Print Widget to PDF : Error with Icon

AmirHammoutene

Hello,

I try to print to PDF an entire widget that can contain multiple sort of widgets.
The widget to be printed is a tab contained in a QTabWidget.

Here is the code that tries to print :

void MainWindow::print()
{
    quint8 tabIndex = quint8(ui->tabWidget->currentIndex());
    CharacterSheetWidget* widget = dynamic_cast< CharacterSheetWidget* >( ui->tabWidget->widget(tabIndex) );
    QString tabName = ui->tabWidget->tabText(tabIndex);
    QString filePath = QFileDialog::getSaveFileName(this, QString(tr("Print as PDF...")), tabName, "PDF file (*.pdf)");

    if(filePath.isEmpty())
        return;

    QPrinter printer;
    printer.setOutputFormat(QPrinter::PdfFormat);
    printer.setOutputFileName(filePath);
    printer.setPaperSize(QPrinter::A4);
    printer.setResolution(300);
    printer.setFullPage(false);
    printer.setPageMargins(5, 5, 5, 5, QPrinter::Millimeter);

    QString originalStyle = widget->styleSheet();
    widget->setStyleSheet("background-color:white;");

    QPainter painter;
    painter.begin(&printer);
    double xscale = printer.pageRect().width() / double(widget->width());
    double yscale = printer.pageRect().height() / double(widget->height());
    double scale = qMin(xscale, yscale);
    painter.translate(printer.paperRect().center());
    painter.scale(scale, scale);
    painter.translate(- widget->width()/ 2, - widget->height()/ 2);
    painter.setRenderHint(QPainter::Antialiasing, true);
    painter.setRenderHint(QPainter::SmoothPixmapTransform, true);
    widget->render(&painter);
    painter.end();
    widget->setStyleSheet(originalStyle);
}

As I said, the user can add multiple type of widgets.
When the entire widget contains QLabel, QLineEdit, QSpinBox, and even QLabel with a QPixmap, the PDF is generated with no problem.
Here is how I generate the QLabel with QPixmap (the print works)

        QPixmap pix;
        QByteArray bytes = QByteArray::fromBase64(info.imageFileData.toLatin1());
        pix.loadFromData(bytes, "PNG");
        if(!pix.isNull())
        {
            pix = pix.scaled(300, 100, Qt::KeepAspectRatio);
            displayWidget->ui->icon->setPixmap(QPixmap(pix));
        }

info.imageFileData being a QString.

So for the moment everything works.

But, when the user add a QPushButton which contains an icon (icon file that is attributed to the QPushButton via Qt Designer : I added a ressource file, added the .png image, and browsed from Qt Designer to that png file under the property "icon" )
... the print crashes the program, I have a 0 ko pdf and this message :

QPainter::begin: Paint device returned engine == 0, type: 2
QPainter::setRenderHint: Painter must be active to set rendering hints
QPainter::setWorldTransform: Painter not active
QWidget::render: Cannot render with an inactive painter
QPainter::end: Painter not active, aborted
terminate called after throwing an instance of 'std::bad_alloc'
  what():  std::bad_alloc

by debugging, I see that it crash at "painter.end();" line

what's wrong ?
(if you need more information, please tell me)

Christian Ehrlicher

Please provide a minimal testcase so we can reproduce a crash. From a first pov it should not crash. Also which OS and Qt version do you use?

AmirHammoutene

I just wrote a minimal testcase, with a lot of the same conditions from my code, but the print is doin' good.
I don't know what to do ... ?

Windows 10,Qt 5.13.2

AmirHammoutene

Ok, I clean the project, run qmake, recompile and it works...

solved