scn

scn is a minimal abstraction built on top of love2d to manage scenes and transitions.

quickstart

simply copy the file scn.lua into your project, and consume it following the code along section below. you may also use this repository as-is as a template for a brand new love2d project.

code along

main.lua

-- main.lua contents:
local Scn = require("scn")

local MainMenuScene = require("scenes.MainMenu")
local GameplayScene = require("scenes.Gameplay")

love.load = function()
    Scn.register(MainMenuScene) -- default scene
    Scn.register(GameplayScene)
end

love.draw = function()
    Scn.draw()
end

love.update = function(dt)
    Scn.update(dt)
end

scenes/MainMenu.lua

-- scenes/MainMenu.lua contents:

local Scn = require("scn")
local FadeOutTransition = require("transitions.fadeout")

local MainMenuScene = { name = "MainMenu" }
MainMenuScene.__index = MainMenuScene

MainMenuScene.enter = function()
    love.graphics.setBackgroundColor(love.math.colorFromBytes( 36, 37, 41, 255 ))
end

MainMenuScene.draw = function()
    love.graphics.print("Main Menu", love.graphics.getWidth()/2, love.graphics.getHeight()/2)
end

MainMenuScene.update = function(dt)
    if love.keyboard.isDown('space') then
        Scn.switch("Gameplay", FadeOutTransition.new())
    end

    -- you may want to prevent some of your systems from further updating while a transition is playing.
    -- if not Scn.mid_transition then -- prevent other menu buttons from being clicked for example.
        -- input_system.update() 
    -- end
end

MainMenuScene.exit = function()
end

return MainMenuScene

scenes/Gameplay.lua

-- scenes/Gameplay.lua contents:
local Scn = require("scn")
local FadeInTransition = require("transitions.fadein")

local GameplayScene = { name = "Gameplay" }
GameplayScene.__index = GameplayScene

GameplayScene.enter = function(self)
    love.graphics.setBackgroundColor(love.math.colorFromBytes( 100, 149, 237, 255 ))
    Scn.switch("Gameplay", FadeInTransition.new())
end

GameplayScene.draw = function(self)
    love.graphics.print("Gameplay", love.graphics.getWidth()/2, love.graphics.getHeight()/2)
end

GameplayScene.update = function(self, dt)
end

GameplayScene.exit = function(self)
end

return GameplayScene

transitions/fadein.lua

-- transitions/fadein.lua contents:
local DEFAULT_COLOR = { 1,1,1,1 } -- white

local FadeInTransition = {}
FadeInTransition.__index = FadeInTransition

FadeInTransition.new = function(config)
    config = config or {}

    local self = setmetatable({}, FadeInTransition)

    self.target_color = config.color or {0, 0, 0, 0} -- transparent
    self.current_color = { self.target_color[1], self.target_color[2], self.target_color[3], 1 }
    self.speed = (config.speed or 5) / 10
    self.x = config.x or 0
    self.y = config.y or 0
    self.w = config.w or love.graphics.getWidth()
    self.h = config.h or love.graphics.getHeight()

    self.current_progress = 0 -- to 1
    self.completed = false

    return self
end

FadeInTransition.track_progress = function(self)
    self.current_progress = self.current_color[4] + 1
    self.completed = self.current_progress == 1
end

FadeInTransition.update = function(self, dt)
    self.current_color[4] = math.max(self.current_color[4] - self.speed * dt, 0)
    self:track_progress()
end

FadeInTransition.draw = function(self)
    love.graphics.setColor(self.current_color)
        love.graphics.rectangle("fill", self.x, self.y, self.w, self.h)
    love.graphics.setColor(DEFAULT_COLOR)
end

return FadeInTransition

transitions/fadeout.lua

-- transitions/fadeout.lua contents:
local DEFAULT_COLOR = { 1,1,1,1 } -- white

local FadeOutTransition = {}
FadeOutTransition.__index = FadeOutTransition

FadeOutTransition.new = function(config)
    config = config or {}

    local self = setmetatable({}, FadeOutTransition)

    self.target_color = config.color or {0, 0, 0, 1} -- black
    self.current_color = { self.target_color[1], self.target_color[2], self.target_color[3], 0 }
    self.speed = (config.speed or 5) / 10
    self.x = config.x or 0
    self.y = config.y or 0
    self.w = config.w or love.graphics.getWidth()
    self.h = config.h or love.graphics.getHeight()

    self.current_progress = 0 -- to 1
    self.completed = false

    return self
end

FadeOutTransition.track_progress = function(self)
    self.current_progress = self.current_color[4] / 1
    self.completed = self.current_progress == 1
end

FadeOutTransition.update = function(self, dt)
    self.current_color[4] = math.min(self.current_color[4] + self.speed * dt, 1)
    self:track_progress()
end

FadeOutTransition.draw = function(self)
    love.graphics.setColor(self.current_color)
        love.graphics.rectangle("fill", self.x, self.y, self.w, self.h)
    love.graphics.setColor(DEFAULT_COLOR)
end

return FadeOutTransition

the transition will be triggered in the MainMenu scene when you press the space key.

LICENSE

scn is licensed under the MIT LICENSE