MG/Lua

Glest versions 3.2.0 and newer includes lua scripting functionality for scripted scenarios.

The game includes 2 tutorial scenarios and one scripted normal scenario(storming) now. These demo scenarios show a bit what's possible now. Have a look at them if you want to learn it.

Useful Links

Lua/XML Intermixture Problem

Due to XML's nature of using angle brackets for elements the parser will get confused and give an error if you try to use the left angle bracket in the scenario's XML file.

A solution is to either swap the logic:

ie. if you wanted,
a <= b
you would have to do,
b >= a

Or use an external lua file as mentioned in the next section.

Loading a Lua File

To run Lua code in an external file you use the dofile function and provide the file path from the executable.

Example:

dofile("gae_scenarios/Tutorials/basic_tutorial/startup.lua")

Language System

Each scenario is stored in its own folder. In this folder should be an xml file of the same name as the folder with xml as the extension. Glest also looks for a lng file (scenario_name_english.lng as default) to allow for translations of text.

Example

In advanced_tutorial.xml is :
showMessage('MagicBrief', 'GlestAdvancedTutorial')

In advanced_tutorial_english.lng is :
MagicBrief=You are in command of the Magic faction, which uses mages and summoned creatures to fight.

Coordinates

Coordinates are specified as an array of two elements, the 'x' coordinate in the first element, and the 'y' coordinate in the second.

The origin {0,0} is at the 'top left' (or north-west if you like) of the screen. A map's size is defined in 'Tiles', each of which is a block of 2x2 Cells. For technical reasons the last row & column of Tiles are not valid. So a 64 * 64 map is (64-1)*2 = 126 Cells wide and high. The co-ordinates you supply in LUA are Cell coordinates, not Tile coordinates, and are 'zero indexed' (the first one is 0, the last is NumCells - 1).

eg. A 128 x 128 Map has 254 x 254 Cells. The northwest corner is {0,0} and the southeast corner is {253,253}.

When a function returns a 'Vec2i' you can access the individual co-ordinates by sub-scripting the array,

myPos = someFunction () 
x = myPos[1]
y = myPos[2]

When ever there is a parameter requiring positions of type Vec2i you can use the format {x,y} (where x and y are number values within the required range, as defined above) to select a position on the map.

someFunction ( {x,y} )

Here 'x' and 'y' could be numbers, variables, or 'expressions'.

You can also pass a 'pre created' array to these functions, which may be useful for scripting advanced scenarios.

Faction Index and Players

You need to specify the players like:

<players>
	<player control="human" faction="tech" team="1"/>
	<player control="cpu" faction="magic" team="2"/>
	<player control="closed"/>
	<player control="closed"/>		
</players>

The first player's factionIndex is 0. The second player's factionIndex is 1 and so on. There must be exactly 4 player tags.

Commands

WARNING: All of these functions return type void and should not be used as arguments for other functions.

showMessage ( text, header )

Displays a message box on the screen, that will have to be dismissed by the player.

Parameters:
text - a string identifying the text from a language file
header - a string identifying the title bar text from a language file

setDisplayText ( text )

Displays a message at the top of the 'playing area'. Will remain until dismissed with clearDisplayText() or setDisplayText() is called again.

Parameters:
text - a string identifying the text from a language file

clearDisplayText ()

Clears the message from the top of the playing area, previously set with setDisplayText().

setCameraPosition ( pos )

Move the camera to the coordinates of pos.

Parameters:
pos - an array of two elements, specifying the co-ordinates {x,y}

createUnit ( unit, faction, pos )

Spawns a unit. If pos is occupied a nearby cell will be chosen. The game attempts to keep a 2 cell 'border' between the new unit and other units or objects (ie. trees). Warning: If a position can not be found, the game crashes.

Parameters:
unit - name of a unit in the loaded factions.
faction - the index of the faction this unit will belong to.
pos - an array of two elements, specifying the co-ordinates {x,y}

giveResource ( resource, faction, amount )

Give an amount of a specified resource to a player, negative values are valid and have the obvious effect.
Parameters:
resource - a corresponding resource in the tech tree
faction - the index of the faction to give the resource
amount - the amount of resource the faction will receive

givePositionCommand ( unitId, command, pos )

Instruct a unit to carry out a command of type 'attack' or 'move'.

Parameters:
unitId - the id of a unit that has an attack and/or move command.
command - the type of command to carry out ('attack' or 'move')
pos - an array of two elements, specifying the co-ordinates {x,y}

giveProductionCommand ( unitId, produced )

Instruct a unit to carry out a command of type 'produce'.

Parameters:
unitId - the id of a unit that is to produce the new unit.
produced - the type of unit to create. (ie. "worker")

giveUpgradeCommand ( unitId, upgrade )

Instruct a unit to carry out a command of type 'upgrade'.

Parameters:
unitId - the id of the unit to perform the upgrade.
upgrade - the type of upgrade to perform. (ie. "hell_gate")

setPlayerAsWinner ( faction )

Sets the player with index 'faction' as the winner, would typically be followed by endGame().

Parameters:
faction - the index of the faction [0-3, Player1=0]

endGame ()

End the scenario, usually would be called after setPlayerAsWinner() when victory conditions have been met.

DisplayFormattedText (const char *fmt,...)

Displays a message at the top of the 'playing area'. Will remain until dismissed with clearDisplayText() or setDisplayText() is called again.

Parameters: fmt - a string identifying the format of text (like in printf) ... - variable parameter list to pass values to fmt (like in printf)