Merge branch 'pull/5451' into 1.13-pre

# Conflicts:
#	patches/minecraft/net/minecraft/entity/player/EntityPlayer.java.patch

src/main/java/net/minecraftforge/fml/network/FMLPlayHandler.java

@@ -33,5 +33,6 @@ public class FMLPlayHandler
     static
     {
         channel.registerMessage(0, FMLPlayMessages.SpawnEntity.class, FMLPlayMessages.SpawnEntity::encode, FMLPlayMessages.SpawnEntity::decode, FMLPlayMessages.SpawnEntity::handle);
+        channel.registerMessage(1, FMLPlayMessages.OpenContainer.class, FMLPlayMessages.OpenContainer::encode, FMLPlayMessages.OpenContainer::decode, FMLPlayMessages.OpenContainer::handle);
     }
 }

src/main/java/net/minecraftforge/fml/network/FMLPlayMessages.java

@@ -19,15 +19,20 @@
 
 package net.minecraftforge.fml.network;
 
+import io.netty.buffer.ByteBuf;
+import io.netty.buffer.Unpooled;
 import net.minecraft.client.Minecraft;
+import net.minecraft.client.gui.GuiScreen;
 import net.minecraft.entity.Entity;
 import net.minecraft.entity.EntityTracker;
 import net.minecraft.entity.EntityType;
 import net.minecraft.network.PacketBuffer;
+import net.minecraft.util.ResourceLocation;
 import net.minecraft.util.math.MathHelper;
 import net.minecraftforge.fml.common.registry.IEntityAdditionalSpawnData;
 
 import java.util.UUID;
+import java.util.function.Function;
 import java.util.function.Supplier;
 
 public class FMLPlayMessages
@@ -156,4 +161,45 @@ public class FMLPlayMessages
             ctx.get().setPacketHandled(true);
         }
     }
+
+    public static class OpenContainer
+    {
+        private final ResourceLocation id;
+        private final int windowId;
+        private final byte[] additionalData;
+
+        public OpenContainer(ResourceLocation id, int windowId, byte[] additionalData)
+        {
+            this.id = id;
+            this.windowId = windowId;
+            this.additionalData = additionalData;
+        }
+
+        public static void encode(OpenContainer msg, PacketBuffer buf)
+        {
+            buf.writeResourceLocation(msg.id);
+            buf.writeVarInt(msg.windowId);
+            buf.writeByteArray(msg.additionalData);
+        }
+
+        public static OpenContainer decode(PacketBuffer buf)
+        {
+            return new OpenContainer(buf.readResourceLocation(), buf.readVarInt(), buf.readByteArray());
+        }
+
+        public static void handle(OpenContainer msg, Supplier<NetworkEvent.Context> ctx)
+        {
+            ctx.get().enqueueWork(() -> {
+                Supplier<Function<ByteBuf, GuiScreen>> sup = NetworkRegistry.guiHandlers.get(msg.id);
+                if (sup != null) {
+                    GuiScreen gui = sup.get().apply(Unpooled.wrappedBuffer(msg.additionalData));
+                    if (gui != null) {
+                        Minecraft.getInstance().displayGuiScreen(gui);
+                        Minecraft.getInstance().player.openContainer.windowId = msg.windowId;
+                    }
+                }
+            });
+            ctx.get().setPacketHandled(true);
+        }
+    }
 }

src/main/java/net/minecraftforge/fml/network/NetworkHooks.java

@@ -19,15 +19,21 @@
 
 package net.minecraftforge.fml.network;
 
+import io.netty.buffer.ByteBuf;
 import net.minecraft.entity.Entity;
 import net.minecraft.entity.player.EntityPlayerMP;
+import net.minecraft.inventory.Container;
 import net.minecraft.network.NetHandlerPlayServer;
 import net.minecraft.network.NetworkManager;
 import net.minecraft.network.Packet;
 import net.minecraft.network.handshake.client.CPacketHandshake;
 import net.minecraft.server.network.NetHandlerLoginServer;
 import net.minecraft.util.ResourceLocation;
+import net.minecraft.world.IInteractionObject;
+import net.minecraftforge.common.MinecraftForge;
+import net.minecraftforge.event.entity.player.PlayerContainerEvent;
 
+import javax.annotation.Nullable;
 import java.util.Objects;
 
 public class NetworkHooks
@@ -80,4 +86,26 @@ public class NetworkHooks
     {
         return FMLHandshakeHandler.tickLogin(networkManager);
     }
+
+    public static void openGui(EntityPlayerMP player, IInteractionObject container, @Nullable ByteBuf extraData)
+    {
+        ResourceLocation id = new ResourceLocation(container.getGuiID());
+        Container c = container.createContainer(player.inventory, player);
+        player.closeScreen();
+        player.getNextWindowId();
+        player.openContainer = c;
+        player.openContainer.windowId = player.currentWindowId;
+        player.openContainer.addListener(player);
+        MinecraftForge.EVENT_BUS.post(new PlayerContainerEvent.Open(player, c));
+
+        byte[] additional;
+        if (extraData == null) {
+            additional = new byte[0];
+        } else {
+            additional = new byte[extraData.readableBytes()];
+            extraData.readBytes(additional);
+        }
+        FMLPlayMessages.OpenContainer msg = new FMLPlayMessages.OpenContainer(id, player.currentWindowId, additional);
+        FMLPlayHandler.channel.sendTo(msg, player.connection.getNetworkManager(), NetworkDirection.PLAY_TO_CLIENT);
+    }
 }

src/main/java/net/minecraftforge/fml/network/NetworkRegistry.java

@@ -19,6 +19,8 @@
 
 package net.minecraftforge.fml.network;
 
+import io.netty.buffer.ByteBuf;
+import net.minecraft.client.gui.GuiScreen;
 import net.minecraft.nbt.NBTTagCompound;
 import net.minecraft.nbt.NBTTagList;
 import net.minecraft.network.NetworkManager;
@@ -33,7 +35,9 @@ import org.apache.logging.log4j.Marker;
 import org.apache.logging.log4j.MarkerManager;
 
 import java.util.*;
+import java.util.concurrent.ConcurrentHashMap;
 import java.util.function.BiFunction;
+import java.util.function.Function;
 import java.util.function.Predicate;
 import java.util.function.Supplier;
 import java.util.stream.Collectors;
@@ -47,6 +51,21 @@ public class NetworkRegistry
     private static final Marker NETREGISTRY = MarkerManager.getMarker("NETREGISTRY");
 
     private static Map<ResourceLocation, NetworkInstance> instances = new HashMap<>();
+    static final Map<ResourceLocation, Supplier<Function<ByteBuf, GuiScreen>>> guiHandlers = new ConcurrentHashMap<>();
+
+    /**
+     * Registers a client-side GUI handler for the given ID.
+     * The function takes any extra data provided to {@link net.minecraft.entity.player.EntityPlayer#openGui}
+     * and returns a {@link GuiScreen} to display.
+     * Call this during {@link net.minecraftforge.fml.event.lifecycle.FMLClientSetupEvent}.
+     * This method is safe to call in parallel mod loading
+     * @param id
+     * @param handler
+     */
+    public static void registerGui(ResourceLocation id, Supplier<Function<ByteBuf, GuiScreen>> handler)
+    {
+        guiHandlers.put(id, handler);
+    }
 
     /**
      * Special value for clientAcceptedVersions and serverAcceptedVersions predicates indicating the other side lacks