Resizing widgets in QTabWidget leaves blank space if border disabled

04CH

I have QTabWidget with widgets that have fixed size depending on font size in it.

I want to disable border of QTabWidget, so i use this line of code:

setStyleSheet("QTabWidget::pane { border: 0; }");

But now, when i resize widgets i have an empty gaps on bottom and right side (~3 - 5px).
If not use this line of code, then after resizing on each side of widget these gaps are equal.

This is resizing code (SessionsWidget inherits QTabWidget):

void SessionsWidget::updateSize(int size)
{
    static_cast<Placeholder*>(widget(0))->setFontSize(size);
    for (auto i = 1; i < count(); ++i)
        static_cast<Terminal*>(widget(i))->setFontSize(size);
}

void Terminal::setFontSize(int size)
{
    m_Impl->m_Display->setFontSize(size);
}

void Display::setFontSize(int size)
{
    auto currentFont = font();
    currentFont.setPointSize(size);
    setFont(currentFont);
    updateSize();
}

void Display::updateSize()
{
    QFontMetrics metrics(font());

    m_FontHeight = metrics.height();
    m_FontWidth = metrics.horizontalAdvance("A");

    setFixedSize(m_FontWidth * 80, m_FontHeight * 25);

    update();
}

How to fix this? Thanks