https://bugs.kde.org/show_bug.cgi?id=496614
--- Comment #2 from Jaime Torres <jtam...@gmail.com> --- I've found the culprit, a wrongly configured .drirc file <driconf> <device screen="0" driver="r600"> <application name="Default"> <option name="force_glsl_extensions_warn" value="false" /> <option name="mesa_glthread" value="true" /> <option name="mesa_no_error" value="true" /> </application> </device> </driconf> The question I ask myself is: Why this wrong dri configuration only affects the tabbox? Renaming the file and restarting the session, the tabbox works as expected. Also this warning is produced. file:///usr/share/kwin/tabbox/thumbnail_grid/contents/ui/main.qml:170:37: Unable to assign [undefined] to bool -- You are receiving this mail because: You are watching all bug changes.