Inbox
Drag the divider — the toolbar line above it is the tracking separator
Split View
/ NSSplitView · NSSplitViewItem /
also called split pane, splitter view, multi-pane layout, navigation split view
A split view divides one window region into two or more panes that can resize independently. The line between them is a split-view divider or splitter when it can be dragged, not merely a decorative separator. A sidebar is one specialized pane and can collapse while the remaining pane expands.
Anatomy — every part, named
- 1Pane (split-view item)
NSSplitViewItemEach independently sized region on either side of the divider is a pane, represented by an NSSplitViewItem.
- 2Split-view divider (splitter)
NSSplitView.dividerThickness“The line between the two panes that I drag” is the split-view divider, also called a splitter.
- 3Sidebar collapse behavior
NSSplitViewItem.collapseBehaviorThe way a sidebar folds away and yields its width to the next pane is its collapse behavior.
- 4Tracking separator toolbar item
NSTrackingSeparatorToolbarItemThe toolbar divider that stays exactly above a moving split-view divider is a tracking separator.
Prompt — paste into your agent
Build a native Split View with NSSplitView and NSSplitViewItem (SwiftUI: NavigationSplitView), using a draggable divider between independently sized panes. Give a sidebar item native collapse behavior and align any toolbar boundary with NSTrackingSeparatorToolbarItem.
In code
The exact names this thing goes by in code — each row is one framework’s word for it. Use the row that matches your project (or paste it into your prompt).
| AppKit | NSSplitView | |
| AppKit | NSSplitViewItem | |
| SwiftUI | NavigationSplitView | |
| AppKit | NSSplitViewController |