how to remove the white border of the canvas

[gonna]

how to remove the white border of the canvas,between the curve and the border of the QwtPlot
Screenshot.png

[Uwe]

Such a border might result from your scales or some layout attributes - hard to know from a screenshot only.

But probably you want to do this:

plot->plotLayout()->setCanvasMargin( 0 );

plot->plotLayout()->setCanvasMargin( 0 );

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Uwe