move UIBuilder creation into the layout

lib/simple_ui/builder.lua

@@ -5,13 +5,12 @@
 local builder = {}
 builder.__index = builder
 
-local function new(elementTree)
-    local l = {}
-    l.elementTree = elementTree
-    l._cache = {}
+--- @return UIBuilder
+local function new(from)
+    from._cache = {}
 
-    setmetatable(l, builder)
-    return l
+    setmetatable(from, builder)
+    return from
 end
 
 --- @param element? UIElement

lib/simple_ui/level/test.lua

@@ -2,9 +2,11 @@ local ScreenArea = require "lib.simple_ui.screen_area"
 local Center = require "lib.simple_ui.center"
 local Placeholder = require "lib.simple_ui.placeholder"
 local Padding = require "lib.simple_ui.padding"
+local Builder = require "lib.simple_ui.builder"
 
 
-return ScreenArea:new {
+return Builder {
+    elementTree = ScreenArea:new {
         build = function(self)
             return
                 (love.timer.getTime() / 2) % 2 < 1 and
@@ -22,3 +24,4 @@ return ScreenArea:new {
                 }
         end
     }
+}

main.lua

@@ -2,8 +2,7 @@
 
 local character = require "lib/character/character"
 require "lib/tree"
-local UIBuilder = require("lib.simple_ui.builder")
-local testLayout = UIBuilder(require "lib.simple_ui.level.test")
+local testLayout = require("lib.simple_ui.level.test")
 
 function love.conf(t)
     t.console = true