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BlockDefinition & BlockDefinitionBuilder

Package: net.astronomy.multilib.api.block

Block-level multiblock metadata - properties of a Block itself, independent of any single MultiblockDefinition. Accessed via MultiLib.block(block).

Why separate from MultiblockDefinition

Some facts are about the block, not any one pattern using it — "always the core of multiblock X," "has its own facing," "preserves its inventory when dismantled." BlockDefinitionBuilder captures those once, so every structure reusing the block benefits.

BlockDefinitionBuilder

public final class BlockDefinitionBuilder {
    public BlockDefinitionBuilder core(ResourceLocation... multiblockIds);
    public BlockDefinitionBuilder wallSharing(boolean enabled);
    public BlockDefinitionBuilder ioPort();
    public BlockDefinitionBuilder dropOriginalOnBreak();
    public BlockDefinitionBuilder mainFace();
    public BlockDefinition build();
}

core(ResourceLocation... multiblockIds)

Declares this block as the core of one or more multiblocks, by id. When that multiblock's own MultiblockBuilder doesn't call .core(char), the symbol mapped to this block is auto-assigned as the core symbol at build time. If the multiblock's builder explicitly declares a different block as core, registration of that multiblock fails with a logged error (game load continues; only that one structure ends up unregistered).

wallSharing(boolean enabled)

Overrides wall sharing for this block specifically when used as a core/activation symbol (disabled by default for those roles). Has no effect on non-core usages of the block - those already go through the existing priority chain (symbol override → block declaration → definition flag → default). See Advanced Features § Wall sharing.

ioPort()

Marks this block as an IO port: item/fluid/energy capability requests on it are automatically forwarded to the controller block entity of whatever multiblock instance it's currently part of (via IOPortCapabilityHandler).

dropOriginalOnBreak()

When a multiblock containing this block is dismantled, this block keeps its block entity data and drops normally (preserving NBT/inventory via vanilla drop logic) instead of being wiped to a clean copy of itself. See BlockBreakHandler.dismantleRemainingBlocks(...).

mainFace()

Marks this block as having a meaningful placed facing of its own (a FACING/HORIZONTAL_FACING blockstate property, like a furnace). When used as a multiblock's core, the ghost overlay and auto-place preview orientation is pinned to the block's actual in-world facing instead of following the player's look direction. See the Directional Cores Guide.

build()

Constructs the BlockDefinition and registers it into BlockDefinitionRegistry. Unlike MultiblockBuilder.build(), there's no validation step that can silently skip registration here.

BlockDefinition

The built, immutable result.

public final class BlockDefinition {
    public Block getBlock();
    public Set<ResourceLocation> getCoreOfMultiblocks();
    public boolean isCoreOf(ResourceLocation multiblockId);
    public boolean declaresCore();
    public Optional<Boolean> getWallSharingOverride();
    public boolean isIoPort();
    public boolean isDropOriginalOnBreak();
    public boolean hasMainFace();
}

Example

MultiLib.block(MyBlocks.REACTOR_CORE)
        .core(ResourceLocation.fromNamespaceAndPath("examplemod", "reactor"))
        .mainFace()
        .ioPort()
        .build();

With this declared, the examplemod:reactor MultiblockBuilder doesn't need to call .core(...) at all (as long as only one symbol maps to REACTOR_CORE) - and the ghost overlay for that structure will always preview in the direction the core block is actually facing, not the direction the player is looking.

See also