private static Font getKDEFont() {
		List<String> kdeglobals = readConfig( "kdeglobals" );
		List<String> kcmfonts = readConfig( "kcmfonts" );

		String generalFont = getConfigEntry( kdeglobals, "General", "font" );
		String forceFontDPI = getConfigEntry( kcmfonts, "General", "forceFontDPI" );

		String family = "sansserif";
		int style = Font.PLAIN;
		int size = 10;

		if( generalFont != null ) {
			List<String> strs = StringUtils.split( generalFont, ',' );
			try {
				family = strs.get( 0 );
				size = Integer.parseInt( strs.get( 1 ) );
				if( "75".equals( strs.get( 4 ) ) )
					style |= Font.BOLD;
				if( "1".equals( strs.get( 5 ) ) )
					style |= Font.ITALIC;
			} catch( RuntimeException ex ) {
				LoggingFacade.INSTANCE.logConfig( "FlatLaf: Failed to parse 'font=" + generalFont + "'.", ex );
			}
		}

		// font dpi
		int dpi = 96;
		if( forceFontDPI != null && !isSystemScaling() ) {
			try {
				dpi = Integer.parseInt( forceFontDPI );
				if( dpi <= 0 )
					dpi = 96;
				if( dpi < 50 )
					dpi = 50;
			} catch( NumberFormatException ex ) {
				LoggingFacade.INSTANCE.logConfig( "FlatLaf: Failed to parse 'forceFontDPI=" + forceFontDPI + "'.", ex );
			}
		}

		// scale font size
		double fontScale = dpi / 72.0;
		double dsize = size * fontScale;
		size = (int) (dsize + 0.5);
		if( size < 1 )
			size = 1;

		return FlatLaf.createCompositeFont( family, style, size );
	}
Gets the default font for KDE from KDE configuration files.

The Swing fonts are not updated when the user changes system font size
(System Settings > Fonts > Force Font DPI). An application restart is necessary.
This is the same behavior as in native KDE applications.

The "display scale factor" (kdeglobals: [KScreen] > ScaleFactor) is not used
KDE also does not use it to calculate font size. Only forceFontDPI is used by KDE.
If user changes "display scale factor" (System Settings > Display and Monitors >
Displays > Scale Display), the forceFontDPI is also changed to reflect the scale factor.
flatlaf-core/src/main/java/com/formdev/flatlaf/LinuxFontPolicy.java