setting width of QTreeView branch indicator

Hi folks!

I need to change width of branch indicator of QTreeView, but i cannot find corresponding parameter in QStyle class.

https://wmpics.pics/di-3W5P.png

I've tried to reimplement all virtual methods in QCommonStyle class which return int, QSize or QRect but the width of branch indicator is always 20.

Code:

---

void drawPrimitive(PrimitiveElement elem, const QStyleOption *option, QPainter *painter, const QWidget *widget = nullptr) const
	{
		if (elem == PE_IndicatorBranch)
				if (option->state & State_Children) {
					const int width = option->rect.width(); // width is always 20
					painter->setPen(QPen(Qt::red));
					painter->drawRect(option->rect);
				}
	}

---

https://wmpics.pics/di-7K83.png

I know that it seems to be possible to do using stylesheets, but i need to do that in styles, no stylesheets.
How could i resize this indicator?

I would take a look at http://doc.qt.io/qt-5/qtreeview.html#indentation-prop