The unplug() and startDrag() functions of QMainWindowLayout and QDockWidget used a boolean argument specifying whether a single dock widget or a group of dock widgets should be unplugged. The argument defaulted to true. That has lead to inconsistent unplug operations, broken item_lists and crashes, especially when the methods were called without an argument. To improve code readability, replace bool trap with a meaningful enum. Remove default arguments, in order to force explicit calls. This patch does not change behavior, it is just carved out to facilitate reviews. Task-number: QTBUG-118578 Task-number: QTBUG-118579 Pick-to: 6.6 6.5 Change-Id: I50341b055f0bb76c2797b2fb1126a10de1fee7dd Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>