As retrofitting high DPI support into such a large range of both KDE and third party applications is risky to do without breakage, progress is deliberately slow and gradual in order to do this right.
The good news is I get to write lots of blog posts as we make the continual steps forwards.
* High DPI Scaling via a hidden config option for early testing
* User facing dialog with the screen management settings for scaling
* Automtatically enabled. Providing we see positive feedback in this release.
Plasma 5.4 brings a new setting to adjust the screen scaling to match your device.
In the new setting we've tried to simplify things to a simple slider which adjusts both font size which we have full control over, and then above a certain threshold adjusting the entire UI which we can only do at integer values (i.e doubling the size). This is to support the semi-high screens and the current generation all in the same place.
It's still far from what I'd like to achieve overall, but it does the job of making some devices usable.
With High DPI support enabled you will see one of three things amongst your applications:
We've tried to make sure the most common, important KDE applications (Dolphin, Konsole, Kate and so on) fit into that top category. An app like xfig or dia, will remain in the bottom category until Wayland.
There's also a slim chance there may also be some breakage.
If so please do file a bug report as soon as possible and tag me to the CC list.
Props especially go to Christoph Cullman and Alex Fiestas for their help on some of the applications.