Qwt multiaxis bug - can't set color for OpenGL canvas

[Vasya]

Dear Uwe,

I'm trying to change background color of QwtPlotOpenGLCanvas from black to white but it doesn't seem to work in multiaxis branch. By the way previously I worked with Qwt from trunk and there it worked fine.

QwtPlot* plot = new QwtPlot;
    QwtPlotOpenGLCanvas *canvas = new QwtPlotOpenGLCanvas(); // NEW OpenGL Canvas
    plot->setCanvasBackground( Qt::white );
    plot->setCanvas(canvas);

QwtPlot* plot = new QwtPlot;
    QwtPlotOpenGLCanvas *canvas = new QwtPlotOpenGLCanvas(); // NEW OpenGL Canvas
    plot->setCanvasBackground( Qt::white );
    plot->setCanvas(canvas);

To copy to clipboard, switch view to plain text mode 

the canvas is black