BUILD 02

- major code reorganization into multiple classes
- added support for pixel-based unit of measurement
- further simplified some "black magic" constants
- implemented margins to simulate container element
- revamped translation interface for stateful use
- various improvements to element parameter parsing

README.txt

@@ -1,4 +1,4 @@
-Scarlet Mod v1.0
+Scarlet Mod v1.1
 By Leslie Krause
 
 Scarlet is a thin-wrapper library for Minetest that provides a logical, uniform system of
@@ -20,6 +20,14 @@ Revision History
 Version 1.0b (18-May-2019)
   - initial alpha version
 
+Version 1.1b (22-May-2019)
+  - major code reorganization into multiple classes
+  - added support for pixel-based unit of measurement
+  - further simplified some "black magic" constants
+  - implemented margins to simulate container element
+  - revamped translation interface for stateful use
+  - various improvements to element parameter parsing
+
 Compatability
 ----------------------
 
@@ -44,7 +52,7 @@ Source Code License
 
 The MIT License (MIT)
 
-Copyright (c) 2018, Leslie Krause (leslie@searstower.org)
+Copyright (c) 2019, Leslie Krause (leslie@searstower.org)
 
 Permission is hereby granted, free of charge, to any person obtaining a copy of this
 software and associated documentation files (the "Software"), to deal in the Software

init.lua

@@ -5,144 +5,176 @@
 -- Copyright (c) 2019, Leslie E. Krause
 --------------------------------------------------------
 
-ScarletDef = function ( screen_dpi, gui_scaling, has_padding )
+scarlet = { }
 
+------------------------
+-- UnitConversion Class
+------------------------
+
+function UnitConversion( screen_dpi, gui_scaling, has_padding )
+	local self = { }
         local image_size = 0.55 * ( screen_dpi or 72 ) * ( gui_scaling or 1 )
 
 	-- calculate the dot pitch as images per pixel and cells per pixel
 	-- using the "black magic" algorithm from guiFormSpecMenu.cpp
-	local dot_pitch = {
+
+	self.dot_pitch = {
 		-- imgsize (images per pixel)
 		ix = 1 / image_size,
 		iy = 1 / image_size,
 		-- spacing (cells per pixel)
-                x = 1 / ( image_size * 5 / 4 ),
+                x = 1 / image_size * 4 / 5,
-                y = 1 / ( image_size * 15 / 13 )
+                y = 1 / image_size * 13 / 15
 	}
 
 	-- padding width and height in cell units
 	-- original formula: image_size * 3.0 / 8
-	local padding_width = has_padding and 0 or 3 / 10
+	self.padding_width = has_padding and 0.0 or 3 / 10
-	local padding_height = has_padding and 0 or 13 / 40
+	self.padding_height = has_padding and 0.0 or 13 / 40
 
 	-- nominal button height in cell units
 	-- NB: this is 2x the value of m_button_height used internally!
 	-- original formula: image_size * 15.0 / 13 * 0.35
-	local button_height = 0.7
+	self.button_height = 0.7
 
 	-- cell margin width and height in cell units
 	-- original formula: vx * spacing.x - ( spacing.x - imgsize.x )
-	local cell_margin_width = 1 / 5
+	self.cell_margin_width = 1 / 5
-	local cell_margin_height = 2 / 15
+	self.cell_margin_height = 2 / 15
 
-	---------------------------
+	self.units = ( function ( )
-	-- unit conversion objects
-	---------------------------
-
-	local units = ( function ( )
 		-- cell size measurements
 	       	local factors = {
+			d = { x = 1 / 39.6 * 4 / 5, y = 1 / 39.6 * 13 / 15 },
                		i = { x = 4 / 5, y = 13 / 15 },			-- imgsize
 	        	c = { x = 1, y = 1 },				-- spacing (unity)
-        		b = { y = button_height },			-- 2 x m_button_height
+       			b = { y = self.button_height },			-- 2 x m_button_height
 	        }
-        	local function get_x( v, u )
+       		local function get_x( v, u, dot_pitch )
-			return not factors[ u ] and math.floor( v ) * dot_pitch.x or v * factors[ u ].x
+			return not factors[ u ] and math.floor( v ) * self.dot_pitch.x or v * factors[ u ].x
 	        end
-        	local function get_y( v, u )
+       		local function get_y( v, u, dot_pitch )
-			return not factors[ u ] and math.floor( v ) * dot_pitch.y or v * factors[ u ].y
+			return not factors[ u ] and math.floor( v ) * self.dot_pitch.y or v * factors[ u ].y
 	        end
 		return { get_x = get_x, get_y = get_y }
 	end )( )
 
-	local iunits = ( function ( )
+	self.iunits = ( function ( )
 		-- image size measurements
 		local factors = {
+			d = { x = 1 / 39.6, y = 1 / 39.6 },
 			i = { x = 1, y = 1 },				-- imgsize (unity)
 			c = { x = 5 / 4, y = 15 / 13 },			-- spacing
-			b = { y = button_height * 15 / 13 },		-- 2 x m_button_height
+			b = { y = self.button_height * 15 / 13 },	-- 2 x m_button_height
 		}
        		local function get_x( v, u )
-			return not factors[ u ] and math.floor( v ) * dot_pitch.ix or v * factors[ u ].x
+			return not factors[ u ] and math.floor( v ) * self.dot_pitch.ix or v * factors[ u ].x
 	        end
        		local function get_y( v, u )
-			return not factors[ u ] and math.floor( v ) * dot_pitch.iy or v * factors[ u ].y
+			return not factors[ u ] and math.floor( v ) * self.dot_pitch.iy or v * factors[ u ].y
 	        end
 		return { get_x = get_x, get_y = get_y }
 	end )( )
 
-	-----------------------
+	return self
-	-- translation helpers
+end
-	-----------------------
+
+---------------------------
+-- RuntimeTranslator Class
+---------------------------
+
+function RuntimeTranslator( screen_dpi, gui_scaling, has_padding )
+
+	local self = UnitConversion( screen_dpi, gui_scaling, has_padding )	-- extend the base class
+
+	self.margins = { { width = 0.0, height = 0.0 } }
+
+	self.insert_margin = function ( width, height )
+		table.insert( self.margins, 1,
+			{ width = width + self.margins[ 1 ].width, height = height + self.margins[ 1 ].height }
+		)
+	end
+
+	self.remove_margin = function ( )
+		if #self.margins > 1 then
+			table.remove( self.margins, 1 )
+		end
+	end
+
+	self.get_pos = function ( pos_value, pos_units, offsets )
+		if pos_value then
+			local pos_x, u1, pos_y, u2 = string.match( pos_value, "^(-?[0-9.]+)([icpd]?),(-?[0-9.]+)([icpdb]?)$" )
+
+			if not pos_x then return end
+
+			return string.format( "%0.3f,%0.3f",
+				pos_units.get_x( pos_x, u1 ) + offsets[ 1 ] + self.margins[ 1 ].width,
+				pos_units.get_y( pos_y, u2 ) + offsets[ 2 ] + self.margins[ 1 ].height
+			)
+		end
+	end
+
+	self.get_pos_and_dim_x = function ( pos_value, dim_value, pos_units, dim_units, offsets )
+		if pos_value and dim_value then
+			local pos_x, u1, pos_y, u2 = string.match( pos_value, "^(-?[0-9.]+)([icpd]?),(-?[0-9.]+)([icpdb]?)$" )
+			local dim_x, u3 = string.match( dim_value, "^([0-9.]+)([iscp]?)$" )
+
+			if not pos_x or not dim_x then return end
+
+			if u3 == "s" then
+				u3 = "i"
+				offsets[ 3 ] = offsets[ 3 ] + ( dim_x % 1 == 0 and dim_x - 1 or math.floor( dim_x ) ) * self.cell_margin_width
+			end
+
+			return string.format( "%0.3f,%0.3f;%0.3f,0.000",
+				pos_units.get_x( pos_x, u1 ) + offsets[ 1 ] + self.margins[ 1 ].width,
+				pos_units.get_y( pos_y, u2 ) + offsets[ 2 ] + self.margins[ 1 ].height,
+				dim_units.get_x( dim_x, u3 ) + offsets[ 3 ]
+			)
+		end
+	end
+
+	self.get_pos_and_dim = function ( pos_value, dim_value, pos_units, dim_units, offsets )
+		if pos_value and dim_value then
+			local pos_x, u1, pos_y, u2 = string.match( pos_value, "^(-?[0-9.]+)([icpd]?),(-?[0-9.]+)([icpdb]?)$" )
+			local dim_x, u3, dim_y, u4 = string.match( dim_value, "^([0-9.]+)([iscpd]?),([0-9.]+)([iscpdb]?)$" )
+
+			if not pos_x or not dim_x then return end
+
+			if u3 == "s" then
+				u3 = "i"
+				offsets[ 3 ] = offsets[ 3 ] + ( dim_x % 1 == 0 and dim_x - 1 or math.floor( dim_x ) ) * self.cell_margin_width
+			end
+			if u4 == "s" then
+				u4 = "i"
+				offsets[ 4 ] = offsets[ 4 ] + ( dim_y % 1 == 0 and dim_y - 1 or math.floor( dim_y ) ) * self.cell_margin_height
+			end
+
+			return string.format( "%0.3f,%0.3f;%0.3f,%0.3f",
+				pos_units.get_x( pos_x, u1 ) + offsets[ 1 ] + self.margins[ 1 ].width,
+				pos_units.get_y( pos_y, u2 ) + offsets[ 2 ] + self.margins[ 1 ].height,
+				dim_units.get_x( dim_x, u3 ) + offsets[ 3 ],
+				dim_units.get_y( dim_y, u4 ) + offsets[ 4 ]
+			)
+		end
+	end
+
+	return self
+end
+
+------------------------------
+-- Generic Element Subclasses
+------------------------------
 
 local function element( name, params )
 	return name .. "[" .. table.concat( params, ";" ) .. "]"
 end
 
-	local function get_pos( params, pos_units, offsets )
-		local replace = "%0.3f,%0.3f"
-		local pos_x, u1, pos_y, u2 = string.match( params[ 1 ], "^(-?[0-9.]+)([icp]?),(-?[0-9.]+)([icpb]?)$" )
-
-		if not pos_x then return end
-
-		return string.format( replace,
-			pos_units.get_x( pos_x, u1 ) + offsets[ 1 ],
-			pos_units.get_y( pos_y, u2 ) + offsets[ 2 ]
-		)
-	end
-
-	local function get_pos_and_dim_x( params, pos_units, dim_units, offsets )
-		local replace = "%0.3f,%0.3f;%0.3f,0.000"
-		local pos_x, u1, pos_y, u2 = string.match( params[ 1 ], "^(-?[0-9.]+)([icp]?),(-?[0-9.]+)([icpb]?)$" )
-		local dim_x, u3 = string.match( params[ 2 ], "^([0-9.]+)([iscp]?)$" )
-
-		if not pos_x or not dim_x then return end
-
-		if u3 == "s" then
-			u3 = "i"
-			offsets[ 3 ] = offsets[ 3 ] + ( dim_x % 1 == 0 and dim_x - 1 or math.floor( dim_x ) ) * cell_margin_width
-		end
-
-		return string.format( replace,
-			pos_units.get_x( pos_x, u1 ) + offsets[ 1 ],
-			pos_units.get_y( pos_y, u2 ) + offsets[ 2 ],
-			dim_units.get_x( dim_x, u3 ) + offsets[ 3 ]
-		)
-	end
-
-	local function get_pos_and_dim( params, pos_units, dim_units, offsets )
-		local replace = "%0.3f,%0.3f;%0.3f,%0.3f"
-		local pos_x, u1, pos_y, u2 = string.match( params[ 1 ], "^(-?[0-9.]+)([icp]?),(-?[0-9.]+)([icpb]?)$" )
-		local dim_x, u3, dim_y, u4 = string.match( params[ 2 ], "^([0-9.]+)([iscp]?),([0-9.]+)([iscpb]?)$" )
-
-		if not pos_x or not dim_x then return end
-
-		if u3 == "s" then
-			u3 = "i"
-			offsets[ 3 ] = offsets[ 3 ] + ( dim_x % 1 == 0 and dim_x - 1 or math.floor( dim_x ) ) * cell_margin_width
-		end
-		if u4 == "s" then
-			u4 = "i"
-			offsets[ 4 ] = offsets[ 4 ] + ( dim_y % 1 == 0 and dim_y - 1 or math.floor( dim_y ) ) * cell_margin_height
-		end
-
-		return string.format( replace,
-			pos_units.get_x( pos_x, u1 ) + offsets[ 1 ],
-			pos_units.get_y( pos_y, u2 ) + offsets[ 2 ],
-			dim_units.get_x( dim_x, u3 ) + offsets[ 3 ],
-			dim_units.get_y( dim_y, u4 ) + offsets[ 4 ]
-		)
-	end
-
-	------------------------------
-	-- generic element subclasses
-	------------------------------
-
 local function ElemPos( pos_units, length )
-		return function ( name, params )
+	return function ( tx, name, params )
-			local pos = get_pos( params, pos_units, {
+		local pos = tx.get_pos( params[ 1 ], pos_units, {
-				-padding_width,
+			-tx.padding_width,
-				-padding_height
+			-tx.padding_height
 		} )
 		assert( pos and #params == length, "Cannot parse formspec element " .. name .. "[]" )
 		return element( name, { pos, unpack( params, 2 ) } )
@@ -150,10 +182,10 @@ ScarletDef = function ( screen_dpi, gui_scaling, has_padding )
 end
 
 local function ElemPosAndDim( pos_units, dim_units, length, is_unlimited )
-		return function ( name, params )
+	return function ( tx, name, params )
-			local pos_and_dim = get_pos_and_dim( params, pos_units, dim_units, {
+		local pos_and_dim = tx.get_pos_and_dim( params[ 1 ], params[ 2 ], pos_units, dim_units, {
-				-padding_width,
+			-tx.padding_width,
-				-padding_height,
+			-tx.padding_height,
 			0,
 			0
 		} )
@@ -163,10 +195,10 @@ ScarletDef = function ( screen_dpi, gui_scaling, has_padding )
 end
 
 local function ElemPosAndDimX( pos_units, dim_units, length, is_unlimited )
-		return function ( name, params )
+	return function ( tx, name, params )
-			local pos_and_dim_x = get_pos_and_dim_x( params, pos_units, dim_units, {
+		local pos_and_dim_x = tx.get_pos_and_dim_x( params[ 1 ], params[ 2 ], pos_units, dim_units, {
-				-padding_width,
+			-tx.padding_width,
-				-padding_height,
+			-tx.padding_height,
 			0
 		} )
 		assert( pos_and_dim_x and ( #params == length or is_unlimited and #params > length ), "Cannot parse formspec element " .. name .. "[]" )
@@ -175,18 +207,18 @@ ScarletDef = function ( screen_dpi, gui_scaling, has_padding )
 end
 
 ------------------------------
-	-- special element subclasses 
+-- Special Element Subclasses 
 ------------------------------
 
 local function SizeElement( )
 	local pattern = "^(%d+)([iscp]?),(%d+)([iscpb]?)$"
 	local replace = "%0.3f,%0.3f,true"
 
-		return function ( name, params )
+	return function ( tx, name, params )
 		local dim, count = string.gsub( params[ 1 ], pattern, function ( dim_x, u1, dim_y, u2 )
 			return string.format( replace,
-					units.get_x( dim_x, u1 ),
+				tx.units.get_x( dim_x, u1 ),
-					units.get_y( dim_y, u2 )
+				tx.units.get_y( dim_y, u2 )
 			)
 		end )
 		assert( count == 1, "Cannot parse formspec element size[]" )
@@ -194,29 +226,47 @@ ScarletDef = function ( screen_dpi, gui_scaling, has_padding )
 	end
 end
 
+-- list[<inventory_location>;<list_name>;<x>,<y>;<colums>;<rows>]
+
 local function ListElement( )
 	local pattern = "^(%d+)([icp]?),(%d+)([icpb]?)$"
 	local replace = "%0.3f,%0.3f"
 
-		return function ( name, params )
+	return function ( tx, name, params )
-			local pos, count = string.gsub( params[ 3 ], pattern, function ( pos_x, u1, pos_y, u2 )
+		local pos = tx.get_pos( params[ 3 ], tx.units, {
-				return string.format( replace,
+			-tx.padding_width,
-					units.get_x( pos_x, u1 ) - padding_width,
+			-tx.padding_height,
-					units.get_y( pos_y, u2 ) - padding_height
+		} )
-				)
+		assert( pos and ( #params == 4 or #params == 5 ), "Cannot parse formspec element list[]" )
-			end )
-			assert( count == 1, "Cannot parse formspec element list[]" )
 		return element( "list", { params[ 1 ], params[ 2 ], pos, unpack( params, 4 ) } )
 	end
 end
 
-	-- container[<x>,<y>]
+-- margin[]
+-- margin[<x>,<y>]
 
-	local function ContainerElement( )
+local function MarginElement( )
-		return function ( name, params )
+	local pattern = "^(-?[0-9.]+)([icpd]?),(-?[0-9.]+)([icpdb]?)$"
-			local pos = get_pos( params, units, { 0, 0 } )
+
-			assert( pos and #params == 1, "Cannot parse formspec element container[]" )
+	return function ( tx, name, params )
-			return element( "container", { pos } )
+		if #params == 0 then
+			tx.insert_margin( tx.padding_width, tx.padding_height )
+		else
+			local pos_x, u1, pos_y, u2 = string.match( params[ 1 ], pattern )
+			assert( pos_x and #params == 1, "Cannot parse formspec element margin[]" )
+			tx.insert_margin( tx.units.get_x( pos_x, u1 ), tx.units.get_y( pos_y, u2 ) )
+		end
+		return ""	-- remove virtual element
+	end
+end
+
+-- margin_end[]
+
+local function MarginEndElement( )
+	return function ( tx, name, params )
+		assert( #params == 0, "Cannot parse formspec element container_end[]" )
+		tx.remove_margin( )
+		return ""	-- remove virtual element
 	end
 end
 
@@ -226,7 +276,7 @@ ScarletDef = function ( screen_dpi, gui_scaling, has_padding )
 	local pattern = "^(-?%d+),(-?%d+)$"
 	local replace = "%d,%d;0,0"
 
-		return function ( name, params )
+	return function ( tx, name, params )
 		local dim, count = string.gsub( params[ 1 ], pattern, function ( pos_x, pos_y )
 			return string.format( replace, -pos_x, -pos_y )
 		end )
@@ -238,14 +288,14 @@ ScarletDef = function ( screen_dpi, gui_scaling, has_padding )
 -- bgimage[<x>,<y>;<w>,<h>;<texture name>]
 
 local function BgImageElement( )
+	return function ( tx, name, params )
 		-- original formula: vx * spacing.x - ( spacing.x - imgsize.x ) / 2
 		local pos_offset_x = 0.5 * 1 / 5
 		local pos_offset_y = 0.5 * 2 / 15
 
-		return function ( name, params )
+		local pos_and_dim = tx.get_pos_and_dim( params[ 1 ], params[ 2 ], tx.units, tx.units, {
-			local pos_and_dim = get_pos_and_dim( params, units, units, {
+			-tx.padding_width + pos_offset_x,
-				-padding_width + pos_offset_x,
+			-tx.padding_height + pos_offset_y,
-				-padding_height + pos_offset_y,
 			0,
 			0
 		} )
@@ -258,13 +308,13 @@ ScarletDef = function ( screen_dpi, gui_scaling, has_padding )
 -- vertlabel[<x>,<y>;<label>]
 
 local function LabelElement( is_vertical )
+	return function ( tx, name, params )
 		-- original formula: ( vy + 7 / 30 ) * spacing.y - m_button_height
-		local pos_offset_y = -7 / 30 + button_height / 2
+		local pos_offset_y = -7 / 30 + tx.button_height / 2
 
-		return function ( name, params )
+		local pos = tx.get_pos( params[ 1 ], tx.units, {
-			local pos = get_pos( params, units, {
+			-tx.padding_width,
-				-padding_width,
+			-tx.padding_height + pos_offset_y,
-				-padding_height + pos_offset_y,
 		} )
 		assert( pos and #params == 2, "Cannot parse formspec element " .. name .. "[]" )
 		return element( is_vertical and "vertlabel" or "label", { pos, params[ 2 ] } )
@@ -274,13 +324,13 @@ ScarletDef = function ( screen_dpi, gui_scaling, has_padding )
 -- checkbox[<x>,<y>;<w>;<name>;<label>]
 
 local function CheckboxElement( )
+	return function ( tx, name, params )
 		-- original formula: vy * spacing.y + ( imgsize.y / 2 ) - m_button_height
-		local pos_offset_y = -13 / 30 + button_height / 2
+		local pos_offset_y = -13 / 30 + tx.button_height / 2
 
-		return function ( name, params )
+		local pos = tx.get_pos( params[ 1 ], tx.units, {
-			local pos = get_pos( params, units, {
+			-tx.padding_width,
-				-padding_width,
+			-tx.padding_height + pos_offset_y,
-				-padding_height + pos_offset_y,
 		} )
 		assert( pos and #params == 4, "Cannot parse formspec element checkbox[]" )
 		return element( "checkbox", { pos, unpack( params, 3 ) } )
@@ -290,12 +340,12 @@ ScarletDef = function ( screen_dpi, gui_scaling, has_padding )
 -- button[<x>,<y>;<w>;<name>;<label>]
 
 local function ButtonElement( )
-		return function ( name, params )
+	return function ( tx, name, params )
-			local pos_and_dim = get_pos_and_dim( params, units, units, {
+		local pos_and_dim = tx.get_pos_and_dim( params[ 1 ], params[ 2 ], tx.units, tx.units, {
-				-padding_width,
+			-tx.padding_width,
-				-padding_height,
+			-tx.padding_height,
-				cell_margin_width,
+			tx.cell_margin_width,
-				cell_margin_height,
+			tx.cell_margin_height,
 		} )
 		assert( pos_and_dim and #params == 4, "Cannot parse formspec element " .. name .. "[]" )
 		return element( "image_" .. name, { pos_and_dim, "", unpack( params, 3 ) } )
@@ -305,12 +355,12 @@ ScarletDef = function ( screen_dpi, gui_scaling, has_padding )
 -- image_button[<x>,<y>;<w>;<name>;<texture_name>;<label>]
 
 local function ImageButtonElement( )
-		return function ( name, params )
+	return function ( tx, name, params )
-			local pos_and_dim = get_pos_and_dim( params, units, units, {
+		local pos_and_dim = tx.get_pos_and_dim( params[ 1 ], params[ 2 ], tx.units, tx.units, {
-				-padding_width,
+			-tx.padding_width,
-				-padding_height,
+			-tx.padding_height,
-				cell_margin_width,
+			tx.cell_margin_width,
-				cell_margin_height,
+			tx.cell_margin_height,
 		} )
 		assert( pos_and_dim and ( #params == 5 or #params == 8 ), "Cannot parse formspec element " .. name .. "[]" )
 		return element( name, { pos_and_dim, params[ 4 ], params[ 3 ], unpack( params, 5 ) } )
@@ -320,12 +370,12 @@ ScarletDef = function ( screen_dpi, gui_scaling, has_padding )
 -- item_image_button[<x>,<y>;<w>,<h>;<item name>;<name>;<label>]
 
 local function ItemImageButtonElement( )
-		return function ( name, params )
+	return function ( tx, name, params )
-			local pos_and_dim = get_pos_and_dim( params, units, units, {
+		local pos_and_dim = tx.get_pos_and_dim( params[ 1 ], params[ 2 ], tx.units, tx.units, {
-				-padding_width,
+			-tx.padding_width,
-				-padding_height,
+			-tx.padding_height,
-				cell_margin_width,
+			tx.cell_margin_width,
-				cell_margin_height,
+			tx.cell_margin_height,
 		} )
 		assert( pos_and_dim and #params == 5, "Cannot parse formspec element item_image_button[]" )
 		return element( "item_image_button", { pos_and_dim, params[ 4 ], params[ 3 ], params[ 5 ] } )
@@ -335,10 +385,10 @@ ScarletDef = function ( screen_dpi, gui_scaling, has_padding )
 -- textlist[<x>,<y>;<w>,<h>;<name>;...]
 
 local function TextListElement( )
-		return function ( name, params )
+	return function ( tx, name, params )
-			local pos_and_dim = get_pos_and_dim( params, units, units, {
+		local pos_and_dim = tx.get_pos_and_dim( params[ 1 ], params[ 2 ], tx.units, tx.units, {
-				-padding_width,
+			-tx.padding_width,
-				-padding_height,
+			-tx.padding_height,
 			0,
 			0,
 		} )
@@ -350,10 +400,10 @@ ScarletDef = function ( screen_dpi, gui_scaling, has_padding )
 -- dropdown[<x>,<y>;<w>,<h>;<name>;...]
 
 local function DropdownElement( )
-		return function ( name, params )
+	return function ( tx, name, params )
-			local pos_and_dim_x = get_pos_and_dim_x( params, units, units, {
+		local pos_and_dim_x = tx.get_pos_and_dim_x( params[ 1 ], params[ 2 ], tx.units, tx.units, {
-				-padding_width,
+			-tx.padding_width,
-				-padding_height,
+			-tx.padding_height,
 			0,
 			0,
 		} )
@@ -365,11 +415,11 @@ ScarletDef = function ( screen_dpi, gui_scaling, has_padding )
 -- pwdfield[<x>,<y>;<w>;<name>]
 
 local function PwdFieldElement( )
-		return function ( name, params )
+	return function ( tx, name, params )
-			local pos_and_dim_x = get_pos_and_dim_x( params, units, units, {
+		local pos_and_dim_x = tx.get_pos_and_dim_x( params[ 1 ], params[ 2 ], tx.units, tx.units, {
 			0,
-				button_height / 2,
+			tx.button_height / 2,
-				cell_margin_width,
+			tx.cell_margin_width,
 		} )
 		assert( pos_and_dim_x, #params == 3, "Cannot parse formspec element pwdfield[]" )
 		return element( "pwdfield", { pos_and_dim_x, params[ 3 ], "" } )
@@ -379,11 +429,11 @@ ScarletDef = function ( screen_dpi, gui_scaling, has_padding )
 -- field[<x>,<y>;<w>;<name>;<default>]
 
 local function FieldElement( )
-		return function ( name, params )
+	return function ( tx, name, params )
-			local pos_and_dim_x = get_pos_and_dim_x( params, units, units, {
+		local pos_and_dim_x = tx.get_pos_and_dim_x( params[ 1 ], params[ 2 ], tx.units, tx.units, {
 			0,
-				button_height / 2,
+			tx.button_height / 2,
-				cell_margin_width,
+			tx.cell_margin_width,
 		} )
 		assert( pos_and_dim_x and #params == 4, "Cannot parse formspec element field[]" )
 		return element( "field", { pos_and_dim_x, params[ 3 ], "", params[ 4 ] } )
@@ -393,12 +443,12 @@ ScarletDef = function ( screen_dpi, gui_scaling, has_padding )
 -- caption[<x>,<y>;<w>,<h>;<caption>]
 
 local function CaptionElement( )
-		return function ( name, params )
+	return function ( tx, name, params )
-			local pos_and_dim = get_pos_and_dim( params, units, units, {
+		local pos_and_dim = tx.get_pos_and_dim( params[ 1 ], params[ 2 ], tx.units, tx.units, {
 			0,
-				-button_height / 2,
+			-tx.button_height / 2,
-				cell_margin_width,
+			tx.cell_margin_width,
-				cell_margin_height + button_height / 2
+			tx.cell_margin_height + tx.button_height / 2
 		} )
 		assert( pos_and_dim and #params == 3, "Cannot parse formspec element caption[]" )
 		return element( "textarea", { pos_and_dim, "", params[ 3 ], "" } )
@@ -408,12 +458,12 @@ ScarletDef = function ( screen_dpi, gui_scaling, has_padding )
 -- textarea[<x>,<y>;<w>,<h>;<name>;<default>]
 
 local function TextAreaElement( )
-		return function ( name, params )
+	return function ( tx, name, params )
-			local pos_and_dim = get_pos_and_dim( params, units, units, {
+		local pos_and_dim = tx.get_pos_and_dim( params[ 1 ], params[ 2 ], tx.units, tx.units, {
 			0,
-				-button_height / 2,
+			-tx.button_height / 2,
-				cell_margin_width,
+			tx.cell_margin_width,
-				cell_margin_height + button_height / 2
+			tx.cell_margin_height + tx.button_height / 2
 		} )
 		assert( pos_and_dim and #params == 4, "Cannot parse formspec element textarea[]" )
 		return element( "textarea", { pos_and_dim, params[ 3 ], "", params[ 4 ] } )
@@ -424,10 +474,10 @@ ScarletDef = function ( screen_dpi, gui_scaling, has_padding )
 -- vert_scrollbar[<x>,<y>;<w>,<h>;<name>;<value>]
 
 local function ScrollbarElement( orientation )
-		return function ( name, params )
+	return function ( tx, name, params )
-			local pos_and_dim = get_pos_and_dim( params, units, units, {
+		local pos_and_dim = tx.get_pos_and_dim( params[ 1 ], params[ 2 ], tx.units, tx.units, {
-				-padding_width,
+			-tx.padding_width,
-				-padding_height,
+			-tx.padding_height,
 			0,
 			0
 		} )
@@ -439,10 +489,10 @@ ScarletDef = function ( screen_dpi, gui_scaling, has_padding )
 -- area_tooltip[<x>,<y>;<w>,<h>;<name>;<tooltip_text>]
 
 local function AreaTooltipElement( )
-		return function ( name, params )
+	return function ( tx, name, params )
-			local pos_and_dim = get_pos_and_dim( params, units, units, {
+		local pos_and_dim = tx.get_pos_and_dim( params[ 1 ], params[ 2 ], tx.units, tx.units, {
-				-padding_width,
+			-tx.padding_width,
-				-padding_height,
+			-tx.padding_height,
 			0,
 			0
 		} )
@@ -454,8 +504,8 @@ ScarletDef = function ( screen_dpi, gui_scaling, has_padding )
 -- tabheader[<x>,<y>;<w>,<h>;<name>;<tooltip_text>]
 
 local function TabHeaderElement( )
-		return function ( name, params )
+	return function ( tx, name, params )
-			local pos = get_pos( params, units, {
+		local pos = tx.get_pos( params[ 1 ], tx.units, {
 			0,
 			0
 		} )
@@ -464,15 +514,19 @@ ScarletDef = function ( screen_dpi, gui_scaling, has_padding )
 	end
 end
 
-	-------------------
+-------------------------
-	-- element parsers
+-- Translation Interface
-	-------------------
+-------------------------
+
+scarlet.translate = function ( fs, screen_dpi, gui_scaling )
+
+	local tx = RuntimeTranslator( screen_dpi, gui_scaling, false )
 
 	local element_parsers = {
 		size			= SizeElement( ),
 		list			= ListElement( ),
 		background		= BackgroundElement( ),
-		box			= ElemPosAndDim( units, units, 3, false ),
+		box			= ElemPosAndDim( tx.units, tx.units, 3, false ),
 		button			= ButtonElement( ),
 		button_exit		= ButtonElement( ),
 		image_button		= ImageButtonElement( ),
@@ -483,45 +537,39 @@ ScarletDef = function ( screen_dpi, gui_scaling, has_padding )
 		checkbox		= CheckboxElement( ),
 		pwdfield		= PwdFieldElement( ),
 		item_image_button	= ItemImageButtonElement( ),
-		image			= ElemPosAndDim( units, iunits, 3, false ),
+		image			= ElemPosAndDim( tx.units, tx.iunits, 3, false ),
-		item_image		= ElemPosAndDim( units, iunits, 3, false ),
+		item_image		= ElemPosAndDim( tx.units, tx.iunits, 3, false ),
 		field			= FieldElement( ),
 		dropdown		= DropdownElement( ),
 		textlist		= TextListElement( ),
 		vert_scrollbar		= ScrollbarElement( "vertical" ),
 		horz_scrollbar		= ScrollbarElement( "horizontal" ),
-		table			= ElemPosAndDim( units, units, 5, false ),
+		table			= ElemPosAndDim( tx.units, tx.units, 5, false ),
 		textarea		= TextAreaElement( ),
 		caption			= CaptionElement( ),
-		area_tooltip		= AreaTooltipElement( ),		-- added in 5.0 (https://github.com/minetest/minetest/pull/7469)
+		area_tooltip		= AreaTooltipElement( ),		-- not added until 5.0 (https://github.com/minetest/minetest/pull/7469)
-		container		= ContainerElement( ),			-- fixed in 5.0 (https://github.com/minetest/minetest/pull/7497)
+		container		= ElemPos( tx.units, 1 ),		-- not fixed until 5.0 (https://github.com/minetest/minetest/pull/7497)
+		margin			= MarginElement( ),			-- emulation of container[] element
+		margin_end		= MarginEndElement( ),
 		tabheader		= TabHeaderElement( ),
 	}
 
-	-------------------------
-	-- translation interface
-	-------------------------
-
-	local function translate( fs )
 	fs = string.gsub( fs, "([a-z_]+)%[(.-)%]", function( name, parts )
 		local parser = element_parsers[ name ]
 		if parser then
-				local res = parser( name, string.split( parts, ";", true ) )
+			local res = parser( tx, name, parts == "" and { } or string.split( parts, ";", true ) )
 			return res
 		end
 	end )
 
-		minetest.debug( "ACTION", "Result:" .. fs )
+--	minetest.debug( "ACTION", "Result:" .. fs )
 	return fs
 end
 
-	return {
+scarlet.translate_96dpi = function ( fs )
-		-- public method
+	return scarlet.translate( fs, 96, 1 )
-		translate = translate
-	}
 end
 
-scarlet = {
+scarlet.translate_72dpi = function ( fs )
-	translate_96dpi = ScarletDef( 96, 1, false ).translate,
+	return scarlet.translate( fs, 72, 1 )
-	translate_72dpi = ScarletDef( 72, 1, false ).translate
+end
-}