When using a style that wants to draw into the layout's margin (like
macOS style does with group box titles), parts of the widgets would be
clipped by the parent if the available margin is smaller than necessary.
This moves the x/y coordinates to at least 0/0, and adjusts width and
height accordingly.
[ChangeLog][QtWidgets][QLayout] Prevent clipping of group box titles
on macOS (and similar styles that draw into layout margins)
Change-Id: I32148a92858c13fb2325da4d0a2a58996e0e8930
Fixes: QTBUG-67608
Reviewed-by: Paul Olav Tvete <paul.tvete@qt.io>
d0f016ebfb