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c5a10665b8
Spigot still maintains some partial implementation of "tick skipping", a practice in which the MinecraftServer.currentTick field is updated not by an increment of one per actual tick, but instead set to System.currentTimeMillis() / 50. This behaviour means that the tracked tick may "skip" a tick value in case a previous tick took more than the expected 50ms. To compensate for this in important paths, spigot/craftbukkit implements "wall-time". Instead of incrementing/decrementing ticks on block entities/entities by one for each call to their tick() method, they instead increment/decrement important values, like an ItemEntity's age or pickupDelay, by the difference of `currentTick - lastTick`, where `lastTick` is the value of `currentTick` during the last tick() call. These "fixes" however do not play nicely with minecraft's simulation distance as entities/block entities implementing the above behaviour would "catch up" their values when moving from a non-ticking chunk to a ticking one as their `lastTick` value remains stuck on the last tick in a ticking chunk and hence lead to a large "catch up" once ticked again. Paper completely removes the "tick skipping" behaviour (See patch "Further-improve-server-tick-loop"), making the above precautions completely unnecessary, which also rids paper of the previous described incompatibility with non-ticking chunks.
81 lines
5.2 KiB
Diff
81 lines
5.2 KiB
Diff
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Spottedleaf <Spottedleaf@users.noreply.github.com>
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Date: Thu, 11 Jun 2020 17:29:42 -0700
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Subject: [PATCH] Fix piston physics inconsistency - MC-188840
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Pistons invoke physics when they move blocks. The physics can cause
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tnt blocks to ignite. However, pistons (when storing the blocks they "moved")
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don't actually go back to the world state sometimes to check if something
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like that happened. As a result they end up moving the tnt like it was
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never ignited. This resulted in the ability to create machines
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that can duplicate tnt, called "world eaters".
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This patch makes the piston logic retrieve the block state from the world
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prevent this from occuring.
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This patch also sets the moved pos to air immediately after creating
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the moving piston TE. This prevents the block from being updated from
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other physics calls by the piston.
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Tested against the following tnt duper design:
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https://www.youtube.com/watch?v=mS7xxNGhjxs
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This patch also affects every type of machine that utilises
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this mechanic. For example, dead coral is removed by a physics
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update when being moved while it is attached to slimeblocks.
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Standard piston machines that don't destroy or modify the
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blocks they move by physics updates should be entirely
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unaffected.
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This patch fixes https://bugs.mojang.com/browse/MC-188840
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This patch also fixes rail duping and carpet duping.
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diff --git a/src/main/java/net/minecraft/world/level/block/piston/PistonBaseBlock.java b/src/main/java/net/minecraft/world/level/block/piston/PistonBaseBlock.java
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index 530b6af1ca2e0ac81c0a8a55dbc7cf5c796c93ce..4aa34b7df734bb755906b228e0df9eb629569ea0 100644
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--- a/src/main/java/net/minecraft/world/level/block/piston/PistonBaseBlock.java
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+++ b/src/main/java/net/minecraft/world/level/block/piston/PistonBaseBlock.java
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@@ -414,14 +414,26 @@ public class PistonBaseBlock extends DirectionalBlock {
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}
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for (j = list.size() - 1; j >= 0; --j) {
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- blockposition3 = (BlockPos) list.get(j);
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- iblockdata1 = world.getBlockState(blockposition3);
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+ // Paper start - fix a variety of piston desync dupes
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+ boolean allowDesync = io.papermc.paper.configuration.GlobalConfiguration.get().unsupportedSettings.allowPistonDuplication;
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+ BlockPos oldPos = blockposition3 = (BlockPos) list.get(j);
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+ iblockdata1 = allowDesync ? world.getBlockState(oldPos) : null;
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+ // Paper end - fix a variety of piston desync dupes
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blockposition3 = blockposition3.relative(enumdirection1);
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map.remove(blockposition3);
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BlockState iblockdata2 = (BlockState) Blocks.MOVING_PISTON.defaultBlockState().setValue(PistonBaseBlock.FACING, dir);
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world.setBlock(blockposition3, iblockdata2, 68);
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- world.setBlockEntity(MovingPistonBlock.newMovingBlockEntity(blockposition3, iblockdata2, (BlockState) list1.get(j), dir, retract, false));
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+ // Paper start - fix a variety of piston desync dupes
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+ if (!allowDesync) {
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+ iblockdata1 = world.getBlockState(oldPos);
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+ map.replace(oldPos, iblockdata1);
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+ }
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+ world.setBlockEntity(MovingPistonBlock.newMovingBlockEntity(blockposition3, iblockdata2, allowDesync ? list1.get(j) : iblockdata1, dir, retract, false));
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+ if (!allowDesync) {
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+ world.setBlock(oldPos, Blocks.AIR.defaultBlockState(), Block.UPDATE_CLIENTS | Block.UPDATE_KNOWN_SHAPE | Block.UPDATE_MOVE_BY_PISTON | 1024); // set air to prevent later physics updates from seeing this block
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+ }
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+ // Paper end - fix a variety of piston desync dupes
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aiblockdata[i++] = iblockdata1;
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}
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diff --git a/src/main/java/net/minecraft/world/level/block/piston/PistonMovingBlockEntity.java b/src/main/java/net/minecraft/world/level/block/piston/PistonMovingBlockEntity.java
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index 8ea7d7da26e7d5644a8ee1a8d9e4c828c6b70a00..d7b963571c900f0f68005d6954bcd9ef1d9e0b7c 100644
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--- a/src/main/java/net/minecraft/world/level/block/piston/PistonMovingBlockEntity.java
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+++ b/src/main/java/net/minecraft/world/level/block/piston/PistonMovingBlockEntity.java
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@@ -297,7 +297,7 @@ public class PistonMovingBlockEntity extends BlockEntity {
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if (world.getBlockState(pos).is(Blocks.MOVING_PISTON)) {
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BlockState blockState = Block.updateFromNeighbourShapes(blockEntity.movedState, world, pos);
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if (blockState.isAir()) {
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- world.setBlock(pos, blockEntity.movedState, 84);
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+ world.setBlock(pos, blockEntity.movedState, io.papermc.paper.configuration.GlobalConfiguration.get().unsupportedSettings.allowPistonDuplication ? 84 : (84 | Block.UPDATE_CLIENTS)); // Paper - fix a variety of piston desync dupes; force notify (flag 2), it's possible the set type by the piston block (which doesn't notify) set this block to air
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Block.updateOrDestroy(blockEntity.movedState, blockState, world, pos, 3);
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} else {
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if (blockState.hasProperty(BlockStateProperties.WATERLOGGED) && blockState.getValue(BlockStateProperties.WATERLOGGED)) {
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