QwtPlotCanvas Class

[CodeFreak]

Hi everyone.
Hope everything is going well.
I'm beginner.
I want to use QwtPlotCanvas to change some features of plot like background color and ... .
I tried to use QwtPlotCanvas as following:

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
        QwtPlot *BioPlot = new QwtPlot(this);
        setCentralWidget(BioPlot);
 
            QwtPlotCanvas *canvas = new QwtPlotCanvas();
            canvas->setFocusIndicator( QwtPlotCanvas::CanvasFocusIndicator );
            canvas->setFocusPolicy( Qt::StrongFocus );
            canvas->setPalette( Qt::black );
            setCanvas( canvas );
...

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
        QwtPlot *BioPlot = new QwtPlot(this);
        setCentralWidget(BioPlot);
        
            QwtPlotCanvas *canvas = new QwtPlotCanvas();
            canvas->setFocusIndicator( QwtPlotCanvas::CanvasFocusIndicator );
            canvas->setFocusPolicy( Qt::StrongFocus );
            canvas->setPalette( Qt::black );
            setCanvas( canvas );
...

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error: 'setCanvas' was not declared in this scope
setCanvas( canvas );

How can I resolve the error?