en Lua

Lua

Setting up

You can choose to use the Lua programming language for any of your projects. Open your project settings tab, click "Show advanced options" and select Lua as Programming Language.

Your Lua microStudio project can be exported to any target (HTML5, Windows, Mac, Linux, Android...). You can also use any of the rendering APIs for 2D or 3D, as well as any of the proposed optional libs.

Tips

Calling object methods

Be careful when calling object functions (methods) in Lua, you have to use : instead of . as in:

screen:clear()
screen:drawSprite("icon",x,y,50)

Checking user inputs

User inputs can be scanned in microStudio by checking fields in keyboard, touch, mouse or gamepad interfaces. For example, to check if the key A is pressed, you can check keyboard.A. This field can actually have 3 different statuses:

• if you haven't pressed A yet in the current session, keyboard.A is undefined
• keyboard.A is equal to 1 (true in microScript) if you are currently pressing it
• keyboard.A is equal to 0 (false in microScript) if have pressed it before and are not currently pressing it

To check for such fields in Lua, it is recommended to check equality with 1:

  if keyboard.A == 1 then
    -- do something when A is pressed
  end

Instanciating classes

Especially when using alternative graphics libs or optional libs, you may have to instantiate JavaScript objects as if you were using the new operator in JavaScript. To do this, simply call new(class, arguments) on the class you want to instantiate:

  light = new( BABYLON.HemisphericLight, "light", BABYLON.Vector3.new(0, 1, 0), scene)

Passing JavaScript Objects as parameters

The Fengari Lua Virtual Machine does not convert Lua tables into JavaScript Objects. Analogous to the above section, there may be times (such as when using alternative graphics libs as also mentioned above) when the Javascript alternative library requires a JavaScript Object as a parameter and substituting a Lua table won't work. For example, the Babylon.js library debug scene inspector allows the programmer to pass an JavaScript Object to customize the debug scene inspector display to display the inspector as an overlay on the screen:

Passing a Lua table like this will not work:

scene.debugLayer.show({overlay = true})

Instead, create a new JavaScript Object and set each of the key:value pairs in the Javascript Object as follows:

debugOption = new(js.global.Object)
debugOption["overlay"] = true
scene.debugLayer:show(debugOption)

Simple Example

init = function()
  x = 0
  y = 0
end

update = function()
  if keyboard.LEFT == 1 then x = x-1 end
  if keyboard.RIGHT == 1 then x = x+1 end
  if keyboard.UP == 1 then y = y+1 end
  if keyboard.DOWN == 1 then y = y-1 end
end

draw = function()
  screen:clear()
  screen:drawSprite("icon",x,y,50)
end