QWidget::render() paint to painter with wrong offset.

[m.p]

Hi,

I made a custom delegate to my view (list view in a icon mode).

This is a paint method of the delegate:

void PreviewWidget::paint(QPainter *painter, const QStyleOptionViewItem &option,
		   const QModelIndex &index) const
{
	painter->save();
 
	QBrush brush;
	int r = ((double)qrand()/ static_cast<double>( RAND_MAX )) * 255;
	int g= ((double)qrand()/ static_cast<double>( RAND_MAX )) * 255;
	int b = ((double)qrand()/ static_cast<double>( RAND_MAX )) * 255;
	brush.setColor(QColor(r,g,b));
	brush.setStyle(Qt::SolidPattern);
	painter->fillRect(option.rect, brush);
 
	ImagePrev i;
	i.render(painter, option.rect.topLeft());
 
	painter->restore();
}

void PreviewWidget::paint(QPainter *painter, const QStyleOptionViewItem &option,
		   const QModelIndex &index) const
{
	painter->save();

	QBrush brush;
	int r = ((double)qrand()/ static_cast<double>( RAND_MAX )) * 255;
	int g= ((double)qrand()/ static_cast<double>( RAND_MAX )) * 255;
	int b = ((double)qrand()/ static_cast<double>( RAND_MAX )) * 255;
	brush.setColor(QColor(r,g,b));
	brush.setStyle(Qt::SolidPattern);
	painter->fillRect(option.rect, brush);

	ImagePrev i;
	i.render(painter, option.rect.topLeft());

	painter->restore();
}

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Results of rendering widget onto the painter is wrong. Filling painter with random color rect is only to show where widget should be located.

qt-problem.png

Why this offset occur?

[d_stranz]

Why this offset occur?

Probably because you are passing option.rect.topLeft() into the render() call instead of (0,0).

[m.p]

But option.rect.topLeft() is a good position for every item. First will get (0,0), next will get another position according to size of a item (given by sizeHint()). So unfortunately your comment is very wrong.

[norobro]

Here's a bug report on this: QTBUG-26694

Try the workaround in the attachment:

i.render( painter, painter->deviceTransform().map(option.rect.topLeft()));

i.render( painter, painter->deviceTransform().map(option.rect.topLeft()));

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[m.p]

Here's a bug report on this: QTBUG-26694

Try the workaround in the attachment:

i.render( painter, painter->deviceTransform().map(option.rect.topLeft()));

i.render( painter, painter->deviceTransform().map(option.rect.topLeft()));

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It works. Thanks a lot!