QTextEdit transparency in QGraphicsView

David Stephan

I've been trying to make a transparent QTextEdit in a QGraphicsView. However, the background of the QTextEdit is always white. After lots of trial and error I found that text->setFrameShape(QFrame::NoFrame) gets rid of the white background.

Why is QFrame::NoFrame needed?
Why is the coloring different (see image)?

QPlainTextEdit exhibits the same issue.
QLabel and QLineEdit don't have the issue

Environment

Qt 5.9.1
Windows 10
Visual Studio 2015

Example

QMainWindow w;
w.resize(400, 100);
w.setStyleSheet(".QMainWindow{background : black;}");

QWidget bar(&w);
bar.setGeometry(0, 0, 400, 40);
bar.setStyleSheet("background-color : rgb(0,255,0);");

QTextEdit text1(&w);
text1.setText("Working");
text1.setStyleSheet("background-color : rgba(255,0,0,50%); color : white;");
text1.setGeometry(0, 0, 80, 80);

QGraphicsScene scene;
QGraphicsView view(&w);
view.setGeometry(100, 0, 300, 100);
view.setStyleSheet(".QGraphicsView{background : transparent;}");

QTextEdit text2;
text2.setText("Broken");
text2.setStyleSheet("background-color : rgba(255,0,0,50%); color : black;");
text2.setGeometry(0, 0, 80, 80);
scene.addWidget(&text2);

QTextEdit text3;
text3.setText("Almost Working");
text3.setStyleSheet("background-color : rgba(255,0,0,50%); color : white;");
text3.setGeometry(100, 0, 80, 80);
text3.setFrameShape(QFrame::NoFrame);
scene.addWidget(&text3);

QFrame frame;
frame.setStyleSheet("background-color : rgba(255,0,0,50%);");
frame.setGeometry(200, 0, 80, 80);
scene.addWidget(&frame);

view.setScene(&scene);

w.show();

raven-worx

@David-Stephan
i also encountered this a few times and debugging showed that this relies somewhere in the depths of QStyle imeplementations. Sometimes you need to style border and background together. So i bet it would also work when you add border:0; to your stylesheets.

David Stephan

Wow that also works. Thanks

Asperamanca

Just wondering...why not QGraphicsTextItem? Wrapping a QWidget into a QGraphicsScene is always costly and complicated.

David Stephan

@Asperamanca
I wanted QTextEdit's scrollbar.