Why does QPainter::boundingRect returns 0 0?

deleted385

Here's what I've in the window:

and here's the code which generates that:

Window::Window(QWidget *parent) : QWidget(parent){
    printer = new QPrinter();
    printer->setPageSize(QPageSize::A4);
    printer->setPageMargins(QMarginsF(20,20,20,20), QPageLayout::Millimeter);
    document = new QTextDocument(this);
    auto rect = printer->pageRect(QPrinter::Point).size();
    //qDebug() << rect.width() << rect.height();
    document->setPageSize(QSizeF(rect.width(), rect.height()));
    createDocument();
    auto preview = new QPrintPreviewWidget(printer);
    preview->setZoomMode(QPrintPreviewWidget::ZoomMode::FitToWidth);
    connect(preview, &QPrintPreviewWidget::paintRequested, [=]{document->print(printer);});
    auto lay = new QVBoxLayout(this);
    lay->addWidget(preview);
}
void Window::createDocument(){
    QTextCursor cursor(document);
    QTextTableFormat tableFormat;
    tableFormat.setBorder(0);
    tableFormat.setCellSpacing(0);
    tableFormat.setCellPadding(3);
    QVector<QTextLength> columnLengths;
    columnLengths.append(QTextLength(QTextLength::PercentageLength, 40));
    columnLengths.append(QTextLength(QTextLength::PercentageLength, 20));
    columnLengths.append(QTextLength(QTextLength::PercentageLength, 20));
    columnLengths.append(QTextLength(QTextLength::PercentageLength, 20));
    tableFormat.setColumnWidthConstraints(columnLengths);
    int row = 10, column = 4;
    cursor.insertTable(row, column, tableFormat);
    for (int i = 0; i < column; i++) {
        auto cell = cursor.currentTable()->cellAt(0, i);
        QTextTableCellFormat cellFormat;
        cellFormat.setTopBorder(1);
        cellFormat.setBottomBorder(1);
        cellFormat.setBorderBrush(Qt::black);
        cellFormat.setTopBorderStyle(QTextFrameFormat::BorderStyle_Solid);
        cellFormat.setBottomBorderStyle(QTextFrameFormat::BorderStyle_Solid);
        cell.setFormat(cellFormat);
        QTextCharFormat textFormat;
        textFormat.setFontWeight(QFont::Bold);
        QTextBlockFormat blockFormat;
        blockFormat.setAlignment(Qt::AlignCenter);
        cursor.setBlockFormat(blockFormat);
        cursor.insertText("Column " + QString::number(i + 1), textFormat);
        cursor.movePosition(QTextCursor::NextCell);
    }
    QFontMetrics fm(font());
    // w: 481 h:728
    QRectF col1Rect(0,0, 481 * 0.40, fm.boundingRect("tg").height());
    QPainter painter;
    for (int r = 1; r < row; r++) {
        for (int c = 0; c < column; c++) {
            if(c == 0){
                auto col1Text = "Column1 Text Column1 Text Column1 Text Column1";
                auto reqRect = painter.boundingRect(col1Rect, Qt::AlignLeft|Qt::TextWordWrap, col1Text);
                qDebug() << col1Rect.width() << col1Rect.height() << reqRect.width() << reqRect.height();
                cursor.insertText(col1Text);
                cursor.movePosition(QTextCursor::NextCell);
                continue;
            }
            cursor.insertText("Row " + QString::number(r) + " Column " + QString::number(c));
            cursor.movePosition(QTextCursor::NextCell);
        }
    }
}
Window::~Window(){}

in the second for loop of createDocument function, I've

qDebug() << col1Rect.width() << col1Rect.height() << reqRect.width() << reqRect.height();

and it always outputs:

192.4 16 0 0
192.4 16 0 0
...

How to get the correct required height of the desired text?

mpergand

@Emon-Haque said in Why does QPainter::boundingRect returns 0 0?:

QPainter painter; ----> ?????
auto reqRect = painter.boundingRect(col1Rect, Qt::AlignLeft|Qt::TextWordWrap, col1Text);

Use instead:
QRect QFontMetrics::boundingRect(const QRect &rect, int flags, const QString &text, int tabStops = 0, int *tabArray = nullptr) const

deleted385

@mpergand, yes now I get 192 16 148 32.