High-DPI: It’s About the Pixels
High-DPI is the next big hurdle for desktop Linux to overcome; many desktop environments are working towards it, and Plasma is no exception. Admittedly, this is one of the areas where KDE applications still require the most work visually.
The approach taken by the KDE folks is to use the system font size as the basis for simulating the system DPI, so by adjusting the DPI settings of the fonts you set the DPI of the desktop. It’s a bit awkward to think about, and users will not likely know how to achieve a high-DPI desktop at first glance. When adjusting the DPI there’s also a ‘tipping point’ where anything below 180 DPI seems to only adjust the fonts, and anything above 180 DPI ‘snaps’ other assets into higher resolution spaces.
Simulating a high DPI display by manually ramping up to the DPI to 180 and later 220, I was able to do some basic testing to see how well everything holds up for the increasingly photo-quality displays beginning to trickle into the market. Several developers have demonstrated the ability to take advantage of dense displays, though by default applications must specifically enable high-quality graphics individually to avoid compatibility issues – this means that applications leveraging high-quality display-modes will likely do so with excellent effect, though not many (if any) applications do this yet.
The Plasma 5.2 desktop and its various widgets worked marvellously, and scaled up with no difficulty at all; the themes internally use vector graphics and this technical decision has made Plasma incredibly versatile in this manner. I feel as if I could ramp plasma up to inconceivable resolutions and it would shrug it off as “no big thing”. There are rough edges caused by some minor spacing issues on some individual widgets; they may be sorted out for the 5.2 release but I don’t know for sure, what I can say is Plasma as a technology is ready for dense displays.
Applications are a different story, being it’s a case of applications making the necessary tweaks to enable high-DPI support where it’s missing. This isn’t even a KDE-specific issue as most applications regardless of their parent projects have a hard time. The effect is often passable at lower DPI settings but not yet pleasurable, and it depends on your tolerance to design problems to decide if scaling up fonts is ‘enough’.
“Resolution enthusiasts” who are likely the early-adopters of high-DPI will be passing harsh judgement on applications, but they would also praise the Plasma desktop itself. Third party high-DPI support for applications like Steam and Firefox will be much more mixed, but at least with bumped-up font sizes offending applications have a chance to at least be readable.
An aside; as high-resolution graphics resolution becomes increasingly supported, people with poor eyesight will still see tremendous benefits if they bump up a traditional screen as I had done in my testing. My own vision isn’t 20/20 any more, but even a small DPI bump works perfectly on the Plasma Desktop and it makes reading much more comfortable – and I’m keeping mine set at ~120 DPI.