[Octave-bug-tracker] [bug #52940] Regression with "PaperPosition" and printing

[Dan Sebald]

Follow-up Comment #7, bug #52940 (project octave):

Oh yeah, I forgot that I was going to give a reference link to the
QOpenGLWidget class:

http://doc.qt.io/qt-5/qopenglwidget.html

There is plenty discussion there about subtle differences between
QOpenGLWidget and QGLWidget.  One thing that has me wondering is the following
comment:

"
When making OpenGL function calls, it is strongly recommended to avoid calling
the functions directly. Instead, prefer using QOpenGLFunctions (when making
portable applications) or the versioned variants (for example,
QOpenGLFunctions_3_2_Core and similar, when targeting modern, desktop-only
OpenGL). This way the application will work correctly in all Qt build
configurations, including the ones that perform dynamic OpenGL implementation
loading which means applications are not directly linking to an GL
implementation and thus direct function calls are not feasible.
"

And here's an example:


    void paintGL()
    {
        // Draw the scene:
        QOpenGLFunctions *f = QOpenGLContext::currentContext()->functions();
        f->glClear(GL_COLOR_BUFFER_BIT);
        ...
    }


Not surprisingly, there is no use of QOpenGLFunctions in the Octave code. 
Could it be that this offset is addressed in the association between
QOpenGLWidget and the QOpenGLFunctions?  I can only guess why the Qt
developers chose to do things that way; seems to obviate the idea of these
portable OpenGL graphics library functions.

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