Hey Skaruts, I'm not sure what you are trying to do with Love2D, but I thought
this might interest you so I'll paste it here.
It's a demo using the Love API via the Lua VM:
# main.nim
# -- a bunch of glue code to get lua working --
type
luacfunc = proc(luaState: pointer): cint
luaL_reg = object
name: cstring
function: luacfunc
luaL_reg_ref = ref luaL_reg
luaL_reg_list = array[3, luaL_reg]
proc reg(name: cstring, function: luacfunc): luaL_reg_ref =
new result
result.name = name
result.function = function
const luaGlobalsIndex = -10002
const luaRegistryIndex = -10000
var luaState: pointer
proc luaL_ref(lua_State: pointer, t: cint): cint {.importc: "luaL_ref".}
proc luaL_openlib(luaState: pointer, name: cstring, lib: luaL_reg_list,
someval: cint) {.importc: "luaL_openlib".}
proc lua_settop(luaState: pointer, index: cint) {.importc: "lua_settop".}
proc rawgeti(luaState: pointer, index1, index2: cint) {.importc:
"lua_rawgeti".}
proc pop(luaState: pointer, index: cint) = lua_settop(luaState,-(index)-1)
proc getfield(luaState: pointer, a: cint, name: cstring) {.importc:
"lua_getfield".}
proc setfield(luaState: pointer, a: cint, name: cstring) {.importc:
"lua_setfield".}
proc luaPcall(luaState: pointer, a, b, c: cint): cint {.importc:
"lua_pcall".}
proc luaToString(luaState: pointer, index: cint, size: cint): cstring
{.importc: "lua_tolstring".}
proc luaToNumber(luaState: pointer, index: cint): cdouble {.importc:
"lua_tonumber".}
proc luaToBool(luaState: pointer, index: cint): cint {.importc:
"lua_toboolean".}
proc pushNumber(luaState: pointer, number: cdouble) {.importc:
"lua_pushnumber".}
proc pushString(luaState: pointer, s: cstring) {.importc: "lua_pushstring".}
proc pushCClosure(luaState: pointer, function: pointer, a: cint) {.importc:
"lua_pushcclosure".}
proc pushFunction(luaState: pointer, function: pointer) =
luaState.pushCClosure(function, 0)
proc pullString(luaState: pointer, index: cint): string =
$luaToString(luaState, index, 0)
proc pullNumber(luaState: pointer, index: cint): float =
luaToNumber(luaState, index)
proc pullBool(luaState: pointer, index: cint): bool = return
luaToBool(luaState, index) == 1
proc loveFunc(moduleName, funcName: string) =
getfield(luaState, luaGlobalsIndex, "love")
getfield(luaState, -1, moduleName)
getfield(luaState, -1, funcName)
# -- api wrapper --
type Image = distinct cint
proc newImage(filename: string): Image =
loveFunc("graphics", "newImage")
luaState.pushString(filename)
if luaPcall(luaState, 1, 1, 0) != 0:
echo "proc newImage failed on the lua side ->", luaState.pullString(-1)
quit 1
let res = luaState.luaL_ref(luaRegistryIndex).Image
luaState.pop(1)
return res
proc getWidth(self: Image): float =
luaState.rawgeti(luaRegistryIndex, self.cint)
getfield(luaState, -1, "getWidth")
luaState.rawgeti(luaRegistryIndex, self.cint)
if luaPcall(luaState, 1, 1, 0) != 0:
echo "proc getWidth failed on the lua side ->", luaState.pullString(-1)
quit 1
let res = luaState.pullNumber(-1)
luaState.pop(1)
return res
proc getHeight(self: Image): float =
luaState.rawgeti(luaRegistryIndex, self.cint)
getfield(luaState, -1, "getHeight")
luaState.rawgeti(luaRegistryIndex, self.cint)
if luaPcall(luaState, 1, 1, 0) != 0:
echo "proc getHeight failed on the lua side ->", luaState.pullString(-1)
quit 1
let res = luaState.pullNumber(-1)
luaState.pop(1)
return res
proc draw(
image: Image,
x: float, # The position to draw the object (x-axis).
y: float, # The position to draw the object (y-axis).
r: float, # Orientation (radians).
sx: float, # Scale factor (x-axis). Can be negative.
sy: float, # Scale factor (y-axis). Can be negative.
ox: float, # Origin offset (x-axis). (A value of 20 would effectively
move your drawable object 20 pixels to the left.)
oy: float, # Origin offset (y-axis). (A value of 20 would effectively
move your drawable object 20 pixels up.)
kx: float, # Shearing factor (x-axis).
ky: float # Shearing factor (y-axis).
) =
loveFunc("graphics", "draw")
luaState.rawgeti(luaRegistryIndex, image.cint)
luaState.pushNumber(x)
luaState.pushNumber(y)
luaState.pushNumber(r)
luaState.pushNumber(sx)
luaState.pushNumber(sy)
luaState.pushNumber(ox)
luaState.pushNumber(oy)
luaState.pushNumber(kx)
luaState.pushNumber(ky)
if luaPcall(luaState, 10, 0, 0) != 0:
echo "proc draw failed on the lua side ->", luaState.pullString(-1)
quit 1
proc quitLove =
loveFunc("event", "quit")
if luaPcall(luaState, 0, 0, 0) != 0:
echo "proc quit failed on the lua side ->", luaState.pullString(-1)
quit 1
# -- app code below --
var image: Image
proc loadCallback =
image = newImage("sprite.png")
echo "Image width (should be 300): ", image.getWidth()
echo "Image height (should be 205): ", image.getHeight()
proc drawCallback =
draw(image, 10, 10, 0, 1, 1, 0, 0, 0, 0)
proc keypressedCallback(key, scancode: string, isrepeat: bool) =
if key == "escape":
quitLove()
# -- init --
proc drawWrapper(state: pointer): cint =
luaState = state
drawCallback()
proc loadWrapper(state: pointer): cint =
luaState = state
loadCallback()
proc keypressedWrapper(state: pointer): cint =
luaState = state
let key = state.pullString(1)
let scancode = state.pullString(2)
let isrepeat = state.pullBool(3)
keypressedCallback(key, scancode, isrepeat)
proc load(L: pointer): cint {.dynlib, exportc: "luaopen_libmain".} =
{.emit: """NimMain();""".}
luaState = L
echo "lua opened nim lib"
var mylib: luaL_reg_list = [
reg(nil, nil)[],
reg(nil, nil)[],
reg(nil, nil)[]
]
luaL_openlib(L, "libmain", mylib, 0)
pushFunction(L, drawWrapper)
setfield(L, luaGlobalsIndex, "draw")
pushFunction(L, keypressedWrapper)
setfield(L, luaGlobalsIndex, "keypressed")
pushFunction(L, loadWrapper)
setfield(L, luaGlobalsIndex, "load")
return 1
Run
-- main.lua
require "libmain"
function love.load ()
load()
end
function love.draw ()
draw()
end
function love.keypressed (key, scanCode, isRepeat)
keypressed(key, scanCode, isRepeat)
end
Run
Compile and run:
nim c --app:lib main.nim && love .
Run
Result:
You would think that interacting with the engine by going [Nim]-->[Lua]-->[C++]
would be slow but it actually doesn't seem to incur much overhead compared to
just [Lua]-->[C++]
