The "maxDelta must be a positive number" seems to come from setPixelsPerMm in UCSwipeArea. It seems that window->screen()->physicalDotsPerInch() / 25.4 can be negative on Xenial.
The "maxDelta must be a positive number" seems to come from setPixelsPerMm in UCSwipeArea. It seems that window- >screen( )->physicalDots PerInch( ) / 25.4 can be negative on Xenial.