QTabWidget: Mac: The left disabled scroll arrow is painted transparently over the widget text, looks cluttered

On Mac the "disabled left pointing arrow" is painted transparently over the tab text. This looks cluttered against the text of the tab. In other styles the arrow is painted solidly. Maybe it should be painted solidly on Mac.

Reproducible with:

#include <QApplication>
#include <QDialog>
#include <QVBoxLayout>
#include <QTabBar>
#include <QTabWidget>
#include <QLabel>
#include <QtDebug>
#include <QtGui>

int main(int argc,char** argv)
{
QApplication app(argc,argv);

QVBoxLayout* layout = new QVBoxLayout();
QDialog dialog;

QLabel* one = new QLabel("Tab One");
QLabel* two = new QLabel("Tab Two");
QLabel* three = new QLabel("Tab Three");
QLabel* four = new QLabel("Tab Four");
QLabel* five = new QLabel("Tab Five");

QTabBar* tab = new QTabBar(&dialog);
tab->setUsesScrollButtons(true);
tab->addTab("Tab One");
tab->addTab("Tab Two");
tab->addTab("Tab Three");
tab->addTab("Tab Four");
tab->addTab("Tab Five");

tab->adjustSize();

qDebug() << "Width of tab widget: " << tab->width();

layout->addWidget(tab);
dialog.setLayout(layout);
dialog.resize(100,100);

dialog.show();

return app.exec();
};