Lava can spawn fire.

Settable in world.ini, lava can spawn fire to fuel blocks near it. Fix #65.

src/Blocks/BlockFluid.h

@@ -54,3 +54,84 @@ public:
 
 
 
+
+class cBlockLavaHandler :
+	public cBlockFluidHandler
+{
+	typedef cBlockFluidHandler super;
+public:
+
+	cBlockLavaHandler(BLOCKTYPE a_BlockType) :
+		super(a_BlockType)
+	{
+	}
+	
+	
+	/// Called to tick the block
+	virtual void OnUpdate(cChunk & a_Chunk, int a_RelX, int a_RelY, int a_RelZ) override
+	{
+		if (a_Chunk.GetWorld()->ShouldLavaSpawnFire())
+		{
+			// Try to start up to 5 fires:
+			for (int i = 0; i < 5; i++)
+			{
+				TryStartFireNear(a_RelX, a_RelY, a_RelZ, a_Chunk);
+			}
+		}
+	}
+	
+	
+	/// Tries to start a fire near the lava at given coords. Returns true if fire started.
+	static bool TryStartFireNear(int a_RelX, int a_RelY, int a_RelZ, cChunk & a_Chunk)
+	{
+		// Pick a block next to this lava block:
+		int rnd = a_Chunk.GetWorld()->GetTickRandomNumber(cChunkDef::NumBlocks * 8) / 7;
+		int x = (rnd % 3) - 1;         // -1 .. 1
+		int y = ((rnd / 4) % 4) - 1;   // -1 .. 2
+		int z = ((rnd / 16) % 3) - 1;  // -1 .. 1
+		
+		// Check if it's fuel:
+		BLOCKTYPE BlockType;
+		if (
+			!a_Chunk.UnboundedRelGetBlockType(a_RelX + x, a_RelY + y, a_RelZ + z, BlockType) ||
+			!cFireSimulator::IsFuel(BlockType)
+		)
+		{
+			return false;
+		}
+		
+		// Try to set it on fire:
+		static struct
+		{
+			int x, y, z;
+		} CrossCoords[] =
+		{
+			{-1,  0,  0},
+			{ 1,  0,  0},
+			{ 0, -1,  0},
+			{ 0,  1,  0},
+			{ 0,  0, -1},
+			{ 0,  0,  1},
+		} ;
+		int RelX = a_RelX + x;
+		int RelY = a_RelY + y;
+		int RelZ = a_RelZ + z;
+		for (size_t i = 0; i < ARRAYCOUNT(CrossCoords); i++)
+		{
+			if (
+				a_Chunk.UnboundedRelGetBlockType(RelX + CrossCoords[i].x, RelY + CrossCoords[i].y, RelZ + CrossCoords[i].z, BlockType) &&
+				(BlockType == E_BLOCK_AIR)
+			)
+			{
+				// This is an air block next to a fuel next to lava, light it up:
+				a_Chunk.UnboundedRelSetBlock(RelX + CrossCoords[i].x, RelY + CrossCoords[i].y, RelZ + CrossCoords[i].z, E_BLOCK_FIRE, 0);
+				return true;
+			}
+		}  // for i - CrossCoords[]
+		return false;
+	}
+} ;
+
+
+
+