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Comment by 4ad | Hacker News Reader

Last I checked this didn't support HiDPI, a technology invented over 10 years ago.

I have not used Xpra, so I do not know if it has any problems with this, but a priori I do not see why an application like Xpra would need to be aware about the screen resolution. That should be handled by the X clients and servers.

I have used only 4k monitors for more than 10 years in Linux and the only applications with which I frequently had problems were various programs written in Java by morons, which were usually proprietary applications and some times quite expensive, but they lacked such elementary customization features like allowing the user to change the font, or at least its size, while failing to use the configuration settings of the graphic desktop, i.e. the value set for the monitor DPI, like all non-Java programs.

The way Xpra works is that it's both a server and client in it's own right. So it needs to be aware for the final client involved to be able to learn about it from the other side of the chain, so it does need to be aware of it in order for applications to know that they need to adjust themselves. What this results in is that the client you're running through Xpra will just assume it's a normal 96 DPI display from yesteryear usually. I think you can do some stuff to tell Xpra that it should be a higher DPI but that'll also make it so that the application will be gigantic on a low dpi display, something that's pretty typical for X11 since it doesn't properly support mixed DPI environments (i.e. a laptop screen that's high dpi and an external monitor that is low dpi).

X11 supports mixed DPI with the RANDR extension. Applications can use the per-monitor information provided by RANDR to get the DPI information for each output, and use this to calculate font and widget sizes. Everything looks nice as long as you don't have a window spanning multiple screens. The problem is that while Qt has supported this functionality since 5.9, GTK seemingly has no interest in implementing it and most other toolkits or raw Xlib programs don't support it either.

Last I checked (somewhat less than ten years ago), it did do things with DPI. Note that if you were using it with a sorry distro-packaged version it might have been broken because proper DPI support requires a patched X11 dummy video driver or something along those lines, and if you had an unpatched one DPI stuff didn't work.

Similarly, the waylands still don't support screen readers for the differently abled, a technology invented longer ago.

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