[Libreoffice-bugs] [Bug 137804] New: Qt5 printing (from Writer) crashes LibreOffice

[bugzilla-daemon at bugs.documentfoundation.org]

https://bugs.documentfoundation.org/show_bug.cgi?id=137804

            Bug ID: 137804
           Summary: Qt5 printing (from Writer) crashes LibreOffice
           Product: LibreOffice
           Version: 7.1.0.0.alpha0+ Master
          Hardware: All
                OS: Linux (All)
            Status: UNCONFIRMED
          Severity: normal
          Priority: medium
         Component: graphics stack
          Assignee: libreoffice-bugs at lists.freedesktop.org
          Reporter: glogow at fbihome.de

This might be a new or an unveiled bug since fixing bug 125234, but I didn't
test this. It was originally found when the reporter of bug 136915 tried to
print after my fix for it. I reverted that fix and found it still crashed LO
when opening the print dialog.

There is already a fix, so this is just for documentation. While I won't
backport all the fixes for bug 125234 and follow up (see bug 125234 comment
31), fixing this crash is easy enough and independent. The following text is
from the comment I planned to add to bug 136915 originally.

----

Guess I should have just tested printing to PDF. Interestingly it doesn't
happen when running LO in gdb. It did happen in valgrind, but that would just
spew a lot of Qt error messages, starting with:

ASSERT failure in QVector<T>::operator[]: "index out of range", file
/usr/include/x86_64-linux-gnu/qt5/QtCore/qvector.h, line 431
QPainter::begin: A paint device can only be painted by one painter at a time.
QPainter::setClipRegion: Painter not active
QPainter::setPen: Painter not active
QPainter::setCompositionMode: Painter not active
QPainter::begin: A paint device can only be painted by one painter at a time.
QPainter::setClipRegion: Painter not active
QPainter::setPen: Painter not active
...

but also no valgrind backtrace :-(

So I had to stick a std::abort() into the ::Qt5Painter as a reaction to
begin(QPaintDevice *) failures, so the general KDE crash handler could collect
a backtrace for me.

But the real question is: why does LO try to layout quite a few empty strings?

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