add Quadtree.remove (#227)

Co-authored-by: Jonathan Ellis <jbellis@gmail.com>

orx-quadtree/src/commonMain/kotlin/IQuadtree.kt

@@ -35,6 +35,14 @@ interface IQuadtree<T> {
      */
     fun insert(element: T): Boolean
 
+    /**
+     * Remove the given element
+     *
+     * @param element
+     * @return true if the element was present
+     */
+    fun remove(element: T): Boolean
+
     /**
      * Finds which node the element is within (but not necessarily belonging to)
      *

orx-quadtree/src/commonMain/kotlin/Quadtree.kt

@@ -164,6 +164,17 @@ class Quadtree<T>(val bounds: Rectangle, val maxObjects: Int = 10, val mapper: (
         return true
     }
 
+    override fun remove(element: T): Boolean {
+        if (isLeaf) {
+            return objects.remove(element)
+        }
+        val p = mapper(element)
+        val x = if (p.x > bounds.center.x) 1 else 0
+        val y = if (p.y > bounds.center.y) 1 else 0
+        val nodeIndex = x + y * 2
+        return nodes[nodeIndex]!!.remove(element)
+    }
+
     /**
      * Finds which node the element is within (but not necessarily belonging to)
      *

orx-quadtree/src/jvmMain/kotlin/ReadwriteQuadtree.kt

@@ -36,6 +36,12 @@ class ReadwriteQuadtree<T>(val qt: Quadtree<T>) : IQuadtree<T> {
         }
     }
 
+    override fun remove(element: T): Boolean {
+        lock.write {
+            return qt.remove(element)
+        }
+    }
+
     override fun findNode(element: T): Quadtree<T>? {
         lock.read {
             return qt.findNode(element)