IGResizableComboBox is a drag-resizable subclass of NSComboBox—that is, IGResizableComboBox should be usable in place of NSComboBox and it adds a small bar at the bottom of the pop-up list that can be dragged to resize the pop-up list. IGResizableComboBox is published under a 3-clause BSD an MIT license.
It still has some quirks:
behavior is strange when the pop-up is above the combo box (whereas it is usually below)[fixed; when the pop-up is above the combo box, the drag-handle is at the top and the top edge moves while the bottom edge stays fixed at the combo box]the formula for resetting the number of visible items after dragging occurs is not quite right[fixed; dragging now snaps to whole-item positions]
