[1.18.x] Allow blocks to hide faces on a neighboring block (#8300)

* Allow blocks to hide faces on a neighboring block
* Allow blocks to opt-out of external face hiding

src/main/java/net/minecraftforge/client/ForgeHooksClient.java

@@ -1074,4 +1074,9 @@ public class ForgeHooksClient
         MinecraftForge.EVENT_BUS.post(event);
         return event.getResult();
     }
+
+    public static boolean isBlockInSolidLayer(BlockState state)
+    {
+        return ItemBlockRenderTypes.canRenderInLayer(state, RenderType.solid());
+    }
 }

src/main/java/net/minecraftforge/common/extensions/IForgeBlock.java

@@ -32,6 +32,7 @@ import net.minecraft.core.BlockPos;
 import net.minecraft.world.phys.HitResult;
 import net.minecraft.world.phys.Vec3;
 import net.minecraft.server.level.ServerLevel;
+import net.minecraftforge.client.ForgeHooksClient;
 import net.minecraftforge.common.ForgeHooks;
 import net.minecraftforge.common.IPlantable;
 
@@ -44,6 +45,7 @@ import net.minecraft.world.level.LevelReader;
 import net.minecraft.world.level.block.state.BlockState;
 import net.minecraftforge.common.ToolAction;
 import net.minecraftforge.common.ToolActions;
+import net.minecraftforge.fml.loading.FMLEnvironment;
 
 @SuppressWarnings("deprecation")
 public interface IForgeBlock
@@ -749,4 +751,43 @@ public interface IForgeBlock
             return state.isSignalSource() && direction != null;
         }
     }
+
+    /**
+     * Whether this block hides the neighbors face pointed towards by the given direction.
+     * <p>
+     * This method should only be used for blocks you don't control, for your own blocks override
+     * {@link Block#skipRendering(BlockState, BlockState, Direction)} on the respective block instead
+     * <p>
+     * WARNING: This method is likely to be called from a worker thread! If you want to retrieve a
+     *          {@link net.minecraft.world.level.block.entity.BlockEntity} from the given level, make sure to use
+     *          {@link net.minecraftforge.common.extensions.IForgeBlockGetter#getExistingBlockEntity(BlockPos)} to not
+     *          accidentally create a new or delete an old {@link net.minecraft.world.level.block.entity.BlockEntity}
+     *          off of the main thread as this would cause a write operation to the given {@link BlockGetter} and cause
+     *          a CME in the process. Any other direct or indirect write operation to the {@link BlockGetter} will have
+     *          the same outcome.
+     *
+     * @param level The world
+     * @param pos The blocks position in the world
+     * @param state The blocks {@link BlockState}
+     * @param neighborState The neighboring blocks {@link BlockState}
+     * @param dir The direction towards the neighboring block
+     */
+    default boolean hidesNeighborFace(BlockGetter level, BlockPos pos, BlockState state, BlockState neighborState, Direction dir)
+    {
+        return false;
+    }
+
+    /**
+     * Whether this block allows a neighboring block to hide the face of this block it touches.
+     * If this returns true, {@link IForgeBlockState#hidesNeighborFace(BlockGetter, BlockPos, BlockState, Direction)}
+     * will be called on the neighboring block.
+     */
+    default boolean supportsExternalFaceHiding(BlockState state)
+    {
+        if (FMLEnvironment.dist.isClient())
+        {
+            return !ForgeHooksClient.isBlockInSolidLayer(state);
+        }
+        return true;
+    }
 }

src/main/java/net/minecraftforge/common/extensions/IForgeBlockGetter.java

@@ -0,0 +1,49 @@
+/*
+ * Minecraft Forge - Forge Development LLC
+ * SPDX-License-Identifier: LGPL-2.1-only
+ */
+
+package net.minecraftforge.common.extensions;
+
+import net.minecraft.core.BlockPos;
+import net.minecraft.world.level.BlockGetter;
+import net.minecraft.world.level.Level;
+import net.minecraft.world.level.block.entity.BlockEntity;
+import net.minecraft.world.level.chunk.*;
+import org.jetbrains.annotations.Nullable;
+
+public interface IForgeBlockGetter
+{
+    private BlockGetter self() { return (BlockGetter) this; }
+
+    /**
+     * Get the {@link BlockEntity} at the given position if it exists.
+     * <p>
+     * {@link Level#getBlockEntity(BlockPos)} would create a new {@link BlockEntity} if the
+     * {@link net.minecraft.world.level.block.Block} has one, but it has not been placed in the world yet
+     * (This can happen on world load).
+     * @return The BlockEntity at the given position or null if it doesn't exist
+     */
+    @Nullable
+    default BlockEntity getExistingBlockEntity(BlockPos pos)
+    {
+        if (this instanceof Level level)
+        {
+            if (!level.hasChunk(pos.getX(), pos.getZ()))
+            {
+                return null;
+            }
+
+            return level.getChunk(pos).getExistingBlockEntity(pos);
+        }
+        else if (this instanceof LevelChunk chunk)
+        {
+            return chunk.getBlockEntities().get(pos);
+        }
+        else if (this instanceof ImposterProtoChunk chunk)
+        {
+            return chunk.getWrapped().getExistingBlockEntity(pos);
+        }
+        return self().getBlockEntity(pos);
+    }
+}

src/main/java/net/minecraftforge/common/extensions/IForgeBlockState.java

@@ -646,4 +646,31 @@ public interface IForgeBlockState
     {
         return self().getBlock().canConnectRedstone(self(), level, pos, direction);
     }
+
+    /**
+     * Whether this block hides the neighbors face pointed towards by the given direction.
+     * <p>
+     * This method should only be used for blocks you don't control, for your own blocks override
+     * {@link net.minecraft.world.level.block.Block#skipRendering(BlockState, BlockState, Direction)}
+     * on the respective block instead
+     *
+     * @param level The world
+     * @param pos The blocks position in the world
+     * @param neighborState The neighboring blocks {@link BlockState}
+     * @param dir The direction towards the neighboring block
+     */
+    default boolean hidesNeighborFace(BlockGetter level, BlockPos pos, BlockState neighborState, Direction dir)
+    {
+        return self().getBlock().hidesNeighborFace(level, pos, self(), neighborState, dir);
+    }
+
+    /**
+     * Whether this block allows a neighboring block to hide the face of this block it touches.
+     * If this returns true, {@link IForgeBlockState#hidesNeighborFace(BlockGetter, BlockPos, BlockState, Direction)}
+     * will be called on the neighboring block.
+     */
+    default boolean supportsExternalFaceHiding()
+    {
+        return self().getBlock().supportsExternalFaceHiding(self());
+    }
 }