From 4a20eea852198307d73b90af4d4c823a703b54c6 Mon Sep 17 00:00:00 2001
From: Euric <baeuric@gmail.com>
Date: Tue, 4 May 2021 14:24:58 -0700
Subject: [PATCH] Defer monitor tile update when placed by another TE

---
 .../peripheral/monitor/BlockMonitor.java      | 12 +++++++++---
 .../peripheral/monitor/TileMonitor.java       | 19 +++++++++++++++++++
 2 files changed, 28 insertions(+), 3 deletions(-)

diff --git a/src/main/java/dan200/computercraft/shared/peripheral/monitor/BlockMonitor.java b/src/main/java/dan200/computercraft/shared/peripheral/monitor/BlockMonitor.java
index ce4eb0879..ebd2799bb 100644
--- a/src/main/java/dan200/computercraft/shared/peripheral/monitor/BlockMonitor.java
+++ b/src/main/java/dan200/computercraft/shared/peripheral/monitor/BlockMonitor.java
@@ -9,6 +9,7 @@ package dan200.computercraft.shared.peripheral.monitor;
 import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
 
+import dan200.computercraft.api.turtle.FakePlayer;
 import dan200.computercraft.shared.common.BlockGeneric;
 
 import net.minecraft.block.Block;
@@ -71,9 +72,14 @@ public class BlockMonitor extends BlockGeneric {
         BlockEntity entity = world.getBlockEntity(pos);
         if (entity instanceof TileMonitor && !world.isClient) {
             TileMonitor monitor = (TileMonitor) entity;
-            monitor.contractNeighbours();
-            monitor.contract();
-            monitor.expand();
+            // Defer the block update if we're being placed by another TE. See #691
+            if ( livingEntity == null || livingEntity instanceof FakePlayer )
+            {
+                monitor.updateNeighborsDeferred();
+                return;
+            }
+
+            monitor.updateNeighbors();
         }
     }
 
diff --git a/src/main/java/dan200/computercraft/shared/peripheral/monitor/TileMonitor.java b/src/main/java/dan200/computercraft/shared/peripheral/monitor/TileMonitor.java
index 9ef392b25..cddd4e3f5 100644
--- a/src/main/java/dan200/computercraft/shared/peripheral/monitor/TileMonitor.java
+++ b/src/main/java/dan200/computercraft/shared/peripheral/monitor/TileMonitor.java
@@ -54,6 +54,7 @@ public class TileMonitor extends TileGeneric implements IPeripheralTile {
     private ServerMonitor m_serverMonitor;
     private ClientMonitor m_clientMonitor;
     private MonitorPeripheral peripheral;
+    private boolean needsUpdate = false;
     private boolean m_destroyed = false;
     private boolean visiting = false;
     private int m_width = 1;
@@ -98,6 +99,12 @@ public class TileMonitor extends TileGeneric implements IPeripheralTile {
 
     @Override
     public void blockTick() {
+        if ( needsUpdate )
+        {
+            needsUpdate = false;
+            updateNeighbors();
+        }
+
         if (this.m_xIndex != 0 || this.m_yIndex != 0 || this.m_serverMonitor == null) {
             return;
         }
@@ -530,6 +537,18 @@ public class TileMonitor extends TileGeneric implements IPeripheralTile {
         return true;
     }
 
+    void updateNeighborsDeferred()
+    {
+        needsUpdate = true;
+    }
+
+    void updateNeighbors()
+    {
+        contractNeighbours();
+        contract();
+        expand();
+    }
+
     @SuppressWarnings ("StatementWithEmptyBody")
     void expand() {
         while (this.mergeLeft() || this.mergeRight() || this.mergeUp() || this.mergeDown()) {