QHeaderView doesn't change when QTableView's model is reset.

[deleted385]

Here's how the table is defined in the constructor of the widget/view:

table = new QTableView(this);
tableHeader = new TableHeader(table);
tableModel = new QSqlTableModel(table);
table->setHorizontalHeader(tableHeader);
table->setModel(tableModel);
table->setItemDelegate(new TableItemDelegate(table));

on the combobox's selection change, this is called:

void TableWidget::onComboSelectionChanged(int index)
{
    db.open();
    tableModel->setTable(comboModel->data(comboModel->index(index, 0)).toString());
    tableModel->select();
    db.close();
}

and this is how it looks in the ui:

so initially, the table, Surah, had 6 columns and 6 QLineEdit were shown in the header. When I selected the table VerbDef, it'd 4 columns BUT TableHeader showed 6 QLineEdit and same thing happened with the table table, VerbForm. The count() hasn't been updated in TableHeader. If I select some table that has more than 6 columns then the app crashes because there's a shortfall of QLineEdit in the QList<QLineEdit*>, and, as aresult, I get index out of range exception.

Which signal of QTableView/QSqlTableModel should be used to notify QHeaderView about that fact and update the count() and in which slot of QHeaderView?

Here's how the TableHeader has been defined:

TableHeader::TableHeader(QTableView * parent) :
    QHeaderView(Qt::Horizontal, parent)
{
    setDefaultAlignment(Qt::AlignTop | Qt::AlignHCenter);
    connect(this, &TableHeader::sectionResized, this, &TableHeader::updateGeometries);
    connect(parent->horizontalScrollBar(), &QScrollBar::valueChanged, this, &TableHeader::updatePosition);
}
TableHeader::~TableHeader() { }
void TableHeader::showEvent(QShowEvent *e)
{
    qDeleteAll(lineEdits);
    for (int i = 0; i < count(); i++) {
        auto edit = new QLineEdit(this);
        lineEdits.append(edit);
        connect(edit, &QLineEdit::textChanged, this, &TableHeader::textChanged);
        edit->setGeometry(sectionViewportPosition(i), height() / 2, sectionSize(i), height() / 2);
        edit->show();
    }
    QHeaderView::showEvent(e);
}
QSize TableHeader::sizeHint() const
{
    int width = 0;
    int height = 0;
    for (int i = 0; i < count(); i++){
        width += sectionSize(i);
        auto size = sectionSizeFromContents(i);
        width += size.width();
        height = size.height();
    }
    return QSize(width, height * 2);
}
QList<QString> TableHeader::getQueries() { return queries; }
void TableHeader::updateGeometries()
{
    if(!lineEdits.size()) return;
    for (int i = 0; i < count(); i++) {
        auto edit = lineEdits.at(i);
        edit->setGeometry(sectionViewportPosition(i), height() / 2, sectionSize(i), height() / 2);
    }
    QHeaderView::updateGeometries();
}
void TableHeader::updatePosition()
{
    int height = QHeaderView::sizeHint().height();
    for (int i = 0; i < count(); i++){
        auto edit = lineEdits.at(i);
        edit->move(sectionPosition(i) - offset(), height);
    }
}
void TableHeader::textChanged()
{
    queries.clear();
    for (int i = 0; i < count(); i++){
        auto edit = lineEdits.at(i);
        queries.append(edit->text());
    }
    emit queryChanged();
}

[SGaist]

If diff is negative your loop should run for quite a long time.

Shouldn't you rather use the absolute value of count ?

[deleted385]

This, probably, isn't the right way BUT somehow it works:

TableHeader::TableHeader(QTableView * parent) :
    QHeaderView(Qt::Horizontal, parent)
{
    setDefaultAlignment(Qt::AlignTop | Qt::AlignHCenter);
    connect(this, &TableHeader::sectionResized, this, &TableHeader::updateGeometries);
    connect(parent->horizontalScrollBar(), &QScrollBar::valueChanged, this, &TableHeader::updatePosition);
    connect(this, &TableHeader::sectionCountChanged, this, &TableHeader::onSectionCountChanged);
}
TableHeader::~TableHeader() { }
QSize TableHeader::sizeHint() const
{
    if(count() != lineEdits.size()) return QSize(0, 0);
    int width = 0;
    int height = 0;
    for (int i = 0; i < count(); i++){
        width += sectionSize(i);
        auto size = sectionSizeFromContents(i);
        width += size.width();
        height = size.height();
    }
    return QSize(width, height * 2);
}
QList<QString> TableHeader::getQueries() { return queries; }
void TableHeader::updateGeometries()
{
    if(count() != lineEdits.size()) return;
    for (int i = 0; i < count(); i++) {
        auto edit = lineEdits.at(i);
        edit->setGeometry(sectionViewportPosition(i), height() / 2, sectionSize(i), height() / 2);
    }
}
void TableHeader::updatePosition()
{
    int height = QHeaderView::sizeHint().height();
    for (int i = 0; i < count(); i++){
        auto edit = lineEdits.at(i);
        edit->move(sectionPosition(i) - offset(), height);
    }
}
void TableHeader::textChanged()
{
    queries.clear();
    for (int i = 0; i < count(); i++){
        auto edit = lineEdits.at(i);
        queries.append(edit->text());
    }
    emit queryChanged();
}
void TableHeader::onSectionCountChanged(int oldCount, int newCount)
{
    if(oldCount > 0 && newCount == 0) {
        foreach(auto line, lineEdits) line->disconnect();
        qDeleteAll(lineEdits);
    }
    else if(oldCount == 0 && newCount > 0){
        lineEdits.clear();
        for (int i = 0; i < count(); i++) {
            auto edit = new QLineEdit(this);
            lineEdits.append(edit);
            connect(edit, &QLineEdit::textChanged, this, &TableHeader::textChanged);
            edit->show();
        }
    }
}

What's the correct approach of QHeaderView implementation? It'd be nice if we could give it a Layout to render like:

tableHeader = new TableHeader(table);
tableHeader ->setLayout(new VBoxLayout(){ with the columnName and QLineEdit}); // doesn't exist.
table->setHorizontalHeader(tableHeader);

[SGaist]

Hi,

Since your number of line edits depends on the number sections I don't see a problem here.

However there's no need to nuke all and rebuild everything. Just add missing line edits and remove those exceeding.

[deleted385]

@SGaist, good idea, will try that.

[deleted385]

@SGaist, here's what I've now to add/remove extras:

void TableHeader::resetBoxes(int count){
    queries.clear();
    if(count == lineEdits.size()) {
        for (int i = 0; i < lineEdits.size(); i++) {
            lineEdits[i]->setText("");
            queries.append("");
        }
        return;
    }
    int diff = count - lineEdits.size();
    if(diff > 0){
        for (int i = 0; i < diff; i++) {
            auto edit = new QLineEdit(this);
            edit->installEventFilter(this);
            lineEdits.append(edit);
            connect(edit, &QLineEdit::textChanged, this, &TableHeader::textChanged);
            edit->show();
        }
    }
    else{
        for (int i = 0; i < diff; i++) {
            auto line = lineEdits.takeLast();
            line->disconnect();
            //line->deleteLater();
            delete line;
        }
    }
    qDebug() << lineEdits.size();
    for (int i = 0; i < lineEdits.size(); i++) {
        lineEdits[i]->setText("");
        queries.append("");
    }
}

It adds extra line edits if necessary BUT doesn't remove from the QList lineEdits or UI when necessary. So it looks like this:

initially there was 6 line edits, in subsequent two tables there should've been 4 BUT I got 6. Then I've got 10 and finally when I got back to the first table with 6 columns It'd shown 7 line edits in the UI BUT there was 10 in the QList lineEdits. Here's the output of qDebug() << lineEdits.size();:

6
6
6
10
10

[SGaist]

If diff is negative your loop should run for quite a long time.

Shouldn't you rather use the absolute value of count ?

[deleted385]

@SGaist, that was the issue. Now, with these in else block:

else{
    diff = abs(diff);
    for (int i = 0; i < diff; i++) {
        auto line = lineEdits.takeLast();
        delete line;
    }
}

it shows the right number of line edits in header and the qDebug output is also correct. I haven't measured the time BUT feels like this approach is little bit slower than the previous approach (removing all old and adding new).

I also have removed this
connect(this, &TableHeader::sectionCountChanged, this, &TableHeader::onSectionCountChanged);

and call reset directly in the TableWidget:

void TableWidget::queryDatabase(){
    db.open();
    tableModel->setTable(tableName);
    tableHeader->resetBoxes(tableModel->columnCount());
    tableProxy->setQueries(tableHeader->getQueries());
    tableModel->select();
    while (tableModel->canFetchMore()) tableModel->fetchMore();
    db.close();
}