QScrollArea causes crash on close()
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Hello.
In my application, I have a window with a QScrollArea, that contains some labels to be scrolled. Let's name it "ScrollForm". The ScrollForm can be shown from the main window.
The problem is: if I close the ScrollForm using cross in the corner and then reopen it from the main window (using ScrollForm::show()), ScrollForm is not being rendered, and interacting with it causes application to crash. The debugger doesn't show anything useful, it crashes somewhere deep inside Qt.
However, if I call ScrollForm::hide() and then ScrollForm::show(), everything works fine.
I was able to make a workaround by caatching QCloseEvent and ignoring it, hiding ScrollForm instead. However, the Qt manual states that there's no difference between close() and hide() if Qt::WA_DeleteOnClose is disabled (which is the default).
I've tried to disable Qt::WA_DeleteOnClose explicitly, but the behaviour is the same: calling close() and hide() breaks down the window.
Here is the sample code. The commented blocks of code are a workaround:// scrollform.h #pragma once #include <QWidget> namespace Ui { class ScrollForm; } class ScrollForm : public QWidget { Q_OBJECT public: explicit ScrollForm(QWidget *parent = nullptr); ~ScrollForm(); //protected: // void closeEvent(QCloseEvent*); private: Ui::ScrollForm *ui; };// scrollform.cpp #include "scrollform.h" #include "ui_scrollform.h" #include <QVBoxLayout> #include <QLabel> #include <QCloseEvent> ScrollForm::ScrollForm(QWidget *parent) : QWidget(parent), ui(new Ui::ScrollForm) { ui->setupUi(this); setAttribute(Qt::WA_DeleteOnClose, false); QWidget* w = new QWidget; w->setAttribute(Qt::WA_DeleteOnClose, false); ui->scrollArea->setWidget(w); ui->scrollArea->setAttribute(Qt::WA_DeleteOnClose, false); QVBoxLayout* vbl = new QVBoxLayout(w); vbl->setSizeConstraint(QLayout::SetMinAndMaxSize); for(int a=0; a<100; a++) { QLabel* l = new QLabel(); l->setAttribute(Qt::WA_DeleteOnClose, false); l->setText(tr("This is a label number %1").arg(a+1)); vbl->addWidget(l); } } ScrollForm::~ScrollForm() { delete ui; } //void ScrollForm::closeEvent(QCloseEvent *e) //{ // e->ignore(); // hide(); //}Using Linux Mint 19.1 Qt 5.12, clang 6.0.0 or gcc 7.4.0
However, using system-provided Qt 5.9 doesn't cause this bug. Everything works fine. -
What Qt5.12 version exactly? Can you show us the backtrace?
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Qt version 5.12.4 GCC 64 bit
Here is the call stack at the app crash (show, close, show, scroll with mouse wheel somewhere in an unpainted window).
Everything except main.cpp is grayed out.1 QWidgetBackingStore::markDirtyOnScreen qwidgetbackingstore.cpp 727 0x7ffff76f67a3 2 QWidgetPrivate::moveRect qwidgetbackingstore.cpp 919 0x7ffff76f8ca1 3 QWidgetPrivate::setGeometry_sys qwidget.cpp 7351 0x7ffff771c6bd 4 QWidget::move qwidget.cpp 7182 0x7ffff771c974 5 QWidget::move qwidget.h 836 0x7ffff78679df 6 QScrollAreaPrivate::updateWidgetPosition qscrollarea.cpp 181 0x7ffff78679df 7 QAbstractScrollAreaPrivate::_q_vslide qabstractscrollarea.cpp 1542 0x7ffff77cb311 8 QMetaObject::activate qobject.cpp 3801 0x7ffff68404e9 9 QMetaObject::activate qobject.cpp 3654 0x7ffff6840df7 10 QAbstractSlider::valueChanged moc_qabstractslider.cpp 308 0x7ffff77d058e 11 QAbstractSlider::setValue qabstractslider.cpp 546 0x7ffff77d0bc7 12 QAbstractSlider::triggerAction qabstractslider.cpp 635 0x7ffff77d0e02 13 QAbstractSliderPrivate::scrollByDelta qabstractslider.cpp 750 0x7ffff77d17f9 14 QScrollBar::wheelEvent qscrollbar.cpp 509 0x7ffff7868c2c 15 QWidget::event qwidget.cpp 9325 0x7ffff7724790 16 QAbstractSlider::event qabstractslider.cpp 955 0x7ffff77d1955 17 QScrollBar::event qscrollbar.cpp 490 0x7ffff786a8e2 18 QApplicationPrivate::notify_helper qapplication.cpp 3737 0x7ffff76e69ac 19 QApplication::notify qapplication.cpp 3290 0x7ffff76ef464 20 QCoreApplication::notifyInternal2 qcoreapplication.cpp 1084 0x7ffff6814a28 21 QWidget::event qwidget.cpp 9325 0x7ffff7724790 22 QFrame::event qframe.cpp 550 0x7ffff77c8e9e 23 QCoreApplicationPrivate::sendThroughObjectEventFilters qcoreapplication.cpp 1210 0x7ffff68147bd 24 QApplicationPrivate::notify_helper qapplication.cpp 3731 0x7ffff76e6985 25 QApplication::notify qapplication.cpp 3290 0x7ffff76ef464 26 QCoreApplication::notifyInternal2 qcoreapplication.cpp 1084 0x7ffff6814a28 27 QCoreApplication::forwardEvent qcoreapplication.cpp 1099 0x7ffff6814a72 28 QWidgetWindow::handleWheelEvent qwidgetwindow.cpp 848 0x7ffff773f6a6 29 QWidgetWindow::event qwidgetwindow.cpp 308 0x7ffff7740cd3 30 QApplicationPrivate::notify_helper qapplication.cpp 3737 0x7ffff76e69ac 31 QApplication::notify qapplication.cpp 3483 0x7ffff76edaa0 32 QCoreApplication::notifyInternal2 qcoreapplication.cpp 1084 0x7ffff6814a28 33 QCoreApplication::sendSpontaneousEvent qcoreapplication.cpp 1484 0x7ffff6814bee 34 QGuiApplicationPrivate::processWheelEvent qguiapplication.cpp 2185 0x7ffff6e8b177 35 QGuiApplicationPrivate::processWindowSystemEvent qguiapplication.cpp 1845 0x7ffff6e90115 36 QWindowSystemInterface::sendWindowSystemEvents qwindowsysteminterface.cpp 1151 0x7ffff6e6d76b 37 xcbSourceDispatch qxcbeventdispatcher.cpp 105 0x7ffff0a2ecba 38 g_main_context_dispatch 0x7ffff28a4417 39 ?? 0x7ffff28a4650 40 g_main_context_iteration 0x7ffff28a46dc 41 QEventDispatcherGlib::processEvents qeventdispatcher_glib.cpp 422 0x7ffff686be3f 42 QEventLoop::exec qeventloop.cpp 225 0x7ffff68132ea 43 QCoreApplication::exec qcoreapplication.cpp 1385 0x7ffff681bd30 44 main main.cpp 10 0x403baa -
@umod-47 said in QScrollArea causes crash on close():
show, close, show, scroll
Well-known problem with Qt5.12.3/.4 - upgrade to 5.12.5. See QTBUG-76588
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@umod-47 said in QScrollArea causes crash on close():
show, close, show, scroll
Well-known problem with Qt5.12.3/.4 - upgrade to 5.12.5. See QTBUG-76588
@Christian-Ehrlicher
Indeed, updating to 5.12.5 solved the problem. Thanks!
