We are doing little visuals for cargo crates in minecarts

src/main/kotlin/ru/dbotthepony/mc/otm/entity/Ext.kt

@@ -0,0 +1,19 @@
+package ru.dbotthepony.mc.otm.entity
+
+import net.minecraft.network.syncher.EntityDataAccessor
+import net.minecraft.network.syncher.SynchedEntityData
+import net.minecraft.world.entity.Entity
+import kotlin.properties.ReadWriteProperty
+import kotlin.reflect.KProperty
+
+class SynchedEntityDataDelegate<T>(private val type: EntityDataAccessor<T>, private val data: SynchedEntityData) : ReadWriteProperty<Entity, T> {
+	override fun getValue(thisRef: Entity, property: KProperty<*>): T {
+		return data.get(type)
+	}
+
+	override fun setValue(thisRef: Entity, property: KProperty<*>, value: T) {
+		data.set(type, value)
+	}
+}
+
+fun <T> SynchedEntityData.delegate(type: EntityDataAccessor<T>) = SynchedEntityDataDelegate(type, this)

src/main/kotlin/ru/dbotthepony/mc/otm/entity/MinecartCargoCrate.kt

@@ -1,6 +1,10 @@
 package ru.dbotthepony.mc.otm.entity
 
 import net.minecraft.core.NonNullList
+import net.minecraft.network.syncher.EntityDataAccessor
+import net.minecraft.network.syncher.EntityDataSerializers
+import net.minecraft.network.syncher.SynchedEntityData
+import net.minecraft.sounds.SoundSource
 import net.minecraft.world.entity.EntityType
 import net.minecraft.world.entity.player.Inventory
 import net.minecraft.world.entity.vehicle.AbstractMinecartContainer
@@ -10,11 +14,14 @@ import net.minecraft.world.item.Item
 import net.minecraft.world.item.ItemStack
 import net.minecraft.world.level.Level
 import net.minecraft.world.level.block.state.BlockState
+import net.minecraft.world.level.gameevent.GameEvent
 import ru.dbotthepony.mc.otm.block.CargoCrateBlock
 import ru.dbotthepony.mc.otm.block.entity.CargoCrateBlockEntity
+import ru.dbotthepony.mc.otm.core.position
 import ru.dbotthepony.mc.otm.menu.MinecartCargoCrateMenu
 import ru.dbotthepony.mc.otm.registry.MItems
 import ru.dbotthepony.mc.otm.registry.MRegistry
+import ru.dbotthepony.mc.otm.registry.MSoundEvents
 
 class MinecartCargoCrate(
 	type: EntityType<*>,
@@ -48,7 +55,7 @@ class MinecartCargoCrate(
 	}
 
 	override fun getDefaultDisplayBlockState(): BlockState {
-		return block.defaultBlockState().setValue(CargoCrateBlock.IS_OPEN, false)
+		return block.defaultBlockState().setValue(CargoCrateBlock.IS_OPEN, interactingPlayers > 0)
 	}
 
 	override fun getDefaultDisplayOffset(): Int {
@@ -66,4 +73,38 @@ class MinecartCargoCrate(
 	override fun getPickResult(): ItemStack {
 		return ItemStack(item, 1)
 	}
+
+	override fun defineSynchedData() {
+		super.defineSynchedData()
+		entityData.define(INTERACTING_PLAYERS, 0)
+	}
+
+	var interactingPlayers by entityData.delegate(INTERACTING_PLAYERS)
+
+	fun onPlayerOpen() {
+		if (isRemoved)
+			return
+
+		if (interactingPlayers++ == 0) {
+			if (!isRemoved) {
+				level.playSound(null, this, MSoundEvents.CARGO_CRATE_OPEN, SoundSource.BLOCKS, 1f, 0.8f + level.random.nextFloat() * 0.2f)
+				level.gameEvent(GameEvent.CONTAINER_OPEN, position, GameEvent.Context.of(this))
+			}
+		}
+	}
+
+	fun onPlayerClose() {
+		if (interactingPlayers <= 0)
+			return
+
+		if (--interactingPlayers == 0) {
+			if (!isRemoved) {
+				level.gameEvent(GameEvent.CONTAINER_CLOSE, position, GameEvent.Context.of(this))
+			}
+		}
+	}
+
+	companion object {
+		val INTERACTING_PLAYERS: EntityDataAccessor<Int> = SynchedEntityData.defineId(MinecartCargoCrate::class.java, EntityDataSerializers.INT)
+	}
 }

src/main/kotlin/ru/dbotthepony/mc/otm/menu/MinecartCargoCrateMenu.kt

@@ -16,6 +16,8 @@ class MinecartCargoCrateMenu @JvmOverloads constructor(
 ) : MatteryMenu(MMenus.CARGO_CRATE, p_38852_, inventory) {
 	override val storageSlots: List<MatterySlot>
 
+	private val trackedPlayerOpen = !inventory.player.isSpectator
+
 	init {
 		val container = cart as Container? ?: SimpleContainer(CargoCrateBlockEntity.CAPACITY)
 
@@ -25,9 +27,21 @@ class MinecartCargoCrateMenu @JvmOverloads constructor(
 			return@ImmutableList slot
 		}
 
+		if (trackedPlayerOpen) {
+			cart?.onPlayerOpen()
+		}
+
 		addInventorySlots()
 	}
 
+	override fun removed(p_38940_: Player) {
+		super.removed(p_38940_)
+
+		if (trackedPlayerOpen) {
+			cart?.onPlayerClose()
+		}
+	}
+
 	override fun stillValid(player: Player): Boolean {
 		return cart?.stillValid(player) ?: true
 	}