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c++qtpostscriptqwt

Does Qt5 break QwtPlotRenderer postscript support?

I'm trying to use QwtPlotRenderer to save an image of a QwtPlot as a postscript file. This appears supported in the documentation, however whenever I render with the ".ps" extension, nothing happens.

After some research, it appears that Qt5 removed postscript support from QPrinter. Does this mean that Qwt 6.1.2 can't render as a postscript when using Qt 5?

Solution

  • Unfortunately, yes, it does.

    If we take a look into the qwt_plot_renderer.cpp source code, we can see that postscript support doesn't extend to Qt version 5 and higher, almost certainly because it's built on the QPrinter::PostScriptFormat, which has been removed from Qt.

    // Excerpt from qwt_plot_renderer.cpp (ln 257)
else if ( fmt == "ps" )
{
#if QT_VERSION < 0x050000
#ifndef QT_NO_PRINTER
        QPrinter printer;
        printer.setOutputFormat( QPrinter::PostScriptFormat );
        printer.setColorMode( QPrinter::Color );
        printer.setFullPage( true );
        printer.setPaperSize( sizeMM, QPrinter::Millimeter );
        printer.setDocName( title );
        printer.setOutputFileName( fileName );
        printer.setResolution( resolution );

        QPainter painter( &printer );
        render( plot, &painter, documentRect );
#endif
#endif
}

    That said, Qwt does support a variety of portable formats with Qt 5, including PDF and SVG, which are both vector graphics, and one of which is probably suitable for most applications.