[russellbeattie]

The reason Preview works so well is because deep inside Apple's Quartz libraries used to render, rasterize and composite graphics such as windows, docs and images is a version of "Display PDF". Basically, PDF is a native macOS protocol.

The best of my understanding is that NeXT considered Display PDF the successor to Display PostScript and OS X inherited it. I have no idea how much or how little the latest macOS and iOS rely on PDF encoding for their GUIs now, but I know at one point it was an integral part of the windowing and drawing system and is still in there for processing PDF docs.

[BearOso]

It was never an integral part of the windowing system of either operating system. That idea never panned out. Quartz's drawing functions included what was needed for postscript, but the UI was done solely with bitmaps and cached bitmaps. There's PDF APIs in there, but they're not anything special, like being super fast, efficient, or hardware-accelerated.