Virtually all code in Qt that inspects a QRegion does
so by calling rects(), which returns a QVector<QRect>.
But rects() has a problem: A QRegion that contains just
one rectangle internally is not represented by a QVector,
and the mere act of calling rects() makes QRegion create
one.
So, expose the fact that QRegion is a container of QRects
to users by providing iterators and begin()/end(), which
can be nothrow, since for the one-rectangle case, instead
of vectorize()ing the region, we just return pointers to
(and one past) the 'extent' rectangle.
As a consequence, the iterator type is just const QRect*,
but I think that whatever containers QRegion may use under
the hood in the future, it will be certainly one that is
layout-compatible with a C array.
No mutable iterators are provided, since QRegion maintains
a running bounding-rect, so a mutable iterator would have
to call into QRegion for every change, which doesn't make
sense.
[ChangeLog][QtGui][QRegion] Is now iterable as a container
of QRects: added {c,}{r,}{begin,end}().
Change-Id: I2fa565fac0c1d26e2c0937604b23763cd4e23604
Reviewed-by: Olivier Goffart (Woboq GmbH) <ogoffart@woboq.com>
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