[Interest] Double free in QItemDelegate editor

[Jérôme Godbout]

Shouldn't the FileDialog belong to the Window and not to the editor? Try without parent or parent to the top window on your dialog you can make it modal if you need to lock down the window. That would prevent the editor destruction to wrongly destroy the Dialog.

-----Original Message-----
From: Interest <interest-bounces at qt-project.org> On Behalf Of Kyle Edwards via Interest
Sent: September 4, 2020 3:20 PM
To: interest at qt-project.org
Subject: Re: [Interest] Double free in QItemDelegate editor

On 9/4/20 2:40 PM, Kyle Edwards wrote:
> After some more investigation, I've learned more about the nature of 
> the problem.
>
> The createEditor() override returns a button which, when clicked, 
> opens a file dialog (through QFileDialog::getOpenFileName() - this 
> will be important in a bit). The opening of this dialog causes the 
> editor to lose focus, which result in QAbstractItemDelegate emitting 
> its closeEditor() signal, which in turn destroys the editor. The 
> destroying of the editor also attempts to delete the file dialog, 
> since it's a child of the editor. However, the file dialog was 
> allocated on the stack by QFileDialog::getOpenFileName(). So, 
> attempting to delete the stack-allocated dialog results in a crash.
>
> So I guess the question is, how do I prevent QAbstractItemDelegate 
> from emitting closeEditor() when the file dialog opens? Either that or 
> prevent closeEditor() from actually closing the editor... I see 
> something in QAbstractItemView::closeEditor() about an editor being 
> "persistent", does that have anything to do with this?

I now have a minimum working test case:

// BEGIN

#include<QItemDelegate>
#include<QApplication>
#include<QFileDialog>
#include<QLineEdit>
#include<QResizeEvent>
#include<QStandardItemModel>
#include<QToolButton>
#include<QTreeView>
#include<QWidget>
classTestEdit: publicQLineEdit
{
Q_OBJECT
public:
TestEdit(QWidget*parent= nullptr);
voidresizeEvent(QResizeEvent*e) override; public slots:
voidchooseFile();
private:
QToolButton* toolButton;
};
TestEdit::TestEdit(QWidget*parent)
: QLineEdit(parent)
{
this->toolButton= newQToolButton(this);
this->toolButton->setText("...");
QObject::connect(this->toolButton, SIGNAL(clicked(bool)), this, SLOT(chooseFile())); }
voidTestEdit::resizeEvent(QResizeEvent*e)
{
// make the tool button fit on the right side inth= e->size().height(); // move the line edit to make room for the tool button
this->setContentsMargins(0, 0, h, 0);
// put the tool button in its place
this->toolButton->resize(h, h);
this->toolButton->move(this->width() - h, 0);
}
voidTestEdit::chooseFile()
{
autopath= QFileDialog::getOpenFileName(this, "title", QString(), QString(), nullptr, QFileDialog::DontResolveSymlinks);
if(!path.isEmpty()) {
this->setText(path);
}
}
classTestItemDelegate: publicQItemDelegate { Q_OBJECT
public:
QWidget*createEditor(QWidget*parent, constQStyleOptionViewItem&option,
constQModelIndex&index) constoverride;
};
QWidget*TestItemDelegate::createEditor(QWidget*parent,
constQStyleOptionViewItem&option, constQModelIndex&index) const { returnnewTestEdit(parent); } intmain(intargc, char**argv) { QApplicationapp(argc, argv); QWidgetwindow; QTreeViewview(&window);
auto* model= newQStandardItemModel;
view.setModel(model);
model->insertRow(0);
model->insertColumn(0);
model->setData(model->index(0, 0), "Hello");
view.setItemDelegate(newTestItemDelegate);
window.show();
returnapp.exec();
}
#include"qttest.moc"
// END
Run the program, double click the "Hello" item, a line editor will appear, click the button on the right to open the dialog, and then the invalid delete happens.
Kyle
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