Lua in SpringRTS/Callouts

Callouts are just functions defined in Spring that you can run at any point. The difference between callins and callouts is that callins are practically event invokers while callouts are functions that are ready to be used by you. The nature of callous is exactly the same with any function. They can return values, they can change values or both. Keep in mind that the synced/unsynced theory should still be taken in consideration.
Trying for example to change the value of a game parameter via a callout in a widget is not permitted.

Example of callout:

teamID=Spring.GetUnitTeam(unitID)

In the above example we pass unitID as an argument to function GetUnitTeam(). GetUnitTeam returns the ID of the team which we store to our variable(teamID).

Callout name	Description	Synced mode	Unsynced mode	Arguments	Return values
Spring.AddGrass				x, y, z	nil
Spring.AddHeightMap	can only be called in SetHeightMapFunc			x, z, height	nil number newHeight
Spring.AddSmoothMesh	can only be called in SetSmoothMeshFunc			x, z, height	nil number newHeight
Spring.AddTeamResource				teamID, resourceName, resourceAmount	nil
Spring.AddUnitDamage				unitID, damageAmount [, number paralyze = 0 [, attackerID = -1 [, weaponID = -1[, impulse_x [, impulse_y [, impulse_z ]]] ]]]	nil
Spring.AddUnitImpulse				unitID, x, y, z	nil
Spring.AddUnitResource				unitID, resourceName, resourceAmount	nil
Spring.AddUnitSeismicPing				unitID, pingSize	nil
Spring.AdjustHeightMap				x1, z1 [, x2, z2], height	nil
Spring.AdjustSmoothMesh				x1, z1 [, x2, z2], height	nil
Spring.CallCOBScript				unitID, funcID string funcName, number retArgs, COBArg1, COBArg2, ...	number returnValue, number retArg1, number retArg2, ...
Spring.CallCOBScriptCB	broken in 0.78.2.1; will be removed with the introduction of Lua as COB replacement			funcName, number retArgs, COBArg1, COBArg2, ...	number returnValue, number CallbackData, number retArg1, number retArg2, ...
Spring.CreateFeature				defName featureID, x, y, z[,number heading [, allyTeamID ]]	featureID
Spring.CreateUnit	offmap positions are clamped! you still can use MoveCtrl todo so			number unitDefID, x, y, z, number facing string "facing", teamID, [boolean build = false]	unitID,
Spring.DestroyFeature				featureID	nil
Spring.DestroyUnit				unitID, [boolean selfd = false,], [boolean reclaimed = false,], [number attackerID]	nil
Spring.EditUnitCmdDesc		Yes	No	unitID, number cmdDescID, table cmdArray	nil
Spring.GameOver	Will declare game over. New in version 0.83.x			[ [1] = allyTeamID1, [2] = allyTeamID2, .. ]	nil
Spring.GetCOBScriptID				unitID, funcName	funcID
Spring.GetUnitCOBValue				unitID, [, boolean splitData=false], number COBValue[, number param1 [,number param2 [, number param3 [, number param4 ] ] ] ]	number result1, number result2
Spring.GiveOrderArrayToUnitArray				unitArray = { [1] = unitID, etc... },orderArray = {{ number cmdID,{number, etc...}, params{"alt", "ctrl", "shift", "right"} options}, ..}	nil
Spring.GiveOrderArrayToUnitMap				unitMap = { [unitID] = dontCare, etc... }, orderArray = {{ number cmdID,{number, etc...}, params{"alt", "ctrl", "shift", "right"} options}, ..}	nil
Spring.GiveOrderToUnit				unitID, number cmdID, params = {number, etc...}, options = {"alt", "ctrl", "shift", "right"}	nil
Spring.GiveOrderToUnitArray				unitArray = { [1] = unitID, etc... },number cmdID,params = {number, etc...},options = {"alt", "ctrl", "shift", "right"}	nil
Spring.GiveOrderToUnitMap				unitMap = { [unitID] = dontCare, etc... },number cmdID,params = {number, etc...},options = {"alt", "ctrl", "shift", "right"}	nil
Spring.InsertUnitCmdDesc				unitID, [, number cmdDescID ] , table cmdArray	nil
Spring.KillTeam	Will declare a team to be dead. New in version 0.83.x			teamID	nil
Spring.LevelHeightMap				x1, z1 [, x2, z2], height	nil
Spring.LevelSmoothMesh				x1, z1 [, x2, z2], height	nil
Spring.RemoveBuildingDecal				unitID,	nil
Spring.RemoveGrass				x, y, z	nil
Spring.RemoveUnitCmdDesc				unitID, [, number cmdDescID ]	nil
Spring.RevertHeightMap				x1, z1 [, x2, z2], number origFactor	nil
Spring.RevertSmoothMesh				x1, z1 [, x2, z2], number origFactor	nil
Spring.SetExperienceGrade				number expGrade[, number ExpPowerScale [, number ExpHealthScale [, number ExpReloadScale ]]]	nil
Spring.SetFeatureAlwaysVisible				featureID, boolean enable	nil
Spring.SetFeatureCollisionVolumeData				featureID, number scaleX, number scaleY, number scaleZ, number offsetX, number offsetY, number offsetX, number vType, number tType, number Axis	nil
Spring.SetFeatureDirection				featureID, x, y, z	nil
Spring.SetFeatureHealth				featureID, number health	nil
Spring.SetFeatureNoSelect				featureID, boolean noSelect	nil
Spring.SetFeaturePosition				featureID, x, y, z [, boolean snapToGround]	nil
Spring.SetFeatureReclaim				featureID, number reclaimLeft	nil
Spring.SetFeatureResurrect				string facing ]	nil
Spring.SetHeightMap	can only be called in SetHeightMapFunc			x, z, number height [,number terraform = 1]	number absHeightDiff
Spring.SetHeightMapFunc				lua_function [, arg1 ,[ arg2 [, ... ] ]	number absTotalHeightMapAmountChanged
Spring.SetMapSquareTerrainType				x, z, int newType	int oldType
Spring.SetNoPause				boolean noPause	nil
Spring.SetProjectileCEG				number projID, string ceg_name	nil
Spring.SetProjectileCollision				number projID	nil
Spring.SetProjectileGravity				number projID [, number grav = 0]	nil
Spring.SetProjectileMoveControl	disables engine movecontrol, so lua can fully control the physics			number projID, boolean enable	nil
Spring.SetProjectilePosition				number projID [, number x = 0 [, number y = 0 [, number z = 0 ]]]	nil
Spring.SetProjectileSpinAngle				number projID [, number spinAngle = 0]	nil
Spring.SetProjectileSpinSpeed				number projID [, number speed = 0]	nil
Spring.SetProjectileSpinVec				number projID [, number x = 0 [, number y = 0 [, number z = 0]]]	nil
Spring.SetProjectileVelocity				number projID [, number x = 0 [, number y = 0 [, number z = 0 ]]]	nil
Spring.SetSmoothMesh can only be called in SetSmoothMeshFunc				x, z, number height [,number terraform = 1]	number absHeightDiff
Spring.SetSmoothMeshFunc				lua_function [, arg1 ,[ arg2 [, ... ] ]	number absTotalHeightMapAmountChanged
Spring.SetTeamResource				teamID, string resource, number amount	nil
Spring.SetTeamShareLevel				"energy", number amount	nil
Spring.SetTerrainTypeData				int typeIndex[, number speedTanks = nil ][, number speedKBOTs = nil ][, number speedHovers = nil ][, number speedShips = nil ]	boolean true
Spring.SetUnitAlwaysVisible				unitID, boolean alwaysVisible	nil
Spring.SetUnitArmored				unitID, boolean armored	nil
Spring.SetUnitBlocking				unitID, boolean blocking [, boolean collide ]	nil
Spring.SetUnitBuildSpeed				number builderID, number buildSpeed, [ number repairSpeed [, number reclaimSpeed [,number resurrectSpeed [, number captureSpeed [, number terraformSpeed ]] ]]]	nil
Spring.SetUnitCOBValue				unitID, number COBValue, number param1 [,number param2]	nil
Spring.SetUnitCloak				number scriptCloak, [ number decloakDistance | boolean decloakAbs ]	nil
Spring.SetUnitCollisionVolumeData				unitID, number scaleX, number scaleY, number scaleZ, number offsetX, number offsetY, number offsetX, number vType, number tType, number Axis	nil
Spring.SetUnitCosts				unitID, { [ buildTime = number amount ], [ metalCost = number amount ], [ energyCost = number amount ]}	nil
Spring.SetUnitExperience				unitID, number experience	nil
Spring.SetUnitFlanking				unitID, string "mode", number mode	nil
Spring.SetUnitFuel				unitID, number fuel	nil
Spring.SetUnitHealth				{ [ health = number health ],[ capture = number capture ],[ paralyze = number paralyze ],[ build = number build ] }	nil
Spring.SetUnitLineage	Removed from version 0.83.x			unitID, number teamID [, boolean isRoot]	nil
Spring.SetUnitLosMask				table losTypes	nil
Spring.SetUnitLosState				table losTypes	nil
Spring.SetUnitMaxHealth				unitID, number maxHealth	nil
Spring.SetUnitMetalExtraction				unitID, number depth [,number range]	nil
Spring.SetUnitMoveGoal	used by default commands to get in build-,attackrange etc.			unitID, x, y, z, [, number radius = 0 [, number speed = unit] ]	nil
Spring.SetUnitNeutral				unitID, boolean neutral	nil
Spring.SetUnitPhysics				unitIDnumber posx, number posy, number posz,number velx, number vely, number velz,number rotx, number roty, number rotz,	nil
Spring.SetUnitPieceCollisionVolumeData				unitID, number pieceIndex, boolean affectLocal, boolean affectGlobal, boolean enableLocal, boolean enableGlobal, number scaleX, number scaleY, number scaleZ, number offsetX, number offsetY, number offsetZ, number vType, number Axis	nil
Spring.SetUnitPosition				unitID, x, number z [, boolean alwaysAboveSea]	nil
Spring.SetUnitResourcing				unitID, resourceName, resourceAmount unitID, resourceName=resourceAmount	nil
Spring.SetUnitRotation				unitID, number rotx, number roty, number rotz	nil
Spring.SetUnitSensorRadius				unitID, string type, number radius	number newRadius
Spring.SetUnitShieldState				unitID, [, number weaponID = -1] [, boolean enabled] [, number power]	nil
Spring.SetUnitSonarStealth				unitID, boolean sonarStealth	nil
Spring.SetUnitStealth				unitID, boolean stealth	nil
Spring.SetUnitStockpile				unitID, [, number stockpile [, number buildPercent ]]	nil
Spring.SetUnitTarget				x, y, z, [ boolean dgun = false ]	nil
Spring.SetUnitToFeature				boolean tofeature	nil
Spring.SetUnitTooltip				unitID, string "tooltip"	nil
Spring.SetUnitTravel				unitID, number travel [, number travelPeriod]	nil
Spring.SetUnitVelocity				unitID, number velx, number vely, number velz	nil
Spring.SetUnitWeaponState				table states	nil
Spring.ShareTeamResource	0.82 and later			number teamID_src, number teamID_recv, resource, number amount	nil
Spring.SpawnCEG				string "cegname", number posX = 0, number posY = 0, number posZ = 0, number dirX = 0, number dirY = 0, number dirZ = 0, number radius = 0, number damage = 0	nil
Spring.TransferFeature				featureID number teamID	nil
Spring.TransferUnit				unitID, numer newTeamID,[boolean given = true]	nil
Spring.UseTeamResource				{ metal = number amount, energy = number amount}	boolean hadEnough
Spring.UseUnitResource				unitID, resourceName, resourceAmount unitID, resourceName = resourceAmount}	boolean success
Spring.GetAllyTeamList					{ [1] = number allyTeamID, etc... }