#include <QApplication>
#include <QTreeWidget>

int main(int argc, char* argv[])
{
    QApplication app(argc, argv);
    app.setStyleSheet(R"(

QAbstractItemView {
  color: #DCDCDC;
  background-color: #1E1E1E;
  alternate-background-color: #262626;
  border-color: #3F3F46;
}

QAbstractItemView::item:selected,
QAbstractItemView::item:selected:hover {
  background-color: #3399FF;
  color: #F1F1F1;
}

QTreeView::indicator {
  background-color: #2D2D30;
  border-color: #3F3F46;
  width: 13px;
  height: 13px;
  border-style: solid;
  border-width: 1px;
}

QTreeView::indicator {
  width: 15px;
  height: 15px;
}
    )");

    QTreeWidget *w = new QTreeWidget();
    w->setAlternatingRowColors(true);
    QTreeWidgetItem *wa = new QTreeWidgetItem({"a"}),
        *wb = new QTreeWidgetItem({"b"});

    wa->setCheckState(0, Qt::CheckState::Unchecked);
    wb->setCheckState(0, Qt::CheckState::Checked);
    w->addTopLevelItems({wa, wb});
    w->show();

    return app.exec();
}