Changelog

[1.4.16-1.20.1-fabric] - 2026-05-09

Security & Critical Bug Fixes

• Fixed UUID mismatch in multiplayer screen texture cleanup (ClientMod.java)

  • S2C_STOP_SCREEN and S2C_SCREEN were using mcc.player.getUuid() for remove() instead of pcOwner.
  • This caused screen textures from other players to never be destroyed, leading to a severe memory leak (NativeImage, NativeImageBackedTexture, Identifier).
  • Also fixed a double-close bug where vmScreenTextureNI.close() was called instead of vmScreenTextureNIBT.close() in S2C_SCREEN.

• Fixed component loss when placing last PC case from stack (ItemPCCase.java, ItemPCCaseSidepanel.java)

  • decrement(1) was called before reading NBT data. When count == 1, the stack became EMPTY and getNbt() returned null, causing permanent loss of all PC components (motherboard, CPU, RAM, HDD, ISO).
  • Now NBT is saved to a local variable before decrementing.

• Fixed server crash on missing inventory item (MainMod.java)

  • removeStck() threw RuntimeException when an item was not found, crashing the entire server.
  • Replaced with logging via LOGGER.error() and graceful return.
  • Also hardened against desync between contains() check and removeStck() execution.

• Fixed ClassCastException exploit in C2S_ORDER (MainMod.java)

  • No validation that readItemStack().getItem() is actually an OrderableItem. A malicious client could send any item, causing a server crash.
  • Added instanceof OrderableItem check with logging of invalid packets.
  • Same fix applied to S2C_SYNC_ORDER handler in ClientMod.java.

• Fixed IllegalArgumentException in C2S_ADD_CPU / C2S_ADD_RAM (MainMod.java)

  • When dividedBy or mb values did not match expected constants, lookingFor remained null, causing new ItemStack(null) → server crash.
  • Added lookingFor != null guard before creating ItemStack.

• Fixed HDD removal ignoring NBT (MainMod.java)

  • removeStck() matched only by Item type, not NBT. If a player had multiple HDDs with different VHD files, the wrong disk could be removed.
  • Enhanced removeStck() to prefer exact NBT match before falling back to type-only match.

• Fixed VM always created with only 1 CPU (GuiPCEditing.java)

  • Math.min(1, ...) in the "create new VM" branch always returned 1, regardless of host CPU count or player settings. The "modify existing" branch already used correct Math.max(1, ...).
  • Fixed to Math.max(1, ...) — VM now gets the correct number of CPUs.

• Fixed ConcurrentModificationException in ServerMixin (ServerMixin.java)

  • MainMod.orders.remove() was called during for-each iteration over HashMap.values(), guaranteeing a crash every time an order completed.
  • Implemented deferred removal: collect keys to remove in a list, then delete after the loop.

• Fixed NPE when sending packets to disconnected players (ServerMixin.java)

  • playerManager.getPlayer() could return null if a player logged out. Calling .getWorld() or ServerPlayNetworking.send(null, ...) caused NPE.
  • Added null checks before all getPlayer() usages.

• Fixed deadlock in insertISO (GuiPCEditing.java)

  • wait() without while loop and without timeout — if notify() was called before wait(), the thread hung forever.
  • Replaced with while (condition) { lock.wait(5000); } pattern using a shared ClientMod.VM_TURNING_ON_LOCK.
  • Also fixed the case where a new GuiPCEditing instance had a different monitor object than the one notify() was called on.

• Fixed busy-wait burning 100% CPU in turnOffPC (GuiPCEditing.java)

  • while(ClientMod.vmTurningOn) {} was an infinite spin-loop.
  • Replaced with Thread.sleep(50) inside the loop. Also added volatile to vmTurningOn so the thread actually sees state changes.

• Fixed Timer thread leak in GuiFocus (GuiFocus.java)

  • A new Timer was created every time GuiFocus opened, but cancel() was only called on NullPointerException (singleplayer). In multiplayer, timers leaked indefinitely.
  • Timer is now stored as a field and cancelled in removed().

• Fixed NPE-based control flow in singleplayer (GuiFocus.java)

  • getCurrentServerEntry().address throws NPE in singleplayer. The code used catch(NullPointerException) as control flow.
  • Replaced with explicit == null check.

• Fixed resource leak in VBoxManage (VBoxManage.java)

  • BufferedReader and InputStream were not closed in finally, leaking file descriptors on exceptions.
  • Wrapped in try-with-resources.

• Fixed FileWriter not closed on exception (ClientMod.java)

  • increaseVHDNum() opened a FileWriter without try-with-resources or finally. On any exception, the file handle leaked.
  • Wrapped in try-with-resources.

• Fixed Unpooled.buffer() leaks across all packet handlers

  • new PacketByteBuf(Unpooled.buffer()) was used in ClientMod.java, GuiPCEditing.java, ServerMixin.java, and PlayerManagerMixin.java instead of PacketByteBufs.create().
  • Replaced all instances with the proper Fabric API method.

• Fixed regex bug in hard drive selection (GuiCreateHarddrive.java)

  • split(" | ") treated " | " as a regex (space OR space), effectively equivalent to split(" ").
  • Any VHD filename containing a space was broken. Replaced with indexOf(" | ") + substring() for literal matching.

• Fixed iron ingot overpayment loss (EntityDeliveryChest.java)

  • When a player overpaid, is.increment() was called on an already-empty ItemStack (after decrement()), causing the excess ingots to be permanently lost.
  • Fixed by saving the count before decrement(), then creating a new ItemStack for the refund and using player.getInventory().offerOrDrop().

• Fixed matrix stack imbalance on exception (HeldItemMixin.java)

  • matrices.push() in HEAD and matrices.pop() in TAIL were not atomic. An exception between them left the stack unbalanced.
  • Wrapped rendering in try-finally to guarantee matrices.pop().

• Fixed NBT key inconsistency (EntityPC.java, ItemPCCase.java, ItemPCCaseSidepanel.java)

  • Constructor used different NBT keys (x64, MoboInstalled, GPUInstalled, RAMSlot0, VHDName, ISOName) than readCustomDataFromNbt / writeCustomDataToNbt (X64, MotherboardInstalled, GpuInstalled, GbRamSlot0, HardDriveFileName, IsoFileName).
  • This worked only because the two paths never crossed, but was a refactoring minefield.
  • Unified all keys to match writeCustomDataToNbt format. Added backward compatibility in constructor to read both old and new keys.

New Features

• Transition to VBoxManage CLI (VBox CLI)

  • Replaced the deprecated VirtualBox JWS (Java Web Services) API with a new VBoxManage.java wrapper that calls the VBoxManage command-line tool directly.
  • The JWS API was removed in VirtualBox 7.0+, making the old mod completely incompatible with modern VirtualBox installations.
  • All VM operations are now performed via CLI:
    • createVm, modifyVm, startVm, powerOffVm
    • storageAttach, addStorageController, removeStorageController
    • mountMedium, unmountMedium
    • putScancodes, putMouseEvent
    • takeScreenshot
    • getVmState, vmExists, discardSavedState
  • Added executeSilent() for optional operations that may fail on newer VBox versions (e.g., --accelerate2dvideo in VBox 7.x).
  • Added connection test (testConnection()) and version detection (getVersion()).

• Support for VirtualBox 7.x and newer

  • VBox 7.0+ removed vboxwebsrv (the SOAP web service). The mod now works with any VirtualBox version that provides VBoxManage.
  • Added parsing of showvminfo --machinereadable output for medium attachment state, compatible with VBox 7.x output format.
  • --accelerate2dvideo is now handled silently (ignored if unsupported) instead of crashing.

Performance Improvements

• Added volatile to all cross-thread shared state (ClientMod.java)

  • vmTurnedOn, vmTurningOn, vmTurningOff, vmUpdateThread, vmTextureBytes, vmTextureBytesSize.
  • Prevents infinite busy-waits and race conditions between the render thread and VM update thread.

• Added synchronized to texture byte transfers (VMRunnable.java + ClientMod.java)

  • vmTextureBytes / vmTextureBytesSize were updated in one thread and read in another without any synchronization, risking torn reads.
  • Added VM_TEXTURE_LOCK with proper synchronized blocks on both write (VM thread) and read (render thread) sides.

• Added synchronized to tablet texture streaming (TabletOS.java)

  • byteArrayInputStream was written by the tablet renderer thread and read by the main render thread without synchronization.
  • Added TEXTURE_SYNC lock with local copy pattern.

• Throttled isMediumEjected() polling (GuiPCEditing.java)

  • Previously called VBoxManage showvminfo every frame (~60 times/second), spawning a new OS process each time.
  • Now checks every 2 seconds, reducing CPU and disk load by ~99%.

• Throttled tablet renderer (GameloopMixin.java)

  • Tablet renderer while(true) loop had no Thread.sleep(), pinning a CPU core at 100%.
  • Added Thread.sleep(33) for ~30 FPS cap.
  • Also replaced silent ConcurrentModificationException swallowing with proper logging.

• Reduced S2C_SYNC_ORDER network spam (ServerMixin.java)

  • Order sync packet was sent 20 times/second per order regardless of whether status changed.
  • Now tracks lastSyncedStatus and only sends the packet when the status actually changes.

Architecture & Code Quality

• Proper use of PacketByteBufs.create() throughout

  • Eliminates manual buffer lifecycle management and potential leaks.

• Added SLF4J/Log4j logging (MainMod.java)

  • Replaced RuntimeException server crashes with LOGGER.error() for inventory desync events.

• Backward compatibility for old NBT saves

  • Old PC cases placed in the world before this update will still load correctly thanks to dual-key reading in EntityPC constructor.