
    Unused << WriteRegUint(
        regKey, regProgressName,
        static_cast<uint32_t>(PreXULSkeletonUIProgress::Completed));
  });

  MOZ_TRY(GetSkeletonUILock());

  bool explicitProfile = false;
  MOZ_TRY(ValidateCmdlineArguments(argc, argv, &explicitProfile));
  MOZ_TRY(ValidateEnvVars());

  auto enabledResult =
      ReadRegBool(regKey, GetRegValueName(binPath.get(), sEnabledRegSuffix));
  if (enabledResult.isErr()) {
    return Err(PreXULSkeletonUIError::EnabledKeyDoesNotExist);
  }
  if (!enabledResult.unwrap()) {
    return Err(PreXULSkeletonUIError::Disabled);
  }
  sPreXULSkeletonUIEnabled = true;

  MOZ_ASSERT(!sAnimatedRects);
  sAnimatedRects = new Vector<ColorRect>();

  MOZ_TRY(LoadGdi32AndUser32Procedures());

  if (!explicitProfile) {
    MOZ_TRY(CheckForStartWithLastProfile());
  }

  WNDCLASSW wc;
  wc.style = CS_DBLCLKS;
  wc.lpfnWndProc = PreXULSkeletonUIProc;
  wc.cbClsExtra = 0;
  wc.cbWndExtra = 0;
  wc.hInstance = hInstance;
  wc.hIcon = sLoadIconW(::GetModuleHandleW(nullptr), gStockApplicationIcon);
  wc.hCursor = sLoadCursorW(hInstance, gIDCWait);
  wc.hbrBackground = nullptr;
  wc.lpszMenuName = nullptr;

  // TODO: just ensure we disable this if we've overridden the window class
  wc.lpszClassName = L"MozillaWindowClass";

  if (!sRegisterClassW(&wc)) {
    return Err(PreXULSkeletonUIError::FailedRegisteringWindowClass);
  }

  uint32_t screenX;
  MOZ_TRY_VAR(screenX, ReadRegUint(regKey, GetRegValueName(binPath.get(),
                                                           sScreenXRegSuffix)));
  uint32_t screenY;
  MOZ_TRY_VAR(screenY, ReadRegUint(regKey, GetRegValueName(binPath.get(),
                                                           sScreenYRegSuffix)));
  uint32_t windowWidth;
  MOZ_TRY_VAR(
      windowWidth,
      ReadRegUint(regKey, GetRegValueName(binPath.get(), sWidthRegSuffix)));
  uint32_t windowHeight;
  MOZ_TRY_VAR(
      windowHeight,
      ReadRegUint(regKey, GetRegValueName(binPath.get(), sHeightRegSuffix)));
  MOZ_TRY_VAR(
      sMaximized,
      ReadRegBool(regKey, GetRegValueName(binPath.get(), sMaximizedRegSuffix)));
  MOZ_TRY_VAR(
      sCSSToDevPixelScaling,
      ReadRegDouble(regKey, GetRegValueName(binPath.get(),
                                            sCssToDevPixelScalingRegSuffix)));
  Vector<CSSPixelSpan> urlbar;
  MOZ_TRY_VAR(urlbar,
              ReadRegCSSPixelSpans(
                  regKey, GetRegValueName(binPath.get(), sUrlbarCSSRegSuffix)));
  Vector<CSSPixelSpan> searchbar;
  MOZ_TRY_VAR(searchbar,
              ReadRegCSSPixelSpans(
                  regKey, GetRegValueName(binPath.get(), sSearchbarRegSuffix)));
  Vector<CSSPixelSpan> springs;
  MOZ_TRY_VAR(springs, ReadRegCSSPixelSpans(
                           regKey, GetRegValueName(binPath.get(),
                                                   sSpringsCSSRegSuffix)));

  if (urlbar.empty() || searchbar.empty()) {
    return Err(PreXULSkeletonUIError::CorruptData);
  }

  EnumSet<SkeletonUIFlag, uint32_t> flags;
  uint32_t flagsUint;
  MOZ_TRY_VAR(flagsUint, ReadRegUint(regKey, GetRegValueName(binPath.get(),
                                                             sFlagsRegSuffix)));
  flags.deserialize(flagsUint);

  if (flags.contains(SkeletonUIFlag::TouchDensity) ||
      flags.contains(SkeletonUIFlag::CompactDensity)) {
    return Err(PreXULSkeletonUIError::BadUIDensity);
  }

  uint32_t theme;
  MOZ_TRY_VAR(theme, ReadRegUint(regKey, GetRegValueName(binPath.get(),
                                                         sThemeRegSuffix)));
  ThemeMode themeMode = static_cast<ThemeMode>(theme);
  if (themeMode == ThemeMode::Default) {
    if (IsSystemDarkThemeEnabled() == true) {
      themeMode = ThemeMode::Dark;
    }
  }
  ThemeColors currentTheme = GetTheme(themeMode);

  if (!VerifyWindowDimensions(windowWidth, windowHeight)) {
    return Err(PreXULSkeletonUIError::BadWindowDimensions);
  }

  int showCmd = SW_SHOWNORMAL;
  DWORD windowStyle = kPreXULSkeletonUIWindowStyle;
  if (sMaximized) {
    showCmd = SW_SHOWMAXIMIZED;
    windowStyle |= WS_MAXIMIZE;
  }

  sPreXULSkeletonUIWindow =
      sCreateWindowExW(kPreXULSkeletonUIWindowStyleEx, L"MozillaWindowClass",
                       L"", windowStyle, screenX, screenY, windowWidth,
                       windowHeight, nullptr, nullptr, hInstance, nullptr);
  if (!sPreXULSkeletonUIWindow) {
    return Err(PreXULSkeletonUIError::CreateWindowFailed);
  }

  sShowWindow(sPreXULSkeletonUIWindow, showCmd);

  sDpi = sGetDpiForWindow(sPreXULSkeletonUIWindow);
  sNonClientHorizontalMargins =
      sGetSystemMetricsForDpi(SM_CXFRAME, sDpi) +
      sGetSystemMetricsForDpi(SM_CXPADDEDBORDER, sDpi);
  sNonClientVerticalMargins = sGetSystemMetricsForDpi(SM_CYFRAME, sDpi) +
                              sGetSystemMetricsForDpi(SM_CXPADDEDBORDER, sDpi);

  if (sMaximized) {
    HMONITOR monitor =
        sMonitorFromWindow(sPreXULSkeletonUIWindow, MONITOR_DEFAULTTONULL);
    if (!monitor) {
      // NOTE: we specifically don't clean up the window here. If we're unable
      // to finish setting up the window how we want it, we still need to keep
      // it around and consume it with the first real toplevel window we
      // create, to avoid flickering.
      return Err(PreXULSkeletonUIError::FailedGettingMonitorInfo);
    }
    MONITORINFO mi = {sizeof(MONITORINFO)};
    if (!sGetMonitorInfoW(monitor, &mi)) {
      return Err(PreXULSkeletonUIError::FailedGettingMonitorInfo);
    }

    sWindowWidth =
        mi.rcWork.right - mi.rcWork.left + sNonClientHorizontalMargins * 2;
    sWindowHeight =
        mi.rcWork.bottom - mi.rcWork.top + sNonClientVerticalMargins * 2;
  } else {
    sWindowWidth = static_cast<int>(windowWidth);
    sWindowHeight = static_cast<int>(windowHeight);
  }

  sSetWindowPos(sPreXULSkeletonUIWindow, 0, 0, 0, 0, 0,
                SWP_FRAMECHANGED | SWP_NOACTIVATE | SWP_NOMOVE |
                    SWP_NOOWNERZORDER | SWP_NOSIZE | SWP_NOZORDER);
  MOZ_TRY(DrawSkeletonUI(sPreXULSkeletonUIWindow, urlbar[0], searchbar[0],
                         springs, currentTheme, flags));
  if (sAnimatedRects) {
    sPreXULSKeletonUIAnimationThread = ::CreateThread(
        nullptr, 256 * 1024, AnimateSkeletonUI, nullptr, 0, nullptr);
  }

  BASE_PROFILER_MARKER_UNTYPED(
      "CreatePreXULSkeletonUI", OTHER,
      MarkerTiming::IntervalUntilNowFrom(skeletonStart));

  return Ok();
}

void CreateAndStorePreXULSkeletonUI(HINSTANCE hInstance, int argc,
                                    char** argv) {
  auto result = CreateAndStorePreXULSkeletonUIImpl(hInstance, argc, argv);

  if (result.isErr()) {
    sErrorReason.emplace(result.unwrapErr());
  }
}

void CleanupProcessRuntime() {
  delete sProcessRuntime;
  sProcessRuntime = nullptr;
}

bool WasPreXULSkeletonUIMaximized() { return sMaximized; }

bool GetPreXULSkeletonUIWasShown() {
  return sPreXULSkeletonUIShown || !!sPreXULSkeletonUIWindow;
}

HWND ConsumePreXULSkeletonUIHandle() {
  // NOTE: we need to make sure that everything that runs here is a no-op if
  // it failed to be set, which is a possibility. If anything fails to be set
  // we don't want to clean everything up right away, because if we have a
  // blank window up, we want that to stick around and get consumed by nsWindow
  // as normal, otherwise the window will flicker in and out, which we imagine
  // is unpleasant.

  // If we don't get 1 here, it means the thread is actually just sleeping, so
  // we don't need to worry about giving out ownership of the window, because
  // the thread will simply exit after its sleep. However, if it is 1, we need
  // to wait for the thread to exit to be safe, as it could be doing anything.
  if (InterlockedIncrement(&sAnimationControlFlag) == 1) {
    ::WaitForSingleObject(sPreXULSKeletonUIAnimationThread, INFINITE);
  }
  ::CloseHandle(sPreXULSKeletonUIAnimationThread);
  sPreXULSKeletonUIAnimationThread = nullptr;
  HWND result = sPreXULSkeletonUIWindow;
  sPreXULSkeletonUIWindow = nullptr;
  free(sPixelBuffer);
  sPixelBuffer = nullptr;
  delete sAnimatedRects;
  sAnimatedRects = nullptr;

  return result;
}

Maybe<PreXULSkeletonUIError> GetPreXULSkeletonUIErrorReason() {
  return sErrorReason;
}

Result<Ok, PreXULSkeletonUIError> PersistPreXULSkeletonUIValues(
    const SkeletonUISettings& settings) {
  if (!sPreXULSkeletonUIEnabled) {
    return Err(PreXULSkeletonUIError::Disabled);
  }

  HKEY regKey;
  MOZ_TRY_VAR(regKey, OpenPreXULSkeletonUIRegKey());
  AutoCloseRegKey closeKey(regKey);

  UniquePtr<wchar_t[]> binPath;
  MOZ_TRY_VAR(binPath, GetBinaryPath());

  MOZ_TRY(WriteRegUint(regKey,
                       GetRegValueName(binPath.get(), sScreenXRegSuffix),
                       settings.screenX));
  MOZ_TRY(WriteRegUint(regKey,
                       GetRegValueName(binPath.get(), sScreenYRegSuffix),
                       settings.screenY));
  MOZ_TRY(WriteRegUint(regKey, GetRegValueName(binPath.get(), sWidthRegSuffix),
                       settings.width));
  MOZ_TRY(WriteRegUint(regKey, GetRegValueName(binPath.get(), sHeightRegSuffix),
                       settings.height));

  MOZ_TRY(WriteRegBool(regKey,
                       GetRegValueName(binPath.get(), sMaximizedRegSuffix),
                       settings.maximized));

  EnumSet<SkeletonUIFlag, uint32_t> flags;
  if (settings.menubarShown) {
    flags += SkeletonUIFlag::MenubarShown;
  }
  if (settings.bookmarksToolbarShown) {
    flags += SkeletonUIFlag::BookmarksToolbarShown;
  }
  if (settings.rtlEnabled) {
    flags += SkeletonUIFlag::RtlEnabled;
  }
  if (settings.uiDensity == SkeletonUIDensity::Touch) {
    flags += SkeletonUIFlag::TouchDensity;
  }
  if (settings.uiDensity == SkeletonUIDensity::Compact) {
    flags += SkeletonUIFlag::CompactDensity;
  }

  uint32_t flagsUint = flags.serialize();
  MOZ_TRY(WriteRegUint(regKey, GetRegValueName(binPath.get(), sFlagsRegSuffix),
                       flagsUint));

  MOZ_TRY(WriteRegDouble(
      regKey, GetRegValueName(binPath.get(), sCssToDevPixelScalingRegSuffix),
      settings.cssToDevPixelScaling));
  MOZ_TRY(WriteRegCSSPixelSpans(
      regKey, GetRegValueName(binPath.get(), sUrlbarCSSRegSuffix),
      &settings.urlbarSpan, 1));
  MOZ_TRY(WriteRegCSSPixelSpans(
      regKey, GetRegValueName(binPath.get(), sSearchbarRegSuffix),
      &settings.searchbarSpan, 1));
  MOZ_TRY(WriteRegCSSPixelSpans(
      regKey, GetRegValueName(binPath.get(), sSpringsCSSRegSuffix),
      settings.springs.begin(), settings.springs.length()));

  return Ok();
}

MFBT_API bool GetPreXULSkeletonUIEnabled() { return sPreXULSkeletonUIEnabled; }

MFBT_API Result<Ok, PreXULSkeletonUIError> SetPreXULSkeletonUIEnabledIfAllowed(
    bool value) {
  // If the pre-XUL skeleton UI was disallowed for some reason, we just want to
  // ignore changes to the registry. An example of how things could be bad if
  // we didn't: someone running firefox with the -profile argument could
  // turn the skeleton UI on or off for the default profile. Turning it off
  // maybe isn't so bad (though it's likely still incorrect), but turning it
  // on could be bad if the user had specifically disabled it for a profile for
  // some reason. Ultimately there's no correct decision here, and the
  // messiness of this is just a consequence of sharing the registry values
  // across profiles. However, whatever ill effects we observe should be
  // correct themselves after one session.
  if (PreXULSkeletonUIDisallowed()) {
    return Err(PreXULSkeletonUIError::Disabled);
  }

  HKEY regKey;
  MOZ_TRY_VAR(regKey, OpenPreXULSkeletonUIRegKey());
  AutoCloseRegKey closeKey(regKey);

  UniquePtr<wchar_t[]> binPath;
  MOZ_TRY_VAR(binPath, GetBinaryPath());
  MOZ_TRY(WriteRegBool(
      regKey, GetRegValueName(binPath.get(), sEnabledRegSuffix), value));

  if (!sPreXULSkeletonUIEnabled && value) {
    // We specifically don't care if we fail to get this lock. We just want to
    // do our best effort to lock it so that future instances don't create
    // skeleton UIs while we're still running, since they will immediately exit
    // and tell us to open a new window.
    Unused << GetSkeletonUILock();
  }

  sPreXULSkeletonUIEnabled = value;

  return Ok();
}

MFBT_API Result<Ok, PreXULSkeletonUIError> SetPreXULSkeletonUIThemeId(
    ThemeMode theme) {
  if (theme == sTheme) {
    return Ok();
  }
  sTheme = theme;

  // If we fail below, invalidate sTheme
  auto invalidateTheme = MakeScopeExit([] { sTheme = ThemeMode::Invalid; });

  HKEY regKey;
  MOZ_TRY_VAR(regKey, OpenPreXULSkeletonUIRegKey());
  AutoCloseRegKey closeKey(regKey);

  UniquePtr<wchar_t[]> binPath;
  MOZ_TRY_VAR(binPath, GetBinaryPath());
  MOZ_TRY(WriteRegUint(regKey, GetRegValueName(binPath.get(), sThemeRegSuffix),
                       static_cast<uint32_t>(theme)));

  invalidateTheme.release();
  return Ok();
}

MFBT_API void PollPreXULSkeletonUIEvents() {
  if (sPreXULSkeletonUIEnabled && sPreXULSkeletonUIWindow) {
    MSG outMsg = {};
    PeekMessageW(&outMsg, sPreXULSkeletonUIWindow, 0, 0, 0);
  }
}

Result<Ok, PreXULSkeletonUIError> NotePreXULSkeletonUIRestarting() {
  if (!sPreXULSkeletonUIEnabled) {
    return Err(PreXULSkeletonUIError::Disabled);
  }

  ::SetEnvironmentVariableW(L"MOZ_SKELETON_UI_RESTARTING", L"1");

  // We assume that we are going to exit the application very shortly after
  // this. It should thus be fine to release this lock, and we'll need to,
  // since during a restart we launch the new instance before closing this
  // one.
  if (sPreXULSKeletonUILockFile != INVALID_HANDLE_VALUE) {
    ::CloseHandle(sPreXULSKeletonUILockFile);
  }
  return Ok();
}

}  // namespace mozilla