Understanding QPainterPath::simplified()

[Kryzon]

Hello.
My implementation of 'paintEvent' is giving a particular result:

void Widget::paintEvent( QPaintEvent * event )
{
	QPainter p ( this );
	p.setPen( QPen( QBrush( Qt::darkRed ), 2 ) );
	p.setBrush( QBrush( Qt::gray ) );
 
	QPainterPath myPath;
	myPath.moveTo( 600.0, 250.0 );
	myPath.cubicTo( 90.0, 50.0, 0.0, 50.0, 50.0, 370.0 );
	myPath.cubicTo( 140.0, 20.0, 10.0, 10.0, 600.0, 250.0 );
 
	myPath.addRect( 10.0, 300.0, 160.0, 34.0 );
 
	QPainterPath result ( myPath.simplified() );
	p.drawPath( result );
}

void Widget::paintEvent( QPaintEvent * event )
{
	QPainter p ( this );
	p.setPen( QPen( QBrush( Qt::darkRed ), 2 ) );
	p.setBrush( QBrush( Qt::gray ) );
	   
	QPainterPath myPath;
	myPath.moveTo( 600.0, 250.0 );
	myPath.cubicTo( 90.0, 50.0, 0.0, 50.0, 50.0, 370.0 );
	myPath.cubicTo( 140.0, 20.0, 10.0, 10.0, 600.0, 250.0 );
	
	myPath.addRect( 10.0, 300.0, 160.0, 34.0 );
		   
	QPainterPath result ( myPath.simplified() );
	p.drawPath( result );
}

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Looking like this:


Shouldn't the intersected region between the rectangle and the bezier path be filled in the path generated by the 'simplified' call?

[wysota]

What fill mode do you have set on the path?

[Kryzon]

Hello.
I'm using WindingFill, but in any case I tested with either of the fill modes and the result is the same.

According to some more research, QPainterPath::simplified will output a path that looks the same as the original when painted.
So for "moveTo" elements like that rectangle I can create a temporary path and then unite both as a boolean operation.
Additionally, QPainterPath::simplified will convert that path which originally has 7 elements into a 145 "lineTo" elements path that is an approximation, so it won't work for what I want.

This is the result from QPainterPath::simplified:


I'll try something with a computational geometry library, and then feed the results back to Qt for rendering.