[bombcar]

They deal with lots of fractional scaling - at first they may have done simple pixel doubling but now the screens are often at non integer ratios.

In fact you can speed it up slightly by making sure the display resolution is exactly “half” the actual resolution so to prevent MacOS from scaling 8x internally first.

[Kwpolska]

The only scales supported by Apple software are integer scales (1x, 2x, 3x). The iPhone 6 Plus had a 2.6x screen — iOS would render at 3x and then scale the image down to fit. https://www.paintcodeapp.com/news/iphone-6-screens-demystifi...

[bombcar]

See https://9to5mac.com/2016/12/02/15-inch-macbook-pro-screen-re... - it renders at 8x or something and scales down inexactly.

[Toutouxc]

The article clearly states that macOS always draws 2x and just displays the result, individual pixels be damned. Anyone can confirm this simply by taking a screenshot and looking at the resolution (screenshots are always the size of the underlying framebuffer)