Update QTableView after hiding columns

[js_dev]

Hello,
I have a question about updating QTableView after hiding some columns. The code below is an extract from my whole code.
Hopefully it shows what I am doing and help to understand my problem.

There is a QSqlTableModel* myDataTableModel with the data to display in QTableView* myDataTableView.
The user's selection of columns to hide is stored in table "tableFilter".
If "bShowColumn" is 1 (One) the row should be shown. If "bShowColumn" is 0 (Zero) the row should be hidden.

The tables with data representet "by strTableName could be different. They could have a different amount of columns and also different names of the columns. Nevertheless I want to show the data in the same view "myDataTableView".

All is fine when I run the code the first time.
Doing this a second time with a different table (strTableName changed) the QTableView is not updated properly and does not show all columns.

What I am doing wrong?

bool hide;
int index;
QString strTableName;  // This is just for the example.
                                     // The name of the table could change and is a parameter of the function

QSqlTableModel* myDataTableModel;

myDataTableModel->setTable(strTableName);--
myDataTableModel->setEditStrategy(QSqlTableModel::OnFieldChange);
myDataTableModel->setHeaderData(myDataTableModel->fieldIndex("run_number"),
                  Qt::Horizontal, "run");

myDataTableModel->select();

ui.mySimDataTableView->setModel(myDataTableModel);

// Hide ID Column
ui.mySimDataTableView->setColumnHidden(myDataTableModel->fieldIndex("idSimData"), true);

QSqlDatabase db = QSqlDatabase::database("DEFAULT");
QSqlQuery stuff(db);

QString s = "SELECT tPropName, bShowColumn FROM tableFilter";

if (stuff.exec(s));
{
 while(stuff.next());
 {
  hide = stuff.value(1);.toInt() == 0;
  index = myDataTableModel()->fieldIndex(stuff.value(0).toString());
  if(index >= 0)
  {
   ui.mySimDataTableView->setColumnHidden(index, hide);
  }
 }
}

[giesbert]

First of all,m you hide columns, not rows :-)

I think, the problem is that you explicitly hide columns, and the perhaps switch the model. You should remove the setColumnHidden and rehide all new hidden rows.

I think, that could help.

[goetz]

Why not use a proxy model (based on "QSortFilterProxyModel":http://doc.qt.nokia.com/stable/qsortfilterproxymodel.html) like in this "wiki article":http://developer.qt.nokia.com/wiki/Filter_Columns_in_a_QFileSystemModel

And don't forget to let the model emit signals (columnAdde/Remove etc.) afterwards to have the view catch up the changes.

[giesbert]

you needn't emit signals if you just filter out rows. There are callback for hiding rows/columns in QSortFilterProxyModel: "filterAcceptsColumn":http://doc.qt.nokia.com/latest/qsortfilterproxymodel.html#filterAcceptsColumn and "filterAcceptsRow":http://doc.qt.nokia.com/latest/qsortfilterproxymodel.html#filterAcceptsRow

Also see the "example in the description of QSortFilterProxyModel":http://doc.qt.nokia.com/latest/qsortfilterproxymodel.html#filtering

[goetz]

Yep. But if the filter rules change after the view has finished displaying items, you must inform the view of the change. Fortunately the Trolls have provided us with slot "invalidateFilter() ":http://doc.qt.nokia.com/latest/qsortfilterproxymodel.html#invalidateFilter for this :-)

[js_dev]

Thanks so far.

I will have a look at the proxy model next week and will also try to unhide the hidden columns before I hide them again.

[js_dev]

Ok, if I do this

// unhide all hidden columns
int rows = myDataTableModel()->rowCount();
for(int i=0; i<rows; i++)
{
 ui.mySimDataTableView->setColumnHidden(i, false);
}

before

ui.mySimDataTableView->setModel(myDataTableModel);

everythink is fine.

Thank you :-)

[giesbert]

[quote author="js_dev" date="1296216104"]Thanks so far.

I will have a look at the proxy model next week and will also try to unhide the hidden columns before I hide them again.[/quote]

If you use the proxy model approach, the setColumnHidden of the view is not needed anymore.

[giesbert]

Ok, if I do this

// unhide all hidden columns
int rows = myDataTableModel()->rowCount();
for(int i=0; i<rows; i++)
{
ui.mySimDataTableView->setColumnHidden(i, false);
}

before

ui.mySimDataTableView->setModel(myDataTableModel);

everythink is fine.

Thank you :-)[/quote]

What is a bit strange:

you iterate over rowCount and call setColumnHidden
This does not fit!

[js_dev]

Oh man - I mixed up rows and columns again :-(
Sorry for the confuision.

It must look like this:

// unhide all hidden columns
int cols = myDataTableModel()->columnCount();
for(int i=0; i<cols; i++)
{
 ui.mySimDataTableView->setColumnHidden(i, false);
}

ui.mySimDataTableView->setModel(myDataTableModel());

[js_dev]

I found another (maybe easier) way to unhide all the previously hidden columns.

If I resize the columns to content after hiding the columns I can get rid of the loop I posted above and the table view shows all the columns I want to see.

Do it like this:

if (stuff.exec(s))
{
 while(stuff.next())
 {
  hide = stuff.value(1).toInt() == 0;
  index = myDataTableModel();->fieldIndex(stuff.value(0).toString());
  if(index >= 0)
  {
   ui.mySimDataTableView->setColumnHidden(index, hide);
  }
 }
}
// This will resize the columns to content and also unhide all previously hidden columns
ui.mySimDataTableView->resizeColumnsToContents();

[giesbert]

As this is not a described behavior, you should take care that it might change in future...