A little and basic animations library and example usage.

animations.lua

-- (c) 2013 Blam
-- Animations.lua

animation = { }
animation.__index = animation
animation.all = { }

function animation.delay(frames)
  local a = animation:new{
		a         = 0, 
		b         = 0, 
		func      = function(a, b, i) return 1 end,
		frameStep = 1/frames,
	}
	return a
end

function animation.createLinear(startValue, endValue, frames)
	local a = animation:new{
		a         = startValue, 
		b         = endValue, 
		func      = animation.linear,
		frameStep = 1/frames,
	}
	return a
end

function animation.createCosine(startValue, endValue, frames)
	local a = animation:new{
		a         = startValue, 
		b         = endValue, 
		func      = animation.cosine,
		frameStep = 1/frames,
	}
	return a
end

function animation.linear(a, b, i)
	return (a*(1-i)+b*i)
end

function animation.cosine(a, b, i)
	local i2 = (1-math.cos(i*math.pi))/2
	return animation.linear(a,b,i2)
end

function animation:new(base)
	local anim = base
	anim.i = 0
	setmetatable(anim, animation)
	return anim
end

function animation:start()
	table.insert(animation.all, self)
	return self
end

function animation:step()
	self.i = self.i + self.frameStep
	local v = self.func(self.a, self.b, self.i)
	return v
end

animationController = { }
animationController.__index = animationController

function animationController:new()
	local ac = { items = { }, object = nil }
	setmetatable(ac, animationController)
	return ac
end

function animationController:addAnimation(value, a)
	table.insert(self.items, {value, a})
end

function animationController:stop(a)
	for i = 1,#self.items do self.items[i] = nil end
	self.items = { }
end

function animationController:update()
	for i = 1,#self.items do
		local a = self.items[i][2]
		local v = a:step()
		if(self.items[i][1] ~= nil) then
			self.object[self.items[i][1]] = v
		end
		if(a.i >= 1) then
			if(a.onEnd ~= nil) then a.onEnd(a) end
			table.remove(self.items,i)
		end
	end
end

function animationController:attach(object)
	object["__animC"] = self
	object["addAnimation"] = function(v, a) animationController.addAnimation(self, v, a) end
	object["stopAnimation"] = function() animationController.stop(self) end
	object["stepAnimation"] = function() animationController.update(self) end
	self.object = object
	return self
end

-- EXAMPLE OF USAGE
gui = { }
gui.bar = { X = 0, Y = 0, width = -1, height = 20, hover = false}
gui.bar.Y = -gui.bar.height
gui.bar.__index = gui.bar
animationController:new():attach(gui.bar)

function gui.bar:show()
	self:stopAnimation()
	local sy = self.Y
	anim = animation.createCosine(sy, 0, 15)
	self.addAnimation("Y", anim)
end

function gui.bar:hide()
	self:stopAnimation()
	local sy = self.Y
	delay = animation.delay(15)
	delay.onEnd = function(a)
		a2 = animation.createCosine(sy, -self.height, 15)
		self.addAnimation("Y", a2)
	end
	self.addAnimation(nil, delay)
end

function gui.bar:update()
	self:stepAnimation()
	self.opacity = (self.Y+(self.height))/(self.height)
	if(self.width == -1) then 
		self.width, h = get_window_size()
	end
end

function gui.bar:draw()
	set_color(0,0,0,self.opacity/2)
	draw_quad(self.X, self.Y+1, self.width, self.height)
	set_color(1,0,0,self.opacity/2)
	draw_quad(self.X, self.Y, self.width, self.height)
	set_color(1,1,1,1)
	draw_text("Test Application 01", self.X+5, self.Y+1, 1)
end

add_hook("draw2d", "drawconsole", function()
	gui.bar:update()
	gui.bar:draw()
end)

add_hook("mouse_move", "showconsole", function(x,y)
	if(y <= gui.bar.height) then
		if(not gui.bar.hover) then
			gui.bar:show()
			gui.bar.hover = true
		end
	else
		if(gui.bar.hover) then
			gui.bar:hide()
			gui.bar.hover = false
		end
	end
end)