Replace QstandItemModel with QAbstractItemModel
-
Hi,
I was wondering if someone can help me with a problem I'm having using QStandardItemModel and perhaps show me to migrate my code to QAbstractItemModel. I have a tree view which is being populated using QStandardItemModel . The problem is when I try to remove rows; a lot of them it takes a long time. An example is removing 40,000+ rows. This used to work fine with Qt versions < 5.11.2. But now I'm migrated to 5.12 and it is extremely slow. Suggestions from others is to use QAbstractItemModel and remove the rows using that model. Below is a sample program which works fine with earlier version of Qt ( < 5.11.2 ).
Can someone show me how to map to QAbstractItemModel or make it work just as fast with QStandardItemModel using the current version of Qt? I did a lot of reading but still don't understand how to do it. I'm fairly new to Qt so I need detail help if possible. I just need to know how to add data to the model for QAbstractItemModel equivalent to QStandardItemModel::setItem and how to remove rows equivalent to QStandardItemModel::removeRows.
Regards,
Dan
#include <QtWidgets>
//QAbstractItemModel Class
void executeTest()
{
int masterRowNumber = 0;
const int numberOfRows = 50000;
const int removeRows = 40000;
const int numCol = 15;QTreeView tv; QStandardItemModel myModel; QElapsedTimer timer; timer.start(); qDebug() << "creating first set of data"; //Now that we have our data lets put into the model tv.setModel(&myModel); tv.setUniformRowHeights(true); //Speeds up scrolling tv.setSortingEnabled(true); //enable sorting for (int row = 0; row < numberOfRows; row++) { //Inserting data into the model for (int col = 0; col < numCol; col++) myModel.setItem(row, col, new QStandardItem(QString::number(row))); masterRowNumber++; } qDebug() << "After first Insert into model" << timer.elapsed(); qDebug() << "Now Deleting Data..."; //sort the data - in the treeView tv.sortByColumn(2, Qt::AscendingOrder); //this causes a long deley in delete //Now that our model is populated and shown in the treeView - lets delete rows // **** It takes forever to delete the first set of rows after the sort. //In 5.12 This is very SLOW!!! but fast in Qt < 5.11.2 tv.setSortingEnabled(false); myModel.removeRows(0, removeRows, QModelIndex()); //remove 40000 rows tv.setModel(&myModel); tv.setSortingEnabled(true); masterRowNumber -= removeRows; qDebug() << "After first delete of rows now creating new set of data" << timer.elapsed(); //now lets add more rows again for (int row = 0; row < numberOfRows; row++) { //Inserting data into the model for (int col = 0; col < numCol; col++) myModel.setItem(masterRowNumber, col, new QStandardItem(QString::number(row))); masterRowNumber++; } qDebug() << "After second insert into model" << timer.elapsed(); qDebug() << "Now Deleting.."; //Again very slow! tv.setSortingEnabled(false); myModel.removeRows(0, removeRows, QModelIndex()); //remove 40000 rows tv.setSortingEnabled(true); masterRowNumber -= removeRows; qDebug() << "After second delete" << timer.elapsed(); qDebug() << "finished";
}
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
executeTest();return a.exec();
}
-
Hi,
I was wondering if someone can help me with a problem I'm having using QStandardItemModel and perhaps show me to migrate my code to QAbstractItemModel. I have a tree view which is being populated using QStandardItemModel . The problem is when I try to remove rows; a lot of them it takes a long time. An example is removing 40,000+ rows. This used to work fine with Qt versions < 5.11.2. But now I'm migrated to 5.12 and it is extremely slow. Suggestions from others is to use QAbstractItemModel and remove the rows using that model. Below is a sample program which works fine with earlier version of Qt ( < 5.11.2 ).
Can someone show me how to map to QAbstractItemModel or make it work just as fast with QStandardItemModel using the current version of Qt? I did a lot of reading but still don't understand how to do it. I'm fairly new to Qt so I need detail help if possible. I just need to know how to add data to the model for QAbstractItemModel equivalent to QStandardItemModel::setItem and how to remove rows equivalent to QStandardItemModel::removeRows.
Regards,
Dan
#include <QtWidgets>
//QAbstractItemModel Class
void executeTest()
{
int masterRowNumber = 0;
const int numberOfRows = 50000;
const int removeRows = 40000;
const int numCol = 15;QTreeView tv; QStandardItemModel myModel; QElapsedTimer timer; timer.start(); qDebug() << "creating first set of data"; //Now that we have our data lets put into the model tv.setModel(&myModel); tv.setUniformRowHeights(true); //Speeds up scrolling tv.setSortingEnabled(true); //enable sorting for (int row = 0; row < numberOfRows; row++) { //Inserting data into the model for (int col = 0; col < numCol; col++) myModel.setItem(row, col, new QStandardItem(QString::number(row))); masterRowNumber++; } qDebug() << "After first Insert into model" << timer.elapsed(); qDebug() << "Now Deleting Data..."; //sort the data - in the treeView tv.sortByColumn(2, Qt::AscendingOrder); //this causes a long deley in delete //Now that our model is populated and shown in the treeView - lets delete rows // **** It takes forever to delete the first set of rows after the sort. //In 5.12 This is very SLOW!!! but fast in Qt < 5.11.2 tv.setSortingEnabled(false); myModel.removeRows(0, removeRows, QModelIndex()); //remove 40000 rows tv.setModel(&myModel); tv.setSortingEnabled(true); masterRowNumber -= removeRows; qDebug() << "After first delete of rows now creating new set of data" << timer.elapsed(); //now lets add more rows again for (int row = 0; row < numberOfRows; row++) { //Inserting data into the model for (int col = 0; col < numCol; col++) myModel.setItem(masterRowNumber, col, new QStandardItem(QString::number(row))); masterRowNumber++; } qDebug() << "After second insert into model" << timer.elapsed(); qDebug() << "Now Deleting.."; //Again very slow! tv.setSortingEnabled(false); myModel.removeRows(0, removeRows, QModelIndex()); //remove 40000 rows tv.setSortingEnabled(true); masterRowNumber -= removeRows; qDebug() << "After second delete" << timer.elapsed(); qDebug() << "finished";
}
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
executeTest();return a.exec();
}
@leinad said in Replace QstandItemModel with QAbstractItemModel:
Suggestions from others is to use QAbstractItemModel and remove the rows using that model.
I doubt it's going to solve anything. smells like a view problem.
What is the resize policy you set on the headers of the view?
-
@mrjj said in Replace QstandItemModel with QAbstractItemModel:
treeWidget->header()->setSectionResizeMode(QHeaderView::ResizeToContents);
Both did not work. It can easily be tested in the sample code provided. The thing is remove rows worked perfectly fine and fast prior to 5.11.2. I don't see how setting the header will speed up removing rows from the model. I'm guessing I really need to subclass using QAbstractItemModel. Any help in doing that would be great.
-
@leinad
Hi
I think more like something like
treeWidget->header()->setStretchLastSection(true);
or
treeWidget->header()->setSectionResizeMode(QHeaderView::ResizeToContents);@mrjj It's due a change in QStandardItemModel - see https://bugreports.qt.io/browse/QTBUG-78324 but I've no idea how to fix it without reverting the change. Therefore going to a custom model is (sadly) currently the way to go.
-
This is why I respectfully request how to do this. I'm trying using the following example: https://doc.qt.io/qt-5/qtwidgets-itemviews-simpletreemodel-example.html but running into issues.
-
Your example above uses a QTreeView but the data model looks like a table - so what do you need?
-
-
@leinad said in Replace QstandItemModel with QAbstractItemModel:
You can see that "tv" is initialized as a treeview
It does not matter what view you are using but what model you really use - your example code clearly shows us a table structure, not a tree structure - therefore my question...
-
So you don't need to implement a tree model and can use QAbstractTableModel as base instead which is much easier.
-
I have this code fragment which I'm having issues. I'm using QAbstractTableModel as suggested.
topTreeViewModel = new TopTreeViewModel();
void TopTreeViewModel::insertRowsIntoModel(int rowNumber, QList<QList<QStandardItem *>> QStandardItemList, TopTreeViewModel *model, QModelIndex parent)
{
beginInsertRows(QModelIndex(), rowNumber, rowNumber + QStandardItemList[0].size() - 1); //QModelIndex, rowNumber, numberOfRows
model->insertRows(rowNumber, QStandardItemList[0].size(), parent);
for(int rows = 0; rows < QStandardItemList.size(); rows++)
{for(int col = 0; col < QStandardItemList[rows].size(); col++) { QModelIndex index = model->index(rowNumber + rows, col, parent); model->setData(index, QStandardItemList[rows][col]->text(), Qt::DisplayRole); } } endInsertRows(); emit(dataChanged(parent, parent));
}
I call it by using the following in another mainWindow:
metaDataModel->insertRowsIntoModel(rowNumber, QStandardItemList, metaDataModel, parent);
rowNumber += QStandardItemList.size();I get an exception in beginInsertRows(); If I comment it out the data is correct but not displayed in the treeView.
The header is declared as follows (there are other methods but this is the one causing issues. Any help?
#ifndef TOPTREEVIEWMODEL_H
#define TOPTREEVIEWMODEL_H#include <QObject> #include <QAbstractTableModel> #include <QStandardItem> #include <QDebug>
class TopTreeViewModel : public QAbstractTableModel
{
Q_OBJECTpublic:
TopTreeViewModel(QObject *parent=0);
~TopTreeViewModel();public:
void insertRowsIntoModel(int rowNumber, QList<QList<QStandardItem *>> QStandardItemList, TopTreeViewModel *model, QModelIndex parent);
};
#endif // TOPTREEVIEWMODEL_H
-
I have this code fragment which I'm having issues. I'm using QAbstractTableModel as suggested.
topTreeViewModel = new TopTreeViewModel();
void TopTreeViewModel::insertRowsIntoModel(int rowNumber, QList<QList<QStandardItem *>> QStandardItemList, TopTreeViewModel *model, QModelIndex parent)
{
beginInsertRows(QModelIndex(), rowNumber, rowNumber + QStandardItemList[0].size() - 1); //QModelIndex, rowNumber, numberOfRows
model->insertRows(rowNumber, QStandardItemList[0].size(), parent);
for(int rows = 0; rows < QStandardItemList.size(); rows++)
{for(int col = 0; col < QStandardItemList[rows].size(); col++) { QModelIndex index = model->index(rowNumber + rows, col, parent); model->setData(index, QStandardItemList[rows][col]->text(), Qt::DisplayRole); } } endInsertRows(); emit(dataChanged(parent, parent));
}
I call it by using the following in another mainWindow:
metaDataModel->insertRowsIntoModel(rowNumber, QStandardItemList, metaDataModel, parent);
rowNumber += QStandardItemList.size();I get an exception in beginInsertRows(); If I comment it out the data is correct but not displayed in the treeView.
The header is declared as follows (there are other methods but this is the one causing issues. Any help?
#ifndef TOPTREEVIEWMODEL_H
#define TOPTREEVIEWMODEL_H#include <QObject> #include <QAbstractTableModel> #include <QStandardItem> #include <QDebug>
class TopTreeViewModel : public QAbstractTableModel
{
Q_OBJECTpublic:
TopTreeViewModel(QObject *parent=0);
~TopTreeViewModel();public:
void insertRowsIntoModel(int rowNumber, QList<QList<QStandardItem *>> QStandardItemList, TopTreeViewModel *model, QModelIndex parent);
};
#endif // TOPTREEVIEWMODEL_H
@leinad
I haven't attempted to follow all your code, but:beginInsertRows(QModelIndex(), rowNumber, rowNumber + QStandardItemList[0].size() - 1); //QModelIndex, rowNumber, numberOfRows model->insertRows(rowNumber, QStandardItemList[0].size(), parent); for(int rows = 0; rows < QStandardItemList.size(); rows++)
This does not look right, does it? For the "I get an exception in
beginInsertRows();
", I think you mean in the arguments to calling that function. There must be something fundamentally wrong in counting the required rows viaQStandardItemList[0].size()
but indexing/looping viarows < QStandardItemList.size()
. The first has[0]
, the second does not. I would guess the latter is correct, andQStandardItemList[0].size()
is to do with column count? Or maybe I'm going mad....