Showing the close button for a tab when hovering over the tab

[Fuchsiaff]

I have a QTabWidget which has setTabsCloseable(true); and i have a signal connected to it so it would close the tab.
But now I'm wondering how do I hide the button when the cursor isn't on the TabBar and how to show it when it is on the tab bar?

[raven-worx]

@Fuchsiaff
Something like this (UNTESTED):

class MyTabButton : public QPushButton
{
	Q_OBJECT

public:
    MyTabButton(QTabBar* tabBar)
		: QPushButton(tabbar), m_TabBar(tabbar)
    {
		m_TabBar->installEventFilter( this );
		m_OpacityEffect = new QGraphicsOpacityEffect( this );
			m_OpacityEffect->setOpacity( 0.0 );
		this->setGraphicsEffect( m_OpacityEffect );
		
		connect( this, &MyTabButton::clicked, this, [this]{
			QMetaObject::invokeMethod(m_TabBar, "tabCloseRequested", Qt::DirectConnection, Q_ARG(int,this->tabIndex())); // trigger tabCloseRequested(int) signal of tabbar. Alternatively trigger a custom signal and react to that
		});
		
		// INIT YOUR BUTTON PROPERTIES (FIXED SIZE, ICON, ETC.) HERE
	}
	
	virtual bool eventFilter(QObject* watched, QEvent* event)
	{
		if( watched == m_TabBar )
		{
			switch( event->type() )
			{
				case QEvent::HoverMove:
				case QEvent::MouseMove:
				{
					QPoint pos = event->type() == QEvent::HoverMove ? static_cast<QHoverEvent*>(event)->pos() : static_cast<QMouseEvent*>(event)->pos();
					int indexUnderMouse = m_TabBar->tabAt( pos );
					m_OpacityEffect->setOpacity( indexUnderMouse == this->tabIndex() ? 1.0 : 0.0 );
				}
				break;
				case QEvent::WindowDeactivate:
				case QEvent::Leave:
				case QEvent::HoverLeave:
				{
					m_OpacityEffect->setOpacity( 0.0 );
				}
				break;
			}
		}
		return QPushButton::eventFilter( watched, event );
	}
	
private:
	int tabIndex() const {
		for( int i = 0; i < m_TabBar->count(); ++i )
			if( m_TabBar->tabButton(i,QTabBar::RightSide) == this )
				return i;
		return -1;
	}

	QTabBar*				m_TabBar;
	QGraphicsOpacityEffect*	m_OpacityEffect;
};

tabBar->setMouseTracking(true); // might be also work without this

// assign the button to all your closable tabs
tabbar->setTabButton(index, QTabBar::RightSide, new MyTabButton(tabbar));

[JonB]

@raven-worx
Just a question: could most of this be done via a QSS stylesheet :hover etc.?

[raven-worx]

@JonB
i believe thats not possible. (Styling QTabBar)

Close buttons can be basically styled:

QTabBar::close-button {
    image: url(close.png)
    subcontrol-position: left;
}
QTabBar::close-button:hover {
    image: url(close-hover.png)
}

But there is no valid QSS selector to style a close button of a (hovered or even specific) tab:

QTabBar::tab::close-button {} //sub control selectors must always be placed next to an element (next to another sub.control is not allowed)
QTabBar::tab::close-button:hover {} // even if that would be valid, the :hover pseudo-state would refer to the button not the tab
QTabBar::tab:hover::close-button {} // pseudo states must appear at the end of the selector