Qprinter scaled

[IknowQT]

void ExChart::BtnPrinter()
{
    /*QPrinter printer(QPrinter::HighResolution);
    QPrintDialog dialog(&printer, this);
    if (dialog.exec() != QDialog::Accepted)
        return;*/

    QPrinter printer(QPrinter::HighResolution);
    printer.setFullPage(true);

    QPrintPreviewDialog preview(&printer, this);
    connect(&preview, &QPrintPreviewDialog::paintRequested, this, &ExChart::PrintPreview);
    preview.setFixedSize(this->size());
    //connect(&preview, SIGNAL(paintRequested(QPrinter*)), SLOT(printPreview(QPrinter*)));
    preview.exec();
}

void ExChart::PrintPreview(QPrinter* printer)
{
    QPainter* painter = new QPainter(printer);
    painter->begin(printer);
    int ratio = 2;
    // 페인터의 뷰포트 영역을 설정하여 rect에 대입
	QRect rect = painter->viewport();
    QSize size = this->m_pChartViewer->size();
    size.scale(rect.size(), Qt::KeepAspectRatio);
    painter->setViewport(rect.x(), rect.y(), size.width() , size.height() );
    painter->setWindow(rect.x(), rect.y(), size.width()*0.4, size.height() * 0.4); // 0.4

    QPixmap buffer = QPixmap::grabWidget(this->m_pChartViewer);
    buffer.scaled(size, Qt::KeepAspectRatio, Qt::SmoothTransformation);
    // buffer를 인쇄 미리보기 창에 출력
    painter->drawPixmap(0, 0, buffer);
    painter->end();
}

Is there a way to fit it in a horizontal size?
I don't know what setviewport and setwindow do.

Another official document states that QPixmap::grabWidget is no longer used, is there an alternative?

[eyllanesc]

@IknowQT Try with:

    void ExChart::PrintPreview(QPrinter *printer){
        QPainter painter(printer);
        painter.begin(printer);
        QRect rect = painter.viewport();
        QPixmap buffer = m_pChartViewer->grab();
        painter.drawPixmap(0, 0, buffer.scaled(rect.size(), Qt::KeepAspectRatio, Qt::SmoothTransformation));
        painter.end();
    }

[IknowQT]

@eyllanesc

printer->setPageMargins(3, 3, 3, 3, QPrinter::Millimeter);

What's wrong with the margin that doesn't apply to the preview?