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Thread: rowCount does not update after removing widgets from grid layout

  1. #1
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    Default rowCount does not update after removing widgets from grid layout

    I'm trying to dynamically remove/delete rows from a QGridLayout, but I can't seem to get the rowCount() property to update. This is what I'm trying:

    Qt Code:
    1. qDebug()<<"Before: "<<my_grid_layout->rowCount();
    2.  
    3. QLayoutItem *child = my_grid_layout->takeAt(row_index);
    4.  
    5. my_grid_layout->removeItem(child);
    6. my_grid_layout->removeWidget(child->widget());
    7.  
    8. delete child->widget();
    9. delete child;
    10.  
    11. my_grid_layout->update();
    12.  
    13. qDebug()<<"After: "<<my_grid_layout->rowCount();
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    Default Re: rowCount does not update after removing widgets from grid layout

    if you use takeAt() you don't have to call removeItem() and removeWidget(). About the row count I guess it is only increasing not decreasing. But I am not sure about it right now.

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    Default Re: rowCount does not update after removing widgets from grid layout

    Thanks for the reply. I suppose I'll just have to keep track of the row count myself. The rowCount() property is basically useless if it only increases!

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    Default Re: rowCount does not update after removing widgets from grid layout

    Well it really only increases. But also consider following:
    Qt Code:
    1. QWidget *w = new QWidget;
    2. l.addWidget(w, 3, 0);
    3. qWarning() << l.rowCount();
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    it will return 4. So the row property is not what you are expecting!
    And do you need the grid functionality because a QVBoxLayout should work like you expect it.

  5. The following user says thank you to Lykurg for this useful post:

    Ishmael (3rd June 2010)

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    Default Re: rowCount does not update after removing widgets from grid layout

    Actually, in your example, I think rowCount() returns exactly what you would expect. You added a widget to the 4th row (index 3) so it returns 4. The problem is, if you remove that same widget, it still says 4! Anyway, your suggestion to use a QVBoxLayout is a good one. I'll try that. Thanks!

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    Default Re: rowCount does not update after removing widgets from grid layout

    You added a widget to the 4th row (index 3) so it returns 4. The problem is, if you remove that same widget, it still says 4!
    there may be more than one item in the row, so deleting it just because an item was removed is probably not a good idea!
    Got to keep the loonies on the path ...

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    Default Re: rowCount does not update after removing widgets from grid layout

    But this behavior is a bug, or at least incredibly non-intuitive. If I add a single widget at row 3, then delete the only widget in that row, the row count should most certainly not include that row. As it is right now, is is impossible to reduce the size of a grid if at any point an item was added to a row.

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    Default Re: rowCount does not update after removing widgets from grid layout

    What do you propose it does if there a full rows of widget at 0, 1, 2, and 4 and only one widget in row 3, which you then remove? Should row three be removed and the widgets in row four be renumbered and the layout resized? How about if taking out cell in row 3 also makes its column empty? Remove it? Doing this automatically potentially breaks any code that references the grid cells by row and column.

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