QAbstractTableModel data function is called many time.

Taz742

QAbstractTableModeldata function is called many time. When i resize MainWindow i see that it resizes slowly.
I think that it is caused by data function and how can i solve it?

#include "mymodel.h"
#include "QDebug"

MyModel::MyModel(QObject *parent) : QAbstractTableModel(parent)
{

}

int MyModel::rowCount(const QModelIndex &parent) const
{
    return this->array.size();
}

int MyModel::columnCount(const QModelIndex &parent) const
{
    return 5;
}

QVariant MyModel::data(const QModelIndex &index, int role) const
{
    static int cnt = 0;
    qDebug() << "dataaa: " << ++cnt;
    if(role == Qt::DisplayRole) {
        return this->array[index.row()][index.column()];
    }
    return QVariant::Invalid;
}

void MyModel::addNewData(QVector<int> newRow)
{
    qDebug() << "add new data";
    this->array.insert(this->array.begin(), newRow);
    QModelIndex first(createIndex(0, 4)), second(createIndex(this->array.size(), 4));
    emit dataChanged(first, second);
}

void MyModel::atachList(QVector<QVector<int> > v)
{
    beginInsertRows(QModelIndex(), 0, v.size() - 1);
    this->array = v;
    QModelIndex first(createIndex(0, 4)), second(createIndex(this->array.size(), 4));
    emit dataChanged(first, second);
    endInsertRows();
}


void MainWindow::on_pushButton_clicked()
{
    MyModel *model = static_cast<MyModel*>(ui->tableView->model());
    QVector<int> v;
    v.push_back(5);
    v.push_back(15);
    v.push_back(25);
    v.push_back(35);
    v.push_back(45);
    model->addNewData(v);
}

void MainWindow::on_pushButton_2_clicked()
{
    QVector<QVector<int> > array;
    for (int i = 1; i <= 1000; i++) {
        QVector<int> v;
        for (int j = 1; j <= 5; j++) {
            v.push_back((i + j) * 10);
        }
        array.push_back(v);
    }
    MyModel *model = static_cast<MyModel*>(ui->tableView->model());
    model->atachList(array);
}

SGaist

Hi,

Printing in the data function might slow things down a bit.

What else do you have in your MainWindow ?

Taz742

@SGaist
I have just one tableView button and frame. http://b.pix.ge:81/j/zmvkw.gif http://a.pix.ge:81/n/sxo8n.gif

mrjj

Hi
It seems the sliding out effect ( altering the area for the TableView)
cause full redraw of all 5000 items. ( 1000 rows, 5 cols)

Its easy to see from sample fi you first open/collapse a few times, then presses
the attach button and fill the table. then try again.

This is also supported from the fact that smaller window or few rows removes this
noticeable delay.

sample to test with.
https://www.dropbox.com/s/rfgcpf7ueh1npha/MyTableViewModel.zip?dl=0

VRonin

To add to @mrjj

data is called multiple times with different roles but given your initail if it should execute very fast.
addNewData forces a refresh fo the whole model, is this what you really want?
addNewData does not call beginInsertRows/endInsertRow
emitting dataChanged on an index of thew inserted row before calling endInsertRows I would call undefined behaviour (officially that row does not exist yet so how can its data change?)