Multi bossbar support

server/player/player.go

@@ -341,17 +341,22 @@ func (p *Player) RemoveScoreboard() {
 	p.session().RemoveScoreboard()
 }
 
-// SendBossBar sends a boss bar to the player, so that it will be shown indefinitely at the top of the
-// player's screen.
-// The boss bar may be removed by calling Player.RemoveBossBar().
-func (p *Player) SendBossBar(bar bossbar.BossBar) {
-	p.session().SendBossBar(bar.Text(), bar.Colour().Uint8(), bar.HealthPercentage())
+// SendBossBar sends a boss bar to the player on the specified channel, so that it will be shown indefinitely at the top of the
+// player's screen. The boss bar can support multiple channels.
+// The boss bar may be removed by calling Player.RemoveBossBar(channel).
+func (p *Player) SendBossBar(channel int, bar bossbar.BossBar) {
+	p.session().SendBossBar(channel, bar.Text(), bar.Colour().Uint8(), bar.HealthPercentage())
 }
 
-// RemoveBossBar removes any boss bar currently active on the player's screen. If no boss bar is currently
-// present, nothing happens.
-func (p *Player) RemoveBossBar() {
-	p.session().RemoveBossBar()
+// RemoveBossBar removes the boss bar currently active on the specified channel on the player's screen.
+// If no boss bar is currently active on the given channel, nothing happens.
+func (p *Player) RemoveBossBar(channel int) {
+	p.session().RemoveBossBar(channel)
+}
+
+// BossBarChannelIDs returns a list of all channel IDs that are currently active on the player's screen.
+func (p *Player) BossBarChannelIDs() []int {
+	return p.session().BossBarChannelIDs()
 }
 
 // Chat writes a message in the global chat (chat.Global). The message is prefixed with the name of the

server/session/session.go

@@ -82,6 +82,8 @@ type Session struct {
 	joinMessage, quitMessage string
 
 	closeBackground chan struct{}
+
+	bossBarChannelRuntimeIDs map[int]uint64
 }
 
 // Conn represents a connection that packets are read from and written to by a Session. In addition, it holds some
@@ -148,23 +150,24 @@ func New(conn Conn, maxChunkRadius int, log Logger, joinMessage, quitMessage str
 
 	s := &Session{}
 	*s = Session{
-		openChunkTransactions:  make([]map[uint64]struct{}, 0, 8),
-		closeBackground:        make(chan struct{}),
-		ui:                     inventory.New(54, s.handleInterfaceUpdate),
-		handlers:               map[uint32]packetHandler{},
-		entityRuntimeIDs:       map[world.Entity]uint64{},
-		entities:               map[uint64]world.Entity{},
-		hiddenEntities:         map[world.Entity]struct{}{},
-		blobs:                  map[uint64][]byte{},
-		chunkRadius:            int32(r),
-		maxChunkRadius:         int32(maxChunkRadius),
-		conn:                   conn,
-		log:                    log,
-		currentEntityRuntimeID: 1,
-		heldSlot:               atomic.NewUint32(0),
-		joinMessage:            joinMessage,
-		quitMessage:            quitMessage,
-		openedWindow:           *atomic.NewValue(inventory.New(1, nil)),
+		openChunkTransactions:    make([]map[uint64]struct{}, 0, 8),
+		closeBackground:          make(chan struct{}),
+		ui:                       inventory.New(54, s.handleInterfaceUpdate),
+		handlers:                 map[uint32]packetHandler{},
+		entityRuntimeIDs:         map[world.Entity]uint64{},
+		entities:                 map[uint64]world.Entity{},
+		hiddenEntities:           map[world.Entity]struct{}{},
+		blobs:                    map[uint64][]byte{},
+		chunkRadius:              int32(r),
+		maxChunkRadius:           int32(maxChunkRadius),
+		conn:                     conn,
+		log:                      log,
+		currentEntityRuntimeID:   1,
+		heldSlot:                 atomic.NewUint32(0),
+		joinMessage:              joinMessage,
+		quitMessage:              quitMessage,
+		openedWindow:             *atomic.NewValue(inventory.New(1, nil)),
+		bossBarChannelRuntimeIDs: map[int]uint64{},
 	}
 
 	s.registerHandlers()
@@ -526,6 +529,9 @@ func (s *Session) sendAvailableEntities(w *world.World) {
 	for _, t := range w.EntityRegistry().Types() {
 		identifiers = append(identifiers, actorIdentifier{ID: t.EncodeEntity()})
 	}
+	// TODO: "minecraft:slime" is used to send the boss bar. This should not be hardcoded.
+	// Remove this when slime is supported.
+	identifiers = append(identifiers, actorIdentifier{ID: "minecraft:slime"})
 	serializedEntityData, err := nbt.Marshal(map[string]any{"idlist": identifiers})
 	if err != nil {
 		panic("should never happen")

server/session/text.go

@@ -114,25 +114,60 @@ func (s *Session) RemoveScoreboard() {
 	s.currentLines.Store([]string{})
 }
 
-// SendBossBar sends a boss bar to the player with the text passed and the health percentage of the bar.
-// SendBossBar removes any boss bar that might be active before sending the new one.
-func (s *Session) SendBossBar(text string, colour uint8, healthPercentage float64) {
-	s.RemoveBossBar()
+// SendBossBar sends a boss bar to the player on the specified channel with the provided text and health percentage.
+// If a boss bar is already active on the given channel, it is removed before the new one is sent.
+func (s *Session) SendBossBar(channel int, text string, colour uint8, healthPercentage float64) {
+	s.RemoveBossBar(channel)
+	s.currentEntityRuntimeID += 1
+	runtimeID := s.currentEntityRuntimeID
+	s.bossBarChannelRuntimeIDs[channel] = runtimeID
+
+	m := protocol.EntityMetadata{}
+	m.SetFlag(protocol.EntityDataKeyFlags, protocol.EntityDataFlagInvisible)
+	m.SetFlag(protocol.EntityDataKeyFlags, protocol.EntityDataFlagSilent)
+	m.SetFlag(protocol.EntityDataKeyFlags, protocol.EntityDataFlagNoAI)
+	m.SetFlag(protocol.EntityDataKeyFlags, protocol.EntityDataFlagFireImmune)
+	m[protocol.EntityDataKeyName] = ""
+	m[protocol.EntityDataKeyScale] = float32(0)
+	m[protocol.EntityDataKeyWidth] = float32(0)
+	m[protocol.EntityDataKeyHeight] = float32(0)
+	m[protocol.EntityDataKeyLeashHolder] = int64(-1)
+
+	s.writePacket(&packet.AddActor{
+		EntityUniqueID:  int64(runtimeID),
+		EntityRuntimeID: runtimeID,
+		EntityType:      "minecraft:slime", // TODO: o not hardcode
+		EntityMetadata:  m,
+	})
 	s.writePacket(&packet.BossEvent{
-		BossEntityUniqueID: selfEntityRuntimeID,
+		BossEntityUniqueID: int64(runtimeID),
 		EventType:          packet.BossEventShow,
 		BossBarTitle:       text,
 		HealthPercentage:   float32(healthPercentage),
 		Colour:             uint32(colour),
 	})
 }
 
-// RemoveBossBar removes any boss bar currently active on the player's screen.
-func (s *Session) RemoveBossBar() {
+// RemoveBossBar removes the boss bar currently active on the specified channel on the player's screen.
+func (s *Session) RemoveBossBar(channel int) {
+	runtimeID, ok := s.bossBarChannelRuntimeIDs[channel]
+	if !ok {
+		return
+	}
 	s.writePacket(&packet.BossEvent{
-		BossEntityUniqueID: selfEntityRuntimeID,
+		BossEntityUniqueID: int64(runtimeID),
 		EventType:          packet.BossEventHide,
 	})
+	s.writePacket(&packet.RemoveActor{EntityUniqueID: int64(runtimeID)})
+}
+
+// BossBarChannelIDs returns a list of all boss bar channel IDs that are currently active on the player's screen.
+func (s *Session) BossBarChannelIDs() []int {
+	var ids []int
+	for id := range s.bossBarChannelRuntimeIDs {
+		ids = append(ids, id)
+	}
+	return ids
 }
 
 const tickLength = time.Second / 20