QPrintPreviewDialog help

**Yaoming** · 25th February 2014, 16:44

Hello there,
I know there are a lot of topics about QPrintPreviewDialog issues, I read a lot of them but it didn't help me so here I am. I need some explanations because I don't understand how it works.
I've got two QPushButtons that will call either the print preview or the print itself.
Here's my code so far:

Qt Code:

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//My printPreview slot
    QPrinter printer(QPrinter::HighResolution);
    QPrintPreviewDialog preview(&printer, this);
    preview.setWindowFlags ( Qt::Window );
    preview.setWindowTitle("AperÃ§u avant impression");
    connect(&preview, SIGNAL(paintRequested(QPrinter *)), SLOT(Impression(QPrinter *)));   //Impression is my print slot. When is paintRequested emitted exactly? I read the documentation but didn't understand....
    preview.exec();
 
 
//My Print slot
    QPainter painter;
    painter.begin(p);   //p is my QPrinter
    double xscale = p->pageRect().width()/double(ui.Onglets->width());
    double yscale = p->pageRect().height()/double(ui.Onglets->height());
    double scale = qMin(xscale, yscale);
    painter.translate(p->paperRect().x() + p->pageRect().width()/2, p->paperRect().y() + p->pageRect().height()/2); // to put my widget in the center of my page
    painter.scale(scale, scale);
    painter.translate(-width()/2, -height()/2);
 
    ui.Onglets->render(&painter);  //Onglets is a QTabWidget

//My printPreview slot
    QPrinter printer(QPrinter::HighResolution);
    QPrintPreviewDialog preview(&printer, this);
    preview.setWindowFlags ( Qt::Window );
    preview.setWindowTitle("AperÃ§u avant impression");
    connect(&preview, SIGNAL(paintRequested(QPrinter *)), SLOT(Impression(QPrinter *)));   //Impression is my print slot. When is paintRequested emitted exactly? I read the documentation but didn't understand....
    preview.exec();


//My Print slot
    QPainter painter;
    painter.begin(p);   //p is my QPrinter
    double xscale = p->pageRect().width()/double(ui.Onglets->width());
    double yscale = p->pageRect().height()/double(ui.Onglets->height());
    double scale = qMin(xscale, yscale);
    painter.translate(p->paperRect().x() + p->pageRect().width()/2, p->paperRect().y() + p->pageRect().height()/2); // to put my widget in the center of my page
    painter.scale(scale, scale);
    painter.translate(-width()/2, -height()/2);

    ui.Onglets->render(&painter);  //Onglets is a QTabWidget

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So far only a part of my window shows up in my preview dialog. This problem comes from my print slot or the print preview one?
Could you please explain to me how it works exactly?
Thanks in advance for your answers.

**ChrisW67** · 25th February 2014, 23:44

The problem is in your Impression(QPrinter *) slot. You determine the scale based on the width() and height() of ui.Onglets. When you translate to the centre, scale, and translate back using the different width() and height() of the containing widget.

**Yaoming** · 26th February 2014, 12:19

Thanks for your answer, I'll work on that.
Could you explain to me how this all thing works please? I hate working on something I don't fully understand... When is the paintRequested signal emitted?

**ChrisW67** · 26th February 2014, 20:44

The preview dialog emits paintRequested() when it needs to draw the previewed content. It does this at once immediately after the dialog is shown, but it may emit the signal again if the user does things like select another printer, page size, or margins using the controls in the dialog. Each time the signal is emitted the preview area starts empty and you should render the entire document onto the supplied printer.