Fix core.wrap_text and make its behaviour consistent with the docs

Code based on initial implementation by @dsohler.

builtin/common/misc_helpers.lua

@@ -308,59 +308,25 @@ function core.formspec_escape(text)
 end
 
 
-function core.wrap_text(text, charlimit)
-	local retval = {}
-
-	local current_idx = 1
-
-	local start,stop = string_find(text, " ", current_idx)
-	local nl_start,nl_stop = string_find(text, "\n", current_idx)
-	local gotnewline = false
-	if nl_start ~= nil and (start == nil or nl_start < start) then
-		start = nl_start
-		stop = nl_stop
-		gotnewline = true
-	end
-	local last_line = ""
-	while start ~= nil do
-		if string.len(last_line) + (stop-start) > charlimit then
-			retval[#retval + 1] = last_line
-			last_line = ""
+function core.wrap_text(text, max_length, as_table)
+	local result = {}
+	local line = {}
+	if #text <= max_length then
+		return as_table and {text} or text
 	end
 
-		if last_line ~= "" then
-			last_line = last_line .. " "
+	for word in text:gmatch('%S+') do
+		local cur_length = #table.concat(line, ' ')
+		if cur_length > 0 and cur_length + #word + 1 >= max_length then
+			-- word wouldn't fit on current line, move to next line
+			table.insert(result, table.concat(line, ' '))
+			line = {}
+		end
+		table.insert(line, word)
 	end
 
-		last_line = last_line .. string_sub(text, current_idx, stop - 1)
-
-		if gotnewline then
-			retval[#retval + 1] = last_line
-			last_line = ""
-			gotnewline = false
-		end
-		current_idx = stop+1
-
-		start,stop = string_find(text, " ", current_idx)
-		nl_start,nl_stop = string_find(text, "\n", current_idx)
-
-		if nl_start ~= nil and (start == nil or nl_start < start) then
-			start = nl_start
-			stop = nl_stop
-			gotnewline = true
-		end
-	end
-
-	--add last part of text
-	if string.len(last_line) + (string.len(text) - current_idx) > charlimit then
-			retval[#retval + 1] = last_line
-			retval[#retval + 1] = string_sub(text, current_idx)
-	else
-		last_line = last_line .. " " .. string_sub(text, current_idx)
-		retval[#retval + 1] = last_line
-	end
-
-	return retval
+	table.insert(result, table.concat(line, ' '))
+	return as_table and result or table.concat(result, '\n')
 end
 
 --------------------------------------------------------------------------------

builtin/mainmenu/common.lua

@@ -250,7 +250,7 @@ end
 
 --------------------------------------------------------------------------------
 function text2textlist(xpos, ypos, width, height, tl_name, textlen, text, transparency)
-	local textlines = core.wrap_text(text, textlen)
+	local textlines = core.wrap_text(text, textlen, true)
 	local retval = "textlist[" .. xpos .. "," .. ypos .. ";" .. width ..
 			"," .. height .. ";" .. tl_name .. ";"
 

builtin/mainmenu/tab_mods.lua

@@ -66,7 +66,7 @@ local function get_formspec(tabview, name, tabdata)
 		if error == nil then
 			local descriptiontext = descriptionfile:read("*all")
 
-			descriptionlines = core.wrap_text(descriptiontext, 42)
+			descriptionlines = core.wrap_text(descriptiontext, 42, true)
 			descriptionfile:close()
 		else
 			descriptionlines = {}

doc/lua_api.txt

@@ -2158,9 +2158,11 @@ Helper functions
     * e.g. `string:split("a,b", ",") == {"a","b"}`
 * `string:trim()`
     * e.g. `string.trim("\n \t\tfoo bar\t ") == "foo bar"`
-* `minetest.wrap_text(str, limit)`: returns a string
-    * Adds new lines to the string to keep it within the specified character limit
+* `minetest.wrap_text(str, limit, [as_table])`: returns a string or table
+    * Adds newlines to the string to keep it within the specified character limit
+      Note that returned lines may be longer than the limit since it only splits at word borders.
     * limit: Maximal amount of characters in one line
+    * as_table: optional, if true return table of lines instead of string
 * `minetest.pos_to_string({x=X,y=Y,z=Z}, decimal_places))`: returns string `"(X,Y,Z)"`
     * Convert position to a printable string
       Optional: 'decimal_places' will round the x, y and z of the pos to the given decimal place.