Fix water-glass and water-lava surfaces

src/mapnode.cpp

@@ -174,6 +174,57 @@ void init_mapnode()
 	
 }
 
+/*
+	Nodes make a face if contents differ and solidness differs.
+	Return value:
+		0: No face
+		1: Face uses m1's content
+		2: Face uses m2's content
+	equivalent: Whether the blocks share the same face (eg. water and glass)
+*/
+u8 face_contents(content_t m1, content_t m2, bool *equivalent)
+{
+	*equivalent = false;
+
+	if(m1 == CONTENT_IGNORE || m2 == CONTENT_IGNORE)
+		return 0;
+	
+	bool contents_differ = (m1 != m2);
+	
+	// Contents don't differ for different forms of same liquid
+	if(content_liquid(m1) && content_liquid(m2)
+			&& make_liquid_flowing(m1) == make_liquid_flowing(m2))
+		contents_differ = false;
+	
+	u8 c1 = content_solidness(m1);
+	u8 c2 = content_solidness(m2);
+
+	bool solidness_differs = (c1 != c2);
+	bool makes_face = contents_differ && solidness_differs;
+
+	if(makes_face == false)
+		return 0;
+	
+	if(c1 == 0)
+		c1 = content_features(m1).visual_solidness;
+	if(c2 == 0)
+		c2 = content_features(m2).visual_solidness;
+	
+	if(c1 == c2){
+		*equivalent = true;
+		// If same solidness, liquid takes precense
+		if(content_features(m1).liquid_type != LIQUID_NONE)
+			return 1;
+		if(content_features(m2).liquid_type != LIQUID_NONE)
+			return 2;
+	}
+	
+	if(c1 > c2)
+		return 1;
+	else
+		return 2;
+}
+
 v3s16 facedir_rotate(u8 facedir, v3s16 dir)
 {
 	/*