auto document variable in ui-document lua script

res/layouts/inventory.xml.lua

@@ -1,6 +1,3 @@
-local Document = require("core:document")
-document = Document.new(DOC_NAME)
-
 function on_open(invid)
     print("OPEN", invid)
 end

res/modules/document.lua

@@ -1,22 +0,0 @@
-local Element = {}
-function Element.new(docname, name)
-    return setmetatable({docname=docname, name=name}, {
-        __index=function(self, k)
-            return gui.getattr(self.docname, self.name, k)
-        end,
-        __newindex=function(self, k, v)
-            gui.setattr(self.docname, self.name, k, v)
-        end
-    })
-end
-
-local Document = {}
-function Document.new(docname)
-    return setmetatable({name=docname}, {
-        __index=function(self, k)
-            return Element.new(self.name, k)
-        end
-    })
-end
-
-return Document

res/scripts/stdlib.lua

@@ -110,4 +110,27 @@ end
 color_mt = {}
 function color_mt.__tostring(self)
     return "rgba("..self[1]..", "..self[2]..", "..self[3]..", "..self[4]..")"
-end
+end
+
+-- class designed for simple UI-nodes access via properties syntax
+local Element = {}
+function Element.new(docname, name)
+    return setmetatable({docname=docname, name=name}, {
+        __index=function(self, k)
+            return gui.getattr(self.docname, self.name, k)
+        end,
+        __newindex=function(self, k, v)
+            gui.setattr(self.docname, self.name, k, v)
+        end
+    })
+end
+
+-- the engine automatically creates an instance for every ui document (layout)
+Document = {}
+function Document.new(docname)
+    return setmetatable({name=docname}, {
+        __index=function(self, k)
+            return Element.new(self.name, k)
+        end
+    })
+end