Added some structor concepts

expcore/gui/concepts/empty.lua

@@ -0,0 +1,26 @@
+--[[-- Core Module - Gui
+    @module Gui
+    @alias Gui
+]]
+
+local Gui = require 'expcore.gui.core'
+
+--[[-- A empty widget that just exists. The root GUI element screen is an empty-widget.
+@element empty
+@tparam string style the style that the element will have
+@usage-- Making a draggable space styled widget
+local draggable_space =
+Gui.clone_concept('empty','draggable_space')
+:set_style('draggable_space')
+]]
+Gui.new_concept('empty')
+:new_property('style')
+:define_draw(function(properties,parent,element)
+    element = parent.add{
+        name = properties.name,
+        type = 'empty-widget',
+        style = properties.style
+    }
+
+    return element
+end)