Viewport overlap issue for multiple instance of openglunderqml causes erasing other

I have created two instances of Squircle(openglunderqml) item

First instance have size 500,500 alignment in center to screen

ex:Mini Player in preview

Second instance have size of screen size alignment to complete screen

ex:Main Player in viewer

Initially Main Player does noting will goto preview there we can see mini player user say ok will launch main player

But during preview I could not see mini player because main player glviewport covering complete screen and its clearing because paint is getting alway its is connected to beforeRendering signal

code:
http://doc.qt.io/qt-5/qtquick-sceneg...l-example.html

I followed above link and made small change glviewport according to instance boundary

Code:

glViewport(m_viewportSize.x(), m_viewportSize.y(), m_viewportSize.width(), m_viewportSize.height());

glclear update

Code:

glClearColor(0, 0, 0, 1);
 
    glScissor(m_ViewportSize.x(),m_ViewportSize.y(), m_ViewportSize.width(), m_ViewportSize.height());
 
    glEnable(GL_SCISSOR_TEST);
    glClear(GL_COLOR_BUFFER_BIT);
    glDisable(GL_SCISSOR_TEST);

main.qml

Code:

import QtQuick 2.0
import OpenGLUnderQML 1.0
 
Item {
    width: 1200
    height: 600
    Test{
        width: 500
        height: 500
        anchors.centerIn: parent
        color: "green"
    }
    Test{
        width: parent.width
        height: parent.height
        anchors.top: parent.top
        anchors.left: parent.left
        color: "red"
    }
}

Test.qml

Code:

import QtQuick 2.0
import OpenGLUnderQML 1.0
 
Rectangle {
 
    opacity: 0.2
    Squircle {
        SequentialAnimation on t {
            NumberAnimation { to: 1; duration: 2500; easing.type: Easing.InQuad }
            NumberAnimation { to: 0; duration: 2500; easing.type: Easing.OutQuad }
            loops: Animation.Infinite
            running: true
        }
    }
    //! [1] //! [2]
    Rectangle {
        color: Qt.rgba(1, 1, 1, 0.7)
        radius: 10
        border.width: 1
        border.color: "white"
        anchors.fill: label
        anchors.margins: -10
    }
 
    Text {
        id: label
        color: "black"
        wrapMode: Text.WordWrap
        text: "The background here is a squircle rendered with raw OpenGL using the 'beforeRender()' signal in QQuickWindow. This text label and its border is rendered using QML"
        anchors.right: parent.right
        anchors.left: parent.left
        anchors.bottom: parent.bottom
        anchors.margins: 20
    }
}

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