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tdf#131533 Qt5 defer dropping clipboard ownership

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This is maybe a Qt bug. Calling QClipboard::setMimeData from
Qt5Clipboard::setContents after a previous call to
QClipboard::clear results in a clipboard ownership failure.
In a terminal you'll see: "QXcbClipboard::setMimeData: Cannot set
X11 selection owner".

Calling Application::Reschedule() after the clear() doesn't help.

The result is a de-sync between the LO's clipboard state and the
real clipboard state, which will lead to a crash on LO shutdown.

I'm not sure this fix is correct. Maybe this could also be handled
by some X11 flush operation. But it's the only working solution I
could find: don't clear, if LO re-claims the ownership later.

I tried to reproduce the ownership error by modifying the Qt
fridgemagnets example, adding some QClipboard::clear and
QClipboard::setMimeData calls to the drop handling, but couldn't
reproduce. Maybe the dynamic Qt5MimeData object is also involved.

Change-Id: I32b6575a78a4b10a2e2b7b189303ab3a40dc69ca
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/90990
Tested-by: Jenkins
Reviewed-by: Michael Weghorn <m.weghorn@posteo.de>
Reviewed-by: Jan-Marek Glogowski <glogow@fbihome.de>
This commit is contained in:
Jan-Marek Glogowski 2020-03-25 18:33:29 +01:00
parent 0069dbf431
commit 313081c070
2 changed files with 25 additions and 4 deletions
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6
vcl/inc/qt5/Qt5Clipboard.hxx
View file

@ -41,6 +41,8 @@ class Qt5Clipboard final
// has to be set, if LO changes the QClipboard itself, so it won't instantly lose
// ownership by it's self-triggered QClipboard::changed handler
bool m_bOwnClipboardChange;
// true, if LO really wants to give up clipboard ownership
bool m_bDoClear;
// if not empty, this holds the setContents provided XTransferable or a Qt5ClipboardTransferable
css::uno::Reference<css::datatransfer::XTransferable> m_aContents;
@ -55,6 +57,10 @@ class Qt5Clipboard final
private Q_SLOTS:
void handleChanged(QClipboard::Mode mode);
void handleClearClipboard();
signals:
void clearClipboard();
public:
// factory function to construct only valid Qt5Clipboard objects by name

23
vcl/qt5/Qt5Clipboard.cxx
View file

@ -30,11 +30,16 @@ Qt5Clipboard::Qt5Clipboard(const OUString& aModeString, const QClipboard::Mode a
, m_aClipboardName(aModeString)
, m_aClipboardMode(aMode)
, m_bOwnClipboardChange(false)
, m_bDoClear(false)
{
assert(isSupported(m_aClipboardMode));
// DirectConnection guarantees the changed slot runs in the same thread as the QClipboard
connect(QApplication::clipboard(), &QClipboard::changed, this, &Qt5Clipboard::handleChanged,
Qt::DirectConnection);
// explicitly queue an event, so we can eventually ignore it
connect(this, &Qt5Clipboard::clearClipboard, this, &Qt5Clipboard::handleClearClipboard,
Qt::QueuedConnection);
}
css::uno::Reference<css::uno::XInterface> Qt5Clipboard::create(const OUString& aModeString)
@ -98,6 +103,13 @@ css::uno::Reference<css::datatransfer::XTransferable> Qt5Clipboard::getContents(
return m_aContents;
}
void Qt5Clipboard::handleClearClipboard()
{
if (!m_bDoClear)
return;
QApplication::clipboard()->clear(m_aClipboardMode);
}
void Qt5Clipboard::setContents(
const css::uno::Reference<css::datatransfer::XTransferable>& xTrans,
const css::uno::Reference<css::datatransfer::clipboard::XClipboardOwner>& xClipboardOwner)
@ -110,15 +122,18 @@ void Qt5Clipboard::setContents(
m_aContents = xTrans;
m_aOwner = xClipboardOwner;
m_bOwnClipboardChange = true;
if (m_aContents.is())
m_bDoClear = !m_aContents.is();
if (!m_bDoClear)
{
m_bOwnClipboardChange = true;
QApplication::clipboard()->setMimeData(new Qt5MimeData(m_aContents), m_aClipboardMode);
m_bOwnClipboardChange = false;
}
else
{
assert(!m_aOwner.is());
QApplication::clipboard()->clear(m_aClipboardMode);
Q_EMIT clearClipboard();
}
m_bOwnClipboardChange = false;
aGuard.clear();