Editable QComboBox with QItemDelegate

[Jmgr]

Hi all

I am trying to customize my QTreeView to get an editable QComboBox into a column.
There are some example on the Net, but I haven't seen any with an editable QComboBox, and mine does not work properly...

Let me explain : if I click into the cell and select an item from the list it works : the selection is saved. But if I enter free text and change the focus, then the text is lost, and my DisplayRole role contains nothing. But if I enter some text again, then it will be saved...

I searched without success some hours but didn't find any clue, so I'm posting here, maybe someone has a good idea about this...

Now, some code :

QWidget *ActionDelegate::createEditor(QWidget *parent, const QStyleOptionViewItem &option, const QModelIndex &index) const
{
	QComboBox *comboBox = new QComboBox(parent);
	comboBox->setEditable(true);
	comboBox->setInsertPolicy(QComboBox::NoInsert);
	comboBox->addItems(index.model()->data(index, CustomRoles::ValueRole).toStringList());
 
	connect(comboBox, SIGNAL(activated(int)), this, SLOT(emitCommitData()));
	connect(comboBox->lineEdit(), SIGNAL(editingFinished()), this, SLOT(emitCommitData()));
 
	QString currentText = index.model()->data(index, Qt::DisplayRole).toString();
	int selectedItem = comboBox->findText(currentText);
	if(selectedItem == -1)
		comboBox->setEditText(index.model()->data(index, Qt::DisplayRole).toString());
	else
		comboBox->setCurrentIndex(selectedItem);
 
	return comboBox;
}

QWidget *ActionDelegate::createEditor(QWidget *parent, const QStyleOptionViewItem &option, const QModelIndex &index) const
{
	QComboBox *comboBox = new QComboBox(parent);
	comboBox->setEditable(true);
	comboBox->setInsertPolicy(QComboBox::NoInsert);
	comboBox->addItems(index.model()->data(index, CustomRoles::ValueRole).toStringList());

	connect(comboBox, SIGNAL(activated(int)), this, SLOT(emitCommitData()));
	connect(comboBox->lineEdit(), SIGNAL(editingFinished()), this, SLOT(emitCommitData()));

	QString currentText = index.model()->data(index, Qt::DisplayRole).toString();
	int selectedItem = comboBox->findText(currentText);
	if(selectedItem == -1)
		comboBox->setEditText(index.model()->data(index, Qt::DisplayRole).toString());
	else
		comboBox->setCurrentIndex(selectedItem);

	return comboBox;
}

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void ActionDelegate::setEditorData(QWidget *editor, const QModelIndex &index) const
{
	QComboBox *comboBox = qobject_cast<QComboBox*>(editor);
 
	comboBox->clear();
	comboBox->addItems(index.model()->data(index, CustomRoles::ValueRole).toStringList());
 
	QString currentText = index.model()->data(index, Qt::DisplayRole).toString();
	int selectedItem = comboBox->findText(currentText);
	if(selectedItem == -1)
		comboBox->setEditText(index.model()->data(index, Qt::DisplayRole).toString());
	else
		comboBox->setCurrentIndex(selectedItem);
}

void ActionDelegate::setEditorData(QWidget *editor, const QModelIndex &index) const
{
	QComboBox *comboBox = qobject_cast<QComboBox*>(editor);

	comboBox->clear();
	comboBox->addItems(index.model()->data(index, CustomRoles::ValueRole).toStringList());
	
	QString currentText = index.model()->data(index, Qt::DisplayRole).toString();
	int selectedItem = comboBox->findText(currentText);
	if(selectedItem == -1)
		comboBox->setEditText(index.model()->data(index, Qt::DisplayRole).toString());
	else
		comboBox->setCurrentIndex(selectedItem);
}

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void ActionDelegate::setModelData(QWidget *editor, QAbstractItemModel *model, const QModelIndex &index) const
{
	QComboBox* comboBox = qobject_cast<QComboBox*>(editor);
 
	QStringList value;
	for(int i=0;i<comboBox->count();++i)
		value.append(comboBox->itemText(i));
 
	int selectedItem = comboBox->findText(comboBox->currentText());
	if(selectedItem == -1)
	{
		model->setData(index, -1, CustomRoles::SelectedItemRole);
		model->setData(index, comboBox->currentText(), Qt::DisplayRole);
	}
	else
	{
		model->setData(index, selectedItem, CustomRoles::SelectedItemRole);
		model->setData(index, comboBox->itemText(selectedItem), Qt::DisplayRole);
	}
 
	model->setData(index, value, CustomRoles::ValueRole);
}

void ActionDelegate::setModelData(QWidget *editor, QAbstractItemModel *model, const QModelIndex &index) const
{
	QComboBox* comboBox = qobject_cast<QComboBox*>(editor);

	QStringList value;
	for(int i=0;i<comboBox->count();++i)
		value.append(comboBox->itemText(i));

	int selectedItem = comboBox->findText(comboBox->currentText());
	if(selectedItem == -1)
	{
		model->setData(index, -1, CustomRoles::SelectedItemRole);
		model->setData(index, comboBox->currentText(), Qt::DisplayRole);
	}
	else
	{
		model->setData(index, selectedItem, CustomRoles::SelectedItemRole);
		model->setData(index, comboBox->itemText(selectedItem), Qt::DisplayRole);
	}

	model->setData(index, value, CustomRoles::ValueRole);
}

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void ActionDelegate::emitCommitData()
{
	emit commitData(qobject_cast<QWidget *>(sender()));
}

void ActionDelegate::emitCommitData()
{
	emit commitData(qobject_cast<QWidget *>(sender()));
}

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CustomRoles::SelectedItemRole represents the currently selected item, or -1 if it's free text
CustomRoles::ValueRole represents all the items of the combo box

[wysota]

You have to play a bit with event filters, so that for example when you focus out of the editor or when you press the enter key, the contents is saved into the model.

[Jmgr]

But why does

connect(comboBox->lineEdit(), SIGNAL(editingFinished()), this, SLOT(emitCommitData()));

connect(comboBox->lineEdit(), SIGNAL(editingFinished()), this, SLOT(emitCommitData()));

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not save the data from the QLineEdit ?

I also noticed that setEditorData is called twice after an edition...

[wysota]

What is emitCommitData()? Is it a slot? The line edit is not the editor widget, but part of it, so your emitCommitData() doesn't make much sense.

[Jmgr]

Well, as I posted on the first post it's a slot which calls

emit commitData(qobject_cast<QWidget *>(sender()));

emit commitData(qobject_cast<QWidget *>(sender()));

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EDIT : Yes, it's a slot

[wysota]

Yeah, but it doesn't make much sense, as the line edit is not the editor.

[Jmgr]

Huh, that is true

Ok, I will look how to use the event filter.

[Jmgr]

It is probably a noobish question, but how do I installEventFilter within createEditor, because since createEditor is const, calling myLineEdit->installEventFilter(this) produces an error...

I doesn't know why it is so complicated to put a simple QComboBox into a cell

Anyway, I tested with having persistent editors : it seems to work, but the method of showing an editor when needed is much better...

[wysota]

You have to cheat using const_cast(). You can take a look at the implementation of QItemDelegate and the factory class it uses to see how it is internally implemented. With all the event filters and stuff.

[Jmgr]

I will look at it, thanks

[faraslacks]

Excuse me, may be it's easy, but what is CustomRoles?

[wysota]

Excuse me, may be it's easy, but what is CustomRoles?

[WIKI=QAbstractItemModel#Custom_item_roles]Custom item roles in ItemViews[/WIKI]