@Niagarer
Good found. :)

@Joel-Bodenmann Two points: 1. You can decompose the path to get each element and work on those independently. 2. You must contend with lines, polylines, ellipses and Bezier splines.

Closes point on a line is simply a vector projection. Bezier splines are more complex. For an approximation you can get polyline approximation to the remainder using parametric equations, then use the same technique for lines. I am writing a book on this subject.

By the way, I recall seeing an article on the method you propose.

There is a reason why there are almost no usable free implementations out there: Because it's harder than one would think at first sight. Maybe start which Shewchuk's papers to get a first idea of the problem.

@Wieland ,nice .......it works ,thanks for reply:)

@Wieland it is example of Qt ,its name diagramscene thanks for reply

@mrjj Well, thanks to you and @kshegunov too. You guys are amazing!

Hi and welcome
It has an overloaded + operator so you can just use that.
Note: This does not delete it as such, it combines.

void SWidget::paintEvent ( QPaintEvent* e ) { QPainter p ( this ); QPainterPath path1; path1.addRect ( 20, 20, 60, 60 ); QPainterPath path2; path2.addEllipse ( 40, 40, 60, 60 ); QPainterPath path3 = path1 + path2; p.drawPath ( path3 ); }