Implement a selection tool for a QQuickPaintedItem

[sheepy]

Hello,
I want to create a selection tool for scribble program.

My scribble area is based on a QPainter in a QQuickPaintedItem.
Now I want to program a feature, that can select a region of the image.

I like to mark the selected area with a dashed outer line like this:
selection-adding.gif
beside a rectangle tool, I want to create a circle tool, too.


My problem is to get a good performance in my implementation. If the user click or dragging the cursor on the area, I want to give realtime feedback (select the area on the fly) but the framerate is very ugly.
My circle selection tool looks like:

void ImageView::selectPoint(const QPointF & point)
{
 
	int radius = 20;
	QPainter painter(&image);
	QBrush brush;
	brush.setStyle(Qt::SolidPattern); // Fix your problem !
	brush.setColor(QColor(60,20,20));;
	selection.addEllipse(point, radius, radius);
	painter.fillPath(selection.simplified(), brush);
	QRect currRect = QRect(point.x()- radius, point.y() - radius,radius+radius, radius+radius);
 
 
 
	update(currRect);
 
 
}

void ImageView::selectPoint(const QPointF & point)
{

	int radius = 20;
	QPainter painter(&image);
	QBrush brush;
	brush.setStyle(Qt::SolidPattern); // Fix your problem !
	brush.setColor(QColor(60,20,20));;
	selection.addEllipse(point, radius, radius);
	painter.fillPath(selection.simplified(), brush);
	QRect currRect = QRect(point.x()- radius, point.y() - radius,radius+radius, radius+radius);



	update(currRect);


}

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I'm also have the problem to draw only the outer line of the selection because I don't clear the image. Is there a option to work with layers (like in a QGraphicsView)?


Best Regards

[anda_skoa]

I'm also have the problem to draw only the outer line of the selection because I don't clear the image. Is there a option to work with layers (like in a QGraphicsView)?

Just put one item onto the other, e.g. make the selection item a child of the main item and fill the parent.

Cheers,
_

[sheepy]

Just put one item onto the other, e.g. make the selection item a child of the main item and fill the parent.
_

Thank you, this works for me!
drawing the path is now okay, but when drawing the outer path (with QPainterPath::simplified () / QPainterPath::union() ) the performance is worse.
Is there another way, so I can merge different paths on the fly?