Thanks for the speedy response and advice. AMD/Radeon has dropped support for series 3000 graphics. My simple solution was to bypass the onboard graphics, insert a more recent graphic card and reboot. Shadowing gone.
in the proprietary driver. The FOSS drivers provided by openSUSE are still working here, on cards both newer and older than your RS780L. I have yet to notice any such shadowing. I have noticed others with font troubles have solved their issues by reinstalling offending fonts. IMO, openSUSE force installs too many fonts with minimal differences among them.