Trying to figure out how hg works...

src/modules/physics/box2d/Shape.cpp

@@ -160,6 +160,67 @@ namespace box2d
 		v[2] = f.groupIndex;
 	}
 	
+	int Shape::setCategory(lua_State * L)
+	{
+		b2FilterData f = shape->GetFilterData();
+		f.categoryBits = (uint16)getBits(L);
+		shape->SetFilterData(f);
+		shape->GetBody()->GetWorld()->Refilter(shape);
+		return 0;
+	}
+
+	int Shape::setMask(lua_State * L)
+	{
+		b2FilterData f = shape->GetFilterData();
+		f.maskBits = ~(uint16)getBits(L);
+		shape->SetFilterData(f);
+		shape->GetBody()->GetWorld()->Refilter(shape);
+		return 0;
+	}
+
+	int Shape::getCategory(lua_State * L)
+	{
+		return pushBits(L, shape->GetFilterData().categoryBits);
+	}
+
+	int Shape::getMask(lua_State * L)
+	{
+		return pushBits(L, ~(shape->GetFilterData().maskBits));
+	}
+	
+	uint16 Shape::getBits(lua_State * L)
+	{
+		// Get number of args.
+		int argc = lua_gettop(L);
+
+		// The new bitset.
+		std::bitset<16> b;
+
+		for(int i = 1;i<=argc;i++)
+		{
+			size_t bpos = (size_t)(lua_tointeger(L, i)-1);
+			if(bpos < 0 || bpos > 16) 
+				return luaL_error(L, "Values must be in range 1-16.");
+			b.set(bpos, true);
+		}
+		
+		return (uint16)b.to_ulong();
+	}
+
+	int Shape::pushBits(lua_State * L, uint16 bits)
+	{
+		// Create a bitset.
+		std::bitset<16> b((unsigned long)bits);
+
+		// Push all set bits.
+		for(int i = 0;i<16;i++)
+			if(b.test(i))
+				lua_pushinteger(L, i+1);
+
+		// Count number of set bits.
+		return (int)b.count();
+	}
+
 	int Shape::setData(lua_State * L)
 	{
 		love::luax_assert_argc(L, 1, 1);

src/modules/physics/box2d/Shape.h

@@ -168,6 +168,13 @@ namespace box2d
 		**/
 		void getFilterData(int * v);
 		
+		int setCategory(lua_State * L);
+		int setMask(lua_State * L);
+		int getCategory(lua_State * L);
+		int getMask(lua_State * L);
+		uint16 getBits(lua_State * L);
+		int pushBits(lua_State * L, uint16 bits);
+
 		/**
 		* This function stores an in-C reference to
 		* arbitrary Lua data in the Box2D shape object.

src/modules/physics/box2d/wrap_CircleShape.cpp

@@ -54,6 +54,10 @@ namespace box2d
 		{ "testSegment", w_Shape_testSegment },
 		{ "setFilterData", w_Shape_setFilterData },
 		{ "getFilterData", w_Shape_getFilterData },
+		{ "setCategory", w_Shape_setCategory },
+		{ "getCategory", w_Shape_getCategory },
+		{ "setMask", w_Shape_setMask },
+		{ "getMask", w_Shape_getMask },
 		{ "setData", w_Shape_setData },
 		{ "getData", w_Shape_getData },
 		{ "getBoundingBox", w_Shape_getBoundingBox },

src/modules/physics/box2d/wrap_PolygonShape.cpp

@@ -54,6 +54,10 @@ namespace box2d
 		{ "testSegment", w_Shape_testSegment },
 		{ "setFilterData", w_Shape_setFilterData },
 		{ "getFilterData", w_Shape_getFilterData },
+		{ "setCategory", w_Shape_setCategory },
+		{ "getCategory", w_Shape_getCategory },
+		{ "setMask", w_Shape_setMask },
+		{ "getMask", w_Shape_getMask },
 		{ "setData", w_Shape_setData },
 		{ "getData", w_Shape_getData },
 		{ "getBoundingBox", w_Shape_getBoundingBox },

src/modules/physics/box2d/wrap_Shape.cpp

@@ -145,6 +145,34 @@ namespace box2d
 		return 3;
 	}
 	
+	int w_Shape_setCategory(lua_State * L)
+	{
+		Shape * t = luax_checkshape(L, 1);
+		lua_remove(L, 1);
+		return t->setCategory(L);
+	}
+	
+	int w_Shape_getCategory(lua_State * L)
+	{
+		Shape * t = luax_checkshape(L, 1);
+		lua_remove(L, 1);
+		return t->getCategory(L);
+	}
+
+	int w_Shape_setMask(lua_State * L)
+	{
+		Shape * t = luax_checkshape(L, 1);
+		lua_remove(L, 1);
+		return t->setMask(L);
+	}
+
+	int w_Shape_getMask(lua_State * L)
+	{
+		Shape * t = luax_checkshape(L, 1);
+		lua_remove(L, 1);
+		return t->getMask(L);
+	}
+
 	int w_Shape_setData(lua_State * L)
 	{
 		Shape * t = luax_checkshape(L, 1);
@@ -180,6 +208,10 @@ namespace box2d
 		{ "testSegment", w_Shape_testSegment },
 		{ "setFilterData", w_Shape_setFilterData },
 		{ "getFilterData", w_Shape_getFilterData },
+		{ "setCategory", w_Shape_setCategory },
+		{ "getCategory", w_Shape_getCategory },
+		{ "setMask", w_Shape_setMask },
+		{ "getMask", w_Shape_getMask },
 		{ "setData", w_Shape_setData },
 		{ "getData", w_Shape_getData },
 		{ "getBoundingBox", w_Shape_getBoundingBox },

src/modules/physics/box2d/wrap_Shape.h

@@ -46,6 +46,10 @@ namespace box2d
 	int w_Shape_testSegment(lua_State * L);
 	int w_Shape_setFilterData(lua_State * L);
 	int w_Shape_getFilterData(lua_State * L);
+	int w_Shape_setCategory(lua_State * L);
+	int w_Shape_getCategory(lua_State * L);
+	int w_Shape_setMask(lua_State * L);
+	int w_Shape_getMask(lua_State * L);
 	int w_Shape_setData(lua_State * L);
 	int w_Shape_getData(lua_State * L);
 	int w_Shape_getBoundingBox(lua_State * L);