Add formspec theming using prepended strings

doc/lua_api.txt

@@ -2001,6 +2001,10 @@ supported. It is a string, with a somewhat strange format.
 Spaces and newlines can be inserted between the blocks, as is used in the
 examples.
 
+WARNING: Minetest allows you to add elements to every single formspec instance
+using player:set_formspec_prepend(), which may be the reason backgrounds are
+appearing when you don't expect them to. See `no_prepend[]`
+
 ### Examples
 
 #### Chest
@@ -2053,6 +2057,10 @@ examples.
 * `position` and `anchor` elements need suitable values to avoid a formspec
   extending off the game window due to particular game window sizes.
 
+#### `no_prepend[]`
+* Must be used after the `size`, `position`, and `anchor` elements (if present).
+* Disables player:set_formspec_prepend() from applying to this formspec.
+
 #### `container[<X>,<Y>]`
 * Start of a container block, moves all physical elements in the container by
   (X, Y).
@@ -4046,6 +4054,13 @@ This is basically a reference to a C++ `ServerActiveObject`
     * Redefine player's inventory form
     * Should usually be called in `on_joinplayer`
 * `get_inventory_formspec()`: returns a formspec string
+* `set_formspec_prepend(formspec)`:
+    * the formspec string will be added to every formspec shown to the user,
+      except for those with a no_prepend[] tag.
+    * This should be used to set style elements such as background[] and
+      bgcolor[], any non-style elements (eg: label) may result in weird behaviour.
+    * Only affects formspecs shown after this is called.
+* `get_formspec_prepend(formspec)`: returns a formspec string.
 * `get_player_control()`: returns table with player pressed keys
     * The table consists of fields with boolean value representing the pressed
       keys, the fields are jump, right, left, LMB, RMB, sneak, aux1, down, up.

src/client.h

@@ -224,7 +224,8 @@ public:
 	void handleCommand_UpdatePlayerList(NetworkPacket* pkt);
 	void handleCommand_ModChannelMsg(NetworkPacket *pkt);
 	void handleCommand_ModChannelSignal(NetworkPacket *pkt);
-	void handleCommand_SrpBytesSandB(NetworkPacket* pkt);
+	void handleCommand_SrpBytesSandB(NetworkPacket *pkt);
+	void handleCommand_FormspecPrepend(NetworkPacket *pkt);
 	void handleCommand_CSMFlavourLimits(NetworkPacket *pkt);
 
 	void ProcessData(NetworkPacket *pkt);
@@ -432,6 +433,10 @@ public:
 	bool sendModChannelMessage(const std::string &channel, const std::string &message);
 	ModChannel *getModChannel(const std::string &channel);
 
+	const std::string &getFormspecPrepend() const
+	{
+		return m_env.getLocalPlayer()->formspec_prepend;
+	}
 private:
 	void loadMods();
 	bool checkBuiltinIntegrity();

src/clientenvironment.h

@@ -78,7 +78,7 @@ public:
 	void step(f32 dtime);
 
 	virtual void setLocalPlayer(LocalPlayer *player);
-	LocalPlayer *getLocalPlayer() { return m_local_player; }
+	LocalPlayer *getLocalPlayer() const { return m_local_player; }
 
 	/*
 		ClientSimpleObjects

src/game.cpp

@@ -2028,7 +2028,7 @@ void Game::openInventory()
 			|| !client->getScript()->on_inventory_open(fs_src->m_client->getInventory(inventoryloc))) {
 		TextDest *txt_dst = new TextDestPlayerInventory(client);
 		GUIFormSpecMenu::create(current_formspec, client, &input->joystick, fs_src,
-			txt_dst);
+			txt_dst, client->getFormspecPrepend());
 		cur_formname = "";
 		current_formspec->setFormSpec(fs_src->getForm(), inventoryloc);
 	}
@@ -2535,7 +2535,7 @@ void Game::handleClientEvent_ShowFormSpec(ClientEvent *event, CameraOrientation
 			new TextDestPlayerInventory(client, *(event->show_formspec.formname));
 
 		GUIFormSpecMenu::create(current_formspec, client, &input->joystick,
-			fs_src, txt_dst);
+			fs_src, txt_dst, client->getFormspecPrepend());
 		cur_formname = *(event->show_formspec.formname);
 	}
 
@@ -2548,7 +2548,8 @@ void Game::handleClientEvent_ShowLocalFormSpec(ClientEvent *event, CameraOrienta
 	FormspecFormSource *fs_src = new FormspecFormSource(*event->show_formspec.formspec);
 	LocalFormspecHandler *txt_dst =
 		new LocalFormspecHandler(*event->show_formspec.formname, client);
-	GUIFormSpecMenu::create(current_formspec, client, &input->joystick, fs_src, txt_dst);
+	GUIFormSpecMenu::create(current_formspec, client, &input->joystick,
+			fs_src, txt_dst, client->getFormspecPrepend());
 
 	delete event->show_formspec.formspec;
 	delete event->show_formspec.formname;
@@ -3210,7 +3211,7 @@ void Game::handlePointingAtNode(const PointedThing &pointed,
 			TextDest *txt_dst = new TextDestNodeMetadata(nodepos, client);
 
 			GUIFormSpecMenu::create(current_formspec, client, &input->joystick, fs_src,
-				txt_dst);
+				txt_dst, client->getFormspecPrepend());
 			cur_formname.clear();
 
 			current_formspec->setFormSpec(meta->getString("formspec"), inventoryloc);
@@ -4105,7 +4106,8 @@ void Game::showPauseMenu()
 	FormspecFormSource *fs_src = new FormspecFormSource(os.str());
 	LocalFormspecHandler *txt_dst = new LocalFormspecHandler("MT_PAUSE_MENU");
 
-	GUIFormSpecMenu::create(current_formspec, client, &input->joystick, fs_src, txt_dst);
+	GUIFormSpecMenu::create(current_formspec, client, &input->joystick,
+			fs_src, txt_dst, client->getFormspecPrepend());
 	current_formspec->setFocus("btn_continue");
 	current_formspec->doPause = true;
 }

src/gui/guiEngine.cpp

@@ -165,6 +165,7 @@ GUIEngine::GUIEngine(JoystickController *joystick,
 			m_texture_source,
 			m_formspecgui,
 			m_buttonhandler,
+			"",
 			false);
 
 	m_menu->allowClose(false);

src/gui/guiFormSpecMenu.cpp

@@ -86,11 +86,13 @@ inline u32 clamp_u8(s32 value)
 GUIFormSpecMenu::GUIFormSpecMenu(JoystickController *joystick,
 		gui::IGUIElement *parent, s32 id, IMenuManager *menumgr,
 		Client *client, ISimpleTextureSource *tsrc, IFormSource *fsrc, TextDest *tdst,
-		bool remap_dbl_click) :
+		std::string formspecPrepend,
+		bool remap_dbl_click):
 	GUIModalMenu(RenderingEngine::get_gui_env(), parent, id, menumgr),
 	m_invmgr(client),
 	m_tsrc(tsrc),
 	m_client(client),
+	m_formspec_prepend(formspecPrepend),
 	m_form_src(fsrc),
 	m_text_dst(tdst),
 	m_joystick(joystick),
@@ -128,11 +130,12 @@ GUIFormSpecMenu::~GUIFormSpecMenu()
 }
 
 void GUIFormSpecMenu::create(GUIFormSpecMenu *&cur_formspec, Client *client,
-	JoystickController *joystick, IFormSource *fs_src, TextDest *txt_dest)
+	JoystickController *joystick, IFormSource *fs_src, TextDest *txt_dest,
+	const std::string &formspecPrepend)
 {
 	if (cur_formspec == nullptr) {
 		cur_formspec = new GUIFormSpecMenu(joystick, guiroot, -1, &g_menumgr,
-			client, client->getTextureSource(), fs_src, txt_dest);
+			client, client->getTextureSource(), fs_src, txt_dest, formspecPrepend);
 		cur_formspec->doPause = false;
 
 		/*
@@ -144,6 +147,7 @@ void GUIFormSpecMenu::create(GUIFormSpecMenu *&cur_formspec, Client *client,
 		*/
 
 	} else {
+		cur_formspec->setFormspecPrepend(formspecPrepend);
 		cur_formspec->setFormSource(fs_src);
 		cur_formspec->setTextDest(txt_dest);
 	}
@@ -2008,7 +2012,6 @@ void GUIFormSpecMenu::regenerateGui(v2u32 screensize)
 		);
 	}
 
-
 	m_slotbg_n = video::SColor(255,128,128,128);
 	m_slotbg_h = video::SColor(255,192,192,192);
 
@@ -2040,7 +2043,7 @@ void GUIFormSpecMenu::regenerateGui(v2u32 screensize)
 
 	/* try to read version from first element only */
 	if (!elements.empty()) {
-		if ( parseVersionDirect(elements[0]) ) {
+		if (parseVersionDirect(elements[0])) {
 			i++;
 		}
 	}
@@ -2067,6 +2070,18 @@ void GUIFormSpecMenu::regenerateGui(v2u32 screensize)
 		}
 	}
 
+	/* "no_prepend" element is always after "position" (or  "size" element) if it used */
+	bool enable_prepends = true;
+	for (; i < elements.size(); i++) {
+		if (elements[i].empty())
+			break;
+
+		std::vector<std::string> parts = split(elements[i], '[');
+		if (parts[0] == "no_prepend")
+			enable_prepends = false;
+		else
+			break;
+	}
 
 	if (mydata.explicit_size) {
 		// compute scaling for specified form size
@@ -2173,12 +2188,19 @@ void GUIFormSpecMenu::regenerateGui(v2u32 screensize)
 	mydata.basepos = getBasePos();
 	m_tooltip_element->setOverrideFont(m_font);
 
-	gui::IGUISkin* skin = Environment->getSkin();
+	gui::IGUISkin *skin = Environment->getSkin();
 	sanity_check(skin);
 	gui::IGUIFont *old_font = skin->getFont();
 	skin->setFont(m_font);
 
 	pos_offset = v2s32();
+
+	if (enable_prepends) {
+		std::vector<std::string> prepend_elements = split(m_formspec_prepend, ']');
+		for (const auto &element : prepend_elements)
+			parseElement(&mydata, element);
+	}
+
 	for (; i< elements.size(); i++) {
 		parseElement(&mydata, elements[i]);
 	}

src/gui/guiFormSpecMenu.h

@@ -287,12 +287,14 @@ public:
 			ISimpleTextureSource *tsrc,
 			IFormSource* fs_src,
 			TextDest* txt_dst,
+			std::string formspecPrepend,
 			bool remap_dbl_click = true);
 
 	~GUIFormSpecMenu();
 
 	static void create(GUIFormSpecMenu *&cur_formspec, Client *client,
-		JoystickController *joystick, IFormSource *fs_src, TextDest *txt_dest);
+		JoystickController *joystick, IFormSource *fs_src, TextDest *txt_dest,
+		const std::string &formspecPrepend);
 
 	void setFormSpec(const std::string &formspec_string,
 			const InventoryLocation &current_inventory_location)
@@ -302,6 +304,11 @@ public:
 		regenerateGui(m_screensize_old);
 	}
 
+	void setFormspecPrepend(const std::string &formspecPrepend)
+	{
+		m_formspec_prepend = formspecPrepend;
+	}
+
 	// form_src is deleted by this GUIFormSpecMenu
 	void setFormSource(IFormSource *form_src)
 	{
@@ -378,6 +385,7 @@ protected:
 	Client *m_client;
 
 	std::string m_formspec_string;
+	std::string m_formspec_prepend;
 	InventoryLocation m_current_inventory_location;
 
 	std::vector<ListDrawSpec> m_inventorylists;

src/network/clientopcodes.cpp

@@ -121,6 +121,7 @@ const ToClientCommandHandler toClientCommandTable[TOCLIENT_NUM_MSG_TYPES] =
 	null_command_handler,
 	null_command_handler,
 	{ "TOCLIENT_SRP_BYTES_S_B",            TOCLIENT_STATE_NOT_CONNECTED, &Client::handleCommand_SrpBytesSandB }, // 0x60
+	{ "TOCLIENT_FORMSPEC_PREPEND",         TOCLIENT_STATE_CONNECTED, &Client::handleCommand_FormspecPrepend }, // 0x61,
 };
 
 const static ServerCommandFactory null_command_factory = { "TOSERVER_NULL", 0, false };

src/network/clientpackethandler.cpp

@@ -1324,6 +1324,15 @@ void Client::handleCommand_SrpBytesSandB(NetworkPacket* pkt)
 	Send(&resp_pkt);
 }
 
+void Client::handleCommand_FormspecPrepend(NetworkPacket *pkt)
+{
+	LocalPlayer *player = m_env.getLocalPlayer();
+	assert(player != NULL);
+
+	// Store formspec in LocalPlayer
+	*pkt >> player->formspec_prepend;
+}
+
 void Client::handleCommand_CSMFlavourLimits(NetworkPacket *pkt)
 {
 	*pkt >> m_csm_flavour_limits >> m_csm_noderange_limit;

src/network/networkprotocol.h

@@ -187,6 +187,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 			'zoom_fov'.
 		Nodebox version 5
 		Add disconnected nodeboxes
+		Add TOCLIENT_FORMSPEC_PREPEND
 */
 
 #define LATEST_PROTOCOL_VERSION 36
@@ -644,7 +645,13 @@ enum ToClientCommand
 		std::string bytes_B
 	*/
 
-	TOCLIENT_NUM_MSG_TYPES = 0x61,
+	TOCLIENT_FORMSPEC_PREPEND = 0x61,
+	/*
+		u16 len
+		u8[len] formspec
+	*/
+
+	TOCLIENT_NUM_MSG_TYPES = 0x62,
 };
 
 enum ToServerCommand
@@ -930,4 +937,3 @@ enum CSMFlavourLimit : u64 {
 	CSM_FL_LOOKUP_NODES = 0x00000010, // Limit node lookups
 	CSM_FL_ALL = 0xFFFFFFFF,
 };
-

src/network/serveropcodes.cpp

@@ -210,4 +210,5 @@ const ClientCommandFactory clientCommandFactoryTable[TOCLIENT_NUM_MSG_TYPES] =
 	null_command_factory,
 	null_command_factory,
 	{ "TOSERVER_SRP_BYTES_S_B",            0, true }, // 0x60
+	{ "TOCLIENT_FORMSPEC_PREPEND",         0, true }, // 0x61
 };

src/player.h

@@ -148,6 +148,7 @@ public:
 	float local_animation_speed;
 
 	std::string inventory_formspec;
+	std::string formspec_prepend;
 
 	PlayerControl control;
 	const PlayerControl& getPlayerControl() { return control; }

src/script/lua_api/l_object.cpp

@@ -1244,6 +1244,37 @@ int ObjectRef::l_get_inventory_formspec(lua_State *L)
 	return 1;
 }
 
+// set_formspec_prepend(self, formspec)
+int ObjectRef::l_set_formspec_prepend(lua_State *L)
+{
+	NO_MAP_LOCK_REQUIRED;
+	ObjectRef *ref = checkobject(L, 1);
+	RemotePlayer *player = getplayer(ref);
+	if (player == NULL)
+		return 0;
+
+	std::string formspec = luaL_checkstring(L, 2);
+
+	player->formspec_prepend = formspec;
+	getServer(L)->reportFormspecPrependModified(player->getName());
+	lua_pushboolean(L, true);
+	return 1;
+}
+
+// get_formspec_prepend(self) -> formspec
+int ObjectRef::l_get_formspec_prepend(lua_State *L)
+{
+	NO_MAP_LOCK_REQUIRED;
+	ObjectRef *ref = checkobject(L, 1);
+	RemotePlayer *player = getplayer(ref);
+	if (player == NULL)
+		 return 0;
+
+	std::string formspec = player->formspec_prepend;
+	lua_pushlstring(L, formspec.c_str(), formspec.size());
+	return 1;
+}
+
 // get_player_control(self)
 int ObjectRef::l_get_player_control(lua_State *L)
 {
@@ -1817,6 +1848,8 @@ const luaL_Reg ObjectRef::methods[] = {
 	luamethod(ObjectRef, set_attribute),
 	luamethod(ObjectRef, set_inventory_formspec),
 	luamethod(ObjectRef, get_inventory_formspec),
+	luamethod(ObjectRef, set_formspec_prepend),
+	luamethod(ObjectRef, get_formspec_prepend),
 	luamethod(ObjectRef, get_player_control),
 	luamethod(ObjectRef, get_player_control_bits),
 	luamethod(ObjectRef, set_physics_override),

src/script/lua_api/l_object.h

@@ -253,6 +253,12 @@ private:
 	// get_inventory_formspec(self) -> formspec
 	static int l_get_inventory_formspec(lua_State *L);
 
+	// set_formspec_prepend(self, formspec)
+	static int l_set_formspec_prepend(lua_State *L);
+
+	// get_formspec_prepend(self) -> formspec
+	static int l_get_formspec_prepend(lua_State *L);
+
 	// get_player_control(self)
 	static int l_get_player_control(lua_State *L);
 

src/server.cpp

@@ -1870,7 +1870,7 @@ void Server::SendPlayerInventoryFormspec(session_t peer_id)
 {
 	RemotePlayer *player = m_env->getPlayer(peer_id);
 	assert(player);
-	if(player->getPeerId() == PEER_ID_INEXISTENT)
+	if (player->getPeerId() == PEER_ID_INEXISTENT)
 		return;
 
 	NetworkPacket pkt(TOCLIENT_INVENTORY_FORMSPEC, 0, peer_id);
@@ -1878,6 +1878,18 @@ void Server::SendPlayerInventoryFormspec(session_t peer_id)
 	Send(&pkt);
 }
 
+void Server::SendPlayerFormspecPrepend(session_t peer_id)
+{
+	RemotePlayer *player = m_env->getPlayer(peer_id);
+	assert(player);
+	if (player->getPeerId() == PEER_ID_INEXISTENT)
+		return;
+
+	NetworkPacket pkt(TOCLIENT_FORMSPEC_PREPEND, 0, peer_id);
+	pkt << FORMSPEC_VERSION_STRING + player->formspec_prepend;
+	Send(&pkt);
+}
+
 u32 Server::SendActiveObjectRemoveAdd(session_t peer_id, const std::string &datas)
 {
 	NetworkPacket pkt(TOCLIENT_ACTIVE_OBJECT_REMOVE_ADD, datas.size(), peer_id);
@@ -2918,6 +2930,14 @@ void Server::reportInventoryFormspecModified(const std::string &name)
 	SendPlayerInventoryFormspec(player->getPeerId());
 }
 
+void Server::reportFormspecPrependModified(const std::string &name)
+{
+	RemotePlayer *player = m_env->getPlayer(name.c_str());
+	if (!player)
+		return;
+	SendPlayerFormspecPrepend(player->getPeerId());
+}
+
 void Server::setIpBanned(const std::string &ip, const std::string &name)
 {
 	m_banmanager->add(ip, name);

src/server.h

@@ -216,6 +216,7 @@ public:
 	bool checkPriv(const std::string &name, const std::string &priv);
 	void reportPrivsModified(const std::string &name=""); // ""=all
 	void reportInventoryFormspecModified(const std::string &name);
+	void reportFormspecPrependModified(const std::string &name);
 
 	void setIpBanned(const std::string &ip, const std::string &name);
 	void unsetIpBanned(const std::string &ip_or_name);
@@ -376,6 +377,7 @@ private:
 	void SendEyeOffset(session_t peer_id, v3f first, v3f third);
 	void SendPlayerPrivileges(session_t peer_id);
 	void SendPlayerInventoryFormspec(session_t peer_id);
+	void SendPlayerFormspecPrepend(session_t peer_id);
 	void SendShowFormspecMessage(session_t peer_id, const std::string &formspec,
 		const std::string &formname);
 	void SendHUDAdd(session_t peer_id, u32 id, HudElement *form);