> Windows is the only one that does this properly. Windows handles high pixel density on a per-application, per-display basis.

This is not our [0] experience. macOS handles things on a per-section-of-window, per-application, per-display basis. You can split a window across two monitors at two different DPIs, and it will display perfectly. This does not happen on Windows, or we have not found the right way to make it work thus far.

[0] ardour.org

> macOS handles things on a per-section-of-window, per-application, per-display basis.

No, it does not. If you have two displays with different physical pixel densities, and especially if they are sufficiently different that Apple will consider one 'Retina' and 'not Retina' (this is usually the case if, for instance, you have your MacBook's display—which probably is 'Retina'—beneath a 2560 × 1440, 336 × 597 mm monitor, which is 'not Retina'), then the part of the window on the non-Retina display will be raster-scaled to account for the difference. This is how KDE Plasma on Wayland handles it, too.

In my opinion, any raster-scaling of vector/text UI is a deal-breaker.

I think there’s one group of people who consider preserving the physical dimensions important that like the macOS approach. For me, if a window is across multiple displays then it’s already broken up and I’m not too bothered about that. What I care about is getting application UI to a reasonable size without blurring. MacOS doesn’t do that.

Actually, the default in MacOS is that the window is only on one monitor, and its the monitor where the cursor was when you last moved the window, so you might have a window appearing invisible because you dragged it near the corner and some sliver ended on another monitor.

Look at this complicated tinkering MacOS makes you do for something as simple as spanning windows across monitors! https://www.arzopa.com/blogs/guide/how-to-make-a-window-span... (OK this last part is slightly facetious but Linux gets dinged for having to go into menus because the writer wants something to work the way it does in on other operating systems the whole time)