xcb: make sure we have a valid m_qimage in backing store

This patch amends a62f1d03560937a306c7586669a46cd9575e9464.

If the initial backing store resize request is called with QSize(0, 0),
we end up with QXcbBackingStoreImage holding a default contructed QImage / m_qimage.
This happens because of the logic in QXcbBackingStoreImage::create(), where
if we detect that the requested segmentSize == 0, we do not allocate
any memory, and thus don't create a valid image in m_qimage. On subsequent
call to QXcbBackingStore::resize() we would only check if QXcbBackingStoreImage
object has been created, but not if it is in a valid state. This obviously
would cause problems.

This patch re-factors the logic to handle better resize to QSize(0, 0). And
make the code cleaner by:

- merging ::create and ::resize as semantically it is always resize().
- dropping unnecessary argument passing.

Task-number: QTBUG-69581
Change-Id: Ied337beb449dea8259fcf6b7d29f0a5bd553019d
Reviewed-by: Błażej Szczygieł <spaz16@wp.pl>
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>

0 files changed, 0 insertions, 0 deletions