Does Qt5 break QwtPlotRenderer postscript support?

Question

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?

Thankfully, PDF is the defacto page description language, and most printers can print PDFs directly without converting them to PS first. Generally speaking, there's little need to emit postscript these days. — Kuba hasn't forgotten Monica, Sep 22 '15 at 15:25
I generally agree, but it depends on your application. If you're trying to manipulate the file in, say, Adobe Illustrator, it's much easier to work with a *.eps file than a *.pdf (or so I'm told by the people paying me to do this). — Nicolas Holthaus, Sep 22 '15 at 15:55
Postscript may be better if you intend to manipulate the result in other ways such as injecting your own code (make rgb -> cmy for example) — joojaa, Dec 01 '15 at 03:28

Nicolas Holthaus · Accepted Answer · 2015-09-22T15:57:42.397

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.

Does Qt5 break QwtPlotRenderer postscript support?

1 Answers1