fixed a bug where wire graphs would not laid down correctly

src/net/torvald/terrarum/gameactors/Actor.kt

@@ -40,7 +40,7 @@ abstract class Actor(val renderOrder: RenderOrder) : Comparable<Actor>, Runnable
      * Valid RefID is equal to or greater than 16777216.
      * @return Reference ID. (16777216-0x7FFF_FFFF)
      */
-    open var referenceID: ActorID = Terrarum.generateUniqueReferenceID(renderOrder) // once this was nullable without initialiser. If you're going to revert to that, add the reason why this should be nullable.
+    open var referenceID: ActorID = Terrarum.generateUniqueReferenceID(renderOrder) // in old time this was nullable without initialiser. If you're going to revert to that, add the reason why this should be nullable.
     var actorValue = ActorValue(this) // FIXME cyclic reference on GSON
     @Volatile var flagDespawn = false
 

src/net/torvald/terrarum/gameactors/BlockMarkerActor.kt

@@ -0,0 +1,49 @@
+package net.torvald.terrarum.gameactors
+
+import com.badlogic.gdx.graphics.Color
+import com.badlogic.gdx.graphics.g2d.SpriteBatch
+import net.torvald.terrarum.CommonResourcePool
+import net.torvald.terrarum.ReferencingRanges
+import net.torvald.terrarum.Terrarum
+import net.torvald.terrarumsansbitmap.gdx.TextureRegionPack
+
+class BlockMarkerActor : ActorWithBody(Actor.RenderOrder.OVERLAY, physProp = PhysProperties.MOBILE_OBJECT) {
+
+    override var referenceID: ActorID = 1048575 // custom refID
+    override val hitbox = Hitbox(0.0, 0.0, 16.0, 16.0)
+
+    var color = Color.YELLOW
+    var shape = 0
+
+    private val blockMarkings: TextureRegionPack
+        get() = CommonResourcePool.getAsTextureRegionPack("blockmarkings_common")
+
+    init {
+        this.referenceID = ReferencingRanges.ACTORS_OVERLAY.last
+        this.isVisible = false
+    }
+
+    override fun drawBody(batch: SpriteBatch) {
+        if (isVisible) {
+            batch.color = color
+            batch.draw(blockMarkings.get(shape, 0), hitbox.startX.toFloat(), hitbox.startY.toFloat())
+        }
+    }
+
+    override fun drawGlow(batch: SpriteBatch) { }
+
+    override fun dispose() {
+    }
+
+    override fun update(delta: Float) {
+        if (isVisible) {
+            hitbox.setPosition(
+                    Terrarum.mouseTileX * 16.0,
+                    Terrarum.mouseTileY * 16.0
+            )
+        }
+    }
+
+    override fun onActorValueChange(key: String, value: Any?) { }
+
+}