[SOLVED] List of visible rows in the viewport of QTableView



  • Hi,

    Is there anyway I can get the list of visible rows in the viewport of QTableView. Currently in the viewportEvent() of QTableView I can get the firstRow and the lastRow by using

    QModelIndex firstRowIndex = indexAt(QPoint(viewport()->rect().x()+5,viewport()->rect().y()+5));
    QModelIndex lastRowIndex = indexAt(QPoint(viewport()->rect().x()+5,viewport()->rect().height()-5));
    

    The requirement is to iterate/update something specific to the visible Rows in the viewport. If the some rows between the first/last row are hidden then I cannot use a for loop which will consume more time (e.g firstRow = 10, lastRow = 9500; )

    Regards
    Sam


  • Lifetime Qt Champion

    Hi,

    IIRC, you can use visualRect to build that list.

    Hope it helps



  • Hi SGaist,

    Thanks for your reply, with visualRect I need to pass the QModelIndex. In order to get the list of rows/items in the viewport of the tableView I now calculate using the height eg.

    int height = 0;
    while (height < viewport()->rect().height())  // viewport() of tableView
    {
      qDebug() << indexAt(QPoint(viewport()->rect().x(),height)).row());
      height += 25;
    }
    

  • Lifetime Qt Champion

    Are you sure about 25 ? You have to be sure that your rows are 50px high otherwise you might miss some



  • Yes, this approach is temporary and I too don't like to do it this way. In fact for my requirement this does not make any difference even if I get the list of rows in the visible viewport(). I'll try to explain in brief what I am trying to achieve.

    I came across an article : Widgets on a header which works perfect for a horizontalHeaderView and also so a verticalHeaderView with few rows. Currently I am implementing the same for a VerticalHeaderView where I have a panel of buttons (eg add/delete) when we click on these button it add/delete a row.

    The only issue right now is performance, if the model is filled with a lot of rows then creating new panels is a time consuming process. My initial idea was to create the instance of these panel only for the visible rows in the viewport but it creates a lag/flickering when the viewport gets updated while scrolling the tableView.

    Another approach is to paint/render a fake panel and create a new instance when the mouse hover/enter the verticalHeader (don't know if this is even possible, with tableView cells this is easy to implement with delegate).

    Thanks for your time !


  • Lifetime Qt Champion

    What do you need to render exactly ?



  • Are you sure indexAt() for every row is not slower then just iterating between indexes and checking that row is not hidden?


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