Congratulations to our 2022 Qt Champions!

Determine Line Count for Certain Font w WordWrap at Runtime

  • I have a function called from QML, where QML passes a TableView index, column width and the string in question. I want to determine the line count so I can then dynamically determine the row height which the TableView rowDegate will use.

    Here's some of the interaction from QML. When I click the row and I'm in the expanded state I want to combine text in columns 2 & 3 and then show that in column 3. I also need to dynamically determine the height of this combined text.

     rowDelegate: Rectangle {
                    id: tvRowDelegate
                    height: 65
                    width: parent.width
                    state: ((sqlELmodel.getExpanded(styleData.row)) ? "expanded" : "collapsed")
                    states: [
                        State {
                            name: "collapsed"
                            PropertyChanges { target: tvRowDelegate; height: 65; }
                        State {
                            name: "expanded"
                            PropertyChanges { target: tvRowDelegate; height: (sqlELmodel.getExpandedSL(styleData.row) === 0) ? 100 : (27*(sqlELmodel.getExpandedSL(styleData.row)) < 100) ? 100 : 27*(sqlELmodel.getExpandedSL(styleData.row)); }
                    MouseArea {
                        anchors.fill: parent
                        onClicked: {
                            var cTxt
                            cTxt = sqlELmodel.combineColumns(styleData.row, 2, 3)
                            sqlELmodel.setExpandedSL(styleData.row, col3.width, cTxt)
                            sqlELmodel.setExpanded(styleData.row, !sqlELmodel.getExpanded(styleData.row))
                            timerRow = styleData.row
                            eventLogView.positionViewAtRow(timerRow, ListView.Beginning)

    This is a C++ object that runs all of my queries for the TableView QML object. I've added a QPlainTextEdit member (pte) and in the constructor I set some defaults so I don't have to do this for every call to setExpandedSL() which will be called as rows are rendered.

    SqlQueryModel::SqlQueryModel(QObject* parent) : QSqlQueryModel(parent) {
        connect(&futureWatcher, SIGNAL(finished()), this, SLOT(valDone()));
        // In constructor increase performance
        QFont viewFont("NotoSans", 19, QFont::Normal);

    Here's the real issue. The show() call works in Win10 just fine but fails on my embedded target and I have no idea why.

    void SqlQueryModel::setExpandedSL(int idx, int w, QString str) {
        // Save the visual number of lines
        qDebug() << "Exp line cnt: " << pte.document()->documentLayout()->documentSize().height();
        ExpandedStrLen[idx] = pte.document()->documentLayout()->documentSize().height();

    I've tried alternates like pte.repaint(), pte.update(), pte.viewport()->... and pte.layout()->...

    Any thoughts on what might cause the call to show() to hang or another way to force the layout to update so I can get the text line count for the font (constructor set) and word wrap mode I've set?


Log in to reply