Instance Method

draggingImageForItems(at:with:offset:)

Returns an image to use for dragging the specified items.

Declaration

func draggingImageForItems(at indexPaths: Set<IndexPath>, with event: NSEvent, offset dragImageOffset: NSPointPointer) -> NSImage

Parameters

indexPaths

The set of NSIndexPath objects corresponding to the items being dragged.

event

The mouse-down event that began the drag operation.

dragImageOffset

The offset value to use when positioning the image. On input, the point is NSZeroPoint, which centers the returned image under the mouse. Custom implementations can return a different point that repositions the drag image by the specified offset values.

Return Value

The image to use for the dragged items.

Discussion

The default implementation of this method creates an image using the visible portions of the dragged items. The resulting image is a snapshot of the dragged items as they currently appear in the collection view but rendered with additional transparency to indicate they are part of a drag operation. This method also updates the dragImageOffset parameter to an appropriate point for dragging the resulting image.

If the delegate implements the collectionView(_:draggingImageForItemsAt:with:offset:) method, the collection view method obtains the drag image from that method instead. If the delegate does not implement that method, the collection view uses the image returned by this method.