Delete QTableWidget selected rows

hbatalha

@VRonin said in Delete QTableWidget selected rows:

@hbatalha said in Delete QTableWidget selected rows:

How would I connect the checkbox when clicked?

QObject::connect(tableWidget->model(),&QAbstractItemModel::dataChanged,[](const QModelIndex& topLeft, const QModelIndex& bottomRight, const QVector<int>& roles){
    if(roles.isEmpty() || roles.contains(Qt::CheckStateRole){
        for(int i=topLeft.row();i<bottomRight.row();++i){
            for(int j=topLeft.column();j<bottomRight.column();++j){
                qDebug() << "Checkbox changed in row " << i << " column " << j;
            }
        }
    }
});

I am trying to change the implementation however it is proving to be quite difficult for me to connect it. I need to connect it in a way that I will know whether I am checking or unchecking the checkbox. I tried this every time I add a row:

        QTableWidgetItem* item = ui->table->item(dest_row, 0);
        item->setData(Qt::CheckStateRole,Qt::Checked); // makes the checkbox appear
        item->setFlags(item->flags() | Qt::ItemIsUserCheckable);

        QObject::connect(ui->table->model(),&QAbstractItemModel::dataChanged,[item](const QModelIndex& topLeft,
                         const QModelIndex& bottomRight, const QVector<int>& roles)
        {
            if(item->data(Qt::CheckStateRole).value<Qt::CheckState>() == Qt::Checked)
            {
                //do something
            }
        });

But it is not practical since it becomes too slow when adding a lot of rows in a loop for example.

VRonin

Are you calling QObject::connect every time you add a row? No, that should only be done once when you create the model (in the constructor)

hbatalha

@VRonin yeah, I just did that to be able to grab the item. What I really want to know is just whether I am checking or unchecking.

VRonin

I see I confused you a bit. See this minimal example on how this works:

#include <QApplication>
#include <QTableWidget>
#include <QPushButton>
#include <QVBoxLayout>
#include <QDebug>

class ExampleWidget : public QWidget{
    Q_DISABLE_COPY(ExampleWidget)
public:
    explicit ExampleWidget(QWidget* parent = nullptr)
        :QWidget(parent)
    {
        tableWidget= new QTableWidget(0,1,this);
        connect(tableWidget->model(),&QAbstractItemModel::dataChanged,this,&ExampleWidget::checkboxChanged);

        addRowButton= new QPushButton(tr("Add Row"),this);
        connect(addRowButton,&QPushButton::clicked,this,&ExampleWidget::addRow);

        QVBoxLayout* mainLay = new QVBoxLayout(this);
        mainLay->addWidget(tableWidget);
        mainLay->addWidget(addRowButton);
    }
private slots:
    void addRow(){
        QTableWidgetItem* item = new QTableWidgetItem;
        const int numRows = tableWidget->rowCount();
        item->setData(Qt::EditRole, numRows+1);
        item->setData(Qt::CheckStateRole,Qt::Checked); // makes the checkbox appear
        item->setFlags(item->flags() | Qt::ItemIsUserCheckable);
        tableWidget->insertRow(numRows);
        tableWidget->setItem(numRows,0,item);
    }
    void checkboxChanged(const QModelIndex& topLeft, const QModelIndex& bottomRight, const QVector<int>& roles){
        if(roles.contains(Qt::CheckStateRole)|| roles.isEmpty()){
            for(int i=topLeft.row();i<=bottomRight.row();++i){
                for(int j=topLeft.column();j<=bottomRight.column();++j){
                    qDebug() << "checkbox changed in row " << i << " column " << j;
                    QTableWidgetItem* item = tableWidget->item(i,j);
                    if(item->data(Qt::CheckStateRole).value<Qt::CheckState>() == Qt::Checked)
                        qDebug() << "checkbox is checked";
                    else
                        qDebug() << "checkbox is uncecked";
                }
            }
        }
    }
private:
    QTableWidget* tableWidget;
    QPushButton* addRowButton;
};

int main(int argc, char *argv[])
{
    QApplication app(argc,argv);
    ExampleWidget wid;
    wid.show();
    return app.exec();
}

As you can see the connect is done only once and it's overall really fast. If you don't want your slot to be triggered when a new item is inserted then you just need to remove || roles.isEmpty()
Forgot to mention this requires Qt >= 5.12

hbatalha

@VRonin A good solution but I do have a question:

void checkboxChanged(const QModelIndex& topLeft, const QModelIndex& bottomRight, const QVector<int>& roles){
        if(roles.contains(Qt::CheckStateRole)|| roles.isEmpty()){
            for(int i=topLeft.row();i<=bottomRight.row();++i){
                for(int j=topLeft.column();j<=bottomRight.column();++j){
                    qDebug() << "checkbox changed in row " << i << " column " << j;
                    QTableWidgetItem* item = tableWidget->item(i,j);
                    if(item->data(Qt::CheckStateRole).value<Qt::CheckState>() == Qt::Checked)
                        qDebug() << "checkbox is checked";
                    else
                        qDebug() << "checkbox is uncecked";
                }
            }
        }
    }

From what I could see, isn't that a little expensive to check all the checkboxes every time one is changed, suppose the user has a table with 2 hundreds rows?

Edit: the topLeft.row() is the exact row where the checkbox is modified so it can be used instead of iterating through all the columns and rows.

VRonin

@hbatalha said in Delete QTableWidget selected rows:

to check all the checkboxes

I'm not checking all the checkboxes. The signal tells you that something has changed in the rectangle with corners topLeft bottomRight so i check only that rectangle. 99% of the cases that rectangle is just a single item (topLeft==bottomRight) so you end up checking only 1 item

hbatalha

@VRonin I think I misspoke, when I say "check all the checkboxes" I mean to check all the checkboxes if they are checked or unchecked.

Anyway, I understand how it works now. Thank you very much.

hbatalha

@VRonin Is there a way to change the checkbox color? maybe inside it.

VRonin

See https://doc.qt.io/qt-5/stylesheet-examples.html#customizing-qtableview

The QTableView's checkbox indicator can also be customized. In the following snippet the indicator background-color in unchecked state is customized:
QTableView::indicator:unchecked {
    background-color: #d7d6d5
}

hbatalha

@VRonin It looked kinda weird. So I tried to change the background-color for both checked and unchecked but it only works for one.
This is the result:

I want a similar result I achieved with a QCheckBox by setting the palette:

The code for QCheckBox:

       QCheckBox *title_ckbox = new QCheckBox(title);
        title_ckbox->setToolTip(title);

        QPalette p = title_ckbox->palette( );
        QColor blue( 0, 0, 255 );
        p.setColor( QPalette::Active, QPalette::Base, blue );
        title_ckbox->setPalette(p);

Is it possible to have something like that?

hbatalha

@VRonin I was able to smooth the problem by doing this:

QTableView::indicator:unchecked {
  border: 1px solid blue
 }

It is not exactly what I wanted but it does it for now.

VRonin

@hbatalha said in Delete QTableWidget selected rows:

Is it possible to have something like that?

class CheckBoxDelegate : public QStyledItemDelegate{
    Q_DISABLE_COPY(CheckBoxDelegate)
public:
    using QStyledItemDelegate::QStyledItemDelegate;
protected:
    void initStyleOption(QStyleOptionViewItem *option, const QModelIndex &index) const override{
        QStyledItemDelegate::initStyleOption(option,index);
        option->palette.setColor( QPalette::Active, QPalette::Base, Qt::blue );
    }
};

tableWidget->setItemDelegate(new CheckBoxDelegate(this));

hbatalha

@VRonin worked like charm. Thank you for all your help and for your time. I really appreciate it.