Setting QwtPlot's canvas as Transparent wthout stylesheet way?

[Uwe]

I have absolutely no idea, what you are looking for, but this sounds like you are talking about transparent backgrounds inside of the same application ( nothing, what has to to do with a composite manager ).

Add the following code to the constructor of Plot:

canvas()->setPaintAttribute(QwtPlotCanvas::BackingStore, false);
canvas()->setPaintAttribute(QwtPlotCanvas::Opaque, false);
canvas()->setAttribute( Qt::WA_OpaquePaintEvent, false );
canvas()->setAutoFillBackground( false );

canvas()->setPaintAttribute(QwtPlotCanvas::BackingStore, false);
canvas()->setPaintAttribute(QwtPlotCanvas::Opaque, false);
canvas()->setAttribute( Qt::WA_OpaquePaintEvent, false );
canvas()->setAutoFillBackground( false );

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Then remove all code from Plot::initGradient

Uwe