add a command to immediately scroll the displayed message by one step

to be used in lieu of the three existing auto-scroll commands in case
you want the LuaC to handle the stepping.

README.md

@@ -46,6 +46,7 @@ The panels also respond to these control messages:
 * "start_scroll" starts the last-displayed message scrolling to the left, automatically moving, and automatically re-starting.  The scroll action will spread across and down a multi-line wall (just set a new, different channel on the first row you want to exclude).
 * "stop_scroll" actually does nothing, since all printable messages automatically stop the timer, but it's a human-readable way to indicate it.
 * "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_step" will immediately advance the last-displayed message by one character.  Omit the "start_scroll" and "scroll_speed" keywords, and use this instead if you want to let your LuaController control the scrolling speed.
 
 If you need vertical scrolling, you will have to handle that yourself (since the size of a screen/wall is not hard-coded).
 

init.lua

@@ -175,13 +175,14 @@ local on_digiline_receive_string = function(pos, node, channel, msg)
 
 	if setchan ~= channel then return end
 	if msg and msg ~= "" and type(msg) == "string" then
-		led_marquee.set_timer(pos, 0)
 		if string.len(msg) > 1 then
 			if msg == "off_multi" or msg == "clear" then
+				led_marquee.set_timer(pos, 0)
 				msg = string.rep(" ", 1024)
 				meta:set_string("last_msg", msg)
 				led_marquee.display_msg(pos, channel, msg)
 			elseif msg == "allon_multi" then
+				led_marquee.set_timer(pos, 0)
 				msg = string.rep(string.char(144), 1024)
 				meta:set_string("last_msg", msg)
 				led_marquee.display_msg(pos, channel, msg)
@@ -190,13 +191,17 @@ local on_digiline_receive_string = function(pos, node, channel, msg)
 				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
-				return -- (the timer is already stopped by receipt of a message)
+				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 msg == "scroll_step" then
+				led_marquee.scroll_text(pos)
 			else
+				led_marquee.set_timer(pos, 0)
 				meta:set_string("last_msg", msg)
 				led_marquee.display_msg(pos, channel, msg)
 			end