Merge branch 'master' into jgrpp

# Conflicts: # src/3rdparty/fmt/core.h # src/command_type.h # src/console_cmds.cpp # src/core/overflowsafe_type.hpp # src/landscape.cpp # src/network/network.cpp # src/newgrf_object.h # src/object_cmd.cpp # src/order_gui.cpp # src/saveload/vehicle_sl.cpp # src/script/api/script_industrytype.cpp # src/script/api/script_object.hpp # src/script/api/script_town.cpp # src/table/object_land.h # src/timetable_cmd.cpp # src/tree_cmd.cpp # src/vehicle_gui.cpp # src/window.cpp
1 year ago · 1bfd96c7f2
parent 8c4c9a8c13 a4a819c983
commit 1bfd96c7f2
64 changed files with 440 additions and 308 deletions
--- a/.github/codeql/codeql-config.yml
+++ b/.github/codeql/codeql-config.yml
@ -0,0 +1,10 @@
+name: openttd
+queries:
+- uses: security-and-quality
+query-filters:
+- exclude:
+    id:
+    # Only feasible way is to move away from fopen; fopen_s is optional C11 and not implemented on most platforms.
+    - cpp/world-writable-file-creation
+    # Basically OpenTTD's coding style for adding things like ..._INVALID to enumerations
+    - cpp/irregular-enum-init
--- a/.github/workflows/codeql.yml
+++ b/.github/workflows/codeql.yml
@ -0,0 +1,78 @@
+name: CodeQL
+
+on:
+  push:
+    branches:
+    - master
+  pull_request:
+    # The branches below must be a subset of the branches above
+    branches:
+    - master
+
+jobs:
+  analyze:
+    name: Analyze
+    runs-on: ubuntu-latest
+    permissions:
+      actions: read
+      contents: read
+      security-events: write
+
+    steps:
+    - name: Checkout
+      uses: actions/checkout@v3
+
+    - name: Install dependencies
+      run: |
+        echo "::group::Update apt"
+        sudo apt-get update
+        echo "::endgroup::"
+
+        echo "::group::Install dependencies"
+        sudo apt-get install -y --no-install-recommends \
+          liballegro4-dev \
+          libfontconfig-dev \
+          libicu-dev \
+          liblzma-dev \
+          liblzo2-dev \
+          libsdl2-dev \
+          zlib1g-dev \
+          # EOF
+        echo "::endgroup::"
+      env:
+        DEBIAN_FRONTEND: noninteractive
+
+    - name: Set number of make jobs
+      run: |
+        echo "MAKEFLAGS=-j$(nproc)" >> $GITHUB_ENV
+
+    - name: Initialize CodeQL
+      uses: github/codeql-action/init@v2
+      with:
+        languages: cpp
+        config-file: ./.github/codeql/codeql-config.yml
+
+    - name: Autobuild
+      uses: github/codeql-action/autobuild@v2
+
+    - name: Perform CodeQL Analysis
+      uses: github/codeql-action/analyze@v2
+      with:
+        category: /language:cpp
+        upload: False
+        output: sarif-results
+
+    - name: Filter out table & generated code
+      uses: advanced-security/filter-sarif@v1
+      with:
+        patterns: |
+          +**/*.*
+          -**/table/*.*
+          -**/generated/**/*.*
+        input: sarif-results/cpp.sarif
+        output: sarif-results/cpp.sarif
+
+    - name: Upload results
+      uses: github/codeql-action/upload-sarif@v2
+      with:
+        sarif_file: sarif-results/cpp.sarif
--- a/regression/regression/result.txt
+++ b/regression/regression/result.txt
@ -88,24 +88,24 @@
 abs( 21): 21

 --AIBase--
-  Rand():       -54346916
-  Rand():       -937374575
-  Rand():       823953997
+  Rand():       -2062310602
+  Rand():       -1780331126
+  Rand():       -397928569
  RandRange(0): 0
  RandRange(0): 0
  RandRange(0): 0
  RandRange(1): 0
  RandRange(1): 0
  RandRange(1): 0
-  RandRange(2): 1
-  RandRange(2): 1
-  RandRange(2): 1
-  RandRange(1000000): 966676
-  RandRange(1000000): 289525
-  RandRange(1000000): 170283
-  Chance(1, 2): false
+  RandRange(2): 0
+  RandRange(2): 0
+  RandRange(2): 0
+  RandRange(1000000): 666804
+  RandRange(1000000): 624059
+  RandRange(1000000): 697029
  Chance(1, 2): true
  Chance(1, 2): false
+  Chance(1, 2): true

 --List--
  IsEmpty():     true
@ -420,144 +420,144 @@
    1098 => 46116
    1099 => 46158
  Randomize ListDump:
-    1 => -200078348
-    2 => -29799264
-    1000 => 1630721656
-    1001 => 959306175
-    1002 => 1527421791
-    1003 => 1259692483
-    1004 => -1289244298
-    1005 => -1572996668
-    1006 => -2069479746
-    1007 => -1819131606
-    1008 => -1007163964
-    1009 => -1185394870
-    1010 => -1471365065
-    1011 => 364354366
-    1012 => -1478084253
-    1013 => 405281367
-    1014 => -11170062
-    1015 => 156767750
-    1016 => 1288924796
-    1017 => 1796884876
-    1018 => -1947073702
-    1019 => -1999614238
-    1020 => -231292809
-    1021 => 966621566
-    1022 => -606766557
-    1023 => -1138727825
-    1024 => -749544262
-    1025 => 2004771271
-    1026 => 686734186
-    1027 => 923274744
-    1028 => -1672035149
-    1029 => -1642064950
-    1030 => 1363389551
-    1031 => -559500928
-    1032 => 1656196991
-    1033 => 1655354425
-    1034 => -1027156689
-    1035 => 1952644328
-    1036 => 1217870217
-    1037 => 242274100
-    1038 => 201816080
-    1039 => 2127464758
-    1040 => 446043650
-    1041 => -319728455
-    1042 => 204701002
-    1043 => -571265398
-    1044 => -1422217131
-    1045 => -391208397
-    1046 => -1822628371
-    1047 => -1499755350
-    1048 => -1422137641
-    1049 => 1621693134
-    1051 => -1428728134
-    1052 => -147587573
-    1053 => 681719500
-    1054 => 1172011190
-    1055 => -1834344882
-    1056 => 1157634586
-    1057 => 1902133676
-    1058 => -1967780161
-    1059 => -1618025531
-    1060 => -810220453
-    1061 => 1582854921
-    1062 => -410004643
-    1063 => 1159917159
-    1064 => -1377804984
-    1065 => -738843914
-    1066 => -1578756103
-    1067 => -464090986
-    1068 => 1711504679
-    1069 => 545330655
-    1070 => 379462570
-    1071 => 514511099
-    1072 => -1813251176
-    1073 => 1424958266
-    1074 => -825255131
-    1075 => 539054595
-    1076 => -1764192010
-    1077 => -1243277769
-    1078 => 2017874281
-    1079 => -1972353607
-    1080 => 1879761467
-    1081 => 1638986560
-    1082 => -1832287507
-    1083 => -492411882
-    1084 => 658940812
-    1085 => -1044199400
-    1086 => 1586504918
-    1087 => -125492611
-    1088 => -1562883174
-    1089 => -1013778441
-    1090 => 1560228607
-    1091 => -550265689
-    1092 => 524767105
-    1093 => -713387661
-    1094 => 1425927738
-    1095 => 942653932
-    1096 => 1233220698
-    1097 => 1313602368
-    1098 => -140318584
-    1099 => 1199179892
+    1 => 688298322
+    2 => -1709546982
+    1000 => 1701392078
+    1001 => -1630848421
+    1002 => -886500935
+    1003 => -196324972
+    1004 => -436037402
+    1005 => -520341784
+    1006 => -1485224804
+    1007 => -311036236
+    1008 => -1503442439
+    1009 => -110945695
+    1010 => -82825175
+    1011 => 46859773
+    1012 => -1199223018
+    1013 => -1190555925
+    1014 => 326384434
+    1015 => 1486817960
+    1016 => -1411425597
+    1017 => -508426854
+    1018 => 820019294
+    1019 => 710762995
+    1020 => -760867032
+    1021 => -709611146
+    1022 => 732190215
+    1023 => 236336673
+    1024 => 740596257
+    1025 => 1135321785
+    1026 => 2067474156
+    1027 => -1395683607
+    1028 => -240528699
+    1029 => 928616892
+    1030 => 1712486685
+    1031 => 1994118287
+    1032 => 1333321243
+    1033 => 194124284
+    1034 => 615083294
+    1035 => 628086450
+    1036 => 498957825
+    1037 => 1359697121
+    1038 => 1888433963
+    1039 => 941623020
+    1040 => -1925663292
+    1041 => -771540264
+    1042 => -1058341359
+    1043 => 182127597
+    1044 => 646955927
+    1045 => -1424621714
+    1046 => 623062612
+    1047 => -1986955586
+    1048 => -1268826980
+    1049 => -456776220
+    1051 => -1112555329
+    1052 => -1532134052
+    1053 => 1960404034
+    1054 => 1573325453
+    1055 => -316619303
+    1056 => 699712177
+    1057 => 863274966
+    1058 => 1728276475
+    1059 => -246695889
+    1060 => 1919485436
+    1061 => 111273464
+    1062 => 125435213
+    1063 => 155132602
+    1064 => -171674076
+    1065 => 655046914
+    1066 => 1577399562
+    1067 => 1028818150
+    1068 => 447058239
+    1069 => -1057920269
+    1070 => -1326215323
+    1071 => -198688588
+    1072 => 1523643051
+    1073 => 231373233
+    1074 => 1121759962
+    1075 => 1449439846
+    1076 => -1615270753
+    1077 => -1509293864
+    1078 => 2116903943
+    1079 => 672822173
+    1080 => -969573911
+    1081 => 1589904755
+    1082 => 1148782015
+    1083 => 663503316
+    1084 => 933352745
+    1085 => 577717039
+    1086 => 402172048
+    1087 => 1812250453
+    1088 => 667300501
+    1089 => -1838825777
+    1090 => -856474776
+    1091 => 420696035
+    1092 => 2131427774
+    1093 => -435303548
+    1094 => -160883878
+    1095 => 1969629634
+    1096 => -555794155
+    1097 => -835119691
+    1098 => -1460907909
+    1099 => -1146924084
  KeepTop(10):
-    1 => -200078348
-    2 => -29799264
-    1000 => 1630721656
-    1001 => 959306175
-    1002 => 1527421791
-    1003 => 1259692483
-    1004 => -1289244298
-    1005 => -1572996668
-    1006 => -2069479746
-    1007 => -1819131606
+    1 => 688298322
+    2 => -1709546982
+    1000 => 1701392078
+    1001 => -1630848421
+    1002 => -886500935
+    1003 => -196324972
+    1004 => -436037402
+    1005 => -520341784
+    1006 => -1485224804
+    1007 => -311036236
  KeepBottom(8):
-    1000 => 1630721656
-    1001 => 959306175
-    1002 => 1527421791
-    1003 => 1259692483
-    1004 => -1289244298
-    1005 => -1572996668
-    1006 => -2069479746
-    1007 => -1819131606
+    1000 => 1701392078
+    1001 => -1630848421
+    1002 => -886500935
+    1003 => -196324972
+    1004 => -436037402
+    1005 => -520341784
+    1006 => -1485224804
+    1007 => -311036236
  RemoveBottom(2):
-    1000 => 1630721656
-    1001 => 959306175
-    1002 => 1527421791
-    1003 => 1259692483
-    1004 => -1289244298
-    1005 => -1572996668
+    1000 => 1701392078
+    1001 => -1630848421
+    1002 => -886500935
+    1003 => -196324972
+    1004 => -436037402
+    1005 => -520341784
  RemoveTop(2):
-    1002 => 1527421791
-    1003 => 1259692483
-    1004 => -1289244298
-    1005 => -1572996668
+    1002 => -886500935
+    1003 => -196324972
+    1004 => -436037402
+    1005 => -520341784
  RemoveList({1003, 1004}):
-    1002 => 1527421791
-    1005 => -1572996668
+    1002 => -886500935
+    1005 => -520341784
  KeepList({1003, 1004, 1005}):
-    1005 => -1572996668
+    1005 => -520341784
  AddList({1005, 4000, 4001, 4002}):
    1005 => 1005
    4000 => 8000
--- a/src/3rdparty/squirrel/squirrel/sqclass.h
+++ b/src/3rdparty/squirrel/squirrel/sqclass.h
@ -10,6 +10,7 @@ struct SQClassMember {
 		val = o.val;
 		attrs = o.attrs;
 	}
+	SQClassMember& operator=(SQClassMember &o) = delete;
 	SQObjectPtr val;
 	SQObjectPtr attrs;
 };
--- a/src/ai/ai_scanner.cpp
+++ b/src/ai/ai_scanner.cpp
@ -14,6 +14,7 @@
 #include "../core/random_func.hpp"

 #include "../script/squirrel_class.hpp"
+#include "../script/api/script_object.hpp"
 #include "ai_info.hpp"
 #include "ai_scanner.hpp"

@ -77,12 +78,7 @@ AIInfo *AIScannerInfo::SelectRandomAI() const
 	}

 	/* Find a random AI */
-	uint pos;
-	if (_networking) {
-		pos = InteractiveRandomRange(num_random_ais);
-	} else {
-		pos = RandomRange(num_random_ais);
-	}
+	uint pos = ScriptObject::GetRandomizer(OWNER_NONE).Next(num_random_ais);

 	/* Find the Nth item from the array */
 	ScriptInfoList::const_iterator it = this->info_single_list.begin();
--- a/src/build_vehicle_gui.cpp
+++ b/src/build_vehicle_gui.cpp
@ -1068,6 +1068,7 @@ static uint ShowAdditionalText(int left, int right, int y, EngineID engine)
 	uint16 callback = GetVehicleCallback(CBID_VEHICLE_ADDITIONAL_TEXT, 0, 0, engine, nullptr);
 	if (callback == CALLBACK_FAILED || callback == 0x400) return y;
 	const GRFFile *grffile = Engine::Get(engine)->GetGRF();
+	assert(grffile != nullptr);
 	if (callback > 0x400) {
 		ErrorUnknownCallbackResult(grffile->grfid, CBID_VEHICLE_ADDITIONAL_TEXT, callback);
 		return y;
--- a/src/company_cmd.cpp
+++ b/src/company_cmd.cpp
@ -596,7 +596,7 @@ Company *DoStartupNewCompany(DoStartupNewCompanyFlag flags, CompanyID company)
 	if (_company_manager_face != 0 && !is_ai && !_networking) {
 		c->face = _company_manager_face;
 	} else {
-		RandomCompanyManagerFaceBits(c->face, (GenderEthnicity)Random(), false, false);
+		RandomCompanyManagerFaceBits(c->face, (GenderEthnicity)Random(), false, _random);
 	}

 	SetDefaultCompanySettings(c->index);
--- a/src/company_gui.cpp
+++ b/src/company_gui.cpp
@ -1751,7 +1751,7 @@ public:

 			/* Randomize face button */
 			case WID_SCMF_RANDOM_NEW_FACE:
-				RandomCompanyManagerFaceBits(this->face, this->ge, this->advanced);
+				RandomCompanyManagerFaceBits(this->face, this->ge, this->advanced, _interactive_random);
 				this->UpdateData();
 				this->SetDirty();
 				break;
--- a/src/company_manager_face.h
+++ b/src/company_manager_face.h
@ -199,15 +199,13 @@ static inline void ScaleAllCompanyManagerFaceBits(CompanyManagerFace &cmf)
 * @param cmf the company manager's face to write the bits to
 * @param ge  the gender and ethnicity of the old company manager's face
 * @param adv if it for the advanced company manager's face window
- * @param interactive is the call from within the user interface?
+ * @param randomizer the source of random to use for creating the manager face
 *
 * @pre scale 'ge' to a valid gender/ethnicity combination
 */
-static inline void RandomCompanyManagerFaceBits(CompanyManagerFace &cmf, GenderEthnicity ge, bool adv, bool interactive = true)
+static inline void RandomCompanyManagerFaceBits(CompanyManagerFace &cmf, GenderEthnicity ge, bool adv, Randomizer &randomizer)
 {
-	/* This method is called from a command when not interactive and
-	 * then we must use Random to get the same result on all clients. */
-	cmf = interactive ? InteractiveRandom() : Random(); // random all company manager's face bits
+	cmf = randomizer.Next(); // random all company manager's face bits

 	/* scale ge: 0 == GE_WM, 1 == GE_WF, 2 == GE_BM, 3 == GE_BF (and maybe in future: ...) */
 	ge = (GenderEthnicity)((uint)ge % GE_END);
--- a/src/console_cmds.cpp
+++ b/src/console_cmds.cpp
@ -313,7 +313,11 @@ DEF_CONSOLE_CMD(ConZoomToLevel)
 		case 2: {
 			uint32 level;
 			if (GetArgumentInteger(&level, argv[1])) {
-				if (level < ZOOM_LVL_MIN) {
+				/* In case ZOOM_LVL_MIN is more than 0, the next if statement needs to be amended.
+				 * A simple check for less than ZOOM_LVL_MIN does not work here because we are
+				 * reading an unsigned integer from the console, so just check for a '-' char. */
+				static_assert(ZOOM_LVL_MIN == 0);
+				if (argv[1][0] == '-') {
 					IConsolePrintF(CC_ERROR, "Zoom-in levels below %u are not supported.", ZOOM_LVL_MIN);
 				} else if (level < _settings_client.gui.zoom_min) {
 					IConsolePrintF(CC_ERROR, "Current client settings do not allow zooming in below level %u.", _settings_client.gui.zoom_min);
@ -322,7 +326,7 @@ DEF_CONSOLE_CMD(ConZoomToLevel)
 				} else if (level > _settings_client.gui.zoom_max) {
 					IConsolePrintF(CC_ERROR, "Current client settings do not allow zooming out beyond level %u.", _settings_client.gui.zoom_max);
 				} else {
-					Window *w = FindWindowById(WC_MAIN_WINDOW, 0);
+					Window *w = GetMainWindow();
 					Viewport *vp = w->viewport;
 					while (vp->zoom > level) DoZoomInOutWindow(ZOOM_IN, w);
 					while (vp->zoom < level) DoZoomInOutWindow(ZOOM_OUT, w);
@ -529,7 +533,7 @@ DEF_CONSOLE_CMD(ConRemove)
 	_console_file_list.ValidateFileList();
 	const FiosItem *item = _console_file_list.FindItem(file);
 	if (item != nullptr) {
-		if (!FiosDelete(item->name)) {
+		if (unlink(item->name) != 0) {
 			IConsolePrintF(CC_ERROR, "%s: Failed to delete file", file);
 		}
 	} else {
@ -1031,6 +1035,7 @@ DEF_CONSOLE_CMD(ConResetCompany)
 		return false;
 	}
 	const NetworkClientInfo *ci = NetworkClientInfo::GetByClientID(CLIENT_ID_SERVER);
+	assert(ci != nullptr);
 	if (ci->client_playas == index) {
 		IConsoleError("Cannot remove company: the server is connected to that company.");
 		return true;
@ -2240,18 +2245,15 @@ DEF_CONSOLE_CMD(ConFont)
 		bool aa = setting->aa;

 		byte arg_index = 2;
-
-		if (argc > arg_index) {
-			/* We may encounter "aa" or "noaa" but it must be the last argument. */
-			if (strcasecmp(argv[arg_index], "aa") == 0 || strcasecmp(argv[arg_index], "noaa") == 0) {
-				aa = strncasecmp(argv[arg_index++], "no", 2) != 0;
-				if (argc > arg_index) return false;
-			} else {
-				/* For <name> we want a string. */
-				uint v;
-				if (!GetArgumentInteger(&v, argv[arg_index])) {
-					font = argv[arg_index++];
-				}
+		/* We may encounter "aa" or "noaa" but it must be the last argument. */
+		if (strcasecmp(argv[arg_index], "aa") == 0 || strcasecmp(argv[arg_index], "noaa") == 0) {
+			aa = strncasecmp(argv[arg_index++], "no", 2) != 0;
+			if (argc > arg_index) return false;
+		} else {
+			/* For <name> we want a string. */
+			uint v;
+			if (!GetArgumentInteger(&v, argv[arg_index])) {
+				font = argv[arg_index++];
 			}
 		}

@ -2282,7 +2284,7 @@ DEF_CONSOLE_CMD(ConFont)
 			InitFontCache(fs == FS_MONO);
 			fc = FontCache::Get(fs);
 		}
-		IConsolePrintF(CC_DEFAULT, "%s: \"%s\" %d %s [\"%s\" %d %s]", FontSizeToName(fs), fc->GetFontName(), fc->GetFontSize(), GetFontAAState(fs) ? "true" : "false", setting->font.c_str(), setting->size, setting->aa ? "true" : "false");
+		IConsolePrintF(CC_DEFAULT, "%s: \"%s\" %d %s [\"%s\" %d %s]", FontSizeToName(fs), fc->GetFontName(), fc->GetFontSize(), GetFontAAState(fs) ? "aa" : "noaa", setting->font.c_str(), setting->size, setting->aa ? "aa" : "noaa");
 	}

 	return true;
--- a/src/core/overflowsafe_type.hpp
+++ b/src/core/overflowsafe_type.hpp
@ -172,7 +172,10 @@ public:
 	inline constexpr bool operator <  (const int other) const { return !(*this >= other); }
 	inline constexpr bool operator <= (const int other) const { return !(*this > other); }

-	inline constexpr operator int64 () const { return this->m_value; }
+	inline constexpr operator T () const { return this->m_value; }
+
+	static inline constexpr OverflowSafeInt<T> max() { return T_MAX; }
+	static inline constexpr OverflowSafeInt<T> min() { return T_MIN; }
 };


--- a/src/error_gui.cpp
+++ b/src/error_gui.cpp
@ -239,7 +239,7 @@ public:
 		int scr_bot = GetMainViewBottom() - 20;

 		Point pt = RemapCoords(this->position.x, this->position.y, GetSlopePixelZOutsideMap(this->position.x, this->position.y));
-		const Viewport *vp = FindWindowById(WC_MAIN_WINDOW, 0)->viewport;
+		const Viewport *vp = GetMainWindow()->viewport;
 		if (this->face == INVALID_COMPANY) {
 			/* move x pos to opposite corner */
 			pt.x = UnScaleByZoom(pt.x - vp->virtual_left, vp->zoom) + vp->left;
--- a/src/game/game_text.cpp
+++ b/src/game/game_text.cpp
@ -225,6 +225,7 @@ public:
 GameStrings *LoadTranslations()
 {
 	const GameInfo *info = Game::GetInfo();
+	assert(info != nullptr);
 	std::string basename(info->GetMainScript());
 	auto e = basename.rfind(PATHSEPCHAR);
 	if (e == std::string::npos) return nullptr;
--- a/src/genworld.cpp
+++ b/src/genworld.cpp
@ -104,6 +104,7 @@ static void _GenerateWorld()

 		SetGeneratingWorldProgress(GWP_MAP_INIT, 2);
 		SetObjectToPlace(SPR_CURSOR_ZZZ, PAL_NONE, HT_NONE, WC_MAIN_WINDOW, 0);
+		ScriptObject::InitializeRandomizers();

 		BasePersistentStorageArray::SwitchMode(PSM_ENTER_GAMELOOP);

@ -337,9 +338,7 @@ void GenerateWorld(GenWorldMode mode, uint size_x, uint size_y, bool reset_setti
 	ShowGenerateWorldProgress();

 	/* Centre the view on the map */
-	if (FindWindowById(WC_MAIN_WINDOW, 0) != nullptr) {
-		ScrollMainWindowToTile(TileXY(MapSizeX() / 2, MapSizeY() / 2), true);
-	}
+	ScrollMainWindowToTile(TileXY(MapSizeX() / 2, MapSizeY() / 2), true);

 	_GenerateWorld();
 }
--- a/src/gfx_layout.cpp
+++ b/src/gfx_layout.cpp
@ -552,8 +552,6 @@ std::unique_ptr<const ParagraphLayouter::Line> FallbackParagraphLayout::NextLine

 			next_run = this->buffer_begin + iter->first;
 			begin = this->buffer;
-
-			last_space = nullptr;
 		}

 		if (IsWhitespace(c)) last_space = this->buffer;
@ -591,7 +589,7 @@ std::unique_ptr<const ParagraphLayouter::Line> FallbackParagraphLayout::NextLine
 		this->buffer++;
 	}

-	if (l->size() == 0 || last_char - begin != 0) {
+	if (l->size() == 0 || last_char - begin > 0) {
 		int w = l->GetWidth();
 		l->emplace_back(iter->second, begin, last_char - begin, w);
 	}
--- a/src/intro_gui.cpp
+++ b/src/intro_gui.cpp
@ -222,7 +222,7 @@ struct SelectGameWindow : public Window {
 		}

 		IntroGameViewportCommand &vc = intro_viewport_commands[this->cur_viewport_command_index];
-		Window *mw = FindWindowByClass(WC_MAIN_WINDOW);
+		Window *mw = GetMainWindow();
 		Viewport *vp = mw->viewport;

 		/* Early exit if the current command hasn't elapsed and isn't animated. */
--- a/src/lang/norwegian_bokmal.txt
+++ b/src/lang/norwegian_bokmal.txt
@ -2076,6 +2076,7 @@ STR_INTRO_TOOLTIP_HIGHSCORE                                     :{BLACK}Vise tav
 STR_INTRO_TOOLTIP_CONFIG_SETTINGS_TREE                          :{BLACK}Vis innstillinger
 STR_INTRO_TOOLTIP_NEWGRF_SETTINGS                               :{BLACK}Vis NewGRF-instillinger
 STR_INTRO_TOOLTIP_ONLINE_CONTENT                                :{BLACK}Se etter nytt og oppdatert innhold for nedlasting
+STR_INTRO_TOOLTIP_AI_SETTINGS                                   :{BLACK}Vis KI innstillinger
 STR_INTRO_TOOLTIP_QUIT                                          :{BLACK}Avslutt 'OpenTTD'

 STR_INTRO_BASESET                                               :{BLACK}Det valgte innebygde grafikksettet mangler {NUM} sprite{P "" r}. Se etter oppdateringer for settet.
--- a/src/linkgraph/linkgraph_gui.cpp
+++ b/src/linkgraph/linkgraph_gui.cpp
@ -721,7 +721,7 @@ LinkGraphLegendWindow::LinkGraphLegendWindow(WindowDesc *desc, int window_number
 {
 	this->InitNested(window_number);
 	this->InvalidateData(0);
-	this->SetOverlay(FindWindowById(WC_MAIN_WINDOW, 0)->viewport->overlay);
+	this->SetOverlay(GetMainWindow()->viewport->overlay);
 }

 /**
--- a/src/main_gui.cpp
+++ b/src/main_gui.cpp
@ -182,7 +182,7 @@ void FixTitleGameZoom(int zoom_adjust)
 {
 	if (_game_mode != GM_MENU) return;

-	Viewport *vp = FindWindowByClass(WC_MAIN_WINDOW)->viewport;
+	Viewport *vp = GetMainWindow()->viewport;

 	/* Adjust the zoom in/out.
 	 * Can't simply add, since operator+ is not defined on the ZoomLevel type. */
--- a/src/misc_cmd.cpp
+++ b/src/misc_cmd.cpp
@ -67,8 +67,10 @@ CommandCost CmdIncreaseLoan(TileIndex tile, DoCommandFlag flags, uint32 p1, uint
 			break;
 	}

-	/* Overflow protection */
-	if (c->money + c->current_loan + loan < c->money) return CMD_ERROR;
+	/* In case adding the loan triggers the overflow protection of Money,
+	 * we would essentially be losing money as taking and repaying the loan
+	 * immediately would not get us back to the same bank balance anymore. */
+	if (c->money > Money::max() - loan) return CMD_ERROR;

 	if (flags & DC_EXEC) {
 		c->money        += loan;
--- a/src/misc_gui.cpp
+++ b/src/misc_gui.cpp
@ -1340,7 +1340,7 @@ static WindowDesc _query_desc(
 */
 void ShowQuery(StringID caption, StringID message, Window *parent, QueryCallbackProc *callback)
 {
-	if (parent == nullptr) parent = FindWindowById(WC_MAIN_WINDOW, 0);
+	if (parent == nullptr) parent = GetMainWindow();

 	for (const Window *w : Window::IterateFromBack()) {
 		if (w->window_class != WC_CONFIRM_POPUP_QUERY) continue;
--- a/src/network/core/game_info.cpp
+++ b/src/network/core/game_info.cpp
@ -358,14 +358,14 @@ void DeserializeNetworkGameInfo(Packet *p, NetworkGameInfo *info, const GameInfo
 		}

 		case 4: {
-			GRFConfig **dst = &info->grfconfig;
-			uint i;
+			/* Ensure that the maximum number of NewGRFs and the field in the network
+			 * protocol are matched to eachother. If that is not the case anymore a
+			 * check must be added to ensure the received data is still valid. */
+			static_assert(std::numeric_limits<uint8>::max() == NETWORK_MAX_GRF_COUNT);
 			uint num_grfs = p->Recv_uint8();

-			/* Broken/bad data. It cannot have that many NewGRFs. */
-			if (num_grfs > NETWORK_MAX_GRF_COUNT) return;
-
-			for (i = 0; i < num_grfs; i++) {
+			GRFConfig **dst = &info->grfconfig;
+			for (uint i = 0; i < num_grfs; i++) {
 				NamedGRFIdentifier grf;
 				switch (newgrf_serialisation) {
 					case NST_GRFID_MD5:
--- a/src/network/network.cpp
+++ b/src/network/network.cpp
@ -649,6 +649,7 @@ void NetworkClose(bool close_admins)
 	delete[] _network_company_states;
 	_network_company_states = nullptr;
 	_network_company_server_id.clear();
+	_network_company_passworded = 0;

 	InitializeNetworkPools(close_admins);

--- a/src/network/network_gui.cpp
+++ b/src/network/network_gui.cpp
@ -2531,6 +2531,6 @@ void ShowNetworkAskRelay(const std::string &server_connection_string, const std:
 {
 	DeleteWindowByClass(WC_NETWORK_ASK_RELAY);

-	Window *parent = FindWindowById(WC_MAIN_WINDOW, 0);
+	Window *parent = GetMainWindow();
 	new NetworkAskRelayWindow(&_network_ask_relay_desc, parent, server_connection_string, relay_connection_string, token);
 }
--- a/src/network/network_server.cpp
+++ b/src/network/network_server.cpp
@ -1744,6 +1744,7 @@ static void NetworkAutoCleanCompanies()

 	if (!_network_dedicated) {
 		const NetworkClientInfo *ci = NetworkClientInfo::GetByClientID(CLIENT_ID_SERVER);
+		assert(ci != nullptr);
 		if (Company::IsValidID(ci->client_playas)) clients_in_company[ci->client_playas] = true;
 	}

@ -2135,6 +2136,7 @@ void NetworkServerDoMove(ClientID client_id, CompanyID company_id)
 	if (client_id == CLIENT_ID_SERVER && _network_dedicated) return;

 	NetworkClientInfo *ci = NetworkClientInfo::GetByClientID(client_id);
+	assert(ci != nullptr);

 	/* No need to waste network resources if the client is in the company already! */
 	if (ci->client_playas == company_id) return;
--- a/src/newgrf.cpp
+++ b/src/newgrf.cpp
@ -4306,7 +4306,6 @@ static ChangeInfoResult ObjectChangeInfo(uint id, int numinfo, int prop, const G
 				/* Swap classid because we read it in BE. */
 				uint32 classid = buf->ReadDWord();
 				(*ospec)->cls_id = ObjectClass::Allocate(BSWAP32(classid));
-				(*ospec)->enabled = true;
 				break;
 			}

@ -10857,7 +10856,7 @@ static void FinaliseObjectsArray()
 		ObjectSpec **&objectspec = file->objectspec;
 		if (objectspec != nullptr) {
 			for (int i = 0; i < NUM_OBJECTS_PER_GRF; i++) {
-				if (objectspec[i] != nullptr && objectspec[i]->grf_prop.grffile != nullptr && objectspec[i]->enabled) {
+				if (objectspec[i] != nullptr && objectspec[i]->grf_prop.grffile != nullptr && objectspec[i]->IsEnabled()) {
 					_object_mngr.SetEntitySpec(objectspec[i]);
 				}
 			}
--- a/src/newgrf_engine.cpp
+++ b/src/newgrf_engine.cpp
@ -658,6 +658,7 @@ static uint32 VehicleGetVariable(Vehicle *v, const VehicleScopeResolver *object,

 			{
 				const Vehicle *w = v->Next();
+				assert(w != nullptr);
 				uint16 altitude = ClampToU16(v->z_pos - w->z_pos); // Aircraft height - shadow height
 				byte airporttype = ATP_TTDP_LARGE;

--- a/src/newgrf_gui.cpp
+++ b/src/newgrf_gui.cpp
@ -1468,6 +1468,9 @@ private:
 				this->avails.push_back(c);
 			} else {
 				const GRFConfig *best = FindGRFConfig(c->ident.grfid, HasBit(c->flags, GCF_INVALID) ? FGCM_NEWEST : FGCM_NEWEST_VALID);
+				/* Never triggers; FindGRFConfig returns either c, or a newer version of c. */
+				assert(best != nullptr);
+
 				/*
 				 * If the best version is 0, then all NewGRF with this GRF ID
 				 * have version 0, so for backward compatibility reasons we
--- a/src/newgrf_object.cpp
+++ b/src/newgrf_object.cpp
@ -60,7 +60,7 @@ ObjectSpec _object_specs[NUM_OBJECTS];
 */
 bool ObjectSpec::IsEverAvailable() const
 {
-	return this->enabled && HasBit(this->climate, _settings_game.game_creation.landscape) &&
+	return this->IsEnabled() && HasBit(this->climate, _settings_game.game_creation.landscape) &&
 			(this->flags & ((_game_mode != GM_EDITOR && !_generating_world) ? OBJECT_FLAG_ONLY_IN_SCENEDIT : OBJECT_FLAG_ONLY_IN_GAME)) == 0;
 }

--- a/src/newgrf_object.h
+++ b/src/newgrf_object.h
@ -21,7 +21,7 @@
 #include "newgrf_commons.h"

 /** Various object behaviours. */
-enum ObjectFlags {
+enum ObjectFlags : uint16 {
 	OBJECT_FLAG_NONE               =       0, ///< Just nothing.
 	OBJECT_FLAG_ONLY_IN_SCENEDIT   = 1 <<  0, ///< Object can only be constructed in the scenario editor.
 	OBJECT_FLAG_CANNOT_REMOVE      = 1 <<  1, ///< Object can not be removed.
@ -62,7 +62,7 @@ static const uint8 OBJECT_SIZE_1X1 = 0x11; ///< The value of a NewGRF's size pro
 void ResetObjects();

 /** Class IDs for objects. */
-enum ObjectClassID {
+enum ObjectClassID : uint16 {
 	OBJECT_CLASS_BEGIN   =      0, ///< The lowest valid value
 	OBJECT_CLASS_MAX     = 0xFFFF, ///< Maximum number of classes.
 	INVALID_OBJECT_CLASS = 0xFFFF, ///< Class for the less fortunate.
@ -91,6 +91,7 @@ enum ObjectViewportMapType {
 struct ObjectSpec {
 	/* 2 because of the "normal" and "buy" sprite stacks. */
 	GRFFilePropsBase<2> grf_prop; ///< Properties related the the grf file
+	AnimationInfo animation;      ///< Information about the animation.
 	ObjectClassID cls_id;         ///< The class to which this spec belongs.
 	StringID name;                ///< The name for this object.

@ -103,15 +104,19 @@ struct ObjectSpec {
 	ObjectFlags flags;            ///< Flags/settings related to the object.
 	ObjectCtrlFlags ctrl_flags;   ///< Extra control flags.
 	uint8 edge_foundation[4];     ///< Edge foundation flags
-	AnimationInfo animation;      ///< Information about the animation.
 	uint16 callback_mask;         ///< Bitmask of requested/allowed callbacks.
 	uint8 height;                 ///< The height of this structure, in heightlevels; max MAX_TILE_HEIGHT.
 	uint8 views;                  ///< The number of views.
 	uint8 generate_amount;        ///< Number of objects which are attempted to be generated per 256^2 map during world generation.
-	bool enabled;                 ///< Is this spec enabled?
 	ObjectViewportMapType vport_map_type; ///< Viewport map type
 	uint16 vport_map_subtype;     ///< Viewport map subtype

+	/**
+	 * Test if this object is enabled.
+	 * @return True iif this object is enabled.
+	 */
+	bool IsEnabled() const { return this->views > 0; }
+
 	/**
 	 * Get the cost for building a structure of this type.
 	 * @return The cost for building.
--- a/src/object_cmd.cpp
+++ b/src/object_cmd.cpp
@ -578,7 +578,7 @@ static void DrawTile_Object(TileInfo *ti, DrawTileProcParams params)
 	int building_z_offset = 0;

 	/* Fall back for when the object doesn't exist anymore. */
-	if (!spec->enabled) {
+	if (!spec->IsEnabled()) {
 		type = OBJECT_TRANSMITTER;
 	} else if ((spec->flags & OBJECT_FLAG_HAS_NO_FOUNDATION) == 0) {
 		if (spec->ctrl_flags & OBJECT_CTRL_FLAG_EDGE_FOUNDATION) {
@ -1222,7 +1222,7 @@ static CommandCost TerraformTile_Object(TileIndex tile, DoCommandFlag flags, int
 					pre_success_checks();
 					return CommandCost(EXPENSES_CONSTRUCTION, _price[PR_BUILD_FOUNDATION]);
 				}
-			} else if (spec->enabled) {
+			} else if (spec->IsEnabled()) {
 				/* allow autoslope */
 				pre_success_checks();
 				return CommandCost(EXPENSES_CONSTRUCTION, _price[PR_BUILD_FOUNDATION]);
--- a/src/order_cmd.cpp
+++ b/src/order_cmd.cpp
@ -1778,6 +1778,7 @@ CommandCost CmdModifyOrder(TileIndex tile, DoCommandFlag flags, uint32 p1, uint3
 	if (sel_ord >= v->GetNumOrders()) return CMD_ERROR;

 	Order *order = v->GetOrder(sel_ord);
+	assert(order != nullptr);
 	switch (order->GetType()) {
 		case OT_GOTO_STATION:
 			if (mof != MOF_NON_STOP && mof != MOF_STOP_LOCATION && mof != MOF_UNLOAD && mof != MOF_LOAD && mof != MOF_CARGO_TYPE_UNLOAD && mof != MOF_CARGO_TYPE_LOAD && mof != MOF_RV_TRAVEL_DIR) return CMD_ERROR;
--- a/src/os/windows/font_win32.cpp
+++ b/src/os/windows/font_win32.cpp
@ -233,54 +233,29 @@ err1:
 }
 #endif /* WITH_FREETYPE */

-class FontList {
-protected:
-	wchar_t **fonts;
-	uint items;
-	uint capacity;
-
-public:
-	FontList() : fonts(nullptr), items(0), capacity(0) { };
-
-	~FontList() {
-		if (this->fonts == nullptr) return;
-
-		for (uint i = 0; i < this->items; i++) {
-			free(this->fonts[i]);
-		}
-
-		free(this->fonts);
-	}
-
-	bool Add(const wchar_t *font) {
-		for (uint i = 0; i < this->items; i++) {
-			if (wcscmp(this->fonts[i], font) == 0) return false;
-		}
+struct EFCParam {
+	FontCacheSettings *settings;
+	LOCALESIGNATURE  locale;
+	MissingGlyphSearcher *callback;
+	std::vector<std::wstring> fonts;

-		if (this->items == this->capacity) {
-			this->capacity += 10;
-			this->fonts = ReallocT(this->fonts, this->capacity);
+	bool Add(const std::wstring_view &font) {
+		for (const auto &entry : this->fonts) {
+			if (font.compare(entry) == 0) return false;
 		}

-		this->fonts[this->items++] = wcsdup(font);
+		this->fonts.emplace_back(font);

 		return true;
 	}
 };

-struct EFCParam {
-	FontCacheSettings *settings;
-	LOCALESIGNATURE  locale;
-	MissingGlyphSearcher *callback;
-	FontList fonts;
-};
-
 static int CALLBACK EnumFontCallback(const ENUMLOGFONTEX *logfont, const NEWTEXTMETRICEX *metric, DWORD type, LPARAM lParam)
 {
 	EFCParam *info = (EFCParam *)lParam;

 	/* Skip duplicates */
-	if (!info->fonts.Add((const wchar_t *)logfont->elfFullName)) return 1;
+	if (!info->Add(logfont->elfFullName)) return 1;
 	/* Only use TrueType fonts */
 	if (!(type & TRUETYPE_FONTTYPE)) return 1;
 	/* Don't use SYMBOL fonts */
@ -463,22 +438,9 @@ void Win32FontCache::ClearFontCache()
 	GLYPHMETRICS gm;
 	MAT2 mat = { {0, 1}, {0, 0}, {0, 0}, {0, 1} };

-	/* Make a guess for the needed memory size. */
-	DWORD size = this->glyph_size.cy * Align(aa ? this->glyph_size.cx : std::max(this->glyph_size.cx / 8l, 1l), 4); // Bitmap data is DWORD-aligned rows.
-	byte *bmp = AllocaM(byte, size);
-	size = GetGlyphOutline(this->dc, key, GGO_GLYPH_INDEX | (aa ? GGO_GRAY8_BITMAP : GGO_BITMAP), &gm, size, bmp, &mat);
-
-	if (size == GDI_ERROR) {
-		/* No dice with the guess. First query size of needed glyph memory, then allocate the
-		 * memory and query again. This dance is necessary as some glyphs will only render with
-		 * the exact matching size; e.g. the space glyph has no pixels and must be requested
-		 * with size == 0, anything else fails. Unfortunately, a failed call doesn't return any
-		 * info about the size and thus the triple GetGlyphOutline()-call. */
-		size = GetGlyphOutline(this->dc, key, GGO_GLYPH_INDEX | (aa ? GGO_GRAY8_BITMAP : GGO_BITMAP), &gm, 0, nullptr, &mat);
-		if (size == GDI_ERROR) usererror("Unable to render font glyph");
-		bmp = AllocaM(byte, size);
-		GetGlyphOutline(this->dc, key, GGO_GLYPH_INDEX | (aa ? GGO_GRAY8_BITMAP : GGO_BITMAP), &gm, size, bmp, &mat);
-	}
+	/* Call GetGlyphOutline with zero size initially to get required memory size. */
+	DWORD size = GetGlyphOutline(this->dc, key, GGO_GLYPH_INDEX | (aa ? GGO_GRAY8_BITMAP : GGO_BITMAP), &gm, 0, nullptr, &mat);
+	if (size == GDI_ERROR) usererror("Unable to render font glyph");

 	/* Add 1 scaled pixel for the shadow on the medium font. Our sprite must be at least 1x1 pixel. */
 	uint shadow = (this->fs == FS_NORMAL) ? ScaleGUITrad(1) : 0;
@ -488,6 +450,10 @@ void Win32FontCache::ClearFontCache()
 	/* Limit glyph size to prevent overflows later on. */
 	if (width > MAX_GLYPH_DIM || height > MAX_GLYPH_DIM) usererror("Font glyph is too large");

+	/* Call GetGlyphOutline again with size to actually render the glyph. */
+	byte *bmp = AllocaM(byte, size);
+	GetGlyphOutline(this->dc, key, GGO_GLYPH_INDEX | (aa ? GGO_GRAY8_BITMAP : GGO_BITMAP), &gm, size, bmp, &mat);
+
 	/* GDI has rendered the glyph, now we allocate a sprite and copy the image into it. */
 	SpriteLoader::Sprite sprite;
 	sprite.AllocateData(ZOOM_LVL_NORMAL, width * height);
--- a/src/saveload/afterload.cpp
+++ b/src/saveload/afterload.cpp
@ -266,6 +266,8 @@ static void InitializeWindowsAndCaches()
 	UpdateAllVirtCoords();
 	ResetViewportAfterLoadGame();

+	ScriptObject::InitializeRandomizers();
+
 	for (Company *c : Company::Iterate()) {
 		/* For each company, verify (while loading a scenario) that the inauguration date is the current year and set it
 		 * accordingly if it is not the case.  No need to set it on companies that are not been used already,
--- a/src/saveload/misc_sl.cpp
+++ b/src/saveload/misc_sl.cpp
@ -36,18 +36,16 @@ ZoomLevel _saved_scrollpos_zoom;

 void SaveViewportBeforeSaveGame()
 {
-	const Window *w = FindWindowById(WC_MAIN_WINDOW, 0);
+	const Window *w = GetMainWindow();

-	if (w != nullptr) {
-		_saved_scrollpos_x = w->viewport->scrollpos_x;
-		_saved_scrollpos_y = w->viewport->scrollpos_y;
-		_saved_scrollpos_zoom = w->viewport->zoom;
-	}
+	_saved_scrollpos_x = w->viewport->scrollpos_x;
+	_saved_scrollpos_y = w->viewport->scrollpos_y;
+	_saved_scrollpos_zoom = w->viewport->zoom;
 }

 void ResetViewportAfterLoadGame()
 {
-	Window *w = FindWindowById(WC_MAIN_WINDOW, 0);
+	Window *w = GetMainWindow();

 	w->viewport->scrollpos_x = _saved_scrollpos_x;
 	w->viewport->scrollpos_y = _saved_scrollpos_y;
--- a/src/saveload/vehicle_sl.cpp
+++ b/src/saveload/vehicle_sl.cpp
@ -497,14 +497,16 @@ void AfterLoadVehicles(bool part_of_load)
 					v->GetImage(v->direction, EIT_ON_MAP, &v->sprite_seq);
 					v->UpdateSpriteSeqBound();

-					/* The plane's shadow will have the same image as the plane, but no colour */
+					/* The aircraft's shadow will have the same image as the aircraft, but no colour */
 					Vehicle *shadow = v->Next();
+					if (shadow == nullptr) SlErrorCorrupt("Missing shadow for aircraft");
 					shadow->sprite_seq.CopyWithoutPalette(v->sprite_seq);
 					shadow->sprite_seq_bounds = v->sprite_seq_bounds;

 					/* In the case of a helicopter we will update the rotor sprites */
 					if (v->subtype == AIR_HELICOPTER) {
 						Vehicle *rotor = shadow->Next();
+						if (rotor == nullptr) SlErrorCorrupt("Missing rotor for helicopter");
 						GetRotorImage(Aircraft::From(v), EIT_ON_MAP, &rotor->sprite_seq);
 						rotor->UpdateSpriteSeqBound();
 					}
--- a/src/screenshot.cpp
+++ b/src/screenshot.cpp
@ -759,7 +759,7 @@ void SetupScreenshotViewport(ScreenshotType t, Viewport *vp, uint32 width, uint3
 		case SC_CRASHLOG: {
 			assert(width == 0 && height == 0);

-			Window *w = FindWindowById(WC_MAIN_WINDOW, 0);
+			Window *w = GetMainWindow();
 			vp->virtual_left   = w->viewport->virtual_left;
 			vp->virtual_top    = w->viewport->virtual_top;
 			vp->virtual_width  = w->viewport->virtual_width;
@ -810,7 +810,7 @@ void SetupScreenshotViewport(ScreenshotType t, Viewport *vp, uint32 width, uint3
 		default: {
 			vp->zoom = (t == SC_ZOOMEDIN) ? _settings_client.gui.zoom_min : ZOOM_LVL_VIEWPORT;

-			Window *w = FindWindowById(WC_MAIN_WINDOW, 0);
+			Window *w = GetMainWindow();
 			vp->virtual_left   = w->viewport->virtual_left;
 			vp->virtual_top    = w->viewport->virtual_top;

--- a/src/script/api/script_base.cpp
+++ b/src/script/api/script_base.cpp
@ -10,17 +10,12 @@
 #include "../../stdafx.h"
 #include "script_base.hpp"
 #include "script_error.hpp"
-#include "../../network/network.h"
-#include "../../core/random_func.hpp"

 #include "../../safeguards.h"

 /* static */ uint32 ScriptBase::Rand()
 {
-	/* We pick RandomRange if we are in SP (so when saved, we do the same over and over)
-	 *   but we pick InteractiveRandomRange if we are a network_server or network-client. */
-	if (_networking) return ::InteractiveRandom();
-	return ::Random();
+	return ScriptObject::GetRandomizer().Next();
 }

 /* static */ uint32 ScriptBase::RandItem(int unused_param)
@ -30,10 +25,7 @@

 /* static */ uint ScriptBase::RandRange(uint max)
 {
-	/* We pick RandomRange if we are in SP (so when saved, we do the same over and over)
-	 *   but we pick InteractiveRandomRange if we are a network_server or network-client. */
-	if (_networking) return ::InteractiveRandomRange(max);
-	return ::RandomRange(max);
+	return ScriptObject::GetRandomizer().Next(max);
 }

 /* static */ uint32 ScriptBase::RandRangeItem(int unused_param, uint max)
--- a/src/script/api/script_base.hpp
+++ b/src/script/api/script_base.hpp
@ -18,9 +18,6 @@
 *
 * @note The random functions are not called Random and RandomRange, because
 *        RANDOM_DEBUG does some tricky stuff, which messes with those names.
- * @note In MP we cannot use Random because that will cause desyncs (scripts are
- *        ran on the server only, not on all clients). This means that
- *        we use InteractiveRandom in MP. Rand() takes care of this for you.
 */
 class ScriptBase : public ScriptObject {
 public:
--- a/src/script/api/script_company.cpp
+++ b/src/script/api/script_company.cpp
@ -93,9 +93,10 @@
 	EnforcePrecondition(false, gender == GENDER_MALE || gender == GENDER_FEMALE);
 	EnforcePrecondition(false, GetPresidentGender(ScriptCompany::COMPANY_SELF) != gender);

+	Randomizer &randomizer = ScriptObject::GetRandomizer();
 	CompanyManagerFace cmf;
-	GenderEthnicity ge = (GenderEthnicity)((gender == GENDER_FEMALE ? (1 << ::GENDER_FEMALE) : 0) | (::InteractiveRandom() & (1 << ETHNICITY_BLACK)));
-	RandomCompanyManagerFaceBits(cmf, ge, false);
+	GenderEthnicity ge = (GenderEthnicity)((gender == GENDER_FEMALE ? (1 << ::GENDER_FEMALE) : 0) | (randomizer.Next() & (1 << ETHNICITY_BLACK)));
+	RandomCompanyManagerFaceBits(cmf, ge, false, randomizer);

 	return ScriptObject::DoCommand(0, 0, cmf, CMD_SET_COMPANY_MANAGER_FACE);
 }
--- a/src/script/api/script_gamesettings.cpp
+++ b/src/script/api/script_gamesettings.cpp
@ -26,6 +26,7 @@
 	if (!IsValid(setting)) return -1;

 	const SettingDesc *sd = GetSettingFromName(setting);
+	assert(sd != nullptr);
 	return sd->AsIntSetting()->Read(&_settings_game);
 }

@ -34,6 +35,7 @@
 	if (!IsValid(setting)) return false;

 	const SettingDesc *sd = GetSettingFromName(setting);
+	assert(sd != nullptr);

 	if ((sd->flags & SF_NO_NETWORK_SYNC) != 0) return false;

--- a/src/script/api/script_industrytype.cpp
+++ b/src/script/api/script_industrytype.cpp
@ -9,6 +9,7 @@

 #include "../../stdafx.h"
 #include "script_industrytype.hpp"
+#include "script_base.hpp"
 #include "script_map.hpp"
 #include "script_error.hpp"
 #include "../../strings_func.h"
@ -120,8 +121,8 @@
 	EnforcePrecondition(false, CanBuildIndustry(industry_type));
 	EnforcePrecondition(false, ScriptMap::IsValidTile(tile));

-	uint32 seed = ::InteractiveRandom();
-	uint32 layout_index = ::InteractiveRandomRange((uint32)::GetIndustrySpec(industry_type)->layouts.size());
+	uint32 seed = ScriptBase::Rand();
+	uint32 layout_index = ScriptBase::RandRange((uint32)::GetIndustrySpec(industry_type)->layouts.size());
 	return ScriptObject::DoCommand(tile, (1 << 16) | (layout_index << 8) | industry_type, seed, CMD_BUILD_INDUSTRY);
 }

@ -129,7 +130,7 @@
 {
 	EnforcePrecondition(false, CanProspectIndustry(industry_type));

-	uint32 seed = ::InteractiveRandom();
+	uint32 seed = ScriptBase::Rand();
 	return ScriptObject::DoCommand(0, industry_type, seed, CMD_BUILD_INDUSTRY);
 }

--- a/src/script/api/script_object.cpp
+++ b/src/script/api/script_object.cpp
@ -395,3 +395,19 @@ ScriptObject::ActiveInstance::~ActiveInstance()

 	NOT_REACHED();
 }
+
+
+/* static */ Randomizer ScriptObject::random_states[OWNER_END];
+
+Randomizer &ScriptObject::GetRandomizer(Owner owner)
+{
+	return ScriptObject::random_states[owner];
+}
+
+void ScriptObject::InitializeRandomizers()
+{
+	Randomizer random = _random;
+	for (Owner owner = OWNER_BEGIN; owner < OWNER_END; owner++) {
+		ScriptObject::GetRandomizer(owner).SetSeed(random.Next());
+	}
+}
--- a/src/script/api/script_object.hpp
+++ b/src/script/api/script_object.hpp
@ -13,6 +13,7 @@
 #include "../../misc/countedptr.hpp"
 #include "../../road_type.h"
 #include "../../rail_type.h"
+#include "../../core/random_func.hpp"

 #include "script_types.hpp"
 #include "../script_suspend.hpp"
@ -67,6 +68,18 @@ public:
 	 */
 	static class ScriptInstance *GetActiveInstance();

+	/**
+	 * Get a reference of the randomizer that brings this script random values.
+	 * @param owner The owner/script to get the randomizer for. This defaults to ScriptObject::GetRootCompany()
+	 */
+	static Randomizer &GetRandomizer(Owner owner = ScriptObject::GetRootCompany());
+
+	/**
+	 * Initialize/reset the script random states. The state of the scripts are
+	 * based on the current _random seed, but _random does not get changed.
+	 */
+	static void InitializeRandomizers();
+
 protected:
 	/**
 	 * Executes a raw DoCommand for the script.
@ -315,6 +328,8 @@ private:
 	 * @param story_page_id The new StoryPageID.
 	 */
 	static void SetNewStoryPageElementID(StoryPageElementID story_page_element_id);
+
+	static Randomizer random_states[OWNER_END]; ///< Random states for each of the scripts (game script uses OWNER_DEITY)
 };

 #endif /* SCRIPT_OBJECT_HPP */
--- a/src/script/api/script_order.cpp
+++ b/src/script/api/script_order.cpp
@ -67,6 +67,7 @@ static const Order *ResolveOrder(VehicleID vehicle_id, ScriptOrder::OrderPositio
 		if (order_position == ScriptOrder::ORDER_INVALID) return nullptr;
 	}
 	const Order *order = v->GetFirstOrder();
+	assert(order != nullptr);
 	while (order->GetType() == OT_IMPLICIT) order = order->next;
 	while (order_position > 0) {
 		order_position = (ScriptOrder::OrderPosition)(order_position - 1);
@ -91,6 +92,7 @@ static int ScriptOrderPositionToRealOrderPosition(VehicleID vehicle_id, ScriptOr

 	int res = (int)order_position;
 	const Order *order = v->orders->GetFirstOrder();
+	assert(order != nullptr);
 	for (; order->GetType() == OT_IMPLICIT; order = order->next) res++;
 	while (order_position > 0) {
 		order_position = (ScriptOrder::OrderPosition)(order_position - 1);
@ -136,6 +138,7 @@ static int ScriptOrderPositionToRealOrderPosition(VehicleID vehicle_id, ScriptOr
 	if (!IsValidVehicleOrder(vehicle_id, order_position)) return false;

 	const Order *order = ::Vehicle::Get(vehicle_id)->GetOrder(ScriptOrderPositionToRealOrderPosition(vehicle_id, order_position));
+	assert(order != nullptr);
 	return order->GetType() == OT_CONDITIONAL;
 }

@ -145,6 +148,7 @@ static int ScriptOrderPositionToRealOrderPosition(VehicleID vehicle_id, ScriptOr
 	if (!IsValidVehicleOrder(vehicle_id, order_position)) return false;

 	const Order *order = ::ResolveOrder(vehicle_id, order_position);
+	assert(order != nullptr);
 	return order->GetType() == OT_DUMMY;
 }

@ -176,6 +180,7 @@ static int ScriptOrderPositionToRealOrderPosition(VehicleID vehicle_id, ScriptOr
 	if (order_position == ORDER_CURRENT) {
 		int cur_order_pos = ::Vehicle::Get(vehicle_id)->cur_real_order_index;
 		const Order *order = ::Vehicle::Get(vehicle_id)->GetFirstOrder();
+		assert(order != nullptr);
 		int num_implicit_orders = 0;
 		for (int i = 0; i < cur_order_pos; i++) {
 			if (order->GetType() == OT_IMPLICIT) num_implicit_orders++;
--- a/src/script/api/script_town.cpp
+++ b/src/script/api/script_town.cpp
@ -303,7 +303,7 @@
 		EnforcePreconditionCustomError(false, ::Utf8StringLength(text) < MAX_LENGTH_TOWN_NAME_CHARS, ScriptError::ERR_PRECONDITION_STRING_TOO_LONG);
 	}
 	uint32 townnameparts;
-	if (!GenerateTownName(&townnameparts)) {
+	if (!GenerateTownName(ScriptObject::GetRandomizer(), &townnameparts)) {
 		ScriptController::DecreaseOps(50000);
 		ScriptObject::SetLastError(ScriptError::ERR_NAME_IS_NOT_UNIQUE);
 		return false;
--- a/src/script/api/script_window.cpp
+++ b/src/script/api/script_window.cpp
@ -46,6 +46,7 @@
 	if (colour != TC_INVALID && (::TextColour)colour >= ::TC_END) return;

 	Window *w = FindWindowById((::WindowClass)window, number);
+	assert(w != nullptr);

 	if (widget == WIDGET_ALL) {
 		if (colour != TC_INVALID) return;
--- a/src/script/script_config.cpp
+++ b/src/script/script_config.cpp
@ -11,6 +11,7 @@
 #include "../settings_type.h"
 #include "../core/random_func.hpp"
 #include "script_info.hpp"
+#include "api/script_object.hpp"
 #include "../textfile_gui.h"
 #include "../string_func.h"

@ -35,7 +36,7 @@ void ScriptConfig::Change(const char *name, int version, bool force_exact_match,
 		 *  for the Script that have the random flag to a random value. */
 		for (const auto &item : *this->info->GetConfigList()) {
 			if (item.flags & SCRIPTCONFIG_RANDOM) {
-				this->SetSetting(item.name, InteractiveRandomRange(item.max_value + 1 - item.min_value) + item.min_value);
+				this->SetSetting(item.name, ScriptObject::GetRandomizer(OWNER_NONE).Next(item.max_value + 1 - item.min_value) + item.min_value);
 			}
 		}

@ -157,7 +158,7 @@ void ScriptConfig::AddRandomDeviation()
 {
 	for (const auto &item : *this->GetConfigList()) {
 		if (item.random_deviation != 0) {
-			this->SetSetting(item.name, InteractiveRandomRange(item.random_deviation * 2 + 1) - item.random_deviation + this->GetSetting(item.name));
+			this->SetSetting(item.name, ScriptObject::GetRandomizer(OWNER_NONE).Next(item.random_deviation * 2 + 1) - item.random_deviation + this->GetSetting(item.name));
 		}
 	}
 }
--- a/src/smallmap_gui.cpp
+++ b/src/smallmap_gui.cpp
@ -969,7 +969,7 @@ void SmallMapWindow::DrawTowns(const DrawPixelInfo *dpi) const
 void SmallMapWindow::DrawMapIndicators() const
 {
 	/* Find main viewport. */
-	const Viewport *vp = FindWindowById(WC_MAIN_WINDOW, 0)->viewport;
+	const Viewport *vp = GetMainWindow()->viewport;

 	Point upper_left_smallmap_coord  = InverseRemapCoords2(vp->virtual_left, vp->virtual_top);
 	Point lower_right_smallmap_coord = InverseRemapCoords2(vp->virtual_left + vp->virtual_width - 1, vp->virtual_top + vp->virtual_height - 1);
@ -1461,7 +1461,7 @@ int SmallMapWindow::GetPositionOnLegend(Point pt)
 			if (click_count > 0) this->mouse_capture_widget = widget;

 			const NWidgetBase *wid = this->GetWidget<NWidgetBase>(WID_SM_MAP);
-			Window *w = FindWindowById(WC_MAIN_WINDOW, 0);
+			Window *w = GetMainWindow();
 			int sub;
 			pt = this->PixelToTile(pt.x - wid->pos_x, pt.y - wid->pos_y, &sub);
 			ScrollWindowTo(this->scroll_x + pt.x * TILE_SIZE, this->scroll_y + pt.y * TILE_SIZE, -1, w);
@ -1732,7 +1732,7 @@ void SmallMapWindow::SetNewScroll(int sx, int sy, int sub)
 */
 void SmallMapWindow::SmallMapCenterOnCurrentPos()
 {
-	const Viewport *vp = FindWindowById(WC_MAIN_WINDOW, 0)->viewport;
+	const Viewport *vp = GetMainWindow()->viewport;
 	Point viewport_center = InverseRemapCoords2(vp->virtual_left + vp->virtual_width / 2, vp->virtual_top + vp->virtual_height / 2);

 	int sub;
@ -2024,7 +2024,7 @@ void ShowSmallMap()
 */
 bool ScrollMainWindowTo(int x, int y, int z, bool instant)
 {
-	bool res = ScrollWindowTo(x, y, z, FindWindowById(WC_MAIN_WINDOW, 0), instant);
+	bool res = ScrollWindowTo(x, y, z, GetMainWindow(), instant);

 	/* If a user scrolls to a tile (via what way what so ever) and already is on
 	 * that tile (e.g.: pressed twice), move the smallmap to that location,
--- a/src/table/object_land.h
+++ b/src/table/object_land.h
@ -121,7 +121,7 @@ static const DrawTileSprites _object_hq[] = {

 #undef TILE_SPRITE_LINE

-#define M(name, size, build_cost_multiplier, clear_cost_multiplier, height, climate, gen_amount, flags) { GRFFilePropsBase<2>(), INVALID_OBJECT_CLASS, name, climate, size, build_cost_multiplier, clear_cost_multiplier, 0, MAX_DAY + 1, flags, OBJECT_CTRL_FLAG_NONE, {0, 0, 0, 0}, {0, 0, 0, 0}, 0, height, 1, gen_amount, true, OVMT_DEFAULT, 0 }
+#define M(name, size, build_cost_multiplier, clear_cost_multiplier, height, climate, gen_amount, flags) { GRFFilePropsBase<2>(), {0, 0, 0, 0}, INVALID_OBJECT_CLASS, name, climate, size, build_cost_multiplier, clear_cost_multiplier, 0, MAX_DAY + 1, flags, OBJECT_CTRL_FLAG_NONE, {0, 0, 0, 0}, 0, height, 1, gen_amount, OVMT_DEFAULT, 0 }

 /* Climates
 * T = Temperate
--- a/src/timetable_cmd.cpp
+++ b/src/timetable_cmd.cpp
@ -36,6 +36,7 @@
 static void ChangeTimetable(Vehicle *v, VehicleOrderID order_number, uint32 val, ModifyTimetableFlags mtf, bool timetabled, bool ignore_lock = false)
 {
 	Order *order = v->GetOrder(order_number);
+	assert(order != nullptr);
 	int total_delta = 0;
 	int timetable_delta = 0;

--- a/src/toolbar_gui.cpp
+++ b/src/toolbar_gui.cpp
@ -904,7 +904,7 @@ static CallBackFunction MenuClickShowAir(int index)

 static CallBackFunction ToolbarZoomInClick(Window *w)
 {
-	if (DoZoomInOutWindow(ZOOM_IN, FindWindowById(WC_MAIN_WINDOW, 0))) {
+	if (DoZoomInOutWindow(ZOOM_IN, GetMainWindow())) {
 		w->HandleButtonClick((_game_mode == GM_EDITOR) ? (byte)WID_TE_ZOOM_IN : (byte)WID_TN_ZOOM_IN);
 		if (_settings_client.sound.click_beep) SndPlayFx(SND_15_BEEP);
 	}
@ -915,7 +915,7 @@ static CallBackFunction ToolbarZoomInClick(Window *w)

 static CallBackFunction ToolbarZoomOutClick(Window *w)
 {
-	if (DoZoomInOutWindow(ZOOM_OUT, FindWindowById(WC_MAIN_WINDOW, 0))) {
+	if (DoZoomInOutWindow(ZOOM_OUT, GetMainWindow())) {
 		w->HandleButtonClick((_game_mode == GM_EDITOR) ? (byte)WID_TE_ZOOM_OUT : (byte)WID_TN_ZOOM_OUT);
 		if (_settings_client.sound.click_beep) SndPlayFx(SND_15_BEEP);
 	}
@ -2196,7 +2196,7 @@ struct MainToolbarWindow : Window {
 	void OnInvalidateData(int data = 0, bool gui_scope = true) override
 	{
 		if (!gui_scope) return;
-		if (FindWindowById(WC_MAIN_WINDOW, 0) != nullptr) HandleZoomMessage(this, FindWindowById(WC_MAIN_WINDOW, 0)->viewport, WID_TN_ZOOM_IN, WID_TN_ZOOM_OUT);
+		HandleZoomMessage(this, GetMainWindow()->viewport, WID_TN_ZOOM_IN, WID_TN_ZOOM_OUT);
 	}

 	static HotkeyList hotkeys;
@ -2577,7 +2577,7 @@ struct ScenarioEditorToolbarWindow : Window {
 	void OnInvalidateData(int data = 0, bool gui_scope = true) override
 	{
 		if (!gui_scope) return;
-		if (FindWindowById(WC_MAIN_WINDOW, 0) != nullptr) HandleZoomMessage(this, FindWindowById(WC_MAIN_WINDOW, 0)->viewport, WID_TE_ZOOM_IN, WID_TE_ZOOM_OUT);
+		HandleZoomMessage(this, GetMainWindow()->viewport, WID_TE_ZOOM_IN, WID_TE_ZOOM_OUT);
 	}

 	void OnQueryTextFinished(char *str) override
--- a/src/town_cmd.cpp
+++ b/src/town_cmd.cpp
@ -2546,7 +2546,7 @@ bool GenerateTowns(TownLayout layout)
 		bool city = (_settings_game.economy.larger_towns != 0 && Chance16(1, _settings_game.economy.larger_towns));
 		IncreaseGeneratingWorldProgress(GWP_TOWN);
 		/* Get a unique name for the town. */
-		if (!GenerateTownName(&townnameparts, &town_names)) continue;
+		if (!GenerateTownName(_random, &townnameparts, &town_names)) continue;
 		/* try 20 times to create a random-sized town for the first loop. */
 		if (CreateRandomTown(20, townnameparts, TSZ_RANDOM, city, layout) != nullptr) current_number++; // If creation was successful, raise a flag.
 	} while (--total);
@ -2560,7 +2560,7 @@ bool GenerateTowns(TownLayout layout)

 	/* If current_number is still zero at this point, it means that not a single town has been created.
 	 * So give it a last try, but now more aggressive */
-	if (GenerateTownName(&townnameparts) &&
+	if (GenerateTownName(_random, &townnameparts) &&
 			CreateRandomTown(10000, townnameparts, TSZ_RANDOM, _settings_game.economy.larger_towns != 0, layout) != nullptr) {
 		return true;
 	}
--- a/src/town_gui.cpp
+++ b/src/town_gui.cpp
@ -1323,7 +1323,7 @@ public:

 	void RandomTownName()
 	{
-		this->townnamevalid = GenerateTownName(&this->townnameparts);
+		this->townnamevalid = GenerateTownName(_interactive_random, &this->townnameparts);

 		if (!this->townnamevalid) {
 			this->townname_editbox.text.DeleteAll();
--- a/src/townname.cpp
+++ b/src/townname.cpp
@ -112,11 +112,12 @@ bool VerifyTownName(uint32 r, const TownNameParams *par, TownNames *town_names)

 /**
 * Generates valid town name.
+ * @param randomizer the source of random data for generating the name
 * @param townnameparts if a name is generated, it's stored there
 * @param town_names if a name is generated, check its uniqueness with the set
 * @return true iff a name was generated
 */
-bool GenerateTownName(uint32 *townnameparts, TownNames *town_names)
+bool GenerateTownName(Randomizer &randomizer, uint32 *townnameparts, TownNames *town_names)
 {
 	TownNameParams par(_settings_game.game_creation.town_name);

@ -130,7 +131,7 @@ bool GenerateTownName(uint32 *townnameparts, TownNames *town_names)
 	 * the other towns may take considerable amount of time (10000 is
 	 * too much). */
 	for (int i = 1000; i != 0; i--) {
-		uint32 r = _generating_world ? Random() : InteractiveRandom();
+		uint32 r = randomizer.Next();
 		if (!VerifyTownName(r, &par, town_names)) continue;

 		*townnameparts = r;
--- a/src/townname_func.h
+++ b/src/townname_func.h
@ -10,12 +10,13 @@
 #ifndef TOWNNAME_FUNC_H
 #define TOWNNAME_FUNC_H

+#include "core/random_func.hpp"
 #include "townname_type.h"

 char *GenerateTownNameString(char *buf, const char *last, size_t lang, uint32 seed);
 char *GetTownName(char *buff, const TownNameParams *par, uint32 townnameparts, const char *last);
 char *GetTownName(char *buff, const Town *t, const char *last);
 bool VerifyTownName(uint32 r, const TownNameParams *par, TownNames *town_names = nullptr);
-bool GenerateTownName(uint32 *townnameparts, TownNames *town_names = nullptr);
+bool GenerateTownName(Randomizer &randomizer, uint32 *townnameparts, TownNames *town_names = nullptr);

 #endif /* TOWNNAME_FUNC_H */
--- a/src/tree_cmd.cpp
+++ b/src/tree_cmd.cpp
@ -457,6 +457,7 @@ void RemoveAllTrees()
 */
 uint PlaceTreeGroupAroundTile(TileIndex tile, TreeType treetype, uint radius, uint count, bool set_zone)
 {
+	dbg_assert(_game_mode == GM_EDITOR); // Due to InteractiveRandom being used in this function
 	dbg_assert(treetype < TREE_TOYLAND + TREE_COUNT_TOYLAND);
 	const bool allow_desert = treetype == TREE_CACTUS;
 	uint planted = 0;
--- a/src/vehicle_cmd.cpp
+++ b/src/vehicle_cmd.cpp
@ -479,6 +479,7 @@ static CommandCost RefitVehicle(Vehicle *v, bool only_this, uint8 num_vehicles,
 			u->cargo_subtype = result.subtype;
 			if (u->type == VEH_AIRCRAFT) {
 				Vehicle *w = u->Next();
+				assert(w != nullptr);
 				w->refit_cap = std::min<uint16>(w->refit_cap, result.mail_capacity);
 				w->cargo_cap = result.mail_capacity;
 				if (w->cargo.TotalCount() > w->refit_cap) w->cargo.Truncate(w->cargo.TotalCount() - w->refit_cap);
--- a/src/vehicle_gui.cpp
+++ b/src/vehicle_gui.cpp
@ -3878,7 +3878,7 @@ public:
 				if (_ctrl_pressed) {
 					ShowExtraViewportWindow(TileVirtXY(v->x_pos, v->y_pos));
 				} else {
-					const Window *mainwindow = FindWindowById(WC_MAIN_WINDOW, 0);
+					const Window *mainwindow = GetMainWindow();
 					if (click_count > 1 && mainwindow->viewport->zoom < ZOOM_LVL_DRAW_MAP) {
 						/* main window 'follows' vehicle */
 						mainwindow->viewport->follow_vehicle = v->index;
@ -3949,8 +3949,8 @@ public:
 	{
 		/* If the hotkey is not for any widget in the UI (i.e. for honking) */
 		if (hotkey == WID_VV_HONK_HORN) {
-			const Window* mainwindow = FindWindowById(WC_MAIN_WINDOW, 0);
-			const Vehicle* v = Vehicle::Get(window_number);
+			const Window *mainwindow = GetMainWindow();
+			const Vehicle *v = Vehicle::Get(window_number);
 			/* Only play the sound if we're following this vehicle */
 			if (mainwindow->viewport->follow_vehicle == v->index) {
 				v->PlayLeaveStationSound(true);
@ -4185,8 +4185,8 @@ bool VehicleClicked(const GUIVehicleGroup &vehgroup)

 void StopGlobalFollowVehicle(const Vehicle *v)
 {
-	Window *w = FindWindowById(WC_MAIN_WINDOW, 0);
-	if (w != nullptr && w->viewport->follow_vehicle == v->index) {
+	Window *w = GetMainWindow();
+	if (w->viewport->follow_vehicle == v->index) {
 		ScrollMainWindowTo(v->x_pos, v->y_pos, v->z_pos, true); // lock the main view on the vehicle's last position
 		w->viewport->follow_vehicle = INVALID_VEHICLE;
 	}
--- a/src/viewport_gui.cpp
+++ b/src/viewport_gui.cpp
@ -68,7 +68,7 @@ public:
 		Point pt;
 		if (tile == INVALID_TILE) {
 			/* No tile? Use center of main viewport. */
-			const Window *w = FindWindowById(WC_MAIN_WINDOW, 0);
+			const Window *w = GetMainWindow();

 			/* center on same place as main window (zoom is maximum, no adjustment needed) */
 			pt.x = w->viewport->scrollpos_x + w->viewport->virtual_width / 2;
@ -101,7 +101,7 @@ public:
 			case WID_EV_ZOOM_OUT: DoZoomInOutWindow(ZOOM_OUT, this); break;

 			case WID_EV_MAIN_TO_VIEW: { // location button (move main view to same spot as this view) 'Paste Location'
-				Window *w = FindWindowById(WC_MAIN_WINDOW, 0);
+				Window *w = GetMainWindow();
 				int x = this->viewport->scrollpos_x; // Where is the main looking at
 				int y = this->viewport->scrollpos_y;

@ -113,7 +113,7 @@ public:
 			}

 			case WID_EV_VIEW_TO_MAIN: { // inverse location button (move this view to same spot as main view) 'Copy Location'
-				const Window *w = FindWindowById(WC_MAIN_WINDOW, 0);
+				const Window *w = GetMainWindow();
 				int x = w->viewport->scrollpos_x;
 				int y = w->viewport->scrollpos_y;

--- a/src/water.h
+++ b/src/water.h
@ -40,6 +40,7 @@ void MakeWaterKeepingClass(TileIndex tile, Owner o);
 void CheckForDockingTile(TileIndex t);

 bool RiverModifyDesertZone(TileIndex tile, void *data);
+void MakeRiverAndModifyDesertZoneAround(TileIndex tile);
 static const uint RIVER_OFFSET_DESERT_DISTANCE = 5; ///< Circular tile search radius to create non-desert around a river tile.

 bool IsWateredTile(TileIndex tile, Direction from);
--- a/src/water_cmd.cpp
+++ b/src/water_cmd.cpp
@ -446,6 +446,18 @@ bool RiverModifyDesertZone(TileIndex tile, void *)
 	return false;
 }

+/**
+ * Make a river tile and remove desert directly around it.
+ * @param tile The tile to change into river and create non-desert around
+ */
+void MakeRiverAndModifyDesertZoneAround(TileIndex tile) {
+	MakeRiver(tile, Random());
+	MarkTileDirtyByTile(tile);
+
+	/* Remove desert directly around the river tile. */
+	CircularTileSearch(&tile, RIVER_OFFSET_DESERT_DISTANCE, RiverModifyDesertZone, nullptr);
+}
+
 /**
 * Build a piece of canal.
 * @param tile end tile of stretch-dragging
--- a/src/window.cpp
+++ b/src/window.cpp
@ -1191,6 +1191,18 @@ Window *FindWindowByClass(WindowClass cls)
 	return nullptr;
 }

+/**
+ * Get the main window, i.e. FindWindowById(WC_MAIN_WINDOW, 0).
+ * If the main window is not available, this function will trigger an assert.
+ * @return Pointer to the main window.
+ */
+Window *GetMainWindow()
+{
+	Window *w = FindWindowById(WC_MAIN_WINDOW, 0);
+	assert(w != nullptr);
+	return w;
+}
+
 /**
 * Delete a window by its class and window number (if it is open).
 * @param cls Window class
@ -2550,7 +2562,7 @@ static EventState HandleViewportScroll()
 		return ES_NOT_HANDLED;
 	}

-	if (_last_scroll_window == FindWindowById(WC_MAIN_WINDOW, 0) && _last_scroll_window->viewport->follow_vehicle != INVALID_VEHICLE) {
+	if (_last_scroll_window == GetMainWindow() && _last_scroll_window->viewport->follow_vehicle != INVALID_VEHICLE) {
 		/* If the main window is following a vehicle, then first let go of it! */
 		const Vehicle *veh = Vehicle::Get(_last_scroll_window->viewport->follow_vehicle);
 		ScrollMainWindowTo(veh->x_pos, veh->y_pos, veh->z_pos, true); // This also resets follow_vehicle
@ -2922,7 +2934,7 @@ const std::chrono::milliseconds TIME_BETWEEN_DOUBLE_CLICK(500); ///< Time betwee
 static void ScrollMainViewport(int x, int y)
 {
 	if (_game_mode != GM_MENU && _game_mode != GM_BOOTSTRAP) {
-		Window *w = FindWindowById(WC_MAIN_WINDOW, 0);
+		Window *w = GetMainWindow();
 		assert(w);

 		w->viewport->dest_scrollpos_x += ScaleByZoom(x, w->viewport->zoom);
--- a/src/window_func.h
+++ b/src/window_func.h
@ -16,6 +16,7 @@

 Window *FindWindowById(WindowClass cls, WindowNumber number);
 Window *FindWindowByClass(WindowClass cls);
+Window *GetMainWindow();
 void ChangeWindowOwner(Owner old_owner, Owner new_owner);

 void ResizeWindow(Window *w, int x, int y, bool clamp_to_screen = true);