Improve the EGL_BAD_MATCH error on certain circumstance

1. Create QQuickView such as m_QuickVew = new QQuickView()

2. call m_QuickVew->winId()

3. Some event is happened, run the following code. ( maybe you can use Timer for simulation.)

 m_QuickVew->setColor(QColor(Qt::transparent));
 m_QuickVew->setSoruce("xxx");

4. Some event is happened, run the following code, (maybe you can use Timer for simulation.)

m_QuickVew->show()

5. EGL_BAD_MATCH error is happened

6. If we call the m_QuickVew->setColor(QColor(Qt::transparent)); before m_QuickVew->winId(). The EGL_BAD_MATCH error in not happened.

Regarding this issue, I hope to consider the following issue also be improved.

• 1) Set QT_WAYLAND_DISABLE_WINDOWDECORATION=1.
• 2) Create QQuickView or QQuickWindow and call the winId() to get the Wid.
• 3) The QWaylandEglWindow object is created with following code by the winId().

  QWaylandEglWindow::QWaylandEglWindow(QWindow *window, QWaylandDisplay *display)
      : QWaylandWindow(window, display)
      , m_clientBufferIntegration(static_cast<QWaylandEglClientBufferIntegration *>(mDisplay->clientBufferIntegration()))
  {
      QSurfaceFormat fmt = window->requestedFormat();
      if (mDisplay->supportsWindowDecoration())
          fmt.setAlphaBufferSize(8);
      // m_eglConfig is created without AlphaBuffer. 
      m_eglConfig = q_configFromGLFormat(m_clientBufferIntegration->eglDisplay(), fmt);
      m_format = q_glFormatFromConfig(m_clientBufferIntegration->eglDisplay(), m_eglConfig, fmt);
     ... 
  }
  

• 4) After then, the application want to change the surface format such as setColor(QColor(Qt::transparent)) by some platform event.
• 5) And then, the application call the setVisible(true) by some platform event.
• 6) In this case, the following code is run.

  void QWaylandEglWindow::updateSurface(bool create)
  {
      ...
      if (sizeWithMargins.isEmpty()) {
          ....
      } else {
          if (m_waylandEglWindow) {
            ... 
          } else if (create && wlSurface() && window()->isVisible()) {  //Note," && window()->isVisible()" is just private patch for our platform.
             ... 
          }
          if (!m_eglSurface && m_waylandEglWindow && create && window()->isVisible()) { //Note," && window()->isVisible()" is just private patch for our platform.
              EGLNativeWindowType eglw = (EGLNativeWindowType) m_waylandEglWindow;
              // Call eglCreateWindowSurface with m_eglConfig which is created by QWaylandEglWindow ctor. 
             // But now, the surface format of our QWindow has the AlphaBuffer. 
              m_eglSurface = eglCreateWindowSurface(m_clientBufferIntegration->eglDisplay(), m_eglConfig, eglw, 0);
              if (Q_UNLIKELY(m_eglSurface == EGL_NO_SURFACE))
                  qCWarning(lcQpaWayland, "Could not create EGL surface (EGL error 0x%x)\n", eglGetError());
          }
      }
  }
  

• 7) And then, the following code is run for the rendering, the "QWaylandGLContext::makeCurrent: eglError: 3009, this: 0x5564a7d9c0" error is happened.

  bool QWaylandGLContext::makeCurrent(QPlatformSurface *surface)
  {
      .... 
      QWaylandEglWindow *window = static_cast<QWaylandEglWindow *>(surface);
      EGLSurface eglSurface = window->eglSurface();
  
      if (!window->needToUpdateContentFBO() && (eglSurface != EGL_NO_SURFACE)) {
          if (!eglMakeCurrent(m_eglDisplay, eglSurface, eglSurface, m_context)) {
              qWarning("QWaylandGLContext::makeCurrent: eglError: %x, this: %p \n", eglGetError(), this);
              return false;
          }
          return true;
      }
  

  • 7.1) I guess that, the gl context of renderer thread is created with updated surface format by 4). But the eglSurface is created with the m_eglConfig. So, I guess that the EGL_BAD_MATCH(eglError: 3009) error is happened.
• 8) Of course, we can fix this issue like following, call the setColor(QColor(Qt::transparent)) before winId() call. And the following guide line was already mentioned by https://doc.qt.io/qt-5.15/qwindow.html#setFormat

  The surface format will be resolved in the create() function. Calling this function after create() has been called will not re-resolve the surface format of the native surface.

• 9) But, for the convenience usage for updating the surface format, I hope that the eglSurface is created by updated eglConfiguration with new surface format.

If you can, please consider the above issue when you improve this issue.