Rework graphical train HUD code

- A basic texture manipulation API is added; currently this is only a
  (selected) subset of texture modifiers provided by MT; the goal is to
  avoid writing (potentially incorrect) texture strings by hand;
- The graphical HUD code is cleaned up; in particular, most code used
  for generating texture patterns are moved to texture.lua so that the
  code can be used outside of the HUD;
- Inactive elements are given the darkslategray background.

A basic unittest is added; however, it needs to be expanded for better
coverage.

Reported-by: Lars Müller <appgurulars@gmx.de>

4 files changed, 281 insertions, 87 deletions

diff --git a/advtrains/init.lua b/advtrains/init.lua
index cc8f8d1..33e5b1d 100644
--- a/advtrains/init.lua
+++ b/advtrains/init.lua
@@ -202,6 +202,7 @@ advtrains.meseconrules =
 advtrains.fpath=minetest.get_worldpath().."/advtrains"
 
 advtrains.speed = dofile(advtrains.modpath.."/speed.lua")
+advtrains.texture = dofile(advtrains.modpath.."/texture.lua")
 
 dofile(advtrains.modpath.."/path.lua")
 dofile(advtrains.modpath.."/trainlogic.lua")
diff --git a/advtrains/spec/texture_spec.lua b/advtrains/spec/texture_spec.lua
new file mode 100644
index 0000000..2e3bd5d
--- /dev/null
+++ b/advtrains/spec/texture_spec.lua
@@ -0,0 +1,19 @@
+package.path = "../?.lua;" .. package.path
+local T = require "texture"
+
+describe("Texture creation", function()
+	it("works", function()
+		assert.same("^.png", tostring(T.raw"^.png"))
+		assert.same("foo\\:bar.png", tostring(T"foo:bar.png"))
+	end)
+end)
+
+describe("Texture modifiers", function()
+	it("work", function()
+		assert.same("x^[colorize:c", tostring(T"x":colorize"c"))
+		assert.same("x^[colorize:c:alpha", tostring(T"x":colorize("c", "alpha")))
+		assert.same("x^[multiply:c", tostring(T"x":multiply"c"))
+		assert.same("x^[resize:2x3", tostring(T"x":resize(2, 3)))
+		assert.same("x^[transformI", tostring(T"x":transform"I"))
+	end)
+end)
diff --git a/advtrains/texture.lua b/advtrains/texture.lua
new file mode 100644
index 0000000..1ecc91b
--- /dev/null
+++ b/advtrains/texture.lua
@@ -0,0 +1,228 @@
+local tx = {}
+setmetatable(tx, {__call = function(_, ...) return tx.base(...) end})
+
+function tx.escape(str)
+	return (string.gsub(tostring(str), [[([%^:\])]], [[\%1]]))
+end
+
+local function getargs(...)
+	return select("#", ...), {...}
+end
+
+local function curry(f, x)
+	return function(...)
+		return f(x, ...)
+	end
+end
+
+local function xmkmodifier(func)
+	return function(self, ...)
+		table.insert(self, (func(...)))
+		return self
+	end
+end
+
+local function mkmodifier(fmt, spec)
+	return xmkmodifier(function(...)
+		local count = select("#", ...)
+		local args = {...}
+		for k, f in pairs(spec) do
+			args[k] = f(args[k])
+		end
+		return string.format(fmt, unpack(args, 1, count))
+	end)
+end
+
+-- Texture object
+local tx_lib = {}
+local tx_mt = {
+	__index = tx_lib,
+	__tostring = function(self)
+		return table.concat(self, "^")
+	end,
+	__concat = function(a, b)
+		return tx.raw(("%s^%s"):format(tostring(a), tostring(b)))
+	end,
+}
+
+function tx.raw(str)
+	return setmetatable({str}, tx_mt)
+end
+function tx.base(str)
+	return tx.raw(tx.escape(str))
+end
+-- TODO: use [fill when 5.8.0 becomes widely used client-side
+function tx.fill(w, h, color)
+	return tx"advtrains_hud_bg.png":resize(w, h):colorize(color)
+end
+
+-- Most texture modifiers
+tx_lib.colorize = xmkmodifier(function(c, a)
+	local str = ("[colorize:%s"):format(tx.escape(c))
+	if a then
+		str = str .. ":" .. a
+	end
+	return str
+end)
+tx_lib.multiply = mkmodifier("[multiply:%s", {tx.escape})
+tx_lib.resize = mkmodifier("[resize:%dx%d", {})
+tx_lib.transform = mkmodifier("[transform%s", {tx.escape})
+
+-- [combine
+
+local combine = {}
+
+function combine:add(x, y, ent)
+	table.insert(self.st, ([[%d,%d=%s]]):format(x, y, tx.escape(tostring(ent))))
+	return self
+end
+
+local combine_mt = {
+	__index = combine,
+	__tostring = function(self)
+		return table.concat(self.st, ":")
+	end,
+}
+
+function tx.combine(w, h, bg)
+	local base = ("[combine:%dx%d"):format(w, h)
+	local obj = setmetatable({width = w, height = h, st = {base}}, combine_mt)
+	if bg then
+		obj:add_fill(0, 0, w, h, bg)
+	end
+	return obj
+end
+
+function combine:add_fill(x, y, ...)
+	return self:add(x, y, tx.fill(...))
+end
+
+local function add_multicolor_fill(n, self, x, y, w, h, ...)
+	local argc, argv = getargs(...)
+	local t = 0
+	for k = 1, argc, 2 do
+		t = t + argv[k]
+	end
+	local newargs = {x, y, w, h}
+	local sk, wk = n, n+2
+	local s = newargs[wk]/t
+	for k = 1, argc, 2 do
+		local v = argv[k] * s
+		newargs[wk] = v
+		newargs[5] = argv[k+1]
+		self:add_fill(unpack(newargs))
+		newargs[sk] = newargs[sk] + v
+	end
+	return self
+end
+combine.add_multicolor_fill_topdown = curry(add_multicolor_fill, 2)
+combine.add_multicolor_fill_leftright = curry(add_multicolor_fill, 1)
+
+local function add_segmentbar(n, self, x, y, w, h, m, c, ...)
+	local argc, argv = getargs(...)
+	local baseargs = {x, y, w, h}
+	local ss = (baseargs[n+2]+m)/c
+	local bs = ss - m
+	for k = 1, argc, 3 do
+		local lower, upper, fill = argv[k], argv[k+1], argv[k+2]
+		lower = math.max(0, math.floor(lower)+1)
+		upper = math.min(c, math.floor(upper))
+		if lower < upper then
+			local args = {x, y, w, h, fill}
+			args[n+2] = bs
+			args[n] = args[n] + ss*lower
+			for i = lower, upper do
+				self:add_fill(unpack(args))
+				args[n] = args[n] + ss
+			end
+		end
+	end
+	return self
+end
+combine.add_segmentbar_topdown = curry(add_segmentbar, 2)
+combine.add_segmentbar_leftright = curry(add_segmentbar, 1)
+
+local function add_lever(n, self, x, y, w, h, hs, ss, val, hf, sf)
+	local baseargs = {x, y, w, h}
+	local sargs = {x, y, w, h, sf}
+	sargs[5-n] = ss
+	sargs[n+2] = baseargs[n+2] + ss - hs
+	for k = 1, 2 do
+		sargs[k] = baseargs[k] + (baseargs[k+2] - sargs[k+2])/2
+	end
+	self:add_fill(unpack(sargs))
+	local hargs = {x, y, w, h, hf}
+	hargs[n+2] = hs
+	hargs[n] = baseargs[n] + (baseargs[n+2]-hs)*val
+	self:add_fill(unpack(hargs))
+	return self
+end
+combine.add_lever_topdown = curry(add_lever, 2)
+combine.add_lever_leftright = curry(add_lever, 1)
+
+--[[ Seven-segment display
+ -1-
+6   2
+ -7-
+5   3
+ -4-
+--]]
+local sevenseg_digits = {
+	["0"] = {1, 2, 3, 4, 5, 6},
+	["1"] = {2, 3},
+	["2"] = {1, 2, 4, 5, 7},
+	["3"] = {1, 2, 3, 4, 7},
+	["4"] = {2, 3, 6, 7},
+	["5"] = {1, 3, 4, 6, 7},
+	["6"] = {1, 3, 4, 5, 6, 7},
+	["7"] = {1, 2, 3},
+	["8"] = {1, 2, 3, 4, 5, 6, 7},
+	["9"] = {1, 2, 3, 4, 6, 7},
+}
+
+function combine:add_str7seg(x0, y0, tw, th, str, fill)
+	--[[ w and h (as width/height of individual (horizontal) segments) have the following properties:
+	tw = n(w+3h)-h
+	th = 2w+3h
+	--]]
+	local len = #str
+	local h = (2*tw-len*th)/(3*len-2)
+	local w = (th-3*h)/2
+	local ws = w+3*h
+	local segs = {
+		{h, 0, w, h},
+		{w+h, h, h, w},
+		{w+h, w+2*h, h, w},
+		{h, 2*(w+h), w, h},
+		{0, w+2*h, h, w},
+		{0, h, h, w},
+		{h, w+h, w, h},
+	}
+	for i = 1, len do
+		for _, k in pairs(sevenseg_digits[string.sub(str, i, i)] or {}) do
+			local s = segs[k]
+			self:add_fill(s[1]+x0, s[2]+y0, s[3], s[4], fill)
+		end
+		x0 = x0 + ws
+	end
+	return self
+end
+
+function combine:add_n7seg(x, y, w, h, n, prec, ...)
+	if not (type(n) == "number" and type(prec) == "number") then
+		error("passed non-numeric value or precision to numeric display")
+	elseif prec < 0 then
+		error("negative length")
+	end
+	local pfx = ""
+	if n >= 0 then
+		n = math.min(10^prec-1, n)
+	else
+		n = math.min(10^(prec-1)-1, -n)
+		pfx = "-"
+	end
+	local str = ("%d"):format(n)
+	return self:add_str7seg(x, y, w, h, pfx .. ("0"):rep(prec-#str-#pfx) .. str, ...)
+end
+
+return tx
diff --git a/advtrains/trainhud.lua b/advtrains/trainhud.lua
index 22aa6cf..b8eb512 100644
--- a/advtrains/trainhud.lua
+++ b/advtrains/trainhud.lua
@@ -1,5 +1,7 @@
 --trainhud.lua: holds all the code for train controlling
 
+local T = advtrains.texture
+
 advtrains.hud = {}
 advtrains.hhud = {}
 
@@ -184,98 +186,41 @@ function advtrains.hud_train_format(train, flip)
 	local vel = advtrains.abs_ceil(train.velocity)
 	local vel_kmh=advtrains.abs_ceil(advtrains.ms_to_kmh(train.velocity))
 	
-	local tlev=train.lever or 1
+	local tlev=train.lever or 3
 	if train.velocity==0 and not train.active_control then tlev=1 end
 	if train.hud_lzb_effect_tmr then
 		tlev=1
 	end
 	
-	local ht = {"[combine:440x110:0,0=(advtrains_hud_bg.png^[resize\\:440x110)"}
+	local hud = T.combine(440, 110, "black")
 	local st = {}
 	if train.debug then st = {train.debug} end
 	
-	-- seven-segment display
-	local function sevenseg(digit, x, y, w, h, m)
-		--[[
-		 -1-
-		2   3
-		 -4-
-		5   6
-		 -7-
-		]]
-		local segs = {
-			{h, 0, w, h},
-			{0, h, h, w},
-			{w+h, h, h, w},
-			{h, w+h, w, h},
-			{0, w+2*h, h, w},
-			{w+h, w+2*h, h, w},
-			{h, 2*(w+h), w, h}}
-		local trans = {
-			[0] = {true, true, true, false, true, true, true},
-			[1] = {false, false, true, false, false, true, false},
-			[2] = {true, false, true, true, true, false, true},
-			[3] = {true, false, true, true, false, true, true},
-			[4] = {false, true, true, true, false, true, false},
-			[5] = {true, true, false, true, false, true, true},
-			[6] = {true, true, false, true, true, true, true},
-			[7] = {true, false, true, false, false, true, false},
-			[8] = {true, true, true, true, true, true, true},
-			[9] = {true, true, true, true, false, true, true}}
-		local ent = trans[digit or 10]
-		if not ent then return end
-		for i = 1, 7, 1 do
-			if ent[i] then
-				local s = segs[i]
-				ht[#ht+1] = sformat("%d,%d=(advtrains_hud_bg.png^[resize\\:%dx%d^%s)",x+s[1], y+s[2], s[3], s[4], m)
-			end
-		end
-	end
-	
 	-- lever
-	ht[#ht+1] = "275,10=(advtrains_hud_bg.png^[colorize\\:cyan^[resize\\:5x18)"
-	ht[#ht+1] = "275,28=(advtrains_hud_bg.png^[colorize\\:white^[resize\\:5x18)"
-	ht[#ht+1] = "275,46=(advtrains_hud_bg.png^[colorize\\:orange^[resize\\:5x36)"
-	ht[#ht+1] = "275,82=(advtrains_hud_bg.png^[colorize\\:red^[resize\\:5x18)"
-	ht[#ht+1] = "292,16=(advtrains_hud_bg.png^[colorize\\:darkslategray^[resize\\:6x78)"
-	ht[#ht+1] = sformat("280,%s=(advtrains_hud_bg.png^[colorize\\:gray^[resize\\:30x18)",18*(4-tlev)+10)
+	hud:add_multicolor_fill_topdown(275, 10, 5, 90, 1, "cyan", 1, "white", 2, "orange", 1, "red")
+	hud:add_lever_topdown(280, 10, 30, 90, 18, 6, (4-tlev)/4, "gray", "darkslategray")
 	-- reverser
-	ht[#ht+1] = sformat("245,10=(advtrains_hud_arrow.png^[transformFY%s)", flip and "" or "^[multiply\\:cyan")
-	ht[#ht+1] = sformat("245,85=(advtrains_hud_arrow.png%s)", flip and "^[multiply\\:orange" or "")
-	ht[#ht+1] = "250,35=(advtrains_hud_bg.png^[colorize\\:darkslategray^[resize\\:5x40)"
-	ht[#ht+1] = sformat("240,%s=(advtrains_hud_bg.png^[resize\\:25x15^[colorize\\:gray)", flip and 65 or 30)
+	hud:add(245, 10, T"advtrains_hud_arrow.png":transform"FY":multiply(flip and "gray" or "cyan"))
+	hud:add(245, 85, T"advtrains_hud_arrow.png":multiply(flip and "orange" or "gray"))
+	hud:add_lever_topdown(240, 30, 25, 50, 15, 5, flip and 1 or 0, "gray", "darkslategray")
 	-- train control/safety indication
-	if train.tarvelocity or train.atc_command then
-		ht[#ht+1] = "10,10=(advtrains_hud_atc.png^[resize\\:30x30^[multiply\\:cyan)"
-	end
-	if train.hud_lzb_effect_tmr then
-		ht[#ht+1] = "50,10=(advtrains_hud_lzb.png^[resize\\:30x30^[multiply\\:red)"
-	end
-	if train.is_shunt then
-		ht[#ht+1] = "90,10=(advtrains_hud_shunt.png^[resize\\:30x30^[multiply\\:orange)"
-	end
+	hud:add(10, 10, T"advtrains_hud_atc.png":resize(30, 30):multiply((train.tarvelocity or train.atc_command) and "cyan" or "darkslategray"))
+	hud:add(50, 10, T"advtrains_hud_lzb.png":resize(30, 30):multiply(train.hud_lzb_effect_tmr and "red" or "darkslategray"))
+	hud:add(90, 10, T"advtrains_hud_shunt.png":resize(30, 30):multiply(train.is_shunt and "orange" or "darkslategray"))
 	-- door
-	ht[#ht+1] = "187,10=(advtrains_hud_bg.png^[resize\\:26x30^[colorize\\:white)"
-	ht[#ht+1] = "189,12=(advtrains_hud_bg.png^[resize\\:22x11)"
-	ht[#ht+1] = sformat("170,10=(advtrains_hud_bg.png^[resize\\:15x30^[colorize\\:%s)", train.door_open==-1 and "white" or "darkslategray")
-	ht[#ht+1] = "172,12=(advtrains_hud_bg.png^[resize\\:11x11)"
-	ht[#ht+1] = sformat("215,10=(advtrains_hud_bg.png^[resize\\:15x30^[colorize\\:%s)", train.door_open==1 and "white" or "darkslategray")
-	ht[#ht+1] = "217,12=(advtrains_hud_bg.png^[resize\\:11x11)"
+	hud:add_fill(187, 10, 26, 30, "white"):add_fill(189, 12, 22, 11, "black")
+	hud:add_fill(170, 10, 15, 30, train.door_open==-1 and "white" or "darkslategray"):add_fill(172, 12, 11, 11, "black")
+	hud:add_fill(215, 10, 15, 30, train.door_open==1 and "white" or "darkslategray"):add_fill(217, 12, 11, 11, "black")
 	-- speed indication(s)
-	sevenseg(math.floor(vel/10), 320, 10, 30, 10, "[colorize\\:red\\:255")
-	sevenseg(vel%10, 380, 10, 30, 10, "[colorize\\:red\\:255")
-	for i = 1, vel, 1 do
-		ht[#ht+1] = sformat("%d,65=(advtrains_hud_bg.png^[resize\\:8x20^[colorize\\:white)", i*11-1)
-	end
-	for i = max+1, 20, 1 do
-		ht[#ht+1] = sformat("%d,65=(advtrains_hud_bg.png^[resize\\:8x20^[colorize\\:darkslategray)", i*11-1)
-	end
+	hud:add_n7seg(320, 10, 110, 90, vel, 2, "red")
+	hud:add_segmentbar_leftright(10, 65, 217, 20, 3, 20, max, 20, "darkslategray", 0, vel, "white")
 	if res and res > 0 then
-		ht[#ht+1] = sformat("%d,60=(advtrains_hud_bg.png^[resize\\:3x30^[colorize\\:red\\:255)", 7+res*11)
+		hud:add_fill(7+res*11, 60, 3, 30, "red")
 	end
 	if train.tarvelocity then
-		ht[#ht+1] = sformat("%d,85=(advtrains_hud_arrow.png^[multiply\\:cyan^[transformFY^[makealpha\\:#000000)", 1+train.tarvelocity*11)
+		hud:add(1+train.tarvelocity*11, 85, T"advtrains_hud_arrow.png":transform"FY":multiply"cyan")
 	end
+	local lzbdisp
 	local lzb = train.lzb
 	if lzb and lzb.checkpoints then
 		local oc = lzb.checkpoints
@@ -285,37 +230,38 @@ function advtrains.hud_train_format(train, flip)
 			if spd == -1 then spd = nil end
 			local c = not spd and "lime" or (type(spd) == "number" and (spd == 0) and "red" or "orange") or nil
 			if c then
-				ht[#ht+1] = sformat("130,10=(advtrains_hud_bg.png^[resize\\:30x5^[colorize\\:%s)",c)
-				ht[#ht+1] = sformat("130,35=(advtrains_hud_bg.png^[resize\\:30x5^[colorize\\:%s)",c)
 				if spd and spd~=0 then
-					ht[#ht+1] = sformat("%d,50=(advtrains_hud_arrow.png^[multiply\\:red^[makealpha\\:#000000)", 1+spd*11) 
+					hud:add(1+spd*11, 50, T"advtrains_hud_arrow.png":multiply"red")
 				end
-				local floor = math.floor
-				local dist = floor(((oc[i].index or train.index)-train.index))
+				local dist = math.floor(((oc[i].index or train.index)-train.index))
 				dist = math.max(0, math.min(999, dist))
-				for j = 1, 3, 1 do
-					sevenseg(floor((dist/10^(3-j))%10), 119+j*11, 18, 4, 2, "[colorize\\:"..c)
-				end
+				lzbdisp = {c = c, d = dist}
 				break
 			end
 		end
 	end
+	if not lzbdisp then
+		lzbdisp = {c = "darkslategray", d = 888}
+	end
+	hud:add_fill(130, 10, 30, 5, lzbdisp.c)
+	hud:add_fill(130, 35, 30, 5, lzbdisp.c)
+	hud:add_n7seg(131, 18, 28, 14, lzbdisp.d, 3, lzbdisp.c)
 	
 	if res and res == 0 then
-		st[#st+1] = attrans("OVERRUN RED SIGNAL! Examine situation and reverse train to move again.")
+		table.insert(st, attrans("OVERRUN RED SIGNAL! Examine situation and reverse train to move again."))
 	end
 	
 	if train.atc_command then
-			st[#st+1] = sformat("ATC: %s%s", train.atc_delay and advtrains.abs_ceil(train.atc_delay).."s " or "", train.atc_command or "")
+		table.insert(st, ("ATC: %s%s"):format(train.atc_delay and advtrains.abs_ceil(train.atc_delay).."s " or "", train.atc_command or ""))
 	end
 	
-	return table.concat(st,"\n"), table.concat(ht,":")
+	return table.concat(st,"\n"), tostring(hud)
 end
 
 local _, texture = advtrains.hud_train_format { -- dummy train object to demonstrate the train hud
 	max_speed = 15, speed_restriction = 15, velocity = 15, tarvelocity = 12,
 	active_control = true, lever = 3, ctrl = {lzb = true}, is_shunt = true,
-	door_open = 1, lzb = {oncoming = {{spd=6, idx=125.7}}}, index = 0,
+	door_open = 1, lzb = {checkpoints = {{speed=6, index=125.7}}}, index = 100,
 }
 
 minetest.register_node("advtrains:hud_demo",{