Allow blocks to define that they are only selectable when item can be placed on it

assets/cubyz/blocks/duckweed.zig.zon

@@ -19,7 +19,7 @@
 	.texture3 = "cubyz:duckweed/3",
 	.item = .{
 		.texture = "duckweed.png",
-		.tags = .{.fluidPlaceable},
+		.placementTags = .{.fluid},
 	},
 	.lodReplacement = "cubyz:air",
 }

assets/cubyz/blocks/lava.zig.zon

@@ -1,7 +1,7 @@
 .{
 	.tags = .{.fluid, .hot},
 	.drops = .{},
-	.selectionRule = .toolEffective,
+	.selectionRule = .placeable,
 	.replaceable = true,
 	.degradable = true,
 	.transparent = true,

assets/cubyz/blocks/lily_pad.zig.zon

@@ -12,7 +12,7 @@
 	.texture = "cubyz:lily_pad",
 	.item = .{
 		.texture = "lily_pad.png",
-		.tags = .{.fluidPlaceable},
+		.placementTags = .{.fluid},
 	},
 	.lodReplacement = "cubyz:air",
 }

assets/cubyz/blocks/water.zig.zon

@@ -1,7 +1,7 @@
 .{
 	.tags = .{.fluid},
 	.drops = .{},
-	.selectionRule = .toolEffective,
+	.selectionRule = .placeable,
 	.replaceable = true,
 	.degradable = true,
 	.transparent = true,

src/blocks.zig

@@ -68,7 +68,7 @@ pub const Ore = struct {
 	seed: u64,
 };
 
-const SelectionRule = enum { always, toolEffective, never };
+const SelectionRule = enum { always, toolEffective, placeable, never };
 
 var _transparent: [maxBlockCount]bool = undefined;
 var _collide: [maxBlockCount]bool = undefined;
@@ -530,14 +530,10 @@ pub const Block = packed struct(u32) { // MARK: Block
 	pub fn isSelectableByItem(self: Block, item: Item) bool {
 		if (item == .baseItem and item.baseItem.block() == self.typ) return true;
 
-		if (self.hasTag(.fluid)) {
-			const fluidPlaceable = item == .baseItem and item.baseItem.hasTag(.fluidPlaceable);
-			return fluidPlaceable;
-		}
-
 		return switch (self.selectionRule()) {
 			.always => true,
 			.toolEffective => item == .proceduralItem and item.proceduralItem.isEffectiveOn(self),
+			.placeable => item == .baseItem and item.baseItem.isPlaceableOn(self),
 			.never => false,
 		};
 	}

src/items.zig

@@ -251,6 +251,12 @@ pub const BaseItemIndex = enum(u16) { // MARK: BaseItemIndex
 	pub fn hasTag(self: BaseItemIndex, tag: Tag) bool {
 		return itemList[@intFromEnum(self)].hasTag(tag);
 	}
+	pub fn hasPlacementTag(self: BaseItemIndex, tag: Tag) bool {
+		return itemList[@intFromEnum(self)].hasPlacementTag(tag);
+	}
+	pub fn isPlaceableOn(self: BaseItemIndex, targetedBlock: Block) bool {
+		return itemList[@intFromEnum(self)].isPlaceableOn(targetedBlock);
+	}
 	pub fn hashCode(self: BaseItemIndex) u32 {
 		return itemList[@intFromEnum(self)].hashCode();
 	}
@@ -268,6 +274,7 @@ pub const BaseItem = struct { // MARK: BaseItem
 	id: []const u8,
 	name: []const u8,
 	tags: []const Tag,
+	placementTags: []const Tag,
 	tooltip: []const u8,
 
 	stackSize: u16,
@@ -287,6 +294,7 @@ pub const BaseItem = struct { // MARK: BaseItem
 		}
 		self.name = allocator.dupe(u8, zon.get([]const u8, "name", id));
 		self.tags = Tag.loadTagsFromZon(allocator, zon.getChild("tags"));
+		self.placementTags = Tag.loadTagsFromZon(allocator, zon.getChild("placementTags"));
 		self.stackSize = zon.get(u16, "stackSize", 120);
 		const material = zon.getChild("material");
 		if (material == .object) {
@@ -356,6 +364,20 @@ pub const BaseItem = struct { // MARK: BaseItem
 		}
 		return false;
 	}
+
+	pub fn hasPlacementTag(self: *const BaseItem, tag: Tag) bool {
+		for (self.placementTags) |other| {
+			if (other == tag) return true;
+		}
+		return false;
+	}
+
+	pub fn isPlaceableOn(self: *const BaseItem, block: Block) bool {
+		for (block.tags()) |tag| {
+			if (self.hasPlacementTag(tag)) return true;
+		}
+		return false;
+	}
 };
 
 /// Generates the texture of a ProceduralItem using the material information.

src/tag.zig

@@ -9,9 +9,8 @@ pub const Tag = enum(u32) {
 	air = 0,
 	fluid = 1,
 	sbbChild = 2,
-	fluidPlaceable = 3,
-	chiselable = 4,
-	playerModel = 5,
+	chiselable = 3,
+	playerModel = 4,
 	_,
 
 	pub fn initTags() void {