Qt 6.10: QComboBox with groups: Select items

[TheoSys]

Hi!

I've developed a class where I use QComboBox with a model containing a QTreeView. With it I can display groups in a QComboBox and select an item. This works well. But I want also be able to select an item and I can't find out how to do this. To make clear what I did, I show the code here:

#include <QComboBox>
#include <QTreeView>
#include <QStandardItemModel>
#include <QLineEdit>

#include "telementbordername.h"
#include "tgraphics.h"

#define SEL_NONE   -1
#define SEL_TOP     0

using namespace Graphics;

TElementBorderName::TElementBorderName(const QString& brd, const QString& name, QWidget *parent)
    : QWidget(parent),
      mName(name)
{
    QList<FAMILY_t> borders = TGraphics::Current().getBorders();

    mCombo = new QComboBox(this);
    mTreeView = new QTreeView(mCombo);
    mTreeView->setHeaderHidden(true);
    mTreeView->setRootIsDecorated(true);
    mTreeView->setExpandsOnDoubleClick(true);
    mTreeView->setUniformRowHeights(true);
    mCombo->setView(mTreeView);

    mModel = new QStandardItemModel(mCombo);
    mModel->setColumnCount(1);
    mModel->setHorizontalHeaderLabels(QStringList() << "Items");

    mParentItem = mModel->invisibleRootItem();
    QStandardItem *top = new QStandardItem("none");
    top->setData(SEL_NONE);
    mParentItem->appendRow(top);
    mSelected = 0;

    for (FAMILY_t border : borders)
    {
        top = new QStandardItem(border.name);
        top->setData(SEL_TOP);
        top->setFlags(top->flags() & ~Qt::ItemIsSelectable);
        mParentItem->appendRow(top);

        for (QString member : border.member)
            top->appendRow(item);
    }

    mCombo->setModel(mModel);
    mCombo->setModelColumn(0);

    if (!brd.isEmpty())
        setBorder(brd);

    connect(mCombo, &QComboBox::currentTextChanged, this, &TElementBorderName::onComboTextChanged);
}

void TElementBorderName::setBorder(const QString& border)
{
    mBorder = border;

    if (!border.isEmpty())
    {
        QLineEdit *line = mCombo->lineEdit();    // This doesn't work! Always nullptr.

        if (!line)
            return;

        line->setText(border);
    }
}

The data coming from TGraphics::Current().getBorders() are looking like this:

void TGraphics::initBorderFamily()
{
    FAMILY_t family;
    family.name = "2D Standard";
    family.member.push_back("Single Line");
    family.member.push_back("Double Line");
    family.member.push_back("Quad Line");
    family.member.push_back("Picture Frame");
    mDraw.borders.push_back(family);

    family.member.clear();
    family.name = "Circles";
    family.member.push_back("Circle 15");
    family.member.push_back("Circle 25");
    family.member.push_back("Circle 35");
    family.member.push_back("Circle 45");
    family.member.push_back("Circle 55");
    family.member.push_back("Circle 65");
    family.member.push_back("Circle 75");
    family.member.push_back("Circle 85");
    family.member.push_back("Circle 95");
    family.member.push_back("Circle 105");
    family.member.push_back("Circle 115");
    family.member.push_back("Circle 125");
    family.member.push_back("Circle 135");
    family.member.push_back("Circle 145");
    family.member.push_back("Circle 155");
    family.member.push_back("Circle 165");
    family.member.push_back("Circle 175");
    family.member.push_back("Circle 185");
    family.member.push_back("Circle 195");
    mDraw.borders.push_back(family);
...
}

As you can see, the name assigned to family.name is the group name and the other names are members of the group.

My problem is that I can select the group names with QComboBox::setCurrentIndex() but I can't find a way to select any of the group members. But that's what I need.
To clarify. I can select any group member in the QComboBox and the signal QComboBox::currentTextChanged() is executed. So I get the selected group member. So far so well. When I create the class I give a previously selected group member to the class and I want this member be visible as a selected member on initialization. This doesn't work and I don't see a way to do it. Does anybody have an idea of how I can do this?

A.T.

[TheoSys]

Because I found the solution in the meantime I reply to my own post. The following code sets the selection as expected:

void TElementBorderName::setBorder(const QString& border)
{
    mBorder = border;

    const QModelIndexList matches = mModel->match(mModel->index(0, 0), Qt::DisplayRole, border, 1, Qt::MatchExactly | Qt::MatchRecursive);

    if (!matches.isEmpty())
    {
        const QModelIndex modelIdx = matches.first();
        // Temporarily set the root to the parent to allow row-based selection
        mCombo->setRootModelIndex(modelIdx.parent());
        mCombo->setCurrentIndex(modelIdx.row());
        // Restore the original root to show the full tree
        mCombo->setRootModelIndex(QModelIndex());
    }
}

A.T.