PocketMine-MP/changelogs/4.18-alpha.md

**For Minecraft: Bedrock Edition 1.19.70**

### Note about API versions
Plugins which don't touch the `pocketmine\network\mcpe` namespace are compatible with any previous 4.x.y version will also run on these releases and do not need API bumps.
Plugin developers should **only** update their required API to this version if you need the changes in this build.

**WARNING: If your plugin uses the `pocketmine\network\mcpe` namespace, you're not shielded by API change constraints.**
Consider using the `mcpe-protocol` directive in `plugin.yml` as a constraint if you're using packets directly.

### Alpha release warning
Alpha releases are **experimental**. Features introduced in these releases are subject to change or removal.

APIs which existed **prior** to this version will continue to work as normal, so plugins which use them will continue to work.

### Highlights
This version makes changes to the internal network system to improve server performance and reduce memory usage.

While these changes don't affect non-internal API, they are still significant enough to warrant a new minor version, as they may break plugins which use the internal network API (not recommended).

# 4.18.0-ALPHA1
Released 16th March 2023.

## General
- Improved server performance in congested areas of the world (lots of players and/or entities in the same area).

## API
### `pocketmine\event\server`
- The following new classes have been added:
  - `DataPacketDecodeEvent` - called before a packet is decoded by a `NetworkSession`; useful to mitigate DoS attacks if PocketMine-MP hasn't been patched against new bugs yet

## Internals
- Introduced new system for broadcasting entity events to network sessions.
  - This change improves performance when lots of players and/or entities are in the same area.
  - New interface `EntityEventBroadcaster` and class `StandardEntityEventBroadcaster` have been added to implement this.
  - All entity-specific `on*()` and `sync*()` methods have been removed from `NetworkSession` (BC break).
  - `NetworkSession` now accepts an `EntityEventBroadcaster` instance in its constructor.
  - `NetworkBroadcastUtils::broadcastEntityEvent()` can be used to efficiently broadcast events to unique broadcasters shared by several network sessions.
- All network sessions now share the same `PacketSerializerContext` and `PacketBroadcaster` by default.
  - Previously, every session had its own context, meaning that broadcast optimisations were not used, causing significant performance losses compared to 3.x.
  - This change improves performance in congested areas by allowing reuse of previously encoded packet buffers for all sessions sharing the same context.
  - Packet broadcasts are automatically encoded separately per unique `PacketSerializerContext` instance. This allows, for example, a multi-version fork to have a separate context for each protocol version, to ensure maximum broadcast efficiency while encoding different packets for different versions.
  - `PacketSerializerContext` is now passed in `NetworkSession::__construct()`, instead of being created by the session.
- `StandardPacketBroadcaster` is now locked to a single `PacketSerializer` context, reducing complexity.
- Introduced `NetworkBroadcastUtils::broadcastPackets()`, replacing `Server->broadcastPackets()`.
- `Server->broadcastPackets()` has been deprecated. It will be removed in a future version.

# 4.18.0-ALPHA2
Released 21st March 2023.

## General
- Included more sections of the network system in Player Network Send timings.
- Changed the names of some timings to make them more user-friendly.
- Removed packet IDs from `receivePacket` and `sendPacket` timings, as they were not very useful.
- Added new specialized timers for the following:
  - Item entity base ticking (merging)
  - Player movement processing
  - Entity movement processing (collision checking section)
  - Projectile movement (all)
  - Projectile movement processing (ray tracing section)

## API
### `pocketmine\crafting`
- The following new API methods have been added:
  - `CraftingManager->getCraftingRecipeIndex() : array<int, CraftingRecipe>` - returns a list of all crafting recipes
  - `CraftingManager->getCraftingRecipeFromIndex(int $index) : ?CraftingRecipe` - returns the crafting recipe at the given index, or null if it doesn't exist

### `pocketmine\inventory\transaction`
- The following API methods have changed signatures:
  - `CraftingTransaction->__construct()` now accepts additional arguments `?CraftingRecipe $recipe = null, ?int $repetitions = null`
- The following new API methods have been added:
  - `TransactionBuilderInventory->getActualInventory() : Inventory` - returns the actual inventory that this inventory is a proxy for

## Internals
### Network
- Introduced support for the `ItemStackRequest` Minecraft: Bedrock network protocol.
  - This fixes a large number of inventory- and crafting-related bugs.
  - This also improves server security by closing off many code pathways that might have been used for exploits. `TypeConverter->netItemStackToCore()` is no longer used in server code, and remains for tool usage only.
  - This system is also significantly more bandwidth-efficient and has lower overhead than the legacy system.
  - This now opens the gateway to easily implement lots of gameplay features which have been missing for a long time, such as enchanting, anvils, looms, and more.
  - Significant changes have been made to `pocketmine\network\mcpe\InventoryManager` internals. These shouldn't affect plugins, but may affect plugins which use internal network API.
  - **No changes have been made to the plugin `InventoryTransaction` API**.
    - This system has been implemented as a shim for the existing PocketMine-MP transaction system to preserve plugin compatibility. Plugins using `InventoryTransactionEvent` should continue to work seamlessly.
    - The `InventoryTransaction` API will be redesigned in a future major version to make use of the new information provided by the `ItemStackRequest` system.
  - `InventoryTransactionPacket` is no longer sent by the client for "regular" inventory actions. However, it is still sent when dropping items, interacting with blocks, and using items.
- Inventory slot and content syncing is now buffered until the end of the tick. This reduces outbound network usage when the client performs multiple transactions in a single tick (e.g. crafting a stack of items).
- Renamed some `InventoryManager` internal properties to make them easier to understand.
- `TypeConverter->createInventoryAction()` has been removed.
- Packet batch limit has been lowered to `100` packets. With the introduction of `ItemStackRequest`, this is more than sufficient for normal gameplay.

### Other
- Use `Vector3::zero()` instead of `new Vector3()` in some places.