feat: Player colours, locator bar functionality.

server/player/player.go

@@ -3,6 +3,7 @@ package player
 import (
 	"fmt"
 	"github.com/df-mc/dragonfly/server/player/debug"
+	"image/color"
 	"math"
 	"math/rand/v2"
 	"net"
@@ -403,6 +404,16 @@ func (p *Player) CloseForm() {
 	p.session().CloseForm()
 }
 
+// ShowLocatorBar enables the vanilla locator bar for the player.
+func (p *Player) ShowLocatorBar() {
+	p.session().EnableLocatorBar(true)
+}
+
+// HideLocatorBar disables the vanilla locator bar for the player.
+func (p *Player) HideLocatorBar() {
+	p.session().EnableLocatorBar(false)
+}
+
 // ShowCoordinates enables the vanilla coordinates for the player.
 func (p *Player) ShowCoordinates() {
 	p.session().EnableCoordinates(true)
@@ -2188,6 +2199,16 @@ func (p *Player) Collect(s item.Stack) (int, bool) {
 	return added, true
 }
 
+// Colour returns the player's colour in the locator bar.
+func (p *Player) Colour() color.RGBA {
+	return p.session().Colour()
+}
+
+// SetColour changes the player's colour in the locator bar.
+func (p *Player) SetColour(colour color.RGBA) {
+	p.session().SetColour(colour)
+}
+
 // Experience returns the amount of experience the player has.
 func (p *Player) Experience() int {
 	return p.experience.Experience()

server/session/player.go

@@ -3,8 +3,10 @@ package session
 import (
 	"encoding/json"
 	"fmt"
+	"github.com/cespare/xxhash/v2"
 	"github.com/df-mc/dragonfly/server/player/debug"
 	"github.com/go-gl/mathgl/mgl32"
+	"golang.org/x/exp/rand"
 	"image/color"
 	"maps"
 	"math"
@@ -578,6 +580,12 @@ func (s *Session) sendGameRules(gameRules []protocol.GameRule) {
 	s.writePacket(&packet.GameRulesChanged{GameRules: gameRules})
 }
 
+// EnableLocatorBar will either enable or disable locator bar for the player depending on the value given.
+func (s *Session) EnableLocatorBar(enable bool) {
+	//noinspection SpellCheckingInspection
+	s.sendGameRules([]protocol.GameRule{{Name: "locatorbar", Value: enable}})
+}
+
 // EnableCoordinates will either enable or disable coordinates for the player depending on the value given.
 func (s *Session) EnableCoordinates(enable bool) {
 	//noinspection SpellCheckingInspection
@@ -590,6 +598,21 @@ func (s *Session) EnableInstantRespawn(enable bool) {
 	s.sendGameRules([]protocol.GameRule{{Name: "doimmediaterespawn", Value: enable}})
 }
 
+// Colour returns the colour of player. Colour is used to indicate a player in the locator bar.
+func (s *Session) Colour() color.RGBA {
+	colour := s.colour.Load()
+	if colour == nil {
+		return color.RGBA{A: 0xFF}
+	}
+	return *colour
+}
+
+// SetColour sets the player colour. Colour is used to indicate a player in the locator bar.
+func (s *Session) SetColour(colour color.RGBA) {
+	s.colour.Store(&colour)
+	sessions.resendList(s)
+}
+
 // HandleInventories starts handling the inventories of the Controllable entity of the session. It sends packets when
 // slots in the inventory are changed.
 func (s *Session) HandleInventories(tx *world.Tx, c Controllable, inv, offHand, enderChest, ui *inventory.Inventory, armour *inventory.Armour, heldSlot *uint32) {
@@ -1053,6 +1076,17 @@ func protocolToSkin(sk protocol.Skin) (s skin.Skin, err error) {
 	return
 }
 
+// randomColour returns random colour based on displayName's hash.
+func randomColour(displayName string) color.RGBA {
+	r := rand.New(rand.NewSource(xxhash.Sum64String(displayName)))
+	return color.RGBA{
+		R: byte(r.Int31n(256)),
+		G: byte(r.Int31n(256)),
+		B: byte(r.Int31n(256)),
+		A: 0xFF,
+	}
+}
+
 // gameTypeFromMode returns the game type ID from the game mode passed.
 func gameTypeFromMode(mode world.GameMode) int32 {
 	if mode.AllowsFlying() && mode.CreativeInventory() {

server/session/session.go

@@ -5,6 +5,7 @@ import (
 	"errors"
 	"fmt"
 	"github.com/df-mc/dragonfly/server/player/debug"
+	"image/color"
 	"io"
 	"log/slog"
 	"net"
@@ -91,6 +92,8 @@ type Session struct {
 	debugShapesAdd    chan debug.Shape
 	debugShapesRemove chan int
 
+	colour atomic.Pointer[color.RGBA]
+
 	closeBackground chan struct{}
 }
 
@@ -176,6 +179,9 @@ func (conf Config) New(conn Conn) *Session {
 		debugShapesAdd:         make(chan debug.Shape, 256),
 		debugShapesRemove:      make(chan int, 256),
 	}
+	colour := randomColour(conn.IdentityData().DisplayName)
+	s.colour.Store(&colour)
+
 	s.openedWindow.Store(inventory.New(1, nil))
 	s.openedPos.Store(&cube.Pos{})
 

server/session/session_list.go

@@ -42,6 +42,16 @@ func (l *sessionList) Remove(s *Session) {
 	l.s = sliceutil.DeleteVal(l.s, s)
 }
 
+func (l *sessionList) resendList(s *Session) {
+	l.mu.Lock()
+	defer l.mu.Unlock()
+
+	for _, other := range l.s {
+		l.unsendSessionFrom(s, other)
+		l.sendSessionTo(s, other)
+	}
+}
+
 func (l *sessionList) Lookup(id uuid.UUID) (*Session, bool) {
 	l.mu.Lock()
 	defer l.mu.Unlock()
@@ -74,6 +84,7 @@ func (l *sessionList) sendSessionTo(s, to *Session) {
 			Username:       s.conn.IdentityData().DisplayName,
 			XUID:           s.conn.IdentityData().XUID,
 			Skin:           skinToProtocol(s.joinSkin),
+			PlayerColour:   s.Colour(),
 		}},
 	})
 }