Set the color of a row in a qtreeview

Is it possible to change the color of a row in a QTreeView based on an index at runtime?

Something like this?

Code:

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void MainWindow::changeTreeViewRowColor(QModelIndex index)
{
    for( int i = 0; i < model.columnCount(); ++i ) {
        model.item( index.row(), i )->setBackground( Qt::red );
    }
}

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Inherit QStyledItemDelegate.

Quote:

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Originally Posted by atomic

Something like this?

Code:

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void MainWindow::changeTreeViewRowColor(QModelIndex index)
{
    for( int i = 0; i < model.columnCount(); ++i ) {
        model.item( index.row(), i )->setBackground( Qt::red );
    }
}

---

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exactly like that, except QDirModel and QFileSystemModel don't have an "item()" method...

Try reimplement this virtual function:

Code:

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bool QFileSystemModel::setData(const QModelIndex & idx, const QVariant & value, int role = Qt::EditRole)

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http://doc.qt.io/qt-5/qfilesystemmodel.html#setData
http://doc.qt.io/qt-5/qabstractitemmodel.html#setData

reimplement it how?

from this post here : http://www.cplusplusdevelop.com/855_3935440/

Quote:

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QFileSystemModel rejects all calls to setData that is not of the role "Qt::EditRole".

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I tried using setData() and Qt::BackgroundRole with QSortFilterProxyModel instead, it still doesn't do anything. I am not sure what exactly I should reimplement setData to do.

Quote:

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Originally Posted by slv1

reimplement it how?

from this post here : http://www.cplusplusdevelop.com/855_3935440/



I tried using setData() and Qt::BackgroundRole with QSortFilterProxyModel instead, it still doesn't do anything. I am not sure what exactly I should reimplement setData to do.

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Implement a custom delegate or a proxy model that will do the colouring. Reimplementing setData() for QDirModel or QFileSystemModel makes little sense.

I implemented a custom QStyledItemDelegate() but :

When I iterate through the items in my model, I decide which delegate method should be used for each item, but then the actual drawing takes place after the loop is over, so the last call of "view->setItemDelegate()" will be considered.

How do I force a repaint of a specific item after setting the right itemDelegate for the view?

Update:
Tried using setItemDelegateForRow(), that doesn't work properly because I'm using a QTreeView and that doesn't have unique rows. What would work is a setItemDelegateForIndex() method......

You should set one delegate for the whole view and teach it to decide about colour of each row it renders.

Quote:

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You should set one delegate for the whole view and teach it to decide about colour of each row it renders.

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Can you please explain the pros and cons of doing it this way vs. implementing a proxy that would change the colour via the data() method and the Qt::BackgroundRole. In both cases, it would seem that "teach it to decide" would require inside knowledge about the model.

Quote:

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Originally Posted by d_stranz

Can you please explain the pros and cons of doing it this way vs. implementing a proxy that would change the colour via the data() method and the Qt::BackgroundRole. In both cases, it would seem that "teach it to decide" would require inside knowledge about the model.

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They are more or less equivalent. Using a custom delegate is a bit faster performance-wise.

Quote:

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Originally Posted by wysota

You should set one delegate for the whole view and teach it to decide about colour of each row it renders.

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I solved this by writing a "QStyledItemDelegate" that takes a list of indexes as arguments. It checks if the current index is in the list and paints accordingly.

Here's the code:

Code:

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class RedRowDelegate : public QStyledItemDelegate
{
	public:
		QDirModel *pModel;
		QList<QModelIndex> *pRedIndexes;
 
		RedRowDelegate::RedRowDelegate(QDirModel *model, QList<QModelIndex> *redIndexes){
			pModel = model;
			pRedIndexes = redIndexes;
		}
 
		void RedRowDelegate::paint(QPainter *painter, const QStyleOptionViewItem &option, const QModelIndex &index) const
		{
			int row = index.row();
 
			if(pRedIndexes->contains(index)){
				painter->fillRect(option.rect, QColor(Qt::red));
			}
 
			QStyledItemDelegate::paint(painter, option, index);
		}
};

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After setting it for the QTreeView like this:

Code:

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tree1->setItemDelegate(new RedRowDelegate(model, redIndexes));

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, the delegate will be called iteratively for all the items in the tree, instead of the default one.

You should be using QPersistentModelIndex instead of QModelIndex.