Add formspec toolkit and refactor mainmenu to use it

Fix crash on using cursor keys in client menu without selected server
Add support for non fixed size tabviews

builtin/mainmenu/tab_texturepacks.lua

@@ -0,0 +1,117 @@
+--Minetest
+--Copyright (C) 2014 sapier
+--
+--This program is free software; you can redistribute it and/or modify
+--it under the terms of the GNU Lesser General Public License as published by
+--the Free Software Foundation; either version 2.1 of the License, or
+--(at your option) any later version.
+--
+--This program is distributed in the hope that it will be useful,
+--but WITHOUT ANY WARRANTY; without even the implied warranty of
+--MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+--GNU Lesser General Public License for more details.
+--
+--You should have received a copy of the GNU Lesser General Public License along
+--with this program; if not, write to the Free Software Foundation, Inc.,
+--51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+
+--------------------------------------------------------------------------------
+local function filter_texture_pack_list(list)
+	retval = {"None"}
+	for _,i in ipairs(list) do
+		if i~="base" then
+			table.insert(retval, i)
+		end
+	end
+	return retval
+end
+
+--------------------------------------------------------------------------------
+local function render_texture_pack_list(list)
+	local retval = ""
+
+	for i, v in ipairs(list) do
+		if retval ~= "" then
+			retval = retval ..","
+		end
+
+		retval = retval .. core.formspec_escape(v)
+	end
+
+	return retval
+end
+
+--------------------------------------------------------------------------------
+local function get_formspec(tabview, name, tabdata)
+	
+	local retval = "label[4,-0.25;".. fgettext("Select texture pack:") .. "]"..
+			"vertlabel[0,-0.25;".. fgettext("TEXTURE PACKS") .. "]" ..
+			"textlist[4,0.25;7.5,5.0;TPs;"
+
+	local current_texture_path = core.setting_get("texture_path")
+	local list = filter_texture_pack_list(core.get_dirlist(core.get_texturepath(), true))
+	local index = tonumber(core.setting_get("mainmenu_last_selected_TP"))
+
+	if index == nil then index = 1 end
+
+	if current_texture_path == "" then
+		retval = retval ..
+			render_texture_pack_list(list) ..
+			";" .. index .. "]"
+		return retval
+	end
+
+	local infofile = current_texture_path ..DIR_DELIM.."info.txt"
+	local infotext = ""
+	local f = io.open(infofile, "r")
+	if f==nil then
+		infotext = fgettext("No information available")
+	else
+		infotext = f:read("*all")
+		f:close()
+	end
+
+	local screenfile = current_texture_path..DIR_DELIM.."screenshot.png"
+	local no_screenshot = nil
+	if not file_exists(screenfile) then
+		screenfile = nil
+		no_screenshot = defaulttexturedir .. "no_screenshot.png"
+	end
+
+	return	retval ..
+			render_texture_pack_list(list) ..
+			";" .. index .. "]" ..
+			"image[0.65,0.25;4.0,3.7;"..core.formspec_escape(screenfile or no_screenshot).."]"..
+			"textarea[1.0,3.25;3.7,1.5;;"..core.formspec_escape(infotext or "")..";]"
+end
+
+--------------------------------------------------------------------------------
+local function main_button_handler(tabview, fields, name, tabdata)
+	if fields["TPs"] ~= nil then
+		local event = core.explode_textlist_event(fields["TPs"])
+		if event.type == "CHG" or event.type == "DCL" then
+			local index = core.get_textlist_index("TPs")
+			core.setting_set("mainmenu_last_selected_TP",
+				index)
+			local list = filter_texture_pack_list(core.get_dirlist(core.get_texturepath(), true))
+			local current_index = core.get_textlist_index("TPs")
+			if current_index ~= nil and #list >= current_index then
+				local new_path = core.get_texturepath()..DIR_DELIM..list[current_index]
+				if list[current_index] == "None" then new_path = "" end
+
+				core.setting_set("texture_path", new_path)
+			end
+		end
+		return true
+	end
+	return false
+end
+
+--------------------------------------------------------------------------------
+tab_texturepacks = {
+	name = "texturepacks",
+	caption = fgettext("Texturepacks"),
+	cbf_formspec = get_formspec,
+	cbf_button_handler = main_button_handler,
+	on_change = nil
+	}