Dear Support-Team, 

I am working on an application where a QOpenGLWidget gets shown and hidden depending on the user input. I intended to use Multisampling. During the first showEvent(..) everything is fine, Calling showEvent(..) again leads to loss of the multisampling. I had a look at the source code of QOpenGLWidget. During the private call of QOpenGLWidgetPrivate::initialize(), the number of samples of the given QSurfaceFormat gets stored in a variable called "requestedSamples", while the number of samples in the stored QSurfaceFormat "requestedFormat" is overwritten with 0. (lines 813 .. 818)

The variable "requestedSamples" is then used in QOpenGLWidgetPrivate::restoreFBO(). This works for the first time the widget is shown. A second call to QOpenGLWidgetPrivate::initialize() leads to storing the overwritten number of samples (0) to the variable requestedSamples and with that it switches of multisampling. 

Best regards