Qt - delete space between qscrollbar and qabstractscrollarea

I have a custom-drawn scrollbar and I'm trying to eliminate some space between a qscrollbar and qabstractscrollarea, this is my code:

MainWindow

Code:

---

MainWindow::MainWindow(QWidget *parent) :
      QMainWindow(parent),
      ui(new Ui::MainWindow)
    {
      ui->setupUi(this);
 
 
 
      // Create the scrollarea control
      CTE* scrollarea = new CTE(this);
      ui->here->addWidget( scrollarea);
    }

---

The scrollarea control

Code:

---

class CTE : public QAbstractScrollArea {
        Q_OBJECT
    public:
        explicit CTE(QWidget *parent = 0);
 
    };
 
    CTE::CTE(QWidget *parent) :
      QAbstractScrollArea(parent)
    {
 
      scr *m_verticalScrollBar = new scr( );
      this->setVerticalScrollBar( m_verticalScrollBar);
      this->setVerticalScrollBarPolicy( Qt::ScrollBarAlwaysOn );
 
      this->setFrameStyle(1);
 
      // Debug code (see image below)
      static_cast<QWidget*>(this->verticalScrollBar()->parent()->parent())->setStyleSheet("QWidget {  background-color: red; }");
      static_cast<QWidget*>(this->verticalScrollBar()->parent())->setStyleSheet("QWidget {  background-color: black; }");
    }

---

and the scrollbar

Code:

---

class scr : public QScrollBar
    {
    public:
      scr();
    };
 
    scr::scr() :
      QScrollBar()
    {
 
    }

---

This is the result and the area I'm trying to eliminate

http://i.stack.imgur.com/1Htjt.png

I can't understand how to get rid of it and especially **who owns that part**. Is it a container that contains my scrollbar and which is a subwidget of MyControl? I have no idea

Can somebody help me out please? I'm using Qt5 on linux and this problem **doesn't show up in Windows with the same exact code**