Error displaying QOpenGLWidget on newer version

[TheEnigmist]

I have an overlay—a transparent, fullscreen window—implemented with QOpenGLWidget in Qt 6.8.0, and it works perfectly. However, after upgrading to Qt 6.10, it no longer functions properly: the background is rendered completely black instead of transparent.

Overlay::Overlay(QWidget* parent): QOpenGLWidget(parent) {
  setWindowFlags(Qt::FramelessWindowHint);
  setWindowFlag(Qt::WindowTransparentForInput);
  setAttribute(Qt::WA_TransparentForMouseEvents);

  setAttribute(Qt::WA_TranslucentBackground);
  setAttribute(Qt::WA_NoSystemBackground, false);
  setWindowFlag(Qt::WindowStaysOnTopHint);

  renderScreen = QGuiApplication::primaryScreen();
  QRect screenGeometry = renderScreen->geometry();
  move(screenGeometry.topLeft());
  setFixedSize(screenGeometry.width() - 1, screenGeometry.height() - 1);

  this->show();
}


void Overlay::initializeGL() {
  QOpenGLFunctions* f = context()->functions();
  f->glClearColor(0.0f, 0.0f, 0.0f, 0.0f);

}

void Overlay::resizeGL(int w, int h) {
  QOpenGLFunctions* f = context()->functions();
  f->glViewport(0, 0, w, h);
}

void Overlay::paintGL() {
  QOpenGLFunctions* f = context()->functions();
  f->glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
  f->glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

  QPainter painter;
  painter.begin(this);
  ...
  painter.end();
}

Has anything changed in Qt since version 6.8.0 that I need to configure to fix this issue?

[SGaist]

Hi,

I would go with a regression but first: 6.10 ? It's not released yet. Can you check with 6.9.0 ?

[TheEnigmist]

I ran some tests with different versions; here are the results:

• 6.8.0: works as expected
• 6.8.3: works as expected
• 6.9.0: background is completely black; the alpha value of 0.0f is ignored
• 6.10.0: background is completely black; the alpha value of 0.0f is ignored

It appears that something went wrong starting with version 6.9.0.

[SGaist]

You should check the bug report system to see if there something about your issue already and if not please open a new ticket providing a minimal compilable reproducer.

[TheEnigmist]

@SGaist said in Error displaying QOpenGLWidget on newer version:

You should check the bug report system to see if there something about your issue already and if not please open a new ticket providing a minimal compilable reproducer.

Created