QT4: Transparent Window with rounded corners

Question

How can I create a partially transparent window with rounded borders (no standard borders)?

(I used Qt::FramelessWindowHint to disable standard border

Answer 1

I had a similar problem where I wanted to paint on a toplevel widget and have only the painted part appear. setWindowOpacity changed the opacity of the painted part, which I didn't want.

this->setAttribute(Qt::WA_TranslucentBackground, true);

changed the opacity of the widget without the painted part. I just tried tossing on a button, and that also displays perfectly opaque. So you should be able to display other children however you like.

Answer 2

I think you should use a widget masks, as seen in the following example from Qt :

http://doc.qt.io/qt-5/qtwidgets-widgets-shapedclock-example.html

I think you'll find what you're looking for in it !

Hope this helps a bit!

Answer 3

 void MainForm::resizeEvent(QResizeEvent * /* event */)
{
    QImage image(this->size(), QImage::Format_Mono);
    image.fill(0);

    if(!this->isFullScreen() && !this->isMaximized())
    {
        image.setPixel(0, 0, 1); image.setPixel(1, 0, 1); image.setPixel(2, 0, 1); image.setPixel(3, 0, 1);
        image.setPixel(0, 1, 1); image.setPixel(1, 1, 1);
        image.setPixel(0, 2, 1);
        image.setPixel(0, 3, 1);

        image.setPixel(width() - 4, 0, 1); image.setPixel(width() - 3, 0, 1); image.setPixel(width() - 2, 0, 1); image.setPixel(width() - 1, 0, 1);
                                                                              image.setPixel(width() - 2, 1, 1); image.setPixel(width() - 1, 1, 1);
                                                                                                                 image.setPixel(width() - 1, 2, 1);
                                                                                                                 image.setPixel(width() - 1, 3, 1);

        image.setPixel(0, height() - 4, 1);
        image.setPixel(0, height() - 3, 1);
        image.setPixel(0, height() - 2, 1); image.setPixel(1, height() - 2, 1);
        image.setPixel(0, height() - 1, 1); image.setPixel(1, height() - 1, 1); image.setPixel(2, height() - 1, 1); image.setPixel(3, height() - 1, 1);

                                                                                                                                                  image.setPixel(width() - 1, height() - 4, 1);
                                                                                                                                                  image.setPixel(width() - 1, height() - 3, 1);
                                                                                                    image.setPixel(width() - 2, height() - 2, 1); image.setPixel(width() - 1, height() - 2, 1);
        image.setPixel(width() - 4, height() - 1, 1); image.setPixel(width() - 3, height() - 1, 1); image.setPixel(width() - 2, height() - 1, 1); image.setPixel(width() - 1, height() - 1, 1);
    }
    this->setMask(QPixmap::fromImage(image));
}