Add mpv config

mpv/scripts/uosc/elements/Curtain.lua

@@ -0,0 +1,35 @@
+local Element = require('elements/Element')
+
+---@class Curtain : Element
+local Curtain = class(Element)
+
+function Curtain:new() return Class.new(self) --[[@as Curtain]] end
+function Curtain:init()
+	Element.init(self, 'curtain', {render_order = 999})
+	self.opacity = 0
+	---@type string[]
+	self.dependents = {}
+end
+
+---@param id string
+function Curtain:register(id)
+	self.dependents[#self.dependents + 1] = id
+	if #self.dependents == 1 then self:tween_property('opacity', self.opacity, 1) end
+end
+
+---@param id string
+function Curtain:unregister(id)
+	self.dependents = itable_filter(self.dependents, function(item) return item ~= id end)
+	if #self.dependents == 0 then self:tween_property('opacity', self.opacity, 0) end
+end
+
+function Curtain:render()
+	if self.opacity == 0 or config.opacity.curtain == 0 then return end
+	local ass = assdraw.ass_new()
+	ass:rect(0, 0, display.width, display.height, {
+		color = config.color.curtain, opacity = config.opacity.curtain * self.opacity,
+	})
+	return ass
+end
+
+return Curtain