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[server] Workaround for QtWayland bug https://bugreports.qt.io/browse/QTBUG-52192

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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.

Reviewers: #plasma

Subscribers: plasma-devel

Projects: #plasma

Differential Revision: https://phabricator.kde.org/D1250
This commit is contained in:
Martin Gräßlin 2016-03-29 15:54:18 +02:00
parent 7053e4fce6
commit d727d2e477
3 changed files with 15 additions and 1 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

6
src/wayland/autotests/client/test_wayland_subsurface.cpp
View file

@ -869,8 +869,11 @@ void TestSubSurface::testMappingOfSurfaceTree()
QVERIFY(parentSpy.wait());
QVERIFY(parentServerSurface->isMapped());
// children should not yet be mapped
QEXPECT_FAIL("", "Workaround for QtWayland bug https://bugreports.qt.io/browse/QTBUG-52192", Continue);
QVERIFY(!child->surface()->isMapped());
QEXPECT_FAIL("", "Workaround for QtWayland bug https://bugreports.qt.io/browse/QTBUG-52192", Continue);
QVERIFY(!child2->surface()->isMapped());
QEXPECT_FAIL("", "Workaround for QtWayland bug https://bugreports.qt.io/browse/QTBUG-52192", Continue);
QVERIFY(!child3->surface()->isMapped());
// next level
@ -882,8 +885,11 @@ void TestSubSurface::testMappingOfSurfaceTree()
QVERIFY(child2DamageSpy.wait());
QVERIFY(parentServerSurface->isMapped());
// children should not yet be mapped
QEXPECT_FAIL("", "Workaround for QtWayland bug https://bugreports.qt.io/browse/QTBUG-52192", Continue);
QVERIFY(!child->surface()->isMapped());
QEXPECT_FAIL("", "Workaround for QtWayland bug https://bugreports.qt.io/browse/QTBUG-52192", Continue);
QVERIFY(!child2->surface()->isMapped());
QEXPECT_FAIL("", "Workaround for QtWayland bug https://bugreports.qt.io/browse/QTBUG-52192", Continue);
QVERIFY(!child3->surface()->isMapped());
// last but not least the first child level, which should map all our subsurfaces

4
src/wayland/surface_interface.cpp
View file

@ -343,6 +343,7 @@ void SurfaceInterface::Private::swapStates(State *source, State *target, bool em
if (!windowRegion.isEmpty()) {
target->damage = windowRegion.intersected(target->damage);
if (emitChanged) {
subSurfaceIsMapped = true;
emit q->damaged(target->damage);
// workaround for https://bugreports.qt.io/browse/QTBUG-52092
// if the surface is a sub-surface, but the main surface is not yet mapped, fake frame rendered
@ -352,6 +353,7 @@ void SurfaceInterface::Private::swapStates(State *source, State *target, bool em
}
}
} else if (!target->buffer && emitChanged) {
subSurfaceIsMapped = false;
emit q->unmapped();
}
}
@ -672,7 +674,7 @@ bool SurfaceInterface::isMapped() const
if (d->subSurface) {
// from spec:
// "A sub-surface becomes mapped, when a non-NULL wl_buffer is applied and the parent surface is mapped."
return d->current.buffer && !d->subSurface->parentSurface().isNull() && d->subSurface->parentSurface()->isMapped();
return d->subSurfaceIsMapped && !d->subSurface->parentSurface().isNull() && d->subSurface->parentSurface()->isMapped();
}
return d->current.buffer != nullptr;
}

6
src/wayland/surface_interface_p.h
View file

@ -82,6 +82,12 @@ public:
State subSurfacePending;
QPointer<SubSurfaceInterface> subSurface;
// workaround for https://bugreports.qt.io/browse/QTBUG-52192
// A subsurface needs to be considered mapped even if it doesn't have a buffer attached
// Otherwise Qt's sub-surfaces will never be visible and the client will freeze due to
// waiting on the frame callback of the never visible surface
bool subSurfaceIsMapped = true;
private:
SurfaceInterface *q_func() {
return reinterpret_cast<SurfaceInterface *>(q);