Make QWidget transparent

Question

I have a QWidget-based overlay widget which should paint some text and take place over the central widget of my application. The problem is that I can't set background of overlay widget to be transparent. What I already tried:

1. setPalette(Qt::transparent);
2. setAttribute( Qt::WA_TranslucentBackground, true );
3. setAttribute( Qt::WA_OpaquePaintEvent, true );
4. setAutoFillBackground(false);
5. setStyleSheet("QWidget{background-color: transparent;}");
6. setAttribute(Qt::WA_NoSystemBackground);

Answer 1

My best guess to show an overlay widget, is convert the widget to a window, resize it to it's contents and move them to the desired position manually.

MainWindow Example, showing the overlay widget in the center of the video widget:

Mwindow::Mwindow() {     widget = new Widget(this); }  void Mwindow::widgetSizeMove() {     if (widget->width() <= videoWidget->width() && widget->height() <= videoWidget->height())     {         widget->setWindowOpacity(1); // Show the widget         QPoint p = videoWidget->mapToGlobal(videoWidget->pos());         int x = p.x() + (videoWidget->width() - widget->width()) / 2;         int y = p.y() + (videoWidget->height() - widget->height()) / 2;         widget->move(x, y);         widget->raise();     }     else     {         widget->setWindowOpacity(0); // Hide the widget     } }  bool Mwindow::event(QEvent *event) {     switch (event->type())     {     case QEvent::Show:         widget->show();         QTimer::singleShot(50, this, SLOT(widgetSizeMove()));          //Wait until the Main Window be shown         break;     case QEvent::WindowActivate:     case QEvent::Resize:     case QEvent::Move:         widgetSizeMove();         break;     default:         break;     }      return QMainWindow::event(event); } 

Widget Example:

Widget::Widget(QWidget *parent) : QWidget(parent) {     setWindowFlags(Qt::Window | Qt::FramelessWindowHint);      setAttribute(Qt::WA_NoSystemBackground);     setAttribute(Qt::WA_TranslucentBackground);     setAttribute(Qt::WA_PaintOnScreen);      setAttribute(Qt::WA_TransparentForMouseEvents); }  void Widget::paintEvent(QPaintEvent*) {     QPainter p(this);     QString text = "Some foo goes here";     QFontMetrics metrics(p.font());     resize(metrics.size(0, text));     p.drawText(rect(), Qt::AlignCenter, text); } 

Example when showing a video with LibVLC:

Answer 2

The best solution is provided by Gökmen Göksel in one of the comments of this article

setStyleSheet("background-color: rgba(0,0,0,0)");