1 files changed, 166 insertions, 0 deletions

diff --git a/src/Blocks/Mixins.h b/src/Blocks/Mixins.h
new file mode 100644
index 000000000..a65fe7b06
--- /dev/null
+++ b/src/Blocks/Mixins.h
@@ -0,0 +1,166 @@
+// Mixins.h
+
+// Provides various mixins for easier cBlockHandler descendant implementations
+
+/* The general use case is to derive a handler from these mixins, providing a suitable base to them:
+class cBlockAir: public cBlockWithNoDrops<cBlockHandler>;
+class cBlockLadder: public cMetaRotator<cClearMetaOnDrop, ...>
+*/
+
+#pragma once
+
+#include "../Item.h"
+
+
+
+
+
+// MSVC generates warnings for the templated AssertIfNotMatched parameter conditions, so disable it:
+#ifdef _MSC_VER
+	#pragma warning(disable: 4127)  // Conditional expression is constant
+#endif
+
+
+
+
+
+template <class Base = cBlockHandler>
+class cBlockWithNoDrops:
+	public Base
+{
+public:
+
+	cBlockWithNoDrops(BLOCKTYPE a_BlockType):
+		Base(a_BlockType)
+	{
+	}
+
+
+
+
+
+	virtual cItems ConvertToPickups(NIBBLETYPE a_BlockMeta, cBlockEntity * a_BlockEntity, const cEntity * a_Digger, const cItem * a_Tool) override
+	{
+		// Don't drop anything:
+		return {};
+	}
+};
+
+
+
+
+
+/** Mixin to clear the block's meta value when converting to a pickup. */
+template <class Base>
+class cClearMetaOnDrop:
+	public Base
+{
+public:
+
+	cClearMetaOnDrop(BLOCKTYPE a_BlockType):
+		Base(a_BlockType)
+	{
+	}
+
+
+
+
+
+	virtual cItems ConvertToPickups(NIBBLETYPE a_BlockMeta, cBlockEntity * a_BlockEntity, const cEntity * a_Digger, const cItem * a_Tool) override
+	{
+		// Reset the meta to zero:
+		return cItem(this->m_BlockType);
+	}
+};
+
+
+
+
+
+/** Mixin for rotations and reflections following the standard pattern of "apply mask, then use a switch".
+Inherit from this class providing your base class as Base, the BitMask for the direction bits in bitmask and the masked value for the directions in North, East, South, West.
+There is also an aptional parameter AssertIfNotMatched, set this if it is invalid for a block to exist in any other state. */
+template <class Base, NIBBLETYPE BitMask, NIBBLETYPE North, NIBBLETYPE East, NIBBLETYPE South, NIBBLETYPE West, bool AssertIfNotMatched = false>
+class cMetaRotator:
+	public Base
+{
+public:
+
+	cMetaRotator(BLOCKTYPE a_BlockType):
+		Base(a_BlockType)
+	{}
+
+
+
+
+
+	virtual NIBBLETYPE MetaRotateCCW(NIBBLETYPE a_Meta) override
+	{
+		NIBBLETYPE OtherMeta = a_Meta & (~BitMask);
+		switch (a_Meta & BitMask)
+		{
+			case South: return East  | OtherMeta;
+			case East:  return North | OtherMeta;
+			case North: return West  | OtherMeta;
+			case West:  return South | OtherMeta;
+		}
+		if (AssertIfNotMatched)
+		{
+			ASSERT(!"Invalid Meta value");
+		}
+		return a_Meta;
+	}
+
+
+
+
+
+	virtual NIBBLETYPE MetaRotateCW(NIBBLETYPE a_Meta) override
+	{
+		NIBBLETYPE OtherMeta = a_Meta & (~BitMask);
+		switch (a_Meta & BitMask)
+		{
+			case South: return West  | OtherMeta;
+			case West:  return North | OtherMeta;
+			case North: return East  | OtherMeta;
+			case East:  return South | OtherMeta;
+		}
+		if (AssertIfNotMatched)
+		{
+			ASSERT(!"Invalid Meta value");
+		}
+		return a_Meta;
+	}
+
+
+
+
+
+	virtual NIBBLETYPE MetaMirrorXY(NIBBLETYPE a_Meta) override
+	{
+		NIBBLETYPE OtherMeta = a_Meta & (~BitMask);
+		switch (a_Meta & BitMask)
+		{
+			case South: return North | OtherMeta;
+			case North: return South | OtherMeta;
+		}
+		// Not Facing North or South; No change.
+		return a_Meta;
+	}
+
+
+
+
+
+	virtual NIBBLETYPE MetaMirrorYZ(NIBBLETYPE a_Meta) override
+	{
+		NIBBLETYPE OtherMeta = a_Meta & (~BitMask);
+		switch (a_Meta & BitMask)
+		{
+			case West: return East | OtherMeta;
+			case East: return West | OtherMeta;
+		}
+		// Not Facing East or West; No change.
+		return a_Meta;
+	}
+};