Following my entries on platform-specific font policies for Mac and Gnome, one of Substance users stepped up and provided an implementation that makes all Substance-powered Swing application pick the correct font sizes when running under the KDE desktop.
Here is a screenshot of a test application running under KDE desktop with font size of 10 and DPI set to 96:
and here is the same application, running under 120DPI, using font size of 10 except for menus which are configured to use italic 8:
The current implementation can be found in the CVS repository and was contributed by Paranoid (many thanks). It parses a few configuration files to get the DPI and font settings, providing fallback values in case these can not be found. Give the latest 4.2dev drop a try and let us know if you’re having any problems on KDE desktop.