Created attachment 102080 [details]
Region where left-click should set focus outlined in orange

In both Dolphin (Version 16.08.2) and Konqueror (Version 4.14.24) clicking in the empty region to the right of the filename fails to set focus on file or directory in single-click/focus follows mouse mode (screenshot provided). 

If you click and drag (even 2 pixels) then focus is properly set. There is no reason a 'click and drag' is required to set focus when a simple 'left-click' has always sufficed (preventing inadvertent selection of neighboring files). For single-click mode, focus has always been set by a single left-click to the right of the filename. With focus follows mouse, the file knows the mouse is overhead as a focus indicator is shown. Somewhere the 'click and drag' that now sets focus needs to be corrected and changed to a simple 'click'. It is horribly distracting to have to try and click-and-drag within the small region to set focus when only a simple click should be required.