Inter-script Communication

Inter-script communication (ISC) allows scripts to communicate with each other, mainly by calling functions in the scripts themselves. It can also be used as a more powerful and intuitive alternative to the registry.

knCall(script: enum | lightuserdata, function: string, [...]): [...]

Call a function in another script, returning its result. The script should either be one of KN_MENU, KN_MOVIE, KN_HUD, or a pointer to a script’s lua_State as a light userdata. The function should be a string naming the function to call. The arguments that will be passed to the function should follow.

If there is an error, it will be raised as a Lua error. This includes an invalid script being specified, the scene containing the target script not being loaded, the function not being found, and the called function itself raising its own error.

There are some notable caveats to the current implementation:

• Integers will be cast to floats due to Lua not exposing any way of telling the difference between an integer and a number.

• Values of the types function, userdata, and thread cannot be copied between scripts and will be replaced by ``nil``.

knOwnHandle(): lightuserdata

Returns a pointer to the script’s lua_State pointer as a light userdata. This is useful for informing “master” scripts like the menu or HUD of room and obstacle scripts via knCall(), so that they themselves can use knCall to call directly into your script.

Examples

Using knCall()

In hud/main.lua:

function addPoints(pts)
    points = points + pts
    return points
end

In obstacles/customtop.lua:

function tick()
    if not mgIsCleared() then
        if mgBodyIsBroken(body) then
            local points = knCall(KN_HUD, "addPoints", 3)
        end
    end
end

Using knOwnHandle()

-- Assume that informCreated(script) and informDestroyed(script) tell the HUD
-- script that these obstacle/room scripts have been created and destroyed,
-- respectively.

-- In obstacle/myobstacle.lua
function init()
    knCall(KN_HUD, "informCreated", knOwnHandle())
end

function shutdown()
    knCall(KN_HUD, "informDestroyed", knOwnHandle())
end

function isCleared()
    return mgIsCleared()
end

-- In hud/main.lua
function draw()
    -- ... maybe in a loop ...
    if knCall(obstacle, "isCleared") then
        -- ... do something interesting! ...
    end
end