The problem is that libinput offers the possibility to not enabled
dragging when tap-to-click is enabled but mutter doesn't. For people who
have a sensitive touchpad and who like tap-to-click option, dragging is
launched even when you don't want it : for example, when you select a
folder, most of the time the folder is dragging whereas just selected or
when you want to select some lines of a text file, several lines are
moved as a cut-paste which is not expected and erase datas.
To fix it, you need to have the possibility to desactivate the drag
option when you use tap-to-click in mutter. Because it's already a
specification of libinput, it remains to add it to mutter.
Implementation with X11 is added too.
https://bugzilla.gnome.org/show_bug.cgi?id=775755
12792f99a0