macOS doesn't handle it at all, a window is never visible on multiple screens at the same time.
Low DPI screens are near unusable anyway on macOS without subpixel rendering
Low DPI screens are near unusable anyway on macOS without subpixel rendering
It absolutely is during dragging. macOS is perfectly capable of drawing a window on two screens at the same time, but it doesn't let a window cross two screens while resting which I think is a really good user experience choice.
Take that, Apple haters.