You also need to implement:
The smaller the region the better - but beside of environments like remote X11 you probably won't notice much difference when returning the complete canvas rectangle.Qt Code:
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In your case the optimal solution would be the rectangle spanned by the w points. See https://qwt.sourceforge.io/class_qwt...04f237062b75fc
Have a look at the implementation of QwtPicker::rubberBandMask - it will help with how to find the rectangle.
HTH,
Uwe
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