Draw text on top of both canvas and plot background?

[Elvis S. <elv...@or...>]

Hi,

I'm trying to do something a bit unorthodox, and was hoping someone could
offer some advice.

I'd like to draw some text (the plot unit) right below the top X axis. The
problem is that the place where I want to draw it straddles both the canvas
and the plot background.

This drawn sketch shows where I want to draw the text "g/t":

[image: desired_result.png]

As you can see, it's visible on both the canvas area and the background.
Thus I can't do this inside drawItems(..), since the text would be cropped
to the canvas area.

I tried overriding the paintEvent in my QwtPlot subclass with:

void ConcentrationsPlot::paintEvent(QPaintEvent *event)
{
    QwtPlot::paintEvent(event);

    const auto topAxis = axisWidget(QwtPlot::xTop);

    auto unitRect = rect();
    unitRect.setTopRight(topAxis->mapTo(this,
topAxis->rect().bottomRight()));

    QPainter painter(this);
    painter.setFont(font());
    painter.drawText(unitRect, "g/t", Qt::AlignTop | Qt::AlignRight);
}

But the problem then is that the left part of the text gets overpainted by
the canvas:

[image: overpainted.png]

Is there anything I can do here? Is there no way to paint completely on top
of the QwtPlot as a whole?

Very thankful for any advice on how to achieve what I want.

Cheers,
Elvis