Radio buttons in a tree view

[notwithstanding]

Relevant code snippets. These aren't the complete methods, just those parts involving the check state (that's probably obvious):

The tree model:

class TreeModel (QAbstractItemModel):
 
    def flags(self, index):
        flags = Qt.ItemIsEnabled
        item = self.get_item(index)
        # ...
        if index.column() is TreeModel.COLUMN_X:
            if item.is_active():
                flags |= Qt.ItemIsSelectable | Qt.ItemIsUserCheckable
        return flags
 
    def data(self, index, role):
        data = QVariant()
        item = self.get_item(index)
        # ...
        if role == Qt.CheckStateRole:
            if index.column() is TreeModel.COLUMN_X:
                if item.is_active():
                    data = QVariant(Qt.Checked)
                else:
                    data = QVariant(Qt.Unchecked)
        return data
 
    def setData(self, index, value, role):
        status = False
        item = self.get_item(index)
        # ...
        if role == Qt.CheckStateRole:
            if index.column() is TreeModel.COLUMN_X:
                if not item.is_active():
                    item.set_active(True)
                else:
                    item.set_active(False)
                status = True
                self.emit(SIGNAL('dataChanged(QModelIndex,QModelIndex)', index, index)
        return status

class TreeModel (QAbstractItemModel):

    def flags(self, index):
        flags = Qt.ItemIsEnabled
        item = self.get_item(index)
        # ...
        if index.column() is TreeModel.COLUMN_X:
            if item.is_active():
                flags |= Qt.ItemIsSelectable | Qt.ItemIsUserCheckable
        return flags

    def data(self, index, role):
        data = QVariant()
        item = self.get_item(index)
        # ...
        if role == Qt.CheckStateRole:
            if index.column() is TreeModel.COLUMN_X:
                if item.is_active():
                    data = QVariant(Qt.Checked)
                else:
                    data = QVariant(Qt.Unchecked)
        return data

    def setData(self, index, value, role):
        status = False
        item = self.get_item(index)
        # ...
        if role == Qt.CheckStateRole:
            if index.column() is TreeModel.COLUMN_X:
                if not item.is_active():
                    item.set_active(True)
                else:
                    item.set_active(False)
                status = True
                self.emit(SIGNAL('dataChanged(QModelIndex,QModelIndex)', index, index)
        return status

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The item delegate. Compare to the implementation of QItemDelegate.drawCheck. It differs only in two places:

• The last line uses QStyle.PE_IndicatorRadioButton instead of QStyle.PE_IndicatorViewItemCheck
• In the last two lines Instead of asking the private implementation for the owning widget (which can't be done), assume it's the tree view.

class TreeRenderer(QItemDelegate):
 
    def drawCheck( self, painter, option, rect, state ):
        '''Draw a radio button instead of a check button for mutually exclusive fields.'''
        if not rect.isValid(): return
        option.rect = rect
        option.state &= ~QStyle.State_HasFocus
        option.state |= {
            Qt.Unchecked:        QStyle.State_Off,
            Qt.PartiallyChecked: QStyle.State_NoChange,
            Qt.Checked:          QStyle.State_On
        }[ state ]
        style = self.view.style() if self.view else QApplication.style()
        style.drawPrimitive( QStyle.PE_IndicatorRadioButton, option, painter, self.view )

class TreeRenderer(QItemDelegate):

    def drawCheck( self, painter, option, rect, state ):
        '''Draw a radio button instead of a check button for mutually exclusive fields.'''
        if not rect.isValid(): return
        option.rect = rect
        option.state &= ~QStyle.State_HasFocus
        option.state |= {
            Qt.Unchecked:        QStyle.State_Off,
            Qt.PartiallyChecked: QStyle.State_NoChange,
            Qt.Checked:          QStyle.State_On
        }[ state ]
        style = self.view.style() if self.view else QApplication.style()
        style.drawPrimitive( QStyle.PE_IndicatorRadioButton, option, painter, self.view )

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[nifei]

Why not implement QItemDelegate::createEditor() .etc to create a radioButton and open it persistent in treeView? in my opinion, Qt::CheckRole behaves like QCheckBox, and if the checked button need to be exclusive, other buttons have to be setChecked(false), every time one button was clicked. i had did similar work before, which needed several exclusive buttonGroups, and QButtonGroup works well.

[spirit]

Why not implement QItemDelegate::createEditor() .etc to create a radioButton and open it persistent in treeView?

imho, it is bad idea, because performance of your application will decrease, because a lot of descendants of QRadioButton are opend. I think the best way is implement your own model/delegate which will allow to use radio-items approach.

[nifei]

imho, it is bad idea, because performance of your application will decrease, because a lot of descendants of QRadioButton are opend. I think the best way is implement your own model/delegate which will allow to use radio-items approach.

thank you. so, as "Delegate Class" part in Qt's doc says, "Delegates are expected to be able to render their contents themselves by implementing the paint() and sizeHint() functions.", it is not expected to keep a real editor widget persistently? if i need a radio button in some cells all the time, what should i do? should i implement CustomDelegate:aint(), and paint pixmaps of radio_on and radio_off in the cells? I used to do this like this:

CustomDelegate::createEditor()
{
return new QRadioButton;
}

and calling QItemView:penPersistentEditor()for each index, or else the editor will be destroyed the editing finishes. i knew it's not a good way i really need a radiobutton in my view.

[spirit]

1) (quick method) you can use add method setExclusive to a view or to a delegate and then reimplement this method QItemDelegate::drawCheck. according to exclusivity you can draw checkbox (just call drawCheck of paren, i.e. QItemDelegate::drawCheck) or radiobox.
2) subclass a needed model, then subclass a needed item, e.g. QStandartItem, add to it mehtod setExclusive and extend methods setChecked for supporting exclusivity () and then reimplement a method QItemDelegate::drawCheck.
I think that's all. I hope, I helped you.

[nifei]

1) (quick method) you can use add method setExclusive to a view or to a delegate and then reimplement this method QItemDelegate::drawCheck. according to exclusivity you can draw checkbox (just call drawCheck of paren, i.e. QItemDelegate::drawCheck) or radiobox.
2) subclass a needed model, then subclass a needed item, e.g. QStandartItem, add to it mehtod setExclusive and extend methods setChecked for supporting exclusivity () and then reimplement a method QItemDelegate::drawCheck.
I think that's all. I hope, I helped you.

thanks a lot. i'll try.