[vetinari]

In the Linux world, you cannot rely on the widget toolkit doing the heavy lifting. The API is defined on the socket protocol level, not on the symbols of the library level, so you have to handle it there. The old xeyes or xfontsel, or other athena, motif, openlook, fltk or whatever forgotten apps, that conform to x11 protocol, must be handled too. The scaling at compositor level is the easy part, Wayland compositors have per-surface flag, how it is supposed to scale in the composition, they are aware also of the scaling needed by each display. The issue is, that the X11 clients - unlike Wayland clients - do not announce what they are capable of. As you noted, both Windows and macOS can fix this in the framework, where Linux cannot. macOS even took the shotgun approach and required a flag in the executable header for the scaling capability announcement part. Such approach is not passable in the Linux world.

But Windows is not a garden of roses either, I still see a fair share of blurry dialogs (until recently, even vscode installer/updater).