Here is a list of all documented functions, variables, defines, enums, and typedefs with links to the documentation:

### - i -

- I2A : tgp.cpp
- I2H : tgp.cpp
- IACT_MAPGENERATION : newgrf_industries.h
- IACT_RANDOMCREATION : newgrf_industries.h
- IACT_USERCREATION : newgrf_industries.h
- IConsoleAddSorted : console.cpp
- IConsoleAliasExec() : console.cpp
- IConsoleAliasGet() : console.cpp , console.h
- IConsoleAliasRegister() : console.cpp , console.h
- IConsoleCmdExec() : console.cpp , console.h
- IConsoleCmdGet() : console.cpp , console.h
- IConsoleCmdHookAdd() : console.cpp , console.h
- IConsoleCmdProc : console.h
- IConsoleCmdRegister() : console.cpp , console.h
- IConsoleCopyInParams() : console.cpp
- IConsoleDebug() : console.cpp , console.h
- IConsoleError() : console.cpp , console.h
- IConsoleHistoryAdd() : console.cpp
- IConsoleHistoryNavigate() : console.cpp
- IConsoleHook : console.h
- IConsoleHookAdd() : console.cpp
- IConsoleHookHandle() : console.cpp
- IConsolePrint() : console.h , console.cpp
- IConsolePrintF() : console.cpp , console.h
- IConsoleVarExec() : console.cpp
- IConsoleVarGet() : console.cpp , console.h
- IConsoleVarGetStringValue() : console.cpp
- IConsoleVarGetValue() : console.cpp
- IConsoleVarHookAdd() : console.cpp , console.h
- IConsoleVarPrintGetValue() : console.cpp , console.h
- IConsoleVarPrintSetValue() : console.cpp , console.h
- IConsoleVarProcAdd() : console.cpp , console.h
- IConsoleVarRegister() : console.cpp , console.h
- IConsoleVarSetStringvalue() : console.cpp
- IConsoleVarSetValue() : console.cpp
- IConsoleVarStringRegister() : console.cpp , console.h
- IConsoleWarning() : console.cpp , console.h
- ICT_MAP_GENERATION : industry.h
- ICT_NORMAL_GAMEPLAY : industry.h
- ICT_SCENARIO_EDITOR : industry.h
- ICT_UNKNOWN : industry.h
- IgnoredPCP : elrail_data.h
- IGT_LIST : settings_internal.h
- IGT_VARIABLES : settings_internal.h
- IncHouseConstructionTick() : town_map.h
- IncIndustryTypeCount() : industry.h
- InclinedFoundation() : slope_func.h
- InclinedSlope() : slope_func.h
- IncreaseBuildingCount() : newgrf_house.cpp , newgrf_house.h
- IncreaseGeneratingWorldProgress() : genworld.h , genworld_gui.cpp
- increaseIndex() : news_gui.cpp
- IncreasePlayerFaceBits() : player_face.h
- INDUSTRY_COMPLETED : industry.h
- INDUSTRY_TRIGGER_256_TICKS : newgrf_industries.h
- INDUSTRY_TRIGGER_CARGO_DELIVERY : newgrf_industries.h
- INDUSTRY_TRIGGER_TILELOOP_PROCESS : newgrf_industries.h
- IndustryAvailabilityCallType : newgrf_industries.h
- INDUSTRYBEH_AFTER_1960 : industry.h
- INDUSTRYBEH_AI_AIRSHIP_ROUTES : industry.h
- INDUSTRYBEH_AIRPLANE_ATTACKS : industry.h
- INDUSTRYBEH_BEFORE_1950 : industry.h
- INDUSTRYBEH_BUILT_ONWATER : industry.h
- INDUSTRYBEH_CAN_SUBSIDENCE : industry.h
- INDUSTRYBEH_CANCLOSE_LASTINSTANCE : industry.h
- INDUSTRYBEH_CHOPPER_ATTACKS : industry.h
- INDUSTRYBEH_CUT_TREES : industry.h
- INDUSTRYBEH_DONT_INCR_PROD : industry.h
- INDUSTRYBEH_NOBUILT_MAPCREATION : industry.h
- INDUSTRYBEH_ONLY_INTOWN : industry.h
- INDUSTRYBEH_ONLY_NEARTOWN : industry.h
- INDUSTRYBEH_PLANT_FIELDS : industry.h
- INDUSTRYBEH_PLANT_ON_BUILT : industry.h
- INDUSTRYBEH_PROD_MULTI_HNDLING : industry.h
- INDUSTRYBEH_PRODCALLBACK_RANDOM : industry.h
- INDUSTRYBEH_TOWN1200_MORE : industry.h
- IndustryBehaviour : industry.h
- IndustryCallbackMask : newgrf_callbacks.h
- IndustryConstructionType : industry.h
- IndustryDirectoryWidgets : industry_gui.cpp
- IndustryGetVariable() : newgrf_industries.cpp , newgrf_industries.h
- INDUSTRYLIFE_BLACK_HOLE : industry.h
- INDUSTRYLIFE_EXTRACTIVE : industry.h
- INDUSTRYLIFE_ORGANIC : industry.h
- INDUSTRYLIFE_PROCESSING : industry.h
- IndustryLifeType : industry.h
- IndustryProductionCallback() : newgrf_industries.cpp , newgrf_industries.h
- INDUSTRYTILE_NOANIM : industry.h
- IndustryTileCallbackMask : newgrf_callbacks.h
- IndustryTrigger : newgrf_industries.h
- IndustryViewWidgets : industry_gui.cpp
- ini_alloc() : settings.cpp
- ini_getgroup() : settings.cpp
- ini_getitem() : settings.cpp
- ini_group_alloc() : settings.cpp
- ini_load() : settings.cpp
- ini_load_setting_list() : settings.cpp
- ini_load_settings() : settings.cpp
- ini_save() : settings.cpp
- ini_save_setting_list() : settings.cpp
- ini_save_settings() : settings.cpp
- IniGroupType : settings_internal.h
- init_BinaryHeap() : queue.cpp , queue.h
- init_Hash() : queue.cpp , queue.h
- init_InsSort() : queue.cpp , queue.h
- InitializeAnimatedTiles() : functions.h , texteff.cpp
- InitializeDisasterVehicle() : disaster_cmd.cpp
- InitializeLanguagePacks() : strings.cpp , strings_func.h
- InitializeSigns() : misc.cpp , signs.cpp
- InitializeTextBuffer() : misc_gui.cpp , textbuf_gui.h
- InitializeUnicodeGlyphMap() : fontcache.cpp
- InitializeWindowsAndCaches() : openttd.cpp
- InitLoading() : oldloader.cpp
- InitNewsItemStructs() : news_gui.cpp , news.h
- InitQuickTimeIfNeeded() : qtmidi.cpp
- InsertTextBufferChar() : misc_gui.cpp
- InsertTextBufferClipboard() : os2.cpp , textbuf_gui.h , unix.cpp , win32.cpp
- int_noise() : tgp.cpp
- interpolated_noise() : tgp.cpp
- IntToReference() : saveload.cpp
- INVALID_DIAGDIR : direction_type.h
- INVALID_DIR : direction_type.h
- INVALID_INDUSTRYTILE : industry.h
- INVALID_INDUSTRYTYPE : industry.h
- INVALID_OWNER : player_type.h
- INVALID_PLAYER : player_type.h
- INVALID_RAILTYPE : rail_type.h
- INVALID_RAILTYPES : rail_type.h
- INVALID_ROADTYPE : road_type.h
- INVALID_ROADTYPES : road_type.h
- INVALID_TILE : tile_type.h
- INVALID_TRACK : track_type.h
- INVALID_TRACK_BIT : track_type.h
- INVALID_TRACKDIR : track_type.h
- INVALID_TRACKDIR_BIT : track_type.h
- InvalidateAutoreplaceWindow() : autoreplace_gui.cpp , autoreplace_gui.h
- InvalidateVehicleOrder() : order.h , order_cmd.cpp
- IS_CUSTOM_SPRITE : sprite.h
- IS_PALETTE_COLOR : gfx_type.h
- IsAllGroupID() : group.h
- IsArticulatedPart() : train.h
- IsBridge() : bridge_map.h
- IsBridgeAbove() : bridge_map.h
- IsBridgeTile() : bridge_map.h
- IsClearGround() : clear_map.h
- IsCloseToTown() : town_cmd.cpp
- IsCompanyHQ() : unmovable_map.h
- IsCompatibleRail() : rail.h
- IsDepotTile() : depot.h
- IsDiagonalTrack() : track_func.h
- IsDiagonalTrackdir() : track_func.h
- IsEngineBuildable() : engine.h , engine.cpp
- IsEngineCountable() : vehicle.cpp
- IsFoundation() : slope_func.h
- IsFreeWagon() : train.h
- IsFrontEngine() : train.h
- IsGenerateWorldThreaded() : genworld.cpp , genworld.h
- IsGeneratingWorld() : genworld.h
- IsGeneratingWorldAborted() : genworld.cpp , genworld.h
- IsGeneratingWorldReadyForPaint() : genworld.h , genworld.cpp
- IsGoodGRFConfigList() : newgrf_config.cpp , newgrf_config.h
- IsHalftileSlope() : slope_func.h
- IsHangar() : station_map.h , station_cmd.cpp
- IsHouseCompleted() : town_map.h
- IsInclinedFoundation() : slope_func.h
- IsInclinedSlope() : slope_func.h
- IsIndustryCompleted() : industry_map.h
- IsInsideBS() : math_func.hpp
- IsInsideMM() : math_func.hpp
- IsLeveledFoundation() : slope_func.h
- IsMultiheaded() : train.h
- IsNeighborRoadTile() : town_cmd.cpp
- IsNonContinuousFoundation() : slope_func.h
- IsNormalAircraft() : aircraft.h
- iso_codes : newgrf_text.cpp
- IsOwnedLand() : unmovable_map.h
- IsOwnedLandTile() : unmovable_map.h
- IsPlainRailTile() : rail_map.h
- IsPossibleCrossing() : road_map.h
- IsRailDepot() : rail_map.h
- IsRailWaypoint() : rail_map.h
- IsRearDualheaded() : train.h
- IsReversingRoadTrackdir() : track_func.h
- IsRoadAllowedHere() : town_cmd.cpp
- IsSignalPresent() : rail_map.h
- IsSlopeWithOneCornerRaised() : slope_func.h
- IsSlopeWithThreeCornersRaised() : slope_func.h
- IsSnowLineSet() : landscape.h
- IsSpecialRailFoundation() : slope_func.h
- IsStatue() : unmovable_map.h
- IsStatueTile() : unmovable_map.h
- IsSteepSlope() : slope_func.h
- IsStraightRoadTrackdir() : track_func.h
- IsTileDepotType() : depot.h
- IsTileOwner() : tile_map.h
- IsTileType() : tile_map.h
- IsTrainEngine() : train.h
- IsTrainWagon() : train.h
- IsTransmitterTile() : unmovable_map.h
- IsTransparencySet() : transparency.h
- IsTunnel() : tunnel_map.h
- IsTunnelInWay() : tunnel_map.cpp , tunnel_map.h
- IsTunnelInWayDir() : tunnel_map.h , tunnel_map.cpp
- IsTunnelTile() : tunnel_map.h
- IsUphillTrackdir() : track_func.h
- IsValidAxis() : direction_func.h
- IsValidChar() : string.cpp , string_func.h
- IsValidCommand() : command.cpp , command_func.h
- IsValidCorner() : slope_func.h
- IsValidDiagDirection() : direction_func.h
- IsValidDirection() : direction_func.h
- IsValidIndustryID() : industry.h
- IsValidPlayerFace() : players.cpp , player_face.h
- IsValidRoadType() : road_func.h
- IsValidSearchPath() : fileio.h
- IsValidTile() : tile_map.h
- IsValidTownID() : town.h
- IsValidTrack() : track_func.h
- IsValidTrackdir() : track_func.h
- IsValidVehicleID() : vehicle_base.h
- IsValidXY() : tgp.cpp
- IsVehicleRefitable() : vehicle_gui.cpp
- IsVehicleServiceIntervalEnabled() : vehicle_gui.cpp
- IsWater() : water_map.h
- IsWateredTile() : water_cmd.cpp
- IsWhitespace() : string_func.h
- ItemAtT() : dbg_helpers.h