don't reset scroll position if re-printing the same message

(causes color code to be displayed raw)

README.md

@@ -49,7 +49,7 @@ The panels also respond to these control messages:
 
 	As it advances through the message, the scroll code will search through the message for a printable character, on each scroll step, basically stripping-out color code, and using just the last one before the new start position.  This is done in order to keep a constant visible speed (the text will still be colored properly though).
 * "stop_scroll" does just what it says - it stops the auto-scroll timer.  
-* "scroll_speed" followed by a decimal number (in the string, not a byte value) sets the time between scroll steps.  Minimum 0.5s, maximum 5s.
+* "scroll_speed" followed by a decimal number (in the string, not a byte value) sets the time between scroll steps.  Minimum 0.2s, maximum 5s.
 * "scroll_step" will immediately advance the last-displayed message by one character.  Omit the above automatic scrolling keywords, and use ONLY this keyword instead if you want to let your LuaController control the scrolling speed.  Optionally, you can follow this with a number and the scroll code will skip forward that many bytes into the message, starting from the current position, before starting the above-mentioned color-vs-character search.  Essentially, this value will roughly translate to the number of printable characters to skip.
 * "get" will read the one character (as a numerical character value) currently displayed by the master panel (by reading its node name)
 * "getstr" will read the last-stored message for the entire lineup/wall (from the master panel's meta).  Note that even if the message has been or is being scrolled, you'll get the original stored message.

init.lua

@@ -143,23 +143,27 @@ end
 led_marquee.set_timer = function(pos, timeout)
 	local timer = minetest.get_node_timer(pos)
 	timer:stop()
+	if not timeout or timeout < 0.2 or timeout > 5 then return false end
+
 	if timeout > 0 then
 		local meta = minetest.get_meta(pos)
+		meta:set_int("timeout", timeout)
 		timer:start(timeout)
 	end
 end
 
 led_marquee.scroll_text = function(pos, elapsed, skip)
+	skip = skip or 1
 	local meta = minetest.get_meta(pos)
 	local msg = meta:get_string("last_msg")
 	local channel = meta:get_string("channel")
 	local index = meta:get_int("index")
 	local color = meta:get_int("last_color")
 	local colorchar = color_to_char[color+1]
-	if not index or index < 1 or not string.byte(msg, index) then index = 1 end
+	if not index or index < 1 then index = 1 end
 	local len = string.len(msg)
-	skip = skip or 1
 	index = index + skip
+	if index > len then index = 1 end
 
 	-- search backward to find the most recent color code in the string
 	local r = index
@@ -174,16 +178,16 @@ led_marquee.scroll_text = function(pos, elapsed, skip)
 	-- search forward to find the next printable symbol after the current index
 	local f = index
 	while f < len do
-		if string.match(string.sub(msg, f, f+1), "/[0-9A-Ra-r]") then
+		if string.match(string.sub(msg, f-1, f), "/[0-9A-Ra-r]") then
 			f = f + 2
 		else
 			break
 		end
 	end
-
 	led_marquee.display_msg(pos, channel, "/"..colorchar..string.sub(msg, f)..string.rep(" ", skip + 1))
+
 	meta:set_int("index", f)
-	if not elapsed or elapsed < 0.5 then return false end
+	if not elapsed or elapsed < 0.2 then return false end
 	return true
 end
 
@@ -318,15 +322,12 @@ local on_digiline_receive_string = function(pos, node, channel, msg)
 				meta:set_int("index", 1)
 			elseif msg == "start_scroll" then
 				local timeout = meta:get_int("timeout")
-				if not timeout or timeout < 0.5 or timeout > 5 then timeout = 0 end
 				led_marquee.set_timer(pos, timeout)
 			elseif msg == "stop_scroll" then
 				led_marquee.set_timer(pos, 0)
 				return
 			elseif string.sub(msg, 1, 12) == "scroll_speed" then
 				local timeout = tonumber(string.sub(msg, 13))
-				if not timeout or timeout < 0.5 or timeout > 5 then timeout = 0 end
-				meta:set_int("timeout", timeout)
 				led_marquee.set_timer(pos, timeout)
 			elseif string.sub(msg, 1, 11) == "scroll_step" then
 				local skip = tonumber(string.sub(msg, 12))
@@ -340,9 +341,12 @@ local on_digiline_receive_string = function(pos, node, channel, msg)
 			else
 				msg = string.gsub(msg, "//", string.char(30))
 				led_marquee.set_timer(pos, 0)
+				local last_msg = meta:get_string("last_msg")
 				meta:set_string("last_msg", msg)
 				led_marquee.display_msg(pos, channel, msg)
-				meta:set_int("index", 1)
+				if last_msg ~= msg then
+					meta:set_int("index", 1)
+				end
 			end
 		else
 			local asc = string.byte(msg)