Adding thumbnails with PDFKit

Today I’m continuing with some ideas from my recent post about using PDFKit. In that post I was using a custom PDF view for an app that would work something like a basic slide presentation app.
Part of that was adding a thumbnail view with PDFThumbnailView, which ended up looking like this.
PDFThumbnailView works with a PDFView and generates thumbnails for pages in the current document. You can tell it how big the thumbnails should be and whether to arrange the thumbnails horiontally or vertically, but that’s about it as far as layout goes.