-- this function will be called from inside the game
function InitLuaUI()
	print( "Initializing Lua User Interface
" )

	-- get root node of 'MainMenu' screen
	root = gui.getScreen("MainMenu").root_node
	root.position = { 100, 100 }
	
	move_image = {
		[1] = { image = "BigItems/GUN11.sti", offset = {40, 100} },
		[2] = { image = "BigItems/GUN33.sti", offset = {40, 200} },
	}
	
	for i in ipairs(move_image) do
		local im = gui.createImage{ parent = root, image = move_image[i].image }
		im.offset = move_image[i].offset

		local t = gui.createTextNode{
			parent = im,
			text = move_image[i].image,
			font = "BLOCKFONT2", foreground = 240, background = 0
		}
		--t.offset = { -1 * im.size[1]/2, -10 }
		t.offset = { 0, -10 }
		
		local re = gui.createRegion{ parent = im }
		re.size = im.size
		
		local move,button = GetMouseCallbacks(im)
		re:define( button, move )
	end
	
	local text = gui.createTextNode{ parent = root }
	text.font = "FONT16ARIAL"
	text.foreground = 134
	text.background = 1
	text.text = "Hello World!"
	text.position = { 640/2 - 40, 20 }

	return 1
end

-- this function creates mouse callbacks (closures)
function GetMouseCallbacks(node)
	local _node = node
	local _lbutton = false
	local _position = {}
	
	local moveCallBack = function(tab)
		if(tab.reason == 64) then
			_lbutton = false
			-- print("lost mouse")
		elseif(tab.reason == 128) then
			-- print("gain mouse")
		end 
		if( _lbutton == true) then
			-- compute relative displacement
			local rd = { 
				tab.mouse_x - _position[1],
				tab.mouse_y - _position[2]
			}
			-- apply displacement to node
			local xy = _node.position
			for i=1,2 do xy[i] = xy[i] + rd[i] end
			_node.position = xy
			
			-- save current mose position
			_position = { tab.mouse_x, tab.mouse_y }
		end
	end
	
	local buttonCallBack = function(tab)
		if(tab.reason == 4) then
			_lbutton = true
			_position = { tab.mouse_x, tab.mouse_y }
		elseif tab.reason == 8 then
			_lbutton = false
		elseif tab.reason == 16 then
			local p = _node.position
			local o = _node.offset
			local t = _node.type;
			print( t )
			print( "  position : " .. p[1] .. ", " .. p[2])
			print( "  offset   : " .. o[1] .. ", " .. o[2])
		end
	end

	return moveCallBack, buttonCallBack
end