QT - QTreeView with different colors for subgroups of the QTreeView items

Question

Does anybody know how to implement/realize a QTreeView with different colors for subgroups of the QTreeView items?
Something like:

Does anybody has done something like that and could give me a link to an tutorial or how to, or sample code would also be good. Currently I have absolutely no idea how to build this.

I'm working with Qt 5.1.1 and using the QTreeView with the QFileSystemModel and the QItemSelectionModel.

I also thought of :
m_TreeView->setStyleSheet(...)
but this only sets the style for the whole treeView or only for the selected ones.

Any suggestions? Thanks a lot for your help!

You could try to look at `QAbstractItemModel::data()` with `Qt::BackgroundRole` as a second argument. — vahancho, Nov 27 '13 at 20:04

Frank Osterfeld · Accepted Answer · 2013-11-28T13:31:40.890

There's Qt::BackgroundRole which can be used to return a QColor to be used by the view to paint an index' background.

As you use an existing item model class (QFileSystemModel), it would be easiest to put a proxy model on top of the file system model just doing the colorization.

Using QIdentityProxyModel:

class ColorizeProxyModel : public QIdentityProxyModel {
    Q_OBJECT
public:
    explicit ColorizeProxyModel(QObject *parent = 0) : QIdentityProxyModel(parent) {}

    QVariant data(const QModelIndex &index, int role = Qt::DisplayRole) const {
        if (role != Qt::BackgroundRole) 
            return QIdentityProxyModel::data(index, role);

        ... find out color for index 
        return color;
    }
};

To use it:

QFileSystemModel *fsModel = new QFileSystemModel(this);
ColorizeProxyModel *colorProxy = new ColorizeProxyModel(this);
colorProxy->setSourceModel(fsModel);
treeView->setModel(colorProxy);

If you need anything more fancy, (like special shapes etc.), you'd need your own item delegate with custom painting (see QStyledItemDelegate).

@user1767754: Here's an explanation what explicit is about: http://stackoverflow.com/questions/121162/what-does-the-explicit-keyword-in-c-mean — Frank Osterfeld, Feb 03 '15 at 13:19

QT - QTreeView with different colors for subgroups of the QTreeView items

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