A protocol that defines a button that controls the collapse of a collection view’s section.


A collection view can support a section that can collapse into a single horizontally scrollable row, similar to the groupings in the icon view in Finder. To ensure that the collection view can communicate with the button that controls the collapsing of a section, the section header view object should conform to this protocol and connect the button’s outlet to sectionCollapseButton.


Providing a Collapse Button

var sectionCollapseButton: NSButton?

A control that lets users collapse and open a collection view section.