StartDrag.kt

    /**
     * Grabs a tile and its properties to prepare for the animateDrag
     * and drop events.
     *
     * @property MouseEvent evt
     */
    private fun startDrag(evt : MouseEvent) {

        val targetNode = evt.target as Node
        val tileTarget = targetNode.findParentOfType(Tile::class)
        val mousePt : Point2D = root.sceneToLocal( evt.sceneX, evt.sceneY )
        moduleBoxItems
                .filter {
                    it.contains(mousePt)
                }
                .apply {
                    // select tile from data grid
                    if (tileTarget is Tile && !workArea.contains(mousePt)) {
                        val title = tileTarget.titleProperty().value

                        tileBuilderController.hashmap[title]?.let {
                            inFlightTileProperties = it
                        }
                        inFlightTile = tileBuilderController.moduleTileBuilder(inFlightTileProperties)
                        inFlightTile.isVisible = false
                        root.children[1].add(inFlightTile)
                        isDragAndDrop = true
                    }
                }

    }

    /**
     * Renders a tile the user can drag to the desired grid location
     *
     * @property MouseEvent evt
     */
    private fun animateDrag(evt : MouseEvent) {

        val mousePt = root.sceneToLocal( evt.sceneX, evt.sceneY )
        val targetNode = evt.target as Node
        val tileTarget = targetNode.findParentOfType(Tile::class)
        if (tileTarget != null) {
            val tileTargetParent = tileTarget.parent
            if( root.contains(mousePt) && (tileTargetParent !is GridPane) ) {

                // animate a rectangle so that the user can follow
                if( !inFlightTile.isVisible ) {
                    inFlightTile.isVisible = true
                }
                inFlightTile.toFront()
                val widthOffset = inFlightTile.widthProperty().value/2
                val heightOffset = inFlightTile.heightProperty().value/2
                inFlightTile.relocate( mousePt.x - widthOffset, mousePt.y - heightOffset)
            }
        }

    }