[Differential] [Request, 16 lines] D1250: [server] Workaround for QtWayland bug https://bugreports.qt.io/browse/QTBUG-52192

[graesslin (Martin Gräßlin)]

graesslin created this revision.
graesslin added a reviewer: Plasma.
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REVISION SUMMARY
  QtWayland doesn't map the parent sub-surfaces in a sub-surface tree.
  According to the spec this would mean also the child sub-surface is not
  mapped. But being strict according to the spec will make applications
  like SystemSettings fail badly. Embedded child windows will not be
  rendered and QtWayland is going to hard freeze. This is not acceptable,
  thus we need to workaround this QtWayland bug till it's fixed.
  
  It's worth mentioning that Weston as the reference compositor also
  doesn't handle this situation according to spec and renders the
  sub-surface. See https://bugs.freedesktop.org/show_bug.cgi?id=94735
  
  The difficult part for the workaround is to determine whether a surface
  should be considered unmapped. E.g. when the parent gets unmapped we need
  to really unmap it. But what's the difference between an unmapped parent
  surface which should be considered mapped and an unmapped parent surface
  which should be considered unmapped?
  
  The implementation goes with considering a new sub-surface always as
  mapped - independently of whether it ever got a buffer attached. As soon
  as it had a buffer attached and it gets unmapped again, it will go back
  to a standard conform way.
  
  The behavior now is not standard conform, thus the autotest is adjusted
  to have QEXPECT_FAIL for the now no longer standard conform areas.

REPOSITORY
  rKWAYLAND KWayland

BRANCH
  subsurface-incorrect-mapping

REVISION DETAIL
  https://phabricator.kde.org/D1250

AFFECTED FILES
  autotests/client/test_wayland_subsurface.cpp
  src/server/surface_interface.cpp
  src/server/surface_interface_p.h

EMAIL PREFERENCES
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To: graesslin, Plasma
Cc: plasma-devel, sebas
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