Hit-existing gate shared by the drag-insert tool hooks. When the consumer
supplies a hitExisting callback, run it at the cursor's world point.
On hit (string id or array of ids), set the selection and return true —
the caller should claim and skip insertion. On miss or when no callback
is supplied, return false.
Hit-existing gate shared by the drag-insert tool hooks. When the consumer supplies a
hitExistingcallback, run it at the cursor's world point. On hit (string id or array of ids), set the selection and returntrue— the caller should claim and skip insertion. On miss or when no callback is supplied, returnfalse.