Packet 51 is used to send updates about large changes to single chunks
and to remove chunks from the client when they get out of range. In the
first case a single packet object is created and queued for all relevant
players. With our current chunk compression scheme this means the first
player to have the packet processed will start the compression and get the
packet correctly but the rest will get garbage.
Since this packet never contains much data it is better to simply handle
compression of it on the main thread like vanilla does instead of putting in
locks and dealing with their overhead and complexity.
When a client tries to break a block it assumes it has done so unless told
otherwise by the server. This means the client also wipes out any tile
entity data it has for the block as well. We do not send this data when
updating the client so clients lose things like text on signs, skull type,
etc when they aren't allowed to break the block.
Skulls need their tile entity in order to create an item correctly when
broken unlike every other block. Instead of sprinkling special cases all
over the code just override dropNaturally for skulls to read from their
tile entity and make sure everything that wants to drop them calls this
method before removing the block. There is only one case where this wasn't
already true so we end up with much less special casing.
Sheep now use the crafting system when breeding to determine what color
their baby should be. This triggers an event but the event wants the
crafting inventory to have a result slot which sheep do not have. This
event could be useful for plugins to control the output of sheep breeding
so instead of disabling it we add a result slot so the event fires without
issue.
If a chunk gets a block added to it that requires the extended block id
nibble array (block id greater than 255) the array is created and saved
with the chunk. When the blocks are verified to make sure they exist these
entries are erased but the extended block id array is not. This causes the
server and client to disagree about how much data a chunk has which makes
the client crash while trying to load the chunk for rendering.
To resolve these issues we now clear the extended block id array on chunk
load if there is no valid data in it.
When a block creates a falling entity the block is not immediately removed
from the world. Instead, the falling entity is responsible for removing it
but only if the block still exists. Due to certain piston mechanics it is
possible to move the block before this check happens and thus the block is
not removed. This should be fine as the entity will kill itself in this
situation. However, the code does not stop here and continues running the
rest of the entity logic which includes either placing a block in the world
or placing a block item in the world depending on the circumstances.
If a block is air we return immediately so miss the cleanup work that would
normally happen in this case in vanilla. This causes us to get in to a
situation where, due to odd packet sending from the client, we never
properly stop an attempt by the client to break a block and thus it
eventually breaks.
We also use our own variable for block damage and never sync it up with the
vanilla one so damage reporting to other clients is not always correct.
The static assertions are not normally evaluated in the JVM, and failed
to fail when the enums went from size 25 to size 26. This meant missing
values would not be detected at runtime and instead return null,
compounding problems later. The switches should never evaluate to null
so will instead throw runtime assertion errors.
Additional unit tests were added to detect new paintings and assure they
have proper, unique mappings. The test checks both that a mapping
exists, is not null, and does not duplicate another mapping.
If a defensive copy is not used in the API, changes to the item are
reflected in memory, but never updated to the client. It also goes
against the general contract provided in Bukkit, where setItem should be
the only way to change the underlying item frame.
Skull blocks store their type in a tile entity and use their block data
as rotation. When breaking a block the block data is used for determining
what item to drop. Simply changing this to use the skull method for getting
their drop data is not enough because their tile entity is already gone.
Therefore we have to special case skulls to get the correct data _and_ get
that data before breaking the block.
On player death player PotionEffects need to be updated so that a player's
invisibility and other effects are removed, otherwise they will persist
after a respawn. This is a carry-over from our use of persistent player
entities.
Some features added in 1.4.2 use the difficulty value as an index to an
array so while before having it set to an invalid value would do nothing
or maybe cause an odd side effect somewhere it now crashes the server. This
patch ensures difficulty values are clamped between 0 and 3, inclusive.
Filtering item data is usually a good idea to make sure we don't have
invalid data or data on items that shouldn't have it. However, anvils
use item data in slightly different way and so running its code for
filtering here causes the data to be corrupted.
