https://bugs.kde.org/show_bug.cgi?id=395988
Bug ID: 395988
Summary: KMainWindow saves invalid window/widget state under Qt
5.11.1
Product: frameworks-kxmlgui
Version: 5.47.0
Platform: Archlinux Packages
OS: Linux
Status: UNCONFIRMED
Severity: major
Priority: NOR
Component: general
Assignee: kdelibs-b...@kde.org
Reporter: max...@smoothware.net
Target Milestone: ---
Qt version 5.11.1
KDE Frameworks 5.47.0
Steps to Reproduce:
1. Start an application where mainwindow:
- inherits KMainWindow (or KXmlGuiWindow)
- contains some widget that has WA_NativeWindow attribute set (or calls
QWidget::winId()) - whether WA_DontCreateNativeAncestors is set is irrelevant
- contains usual QStatusBar, QMenuBar (handled by KMainWindow), optionally
QDockWidgets and a central widget :)
2. Close application
3. Reopen the application
4. Application starts with status/menu bar and dock widgets hidden, only
central widget is visible
Additional information:
Cause of the problem is following commit:
http://code.qt.io/cgit/qt/qtbase.git/commit/?id=e0b5ff4ad583befbecbcbe462998e3ed80899531
- and is related to following Qt bug:
https://bugreports.qt.io/browse/QTBUG-43344
I've posted a bug report here rather than on Qt's bug tracker as I'm not sure
whether it should be worked around somehow in KMainWindow, since I'm not 100%
sure it's actually bug in Qt.
Above commit changed things so window close event gets handled by child widgets
sooner... widgets get destroyed (and hidden) before
QApplication::saveStateRequest triggers KMainWindow::saveState().
KMainWindow::saveMainWindowSettings() then calls
QStatusBar/QMenuBar::isHidden() (which will return true) and updates rc file.
In usual use cases when close event is handled, QMainWindow's children are
destroyed without QWidget::hide() being ever called on them, and this issue
won't happen.
It seems that (in some cases) when one of the widgets has WA_NativeWindow flag
set, all widgets get wrapped into QWindowWidget. In this case QMainWindow is
destroyed with QWindowPrivate::destroy() and in turn child widgets (QMenuBar,
QStatusBar, ...) are destroyed with QWindowPrivate::destroy() which also calls
hide()/setVisible(false) on them and causes this issue.
The application where I've encountered this issue is subtitle composer here
https://github.com/maxrd2/subtitlecomposer. I haven't noticed this issue on
other applications I'm using so far, I suppose WA_NativeWindow flag usage is
not that common in apps that rely on KMainWindow.
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