formatting a QTableView header

mzimmers

Hi all -

My main UI looks like this:

The QTableView is the white box near the top. The first row of text (the "MAC Address Serial Number Device Name" is the header data (set in the model). The line that begins "b4:e6" is the first row of data in the table.

I'd like to improve this display, and the first thing that comes to mind is to visually set off the header from the data. I've looked through the pages on models and tableviews, but I can't find how to go about formatting this. Could someone point me in the right direction?

Thanks...

kshegunov

You can customize the header through returning the appropriate values for the roles from the model. But(!), it'd depend on how your program's organized. How do you populate the header?

mzimmers

Like so:

    m_model->insertColumns(0, TAG_NBRTAGS);
    m_model->setHeaderData(TAG_SERIALNUMBER, Qt::Horizontal, tr("Serial Number"));
    m_model->setHeaderData(TAG_MACADDRESS, Qt::Horizontal, tr("MAC Address"));
    m_model->setHeaderData(TAG_DEVICENAME, Qt::Horizontal, tr("Device Name"));

kshegunov

Okay. Firstly you should use Qt::DisplayRole, not the default Qt::EditRole. Then you can modify further[1]:

Icons - Qt::DecorationRole
Font - Qt::FontRole
Alignment - Qt::TextAlignmentRole

and so on.

[1] http://doc.qt.io/qt-5/qt.html#ItemDataRole-enum

mzimmers

@kshegunov: wow -- this is fairly involved stuff. So, do I need to create a bitmap image of a line to use as an icon that would be my delimiter? (Not sure why font or alignment matter, as I'm trying to modify a data row, not the format of the text in that row.)

Thanks.

kshegunov

@mzimmers said in formatting a QTableView header:

wow -- this is fairly involved stuff. So, do I need to create a bitmap image of a line to use as an icon that would be my delimiter? (Not sure why font or alignment matter, as I'm trying to modify a data row, not the format of the text in that row.)

Not really, no. What you should start with is to use Qt::DisplayRole so not to get the weird header (currently it thinks it's an editor of sorts). As a second step you can set any of the mentioned roles to get more customized looks.

mzimmers

I made the change to DisplayRole, but I don't see a difference in the header. What is it supposed to look like?

kshegunov

@mzimmers said in formatting a QTableView header:

What is it supposed to look like?

I imagined it would be gray after changing the role. Maybe it's just the style you're using. Try setting Qt::BackgroundRole to something to make it distinguishable. (assuming that's what you wanted to do in the first place).

mzimmers

OK, I clearly have no idea what I'm doing. The whole concept of these "roles" eludes me.

I tried this, and it didn't work:

    ui->tableView->horizontalHeader()->setBackgroundRole(QPalette::Window);

kshegunov

Try something like this:

m_model->setHeaderData(TAG_SERIALNUMBER, Qt::Horizontal, QBrush(Qt::red), Qt::BackgroundRole);

Roles give information of what kind of data you are keeping (think of it as the item's properties).

mzimmers

Still no visible change. Do I need to do something to the table view to reflect the change to the model object?

kshegunov

That's very odd. Do you mind sharing the headerData method of your model? Or is the model QStandardItemModel?

mzimmers

My model is defined like this:

    QAbstractItemModel *m_model;    // the main model

But it's initialized like this:

DeviceModel::DeviceModel(QObject *parent) : QObject(parent), m_model(new QStandardItemModel(this))
{
    QString qs;
    QStringList qsl;

    m_model->insertColumns(0, TAG_NBRTAGS);
    m_model->setHeaderData(TAG_SERIALNUMBER, Qt::Horizontal, tr("Serial Number"), Qt::DisplayRole);
    m_model->setHeaderData(TAG_MACADDRESS, Qt::Horizontal, tr("MAC Address"), Qt::DisplayRole);
    m_model->setHeaderData(TAG_DEVICENAME, Qt::Horizontal, tr("Device Name"), Qt::DisplayRole);
    m_model->setHeaderData(TAG_SERIALNUMBER, Qt::Horizontal, QBrush(Qt::red), Qt::BackgroundRole);

Note the use of the QStandardItemModel in the c'tor. (I think VRonin gave me this code, way back when.)

Not sure if this is what you're asking for...

kshegunov

Yes, it is, but only partially. What does your DeviceModel::headerData contain? Does it just delegate to the QStandartItemModel's method?

mzimmers

I'm not doing anything with the header except what I posted above. DeviceModel is my own class that has the actual Qt model as a member:

class DeviceModel : public QObject
{
    Q_OBJECT
private:
    QAbstractItemModel *m_model;    // the main model

kshegunov

@mzimmers said in formatting a QTableView header:

I'm not doing anything with the header except what I posted above. DeviceModel is my own class that has the actual Qt model as a member.

Indeed. My bad, sorry. It's rather odd. As far as I can tell this should be enough to have your header have a red background. As a follow up question: Do you use style sheets?

mzimmers

@kshegunov said in formatting a QTableView header:

As a follow up question: Do you use style sheets?

No, not in this app.

kshegunov

I just tested a project of mine, and it works correctly. Here's what I did:

#include <QBrush>

QVariant MyModel::headerData(int section, Qt::Orientation orientation, int role) const
{
    if (/*role != Qt::DisplayRole || */orientation != Qt::Horizontal || section > columnCount())
        return QVariant();

    if (role == Qt::DisplayRole)
        return columns.byIndex(section).displayName();
    if (role == Qt::BackgroundRole)
        return QBrush(Qt::red);

    return QVariant();
}

I observe the background of the table view's header to be red. It's really odd why it doesn't work for you. Can you retrieve the header data just after you've set it to the model to see if it's correctly stored? I.e.

m_model->setHeaderData(TAG_SERIALNUMBER, Qt::Horizontal, QBrush(Qt::red), Qt::BackgroundRole);
QBrush shouldBeRed = m_model->headerData(TAG_SERIALNUMBER, Qt::Horizontal, Qt::BackgroundRole);

PS: The test was done with Qt 5.11.2 on Linux.

mzimmers

How do I convert a QVariant to a QBrush?

kshegunov

QBrush brush = variant.value<QBrush>();

However you can inspect the data directly in the variant as well, as far as I can see in the watch.