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

doc/menu_lua_api.txt

@@ -1,4 +1,4 @@
-Minetest Lua Mainmenu API Reference 0.4.9
+Minetest Lua Mainmenu API Reference 0.4.10
 ========================================
 
 Introduction
@@ -8,14 +8,14 @@ Description of formspec language to show your menu is in lua_api.txt
 
 Callbacks
 ---------
-engine.buttonhandler(fields): called when a button is pressed.
+core.buttonhandler(fields): called when a button is pressed.
 ^ fields = {name1 = value1, name2 = value2, ...}
-engine.event_handler(event)
+core.event_handler(event)
 ^ event: "MenuQuit", "KeyEnter", "ExitButton" or "EditBoxEnter"
 
 Gamedata
 --------
-The "gamedata" table is read when calling engine.start(). It should contain:
+The "gamedata" table is read when calling core.start(). It should contain:
 {
 	playername     = <name>,
 	password       = <password>,
@@ -27,15 +27,15 @@ The "gamedata" table is read when calling engine.start(). It should contain:
 
 Functions
 ---------
-engine.start()
-engine.close()
+core.start()
+core.close()
 
 Filesystem:
-engine.get_scriptdir()
+core.get_scriptdir()
 ^ returns directory of script
-engine.get_modpath() (possible in async calls)
+core.get_modpath() (possible in async calls)
 ^ returns path to global modpath
-engine.get_modstore_details(modid) (possible in async calls)
+core.get_modstore_details(modid) (possible in async calls)
 ^ modid numeric id of mod in modstore
 ^ returns {
 	id			= <numeric id of mod in modstore>,
@@ -47,7 +47,7 @@ engine.get_modstore_details(modid) (possible in async calls)
 	license		= <short description of license>,
 	rating		= <float value of current rating>
 }
-engine.get_modstore_list() (possible in async calls)
+core.get_modstore_list() (possible in async calls)
 ^ returns {
 	[1] = {
 		id		 = <numeric id of mod in modstore>,
@@ -55,60 +55,60 @@ engine.get_modstore_list() (possible in async calls)
 		basename = <basename for mod>
 	}
 }
-engine.get_gamepath() (possible in async calls)
+core.get_gamepath() (possible in async calls)
 ^ returns path to global gamepath
-engine.get_texturepath() (possible in async calls)
+core.get_texturepath() (possible in async calls)
 ^ returns path to default textures
-engine.get_dirlist(path,onlydirs) (possible in async calls)
+core.get_dirlist(path,onlydirs) (possible in async calls)
 ^ path to get subdirs from
 ^ onlydirs should result contain only dirs?
 ^ returns list of folders within path
-engine.create_dir(absolute_path) (possible in async calls)
+core.create_dir(absolute_path) (possible in async calls)
 ^ absolute_path to directory to create (needs to be absolute)
 ^ returns true/false
-engine.delete_dir(absolute_path) (possible in async calls)
+core.delete_dir(absolute_path) (possible in async calls)
 ^ absolute_path to directory to delete (needs to be absolute)
 ^ returns true/false
-engine.copy_dir(source,destination,keep_soure) (possible in async calls)
+core.copy_dir(source,destination,keep_soure) (possible in async calls)
 ^ source folder
 ^ destination folder
 ^ keep_source DEFAULT true --> if set to false source is deleted after copying
 ^ returns true/false
-engine.extract_zip(zipfile,destination) [unzip within path required]
+core.extract_zip(zipfile,destination) [unzip within path required]
 ^ zipfile to extract
 ^ destination folder to extract to
 ^ returns true/false
-engine.download_file(url,target) (possible in async calls)
+core.download_file(url,target) (possible in async calls)
 ^ url to download
 ^ target to store to
 ^ returns true/false
-engine.get_version() (possible in async calls)
+core.get_version() (possible in async calls)
 ^ returns current core version
-engine.sound_play(spec, looped) -> handle
+core.sound_play(spec, looped) -> handle
 ^ spec = SimpleSoundSpec (see lua-api.txt)
 ^ looped = bool
-engine.sound_stop(handle)
+core.sound_stop(handle)
 
 Formspec:
-engine.update_formspec(formspec)
-engine.get_table_index(tablename) -> index
+core.update_formspec(formspec)
+core.get_table_index(tablename) -> index
 ^ can also handle textlists
-engine.formspec_escape(string) -> string
+core.formspec_escape(string) -> string
 ^ escapes characters [ ] \ , ; that can not be used in formspecs
-engine.explode_table_event(string) -> table
+core.explode_table_event(string) -> table
 ^ returns e.g. {type="CHG", row=1, column=2}
 ^ type: "INV" (no row selected), "CHG" (selected) or "DCL" (double-click)
-engine.explode_textlist_event(string) -> table
+core.explode_textlist_event(string) -> table
 ^ returns e.g. {type="CHG", index=1}
 ^ type: "INV" (no row selected), "CHG" (selected) or "DCL" (double-click)
 
 GUI:
-engine.set_background(type, texturepath)
+core.set_background(type, texturepath)
 ^ type: "background", "overlay", "header" or "footer"
-engine.set_clouds(<true/false>)
-engine.set_topleft_text(text)
-engine.show_keys_menu()
-engine.file_open_dialog(formname,caption)
+core.set_clouds(<true/false>)
+core.set_topleft_text(text)
+core.show_keys_menu()
+core.file_open_dialog(formname,caption)
 ^ shows a file open dialog
 ^ formname is base name of dialog response returned in fields
 ^     -if dialog was accepted "_accepted"
@@ -116,7 +116,7 @@ engine.file_open_dialog(formname,caption)
 ^     -if dialog was canceled "_cancelled"
 ^        will be added to fieldname value is set to formname itself
 ^ returns nil or selected file/folder
-engine.get_screen_info()
+core.get_screen_info()
 ^ returns {
 	density         = <screen density 0.75,1.0,2.0,3.0 ... (dpi)>,
 	display_width   = <width of display>,
@@ -126,7 +126,7 @@ engine.get_screen_info()
 	}
 
 Games:
-engine.get_game(index)
+core.get_game(index)
 ^ returns {
 	id               = <id>,
 	path             = <full path to game>,
@@ -136,10 +136,10 @@ engine.get_game(index)
 	DEPRECATED:
 	addon_mods_paths = {[1] = <path>,},
 }
-engine.get_games() -> table of all games in upper format (possible in async calls)
+core.get_games() -> table of all games in upper format (possible in async calls)
 
 Favorites:
-engine.get_favorites(location) -> list of favorites (possible in async calls)
+core.get_favorites(location) -> list of favorites (possible in async calls)
 ^ location: "local" or "online"
 ^ returns {
 	[1] = {
@@ -156,24 +156,24 @@ engine.get_favorites(location) -> list of favorites (possible in async calls)
 	port          = <port>
 	},
 }
-engine.delete_favorite(id, location) -> success
+core.delete_favorite(id, location) -> success
 
 Logging:
-engine.debug(line) (possible in async calls)
+core.debug(line) (possible in async calls)
 ^ Always printed to stderr and logfile (print() is redirected here)
-engine.log(line) (possible in async calls)
-engine.log(loglevel, line) (possible in async calls)
+core.log(line) (possible in async calls)
+core.log(loglevel, line) (possible in async calls)
 ^ loglevel one of "error", "action", "info", "verbose"
 
 Settings:
-engine.setting_set(name, value)
-engine.setting_get(name) -> string or nil (possible in async calls)
-engine.setting_setbool(name, value)
-engine.setting_getbool(name) -> bool or nil (possible in async calls)
-engine.setting_save() -> nil, save all settings to config file
+core.setting_set(name, value)
+core.setting_get(name) -> string or nil (possible in async calls)
+core.setting_setbool(name, value)
+core.setting_getbool(name) -> bool or nil (possible in async calls)
+core.setting_save() -> nil, save all settings to config file
 
 Worlds:
-engine.get_worlds() -> list of worlds (possible in async calls)
+core.get_worlds() -> list of worlds (possible in async calls)
 ^ returns {
 	[1] = {
 	path   = <full path to world>,
@@ -181,16 +181,16 @@ engine.get_worlds() -> list of worlds (possible in async calls)
 	gameid = <gameid of world>,
 	},
 }
-engine.create_world(worldname, gameid)
-engine.delete_world(index)
+core.create_world(worldname, gameid)
+core.delete_world(index)
 
 Helpers:
-engine.gettext(string) -> string
+core.gettext(string) -> string
 ^ look up the translation of a string in the gettext message catalog
 fgettext(string, ...) -> string
-^ call engine.gettext(string), replace "$1"..."$9" with the given
-^ extra arguments, call engine.formspec_escape and return the result
-engine.parse_json(string[, nullvalue]) -> something (possible in async calls)
+^ call core.gettext(string), replace "$1"..."$9" with the given
+^ extra arguments, call core.formspec_escape and return the result
+core.parse_json(string[, nullvalue]) -> something (possible in async calls)
 ^ see core.parse_json (lua_api.txt)
 dump(obj, dumped={})
 ^ Return object serialized as a string
@@ -202,7 +202,7 @@ core.is_yes(arg) (possible in async calls)
 ^ returns whether arg can be interpreted as yes
 
 Async:
-engine.handle_async(async_job,parameters,finished)
+core.handle_async(async_job,parameters,finished)
 ^ execute a function asynchronously
 ^ async_job is a function receiving one parameter and returning one parameter
 ^ parameters parameter table passed to async_job
@@ -212,8 +212,8 @@ engine.handle_async(async_job,parameters,finished)
 Limitations of Async operations
  -No access to global lua variables, don't even try
  -Limited set of available functions
-	e.g. No access to functions modifying menu like engine.start,engine.close,
-	engine.file_open_dialog
+	e.g. No access to functions modifying menu like core.start,core.close,
+	core.file_open_dialog
 			
 
 Class reference