Formspec: Show a player inventory using core.show_formspec (#15963)

'core.show_formspec' now shows and updates the inventory formspec as if
it was opened using the hotkey on client-side.

doc/lua_api.md

@@ -6872,10 +6872,15 @@ Formspec
 * `core.show_formspec(playername, formname, formspec)`
     * `playername`: name of player to show formspec
     * `formname`: name passed to `on_player_receive_fields` callbacks.
-      It should follow the `"modname:<whatever>"` naming convention.
-    * `formname` must not be empty, unless you want to reshow
-      the inventory formspec without updating it for future opens.
+        * It should follow the `"modname:<whatever>"` naming convention.
+        * If empty: Shows a custom, temporary inventory formspec.
+            * An inventory formspec shown this way will also be updated if
+              `ObjectRef:set_inventory_formspec` is called.
+            * Use `ObjectRef:set_inventory_formspec` to change the player's
+              inventory formspec for future opens.
+            * Supported if server AND client are both of version >= 5.13.0.
     * `formspec`: formspec to display
+    * See also: `core.register_on_player_receive_fields`
 * `core.close_formspec(playername, formname)`
     * `playername`: name of player to close formspec
     * `formname`: has to exactly match the one given in `show_formspec`, or the
@@ -8653,9 +8658,12 @@ child will follow movement and rotation of that bone.
     * Returns `nil` if no attribute found.
 * `get_meta()`: Returns metadata associated with the player (a PlayerMetaRef).
 * `set_inventory_formspec(formspec)`
-    * Redefine player's inventory form
-    * Should usually be called in `on_joinplayer`
+    * Redefines the player's inventory formspec.
+    * Should usually be called at least once in the `on_joinplayer` callback.
     * If `formspec` is `""`, the player's inventory is disabled.
+    * If the inventory formspec is currently open on the client, it is
+      updated immediately.
+    * See also: `core.register_on_player_receive_fields`
 * `get_inventory_formspec()`: returns a formspec string
 * `set_formspec_prepend(formspec)`:
     * the formspec string will be added to every formspec shown to the user,

src/client/game.cpp

@@ -1925,7 +1925,7 @@ void Game::processKeyInput()
 		if (g_settings->getBool("continuous_forward"))
 			toggleAutoforward();
 	} else if (wasKeyDown(KeyType::INVENTORY)) {
-		m_game_formspec.showPlayerInventory();
+		m_game_formspec.showPlayerInventory(nullptr);
 	} else if (input->cancelPressed()) {
 #ifdef __ANDROID__
 		m_android_chat_open = false;
@@ -2714,11 +2714,16 @@ void Game::handleClientEvent_DeathscreenLegacy(ClientEvent *event, CameraOrienta
 
 void Game::handleClientEvent_ShowFormSpec(ClientEvent *event, CameraOrientation *cam)
 {
-	m_game_formspec.showFormSpec(*event->show_formspec.formspec,
-		*event->show_formspec.formname);
+	auto &fs = event->show_formspec;
 
-	delete event->show_formspec.formspec;
-	delete event->show_formspec.formname;
+	if (fs.formname->empty() && !fs.formspec->empty()) {
+		m_game_formspec.showPlayerInventory(fs.formspec);
+	} else {
+		m_game_formspec.showFormSpec(*fs.formspec, *fs.formname);
+	}
+
+	delete fs.formspec;
+	delete fs.formname;
 }
 
 void Game::handleClientEvent_ShowCSMFormSpec(ClientEvent *event, CameraOrientation *cam)

src/client/game_formspec.cpp

@@ -178,6 +178,10 @@ public:
 	const std::string &getForm() const
 	{
 		LocalPlayer *player = m_client->getEnv().getLocalPlayer();
+
+		if (!player->inventory_formspec_override.empty())
+			return player->inventory_formspec_override;
+
 		return player->inventory_formspec;
 	}
 
@@ -304,7 +308,7 @@ void GameFormSpec::showNodeFormspec(const std::string &formspec, const v3s16 &no
 	m_formspec->setFormSpec(formspec, inventoryloc);
 }
 
-void GameFormSpec::showPlayerInventory()
+void GameFormSpec::showPlayerInventory(const std::string *fs_override)
 {
 	/*
 	 * Don't permit to open inventory is CAO or player doesn't exists.
@@ -317,28 +321,35 @@ void GameFormSpec::showPlayerInventory()
 
 	infostream << "Game: Launching inventory" << std::endl;
 
-	PlayerInventoryFormSource *fs_src = new PlayerInventoryFormSource(m_client);
+	auto fs_src = std::make_unique<PlayerInventoryFormSource>(m_client);
 
 	InventoryLocation inventoryloc;
 	inventoryloc.setCurrentPlayer();
 
-	if (m_client->modsLoaded() && m_client->getScript()->on_inventory_open(m_client->getInventory(inventoryloc))) {
-		delete fs_src;
-		return;
+	if (fs_override) {
+		// Temporary overwrite for this specific formspec.
+		player->inventory_formspec_override = *fs_override;
+	} else {
+		// Show the regular inventory formspec
+		player->inventory_formspec_override.clear();
 	}
 
-	if (fs_src->getForm().empty()) {
-		delete fs_src;
+	// If prevented by Client-Side Mods
+	if (m_client->modsLoaded() && m_client->getScript()->on_inventory_open(m_client->getInventory(inventoryloc)))
+		return;
+
+	// Empty formspec -> do not show.
+	if (fs_src->getForm().empty())
 		return;
-	}
 
 	TextDest *txt_dst = new TextDestPlayerInventory(m_client);
 
 	GUIFormSpecMenu::create(m_formspec, m_client, m_rendering_engine->get_gui_env(),
-		&m_input->joystick, fs_src, txt_dst, m_client->getFormspecPrepend(),
+		&m_input->joystick, fs_src.get(), txt_dst, m_client->getFormspecPrepend(),
 		m_client->getSoundManager());
 
 	m_formspec->setFormSpec(fs_src->getForm(), inventoryloc);
+	fs_src.release(); // owned by GUIFormSpecMenu
 }
 
 #define SIZE_TAG "size[11,5.5,true]" // Fixed size (ignored in touchscreen mode)

src/client/game_formspec.h

@@ -34,7 +34,9 @@ struct GameFormSpec
 	// Currently only used for the in-game settings menu.
 	void showPauseMenuFormSpec(const std::string &formspec, const std::string &formname);
 	void showNodeFormspec(const std::string &formspec, const v3s16 &nodepos);
-	void showPlayerInventory();
+	/// If `!fs_override`: Uses `player->inventory_formspec`.
+	/// If ` fs_override`: Uses a temporary formspec until an update is received.
+	void showPlayerInventory(const std::string *fs_override);
 	void showDeathFormspecLegacy();
 	// Shows the hardcoded "main" pause menu.
 	void showPauseMenu();

src/client/localplayer.h

@@ -99,6 +99,8 @@ public:
 
 	std::string hotbar_image = "";
 	std::string hotbar_selected_image = "";
+	/// Temporary player inventory formspec. Empty value = feature inactive.
+	std::string inventory_formspec_override;
 
 	video::SColor light_color = video::SColor(255, 255, 255, 255);
 

src/network/clientpackethandler.cpp

@@ -902,6 +902,7 @@ void Client::handleCommand_InventoryFormSpec(NetworkPacket* pkt)
 
 	// Store formspec in LocalPlayer
 	player->inventory_formspec = pkt->readLongString();
+	player->inventory_formspec_override.clear();
 }
 
 void Client::handleCommand_DetachedInventory(NetworkPacket* pkt)

src/network/serveropcodes.cpp

@@ -178,6 +178,7 @@ const ClientCommandFactory clientCommandFactoryTable[TOCLIENT_NUM_MSG_TYPES] =
 	{ "TOCLIENT_STOP_SOUND",               0, true }, // 0x40
 	{ "TOCLIENT_PRIVILEGES",               0, true }, // 0x41
 	{ "TOCLIENT_INVENTORY_FORMSPEC",       0, true }, // 0x42
+	// ^ `channel` MUST be the same as TOCLIENT_SHOW_FORMSPEC
 	{ "TOCLIENT_DETACHED_INVENTORY",       0, true }, // 0x43
 	{ "TOCLIENT_SHOW_FORMSPEC",            0, true }, // 0x44
 	{ "TOCLIENT_MOVEMENT",                 0, true }, // 0x45

src/remoteplayer.h

@@ -121,6 +121,8 @@ public:
 	u16 protocol_version = 0;
 	u16 formspec_version = 0;
 
+	bool inventory_formspec_overridden = false;
+
 	/// returns PEER_ID_INEXISTENT when PlayerSAO is not ready
 	session_t getPeerId() const { return m_peer_id; }
 

src/script/lua_api/l_object.cpp

@@ -1574,7 +1574,9 @@ int ObjectRef::l_set_inventory_formspec(lua_State *L)
 
 	auto formspec = readParam<std::string_view>(L, 2);
 
-	if (formspec != player->inventory_formspec) {
+	if (player->inventory_formspec_overridden
+			|| formspec != player->inventory_formspec) {
+		player->inventory_formspec_overridden = false;
 		player->inventory_formspec = formspec;
 		getServer(L)->reportInventoryFormspecModified(player->getName());
 	}

src/server.cpp

@@ -1595,11 +1595,10 @@ void Server::SendShowFormspecMessage(session_t peer_id, const std::string &forms
 				(it->second == formname || formname.empty())) {
 			m_formspec_state_data.erase(peer_id);
 		}
-		pkt.putLongString("");
 	} else {
 		m_formspec_state_data[peer_id] = formname;
-		pkt.putLongString(formspec);
 	}
+	pkt.putLongString(formspec);
 	pkt << formname;
 
 	Send(&pkt);
@@ -3397,6 +3396,9 @@ bool Server::showFormspec(const char *playername, const std::string &formspec,
 	if (!player)
 		return false;
 
+	// To allow re-sending the same inventory formspec.
+	player->inventory_formspec_overridden = formname.empty() && !formspec.empty();
+
 	SendShowFormspecMessage(player->getPeerId(), formspec, formname);
 	return true;
 }