I'm building a document viewer on macOS Tahoe with a 3-column NSSplitViewController (sidebar | detail | inspector), trying to replicate how Preview displays PDFs with the page centered in the visible gap between the panels, with content bleeding under them when panning or zooming.
I'm using the approach from Build an AppKit app with the new design (WWDC25):
detailItem.automaticallyAdjustsSafeAreaInsets = true
safeAreaInsets reports the correct values (e.g. left: 208, right: 240), and the frame does extend under both panels. But PDFView with autoScales = true anchors the page to the left edge of the window instead of centering it in the visible gap between the sidebar and inspector.
I can get the page to center correctly by constraining PDFView to view.safeAreaLayoutGuide, but then content no longer extends under the panels when panning or zooming, which defeats the whole purpose.
What's the correct way to center PDFView content within the visible gap while keeping the frame full-width so content bleeds under the panels?
I've attached pictures of how Preview does it.