basic multi-line support

Stack up a wall of LED panels, any horizontal and vertical amount

Set a channel on the upper left panel, leave the others un-set, and
connect a LuaC to it via digilines.

Long strings sent to that channel will be displayed using all panels,
starting at the upper-left and working from left to right, top to
bottom, wrapping from line to line as appropriate (similar to printing
to a shell terminal).

string.char(28) can be inserted anywhere to force a linefeed.

As usual, printing continues from node to node until the program either
finds a panel with a different non-empty channel than the first one, or
it finds a panel that's facing the wrong way.

If the program finds something other than a panel, it wraps to the next
line.  If it finds something other than a panel twice in a row, that
signals that text has wrapped off of the last row, and printing is cut
off.

Lines of panels don't need to be the same length, the program will wrap
as needed.

This commit also gets rid of the end-of-line padding, uses proper
string.rep() to create the all-off and all-on fills (each of which is
1kB), and fixes one or two other minor issues.

Strings are trimmed to 1 kB.

Panels are not erased between prints.

init.lua

@@ -42,43 +42,60 @@ local cbox = {
 	wall_side = { -8/16, -8/16, -8/16, -7/16, 8/16, 8/16 }
 }
 
-local padding = " "
-local allon = string.char(128)
-for i = 1, 64 do
-	padding = padding.." "
-	allon = allon..string.char(144)
-end
-
 local display_string = function(pos, channel, string)
 	if string == "off_multi" then
-		string = ""
+		string = string.rep(" ", 1024)
 	elseif string == "allon_multi" then
-		string = allon
+		string = string.rep(string.char(144), 1024)
 	end
-	local padded_string = string.sub(string..padding, 1, 64)
+	string = string.sub(string, 1, 1024)
 	local master_fdir = minetest.get_node(pos).param2 % 8
 	local master_meta = minetest.get_meta(pos)
 	local last_color = master_meta:get_int("last_color")
-	local pos2 = pos
-
+	local pos2 = table.copy(pos)
 	if not last_color or last_color < 0 or last_color > 27 then
 		last_color = 0
 		master_meta:set_int("last_color", 0)
 	end
-	for i = 1, 64 do
+	local i = 1
+	local len = string.len(string)
+	local wrapped = nil
+	while i <= len do
 		local node = minetest.get_node(pos2)
 		local fdir = node.param2 % 8
 		local meta = minetest.get_meta(pos2)
-		local setchan = meta:get_string("channel")
-		if not string.match(node.name, "led_marquee:char_") or (setchan ~= nil and setchan ~= "" and setchan ~= channel) then break end
-		local asc = string.byte(padded_string, i, i)
-		if master_fdir == fdir and asc > 30 and asc < 256 then
+		local setchan = nil
+		if meta then setchan = meta:get_string("channel") end
+		local asc = string.byte(string, i, i)
+		if not string.match(node.name, "led_marquee:char_") then
+			if not wrapped then
+				pos2.x = pos.x
+				pos2.y = pos2.y-1
+				pos2.z = pos.z
+				wrapped = true
+			else
+				break
+			end
+		elseif string.match(node.name, "led_marquee:char_")
+			and fdir ~= master_fdir or (setchan ~= nil and setchan ~= "" and setchan ~= channel) then
+			break
+		elseif asc == 28 then
+			pos2.x = pos.x
+			pos2.y = pos2.y-1
+			pos2.z = pos.z
+			i = i + 1
+			wrapped = nil
+		elseif asc > 30 and asc < 256 then
 			minetest.swap_node(pos2, { name = "led_marquee:char_"..asc, param2 = master_fdir + (last_color*8)})
 			pos2.x = pos2.x + fdir_to_right[fdir+1][1]
 			pos2.z = pos2.z + fdir_to_right[fdir+1][2]
+			i = i + 1
+			wrapped = nil
 		elseif asc < 28 then
 			last_color = asc
 			master_meta:set_int("last_color", asc)
+			i = i + 1
+			wrapped = nil
 		end
 	end
 end