Item Placement with Signs

src/main/java/net/glowstone/block/blocktype/BlockNeedsAttached.java

@@ -30,6 +30,14 @@ public void updatePhysics(GlowBlock me) {
         }
     }
 
+    /**
+     * Called to determine if the target block can be attached to
+     * when right clicking it.
+     *
+     * @param block The location the block is being placed at.
+     * @param against The face the block is being placed against.
+     * @return Whether the black can be attached to.
+    */
     public boolean canAttachTo(GlowBlock block, BlockFace against) {
         return !(ItemTable.instance().getBlock(
             block.getRelative(against.getOppositeFace()).getType()) instanceof BlockNeedsAttached);

src/main/java/net/glowstone/block/blocktype/BlockSign.java

@@ -2,6 +2,7 @@
 
 import net.glowstone.block.GlowBlock;
 import net.glowstone.block.GlowBlockState;
+import net.glowstone.block.ItemTable;
 import net.glowstone.block.entity.BlockEntity;
 import net.glowstone.block.entity.SignEntity;
 import net.glowstone.chunk.GlowChunk;
@@ -40,4 +41,12 @@ public void afterPlace(GlowPlayer player, GlowBlock block, ItemStack holding,
         GlowBlockState oldState) {
         player.openSignEditor(block.getLocation());
     }
+
+    @Override
+    public boolean canPlaceAt(GlowBlock block, BlockFace against) {
+        Material targetMat = ItemTable.instance().getBlock(
+            block.getRelative(against.getOppositeFace()).getType()).getMaterial();
+        return canAttachTo(block, against) || targetMat == Material.SIGN_POST
+            || targetMat == Material.WALL_SIGN; 
+    }
 }

src/main/java/net/glowstone/block/blocktype/BlockType.java

@@ -315,6 +315,8 @@ public void updatePhysics(GlowBlock block) {
     public final void rightClickBlock(GlowPlayer player, GlowBlock against, BlockFace face,
         ItemStack holding, Vector clickedLoc, EquipmentSlot hand) {
         GlowBlock target = against.getRelative(face);
+        final Material targetMat = ItemTable.instance().getBlock(
+            target.getRelative(face.getOppositeFace()).getType()).getMaterial();
 
         // prevent building above the height limit
         if (target.getLocation().getY() >= target.getWorld().getMaxHeight()) {
@@ -350,7 +352,19 @@ public final void rightClickBlock(GlowPlayer player, GlowBlock against, BlockFac
         }
 
         // call canBuild event
-        boolean canBuild = canPlaceAt(target, face);
+        boolean canBuild = true;
+        switch (targetMat) {
+            case SIGN_POST:
+            case WALL_SIGN:
+                if (player.isSneaking()) {
+                    canBuild = canPlaceAt(target, face);
+                } else {
+                    return;
+                }
+                break;
+            default:
+                canBuild = canPlaceAt(target, face);
+        }
         BlockCanBuildEvent canBuildEvent = new BlockCanBuildEvent(target, getId(), canBuild);
         if (!EventFactory.getInstance().callEvent(canBuildEvent).isBuildable()) {
             //revert(player, target);