qmlui: make use of horizontal gradient
qmlui: make use of horizontal gradient

therefore fix left sidepanel drag

mcallegari/qlcplus,sbenejam/qlcplus,mcallegari/qlcplus,kripton/qlcplus,kripton/qlcplus,kripton/qlcplus,sbenejam/qlcplus,plugz/qlcplus,plugz/qlcplus,sbenejam/qlcplus,sbenejam/qlcplus,sbenejam/qlcplus,mcallegari/qlcplus,sbenejam/qlcplus,mcallegari/qlcplus,plugz/qlcplus,plugz/qlcplus,plugz/qlcplus,mcallegari/qlcplus,kripton/qlcplus,kripton/qlcplus,kripton/qlcplus,plugz/qlcplus,mcallegari/qlcplus,kripton/qlcplus,mcallegari/qlcplus,sbenejam/qlcplus,plugz/qlcplus