Screen blink when App go out from full screen in OpenGL

mmonlab

Hello.

I am having trouble when my application goes to full screen and goes out.
I have 3 displays and I am trying to use OpenGL in my application.
For doing this I am using QApplication::setAttribute(Qt::AA_UseOpenGLES, false);
Drivers in my system supports OpenGL ES 2.0 and every thing looks good except when app goes to full screen.

If I use QApplication::setAttribute(Qt::AA_UseOpenGLES, true), it works propertly.
When I select 'false' or comment this line, three of screen suffer of a awful blink when app goes to fulscreen and more than one blinks when app goes out from full screen.

I thought it was a problem of my app, so I have created a small example to prove it:

C++:
#include <QQmlApplicationEngine>
#include <QtWidgets/QApplication>
#include <QQuickView>

#define QtQuickControlsApplication QApplication
#define qApp (static_cast<QtQuickControlsApplication *>(QtQuickControlsApplication::instance()));

int main(int argc, char *argv[])
{
QtQuickControlsApplication app(argc, argv);
app.setQuitOnLastWindowClosed(true);

//CHANGE THIS BOOLEAN TO 'FALSE' TO REPRODUCE BLINK WHEN GO OUT FROM FULLSCREEN
bool bANGLE_Active = true;
QtQuickControlsApplication::setAttribute(Qt::AA_UseOpenGLES, bANGLE_Active);

//show QML
QQmlApplicationEngine* pEngine = new QQmlApplicationEngine();
pEngine->load(QUrl(QStringLiteral("qrc:/resources/ExampleFullScreen.qml")));

return app.exec();

}

QML:
import QtQuick 2.0
import QtQuick.Controls 1.4
import QtQuick.Window 2.2 // Window.FullScreen
import QtQuick.Controls.Styles 1.3
import QtGraphicalEffects 1.0

ApplicationWindow
{
id: root
objectName: "callToolBar"

visible: true

color: "yellow"
height: 140
width: 400

Rectangle
{
    anchors.fill: parent
    color: "red"
}

// Centered buttons
Row
{
    id: buttons

    anchors { bottom: parent.bottom; bottomMargin: 25; horizontalCenter: parent.horizontalCenter }

    visible: true
    width: childrenRect.width
    height: 50
    spacing: 10
    Button
    {
        id: button2
        text: "Button change visibility"
        onClicked:
        {
            if(root.visibility !== Window.FullScreen)
                root.visibility = Window.FullScreen;
            else
                root.visibility  = Window.Windowed;
        }
    }
}

}

If bANGLE_Active = true, it works.
if bANGLE_Active = false it blinks.

Any ideas??

mmonlab

@mmonlab :
I have reported this issue to QT:
https://bugreports.qt.io/browse/QTBUG-61838