Change formspec to use textarea element.

This also removes the pipe as line separator, and uses real
newlines instead.

To be compatible with older signs, those older signs are *NOT*
updated, and still use the old line handling code. In order to
take advantage of the new UI, old signs will have to be
replaced. This is an unfortunate drawback that cannot be
fixed.

Newly-placed signs will have the new features right away.

signs_lib/init.lua

@@ -250,7 +250,7 @@ local fences_with_sign = { }
 
 -- some local helper functions
 
-local function split_lines_and_words(text)
+local function split_lines_and_words_old(text)
 	local lines = { }
 	local line = { }
 	if not text then return end
@@ -269,6 +269,15 @@ local function split_lines_and_words(text)
 	return lines
 end
 
+local function split_lines_and_words(text)
+	if not text then return end
+	local lines = { }
+	for _, line in ipairs(text:split("\n")) do
+		table.insert(lines, { line })
+	end
+	return lines
+end
+
 local math_max = math.max
 
 local function fill_line(x, y, w, c)
@@ -380,9 +389,10 @@ local function make_sign_texture(lines)
 	return table.concat(texture, "")
 end
 
-local function set_obj_text(obj, text)
+local function set_obj_text(obj, text, new)
+	local split = new and split_lines_and_words or split_lines_and_words_old
 	obj:set_properties({
-		textures={make_sign_texture(split_lines_and_words(text))},
+		textures={make_sign_texture(split(text))},
 		visual_size = TEXT_SCALE,
 	})
 end
@@ -391,9 +401,10 @@ signs_lib.construct_sign = function(pos)
     local meta = minetest.get_meta(pos)
 	meta:set_string(
 		"formspec",
-		"field[text;;${text}]"..
+		"size[6,4]"..
-		"size[4,2]"..
+		"textarea[0,0;6.5,3;text;;${text}]"..
-		"background[-1.25,-0.5;6.5,3;bg_signs_lib.jpg]")
+		"button_exit[2,3;2,1;ok;Write]"..
+		"background[-0.5,-0.5;7,5;bg_signs_lib.jpg]")
 	meta:set_string("infotext", "")
 end
 
@@ -418,9 +429,14 @@ end
 
 signs_lib.update_sign = function(pos, fields)
     local meta = minetest.get_meta(pos)
+    local new
 	if fields then
 		meta:set_string("infotext", make_infotext(fields.text).." ")
 		meta:set_string("text", fields.text)
+		meta:set_int("__signslib_new_format", 1)
+		new = true
+	else
+		new = (meta:get_int("__signslib_new_format") ~= 0)
 	end
     local text = meta:get_string("text")
     if text == nil then return end
@@ -428,7 +444,7 @@ signs_lib.update_sign = function(pos, fields)
     for _, v in ipairs(objects) do
 		local e = v:get_luaentity()
 		if e and e.name == "signs:text" then
-			set_obj_text(v, text)
+			set_obj_text(v, text, new)
 			return
         end
     end
@@ -533,19 +549,17 @@ function signs_lib.determine_sign_type(itemstack, placer, pointed_thing)
 end
 
 function signs_lib.receive_fields(pos, formname, fields, sender)
-	if fields and fields.text then
-		minetest.log("action", S("%s wrote \"%s\" to sign at %s"):format(
-			(sender:get_player_name() or ""),
-			fields.text,
-			minetest.pos_to_string(pos)
-		))
-	end
 	if minetest.is_protected(pos, sender:get_player_name()) then
 		minetest.record_protection_violation(pos,
 			sender:get_player_name())
 		return
 	end
-	if fields and fields.text then
+	if fields and fields.text and fields.ok then
+		minetest.log("action", S("%s wrote \"%s\" to sign at %s"):format(
+			(sender:get_player_name() or ""),
+			fields.text,
+			minetest.pos_to_string(pos)
+		))
 		signs_lib.update_sign(pos, fields)
 	end
 end