default: Improves reading and writing to books. (#2656)

* Allow anyone to write to a book without any text and title.
* Allows saving books without any text or title.
* Adds a "Read" and "Write" tab to written owned books.

Fixes #1743

mods/default/craftitems.lua

@@ -3,6 +3,46 @@
 -- support for MT game translation.
 local S = default.get_translator
 
+local esc = minetest.formspec_escape
+local formspec_size = "size[8,8]"
+
+local function formspec_core(tab)
+	if tab == nil then tab = 1 else tab = tostring(tab) end
+	return "tabheader[0,0;book_header;" ..
+		esc(S("Write")) .. "," ..
+		esc(S("Read")) .. ";" ..
+		tab  ..  ";false;false]"
+end
+
+local function formspec_write(title, text)
+	return "field[0.5,1;7.5,0;title;" .. esc(S("Title:")) .. ";" ..
+			esc(title) .. "]" ..
+		"textarea[0.5,1.5;7.5,7;text;" .. esc(S("Contents:")) .. ";" ..
+			esc(text) .. "]" ..
+		"button_exit[2.5,7.5;3,1;save;" .. esc(S("Save")) .. "]"
+end
+
+local function formspec_read(owner, title, string, text, page, page_max)
+	return "label[0.5,0.5;" .. esc(S("by @1", owner)) .. "]" ..
+		"tablecolumns[color;text]" ..
+		"tableoptions[background=#00000000;highlight=#00000000;border=false]" ..
+		"table[0.4,0;7,0.5;title;#FFFF00," .. esc(title) .. "]" ..
+		"textarea[0.5,1.5;7.5,7;;" ..
+			esc(string ~= "" and string or text) .. ";]" ..
+		"button[2.4,7.6;0.8,0.8;book_prev;<]" ..
+		"label[3.2,7.7;" .. esc(S("Page @1 of @2", page, page_max)) .. "]" ..
+		"button[4.9,7.6;0.8,0.8;book_next;>]"
+end
+
+local function formspec_string(lpp, page, lines, string)
+	for i = ((lpp * page) - lpp) + 1, lpp * page do
+		if not lines[i] then break end
+		string = string .. lines[i] .. "\n"
+	end
+	return string
+end
+
+local tab_number
 local lpp = 14 -- Lines per book's page
 local function book_on_use(itemstack, user)
 	local player_name = user:get_player_name()
@@ -19,8 +59,8 @@ local function book_on_use(itemstack, user)
 	local data = meta:to_table().fields
 
 	if data.owner then
-		title = data.title
+		title = data.title or ""
-		text = data.text
+		text = data.text or ""
 		owner = data.owner
 
 		for str in (text .. "\n"):gmatch("([^\n]*)[\n]") do
@@ -30,37 +70,26 @@ local function book_on_use(itemstack, user)
 		if data.page then
 			page = data.page
 			page_max = data.page_max
-
+			string = formspec_string(lpp, page, lines, string)
-			for i = ((lpp * page) - lpp) + 1, lpp * page do
-				if not lines[i] then break end
-				string = string .. lines[i] .. "\n"
-			end
 		end
 	end
 
 	local formspec
-	local esc = minetest.formspec_escape
+	if title == "" and text == "" then
-	if owner == player_name then
+		formspec = formspec_write(title, text)
-		formspec = "size[8,8]" ..
+	elseif owner == player_name then
-			"field[0.5,1;7.5,0;title;" .. esc(S("Title:")) .. ";" ..
+		local tab = tab_number or 1
-				esc(title) .. "]" ..
+		if tab == 2 then
-			"textarea[0.5,1.5;7.5,7;text;" .. esc(S("Contents:")) .. ";" ..
+			formspec = formspec_core(tab) ..
-				esc(text) .. "]" ..
+				formspec_read(owner, title, string, text, page, page_max)
-			"button_exit[2.5,7.5;3,1;save;" .. esc(S("Save")) .. "]"
+		else
+			formspec = formspec_core(tab) .. formspec_write(title, text)
+		end
 	else
-		formspec = "size[8,8]" ..
+		formspec = formspec_read(owner, title, string, text, page, page_max)
-			"label[0.5,0.5;" .. esc(S("by @1", owner)) .. "]" ..
-			"tablecolumns[color;text]" ..
-			"tableoptions[background=#00000000;highlight=#00000000;border=false]" ..
-			"table[0.4,0;7,0.5;title;#FFFF00," .. esc(title) .. "]" ..
-			"textarea[0.5,1.5;7.5,7;;" ..
-				minetest.formspec_escape(string ~= "" and string or text) .. ";]" ..
-			"button[2.4,7.6;0.8,0.8;book_prev;<]" ..
-			"label[3.2,7.7;" .. esc(S("Page @1 of @2", page, page_max)) .. "]" ..
-			"button[4.9,7.6;0.8,0.8;book_next;>]"
 	end
 
-	minetest.show_formspec(player_name, "default:book", formspec)
+	minetest.show_formspec(player_name, "default:book", formspec_size .. formspec)
 	return itemstack
 end
 
@@ -69,12 +98,37 @@ local max_title_size = 80
 local short_title_size = 35
 minetest.register_on_player_receive_fields(function(player, formname, fields)
 	if formname ~= "default:book" then return end
+	local player_name = player:get_player_name()
 	local inv = player:get_inventory()
 	local stack = player:get_wielded_item()
+	local data = stack:get_meta():to_table().fields
 
-	if fields.save and fields.title and fields.text
+	local title = data.title or ""
-			and fields.title ~= "" and fields.text ~= "" then
+	local text = data.text or ""
-		local new_stack, data
+
+	if fields.book_header ~= nil and data.owner == player_name then
+		local contents
+		local tab = tonumber(fields.book_header)
+		if tab == 1 then
+			contents = formspec_core(tab) ..
+				formspec_write(title, text)
+		elseif tab == 2 then
+			local lines, string = {}, ""
+			for str in (text .. "\n"):gmatch("([^\n]*)[\n]") do
+				lines[#lines+1] = str
+			end
+			string = formspec_string(lpp, data.page, lines, string)
+			contents = formspec_read(player_name, title, string,
+				text, data.page, data.page_max)
+		end
+		tab_number = tab
+		local formspec = formspec_size .. formspec_core(tab) .. contents
+		minetest.show_formspec(player_name, "default:book", formspec)
+		return
+	end
+
+	if fields.save and fields.title and fields.text then
+		local new_stack
 		if stack:get_name() ~= "default:book_written" then
 			local count = stack:get_count()
 			if count == 1 then
@@ -83,11 +137,9 @@ minetest.register_on_player_receive_fields(function(player, formname, fields)
 				stack:set_count(count - 1)
 				new_stack = ItemStack("default:book_written")
 			end
-		else
-			data = stack:get_meta():to_table().fields
 		end
 
-		if data and data.owner and data.owner ~= player:get_player_name() then
+		if data.owner ~= player_name and title ~= "" and text ~= "" then
 			return
 		end
 
@@ -117,8 +169,7 @@ minetest.register_on_player_receive_fields(function(player, formname, fields)
 		end
 
 	elseif fields.book_next or fields.book_prev then
-		local data = stack:get_meta():to_table().fields
+		if not data.page then
-		if not data or not data.page then
 			return
 		end