Add HeldItem::set_slot (#525)

# Objective

This PR adds functionality to allow the server to change the users
selected hotbar slot using `HeldItem::set_slot(36..44)`

---------

Co-authored-by: Carson McManus <[email protected]>

crates/valence_inventory/src/lib.rs

@@ -35,6 +35,7 @@ pub use valence_server::protocol::packets::play::player_action_c2s::PlayerAction
 use valence_server::protocol::packets::play::{
  ClickSlotC2s, CloseHandledScreenC2s, CloseScreenS2c, CreativeInventoryActionC2s, InventoryS2c,
  OpenScreenS2c, PlayerActionC2s, ScreenHandlerSlotUpdateS2c, UpdateSelectedSlotC2s,
+ UpdateSelectedSlotS2c,
 };
 use valence_server::protocol::{VarInt, WritePacket};
 use valence_server::text::IntoText;
@@ -54,6 +55,7 @@ impl Plugin for InventoryPlugin {
  PostUpdate,
  (
  update_client_on_close_inventory.before(update_open_inventories),
+ update_player_selected_slot,
  update_open_inventories,
  update_player_inventories,
  )
@@ -405,6 +407,16 @@ impl HeldItem {
  pub fn slot(&self) -> u16 {
  self.held_item_slot
  }
+
+ pub fn set_slot(&mut self, slot: u16) {
+ // temp
+ assert!(
+ (36..=44).contains(&slot),
+ "slot index of {slot} out of bounds"
+ );
+
+ self.held_item_slot = slot;
+ }
 }
 
 /// The item stack that the client thinks it's holding under the mouse
@@ -1216,18 +1228,31 @@ pub struct UpdateSelectedSlotEvent {
  pub slot: u8,
 }
 
+/// Handles the `HeldItem` component being changed on a client entity, which
+/// indicates that the server has changed the selected hotbar slot.
+fn update_player_selected_slot(mut clients: Query<(&mut Client, &HeldItem), Changed<HeldItem>>) {
+ for (mut client, held_item) in &mut clients {
+ client.write_packet(&UpdateSelectedSlotS2c {
+ slot: (held_item.held_item_slot - PLAYER_INVENTORY_MAIN_SLOTS_COUNT) as u8,
+ });
+ }
+}
+
+/// Client to Server HeldItem Slot
 fn handle_update_selected_slot(
  mut packets: EventReader<PacketEvent>,
  mut clients: Query<&mut HeldItem>,
  mut events: EventWriter<UpdateSelectedSlotEvent>,
 ) {
  for packet in packets.iter() {
  if let Some(pkt) = packet.decode::<UpdateSelectedSlotC2s>() {
- if let Ok(mut held) = clients.get_mut(packet.client) {
+ if let Ok(mut mut_held) = clients.get_mut(packet.client) {
+ let held = mut_held.bypass_change_detection();
  if pkt.slot > 8 {
  // The client is trying to interact with a slot that does not exist, ignore.
  continue;
  }
+
  held.held_item_slot = convert_hotbar_slot_id(pkt.slot);
 
  events.send(UpdateSelectedSlotEvent {