Remove wall-time / unused skip tick protection (#11412)

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.

1 files changed, 137 insertions, 0 deletions

diff --git a/patches/server/0986-Improve-Maps-in-item-frames-performance-and-bug-fixe.patch b/patches/server/0986-Improve-Maps-in-item-frames-performance-and-bug-fixe.patch
new file mode 100644
index 0000000000..30dde1fadd
--- /dev/null
+++ b/patches/server/0986-Improve-Maps-in-item-frames-performance-and-bug-fixe.patch
@@ -0,0 +1,137 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Aikar <[email protected]>
+Date: Fri, 29 Apr 2016 20:02:00 -0400
+Subject: [PATCH] Improve Maps (in item frames) performance and bug fixes
+
+Maps used a modified version of rendering to support plugin controlled
+imaging on maps. The Craft Map Renderer is much slower than Vanilla,
+causing maps in item frames to cause a noticeable hit on server performance.
+
+This updates the map system to not use the Craft system if we detect that no
+custom renderers are in use, defaulting to the much simpler Vanilla system.
+
+Additionally, numerous issues to player position tracking on maps has been fixed.
+
+diff --git a/src/main/java/net/minecraft/server/level/ServerLevel.java b/src/main/java/net/minecraft/server/level/ServerLevel.java
+index c2189752a422f39428b2c0f1408f359f20c388e5..dec865affbaaa71d09806143d13a854100b98f23 100644
+--- a/src/main/java/net/minecraft/server/level/ServerLevel.java
++++ b/src/main/java/net/minecraft/server/level/ServerLevel.java
+@@ -2494,6 +2494,7 @@ public class ServerLevel extends Level implements WorldGenLevel, ca.spottedleaf.
+                             {
+                                 if ( iter.next().player == entity )
+                                 {
++                                    map.decorations.remove(entity.getName().getString()); // Paper
+                                     iter.remove();
+                                 }
+                             }
+diff --git a/src/main/java/net/minecraft/world/entity/player/Player.java b/src/main/java/net/minecraft/world/entity/player/Player.java
+index d0b51d96d6795b5fa03bc195b90324680545b752..09bcbc0ae36e4e69fee87a7e0c49acf496117a39 100644
+--- a/src/main/java/net/minecraft/world/entity/player/Player.java
++++ b/src/main/java/net/minecraft/world/entity/player/Player.java
+@@ -808,6 +808,14 @@ public abstract class Player extends LivingEntity {
+                 return null;
+             }
+             // CraftBukkit end
++            // Paper start - remove player from map on drop
++            if (itemstack.getItem() == Items.FILLED_MAP) {
++                net.minecraft.world.level.saveddata.maps.MapItemSavedData worldmap = net.minecraft.world.item.MapItem.getSavedData(itemstack, this.level());
++                if (worldmap != null) {
++                    worldmap.tickCarriedBy(this, itemstack);
++                }
++            }
++            // Paper end
+ 
+             return entityitem;
+         }
+diff --git a/src/main/java/net/minecraft/world/level/saveddata/maps/MapItemSavedData.java b/src/main/java/net/minecraft/world/level/saveddata/maps/MapItemSavedData.java
+index a43544704109f21bab230dd9bf0401e28f878582..6794466051dd4b725d579b2136c37844995a648e 100644
+--- a/src/main/java/net/minecraft/world/level/saveddata/maps/MapItemSavedData.java
++++ b/src/main/java/net/minecraft/world/level/saveddata/maps/MapItemSavedData.java
+@@ -79,6 +79,7 @@ public class MapItemSavedData extends SavedData {
+     public final Map<String, MapDecoration> decorations = Maps.newLinkedHashMap();
+     private final Map<String, MapFrame> frameMarkers = Maps.newHashMap();
+     private int trackedDecorationCount;
++    private org.bukkit.craftbukkit.map.RenderData vanillaRender = new org.bukkit.craftbukkit.map.RenderData(); // Paper
+ 
+     // CraftBukkit start
+     public final CraftMapView mapView;
+@@ -105,6 +106,7 @@ public class MapItemSavedData extends SavedData {
+         // CraftBukkit start
+         this.mapView = new CraftMapView(this);
+         this.server = (CraftServer) org.bukkit.Bukkit.getServer();
++        this.vanillaRender.buffer = colors; // Paper
+         // CraftBukkit end
+     }
+ 
+@@ -179,6 +181,7 @@ public class MapItemSavedData extends SavedData {
+         if (abyte.length == 16384) {
+             worldmap.colors = abyte;
+         }
++        worldmap.vanillaRender.buffer = abyte; // Paper
+ 
+         RegistryOps<Tag> registryops = registryLookup.createSerializationContext(NbtOps.INSTANCE);
+         List<MapBanner> list = (List) MapBanner.LIST_CODEC.parse(registryops, nbt.get("banners")).resultOrPartial((s) -> {
+@@ -348,7 +351,7 @@ public class MapItemSavedData extends SavedData {
+             --this.trackedDecorationCount;
+         }
+ 
+-        this.setDecorationsDirty();
++        if (mapicon != null) this.setDecorationsDirty(); // Paper - only mark dirty if a change occurs
+     }
+ 
+     public static void addTargetDecoration(ItemStack stack, BlockPos pos, String id, Holder<MapDecorationType> decorationType) {
+@@ -588,6 +591,21 @@ public class MapItemSavedData extends SavedData {
+ 
+     public class HoldingPlayer {
+ 
++        // Paper start
++        private void addSeenPlayers(java.util.Collection<MapDecoration> icons) {
++            org.bukkit.entity.Player player = (org.bukkit.entity.Player) this.player.getBukkitEntity();
++            MapItemSavedData.this.decorations.forEach((name, mapIcon) -> {
++                // If this cursor is for a player check visibility with vanish system
++                org.bukkit.entity.Player other = org.bukkit.Bukkit.getPlayerExact(name); // Spigot
++                if (other == null || player.canSee(other)) {
++                    icons.add(mapIcon);
++                }
++            });
++        }
++        private boolean shouldUseVanillaMap() {
++            return mapView.getRenderers().size() == 1 && mapView.getRenderers().get(0).getClass() == org.bukkit.craftbukkit.map.CraftMapRenderer.class;
++        }
++        // Paper end
+         public final Player player;
+         private boolean dirtyData = true;
+         private int minDirtyX;
+@@ -621,7 +639,9 @@ public class MapItemSavedData extends SavedData {
+         @Nullable
+         Packet<?> nextUpdatePacket(MapId mapId) {
+             MapItemSavedData.MapPatch worldmap_b;
+-            org.bukkit.craftbukkit.map.RenderData render = MapItemSavedData.this.mapView.render((org.bukkit.craftbukkit.entity.CraftPlayer) this.player.getBukkitEntity()); // CraftBukkit
++            if (!this.dirtyData && this.tick % 5 != 0) { this.tick++; return null; } // Paper - this won't end up sending, so don't render it!
++            boolean vanillaMaps = shouldUseVanillaMap(); // Paper
++            org.bukkit.craftbukkit.map.RenderData render = !vanillaMaps ? MapItemSavedData.this.mapView.render((org.bukkit.craftbukkit.entity.CraftPlayer) this.player.getBukkitEntity()) : MapItemSavedData.this.vanillaRender; // CraftBukkit // Paper
+ 
+             if (this.dirtyData) {
+                 this.dirtyData = false;
+@@ -637,6 +657,8 @@ public class MapItemSavedData extends SavedData {
+                 // CraftBukkit start
+                 java.util.Collection<MapDecoration> icons = new java.util.ArrayList<MapDecoration>();
+ 
++                if (vanillaMaps) addSeenPlayers(icons); // Paper
++
+                 for (org.bukkit.map.MapCursor cursor : render.cursors) {
+                     if (cursor.isVisible()) {
+                         icons.add(new MapDecoration(CraftMapCursor.CraftType.bukkitToMinecraftHolder(cursor.getType()), cursor.getX(), cursor.getY(), cursor.getDirection(), Optional.ofNullable(PaperAdventure.asVanilla(cursor.caption()))));
+diff --git a/src/main/java/org/bukkit/craftbukkit/map/RenderData.java b/src/main/java/org/bukkit/craftbukkit/map/RenderData.java
+index 256a131781721c86dd6cdbc329335964570cbe8c..5768cd512ec166f1e8d1f4a28792015347297c3f 100644
+--- a/src/main/java/org/bukkit/craftbukkit/map/RenderData.java
++++ b/src/main/java/org/bukkit/craftbukkit/map/RenderData.java
+@@ -5,7 +5,7 @@ import org.bukkit.map.MapCursor;
+ 
+ public class RenderData {
+ 
+-    public final byte[] buffer;
++    public byte[] buffer; // Paper
+     public final ArrayList<MapCursor> cursors;
+ 
+     public RenderData() {