gridlayout unwanted display

[PstdEr]

Hi below is my application
LoadApplication loads a set of pushbuttons in Gridlayout
nss1.jpeg is the window once LoadApplication is completed.

#include "mainwindow.h"
#include <QtGui>
class QCalendarWidget;
 
void MainWindow::LoadApplication()
{
    int a[] = {0,0,0,1,1,1,2,2,2};
    int b[] = {3,6,9,3,6,9,3,6,9};
 
    if(button[0]){
        delete button[0],button[0]=NULL;
        delete previewGroupBox,previewGroupBox=NULL;
        delete previewLayout,previewLayout=NULL;
        delete calendar,calendar=NULL;
 
        if (Gh)
            delete Gh,Gh=NULL;
    }
 
    if(!Gh){
            Gh = new QGridLayout();
            display -> setLayout(Gh);
    }
 
    for(int i = 0; i < 9; i++)
        {
            button[i] = new QPushButton(QIcon("qt4.png"),NULL,this);
            button[i] -> setIconSize(button[i]->rect().size());
            Gh -> addWidget(button[i],a[i],b[i],1,3);
            button[i]  -> setGeometry(a[i],b[i],100,100);
            button[i]  -> setMaximumSize(100,100);
            connect(button[i],SIGNAL(clicked()),this,SLOT(fun()));
        }
}

#include "mainwindow.h"
#include <QtGui>
class QCalendarWidget;

void MainWindow::LoadApplication()
{
    int a[] = {0,0,0,1,1,1,2,2,2};
    int b[] = {3,6,9,3,6,9,3,6,9};

    if(button[0]){
        delete button[0],button[0]=NULL;
        delete previewGroupBox,previewGroupBox=NULL;
        delete previewLayout,previewLayout=NULL;
        delete calendar,calendar=NULL;

        if (Gh)
            delete Gh,Gh=NULL;
    }

    if(!Gh){
            Gh = new QGridLayout();
            display -> setLayout(Gh);
    }

    for(int i = 0; i < 9; i++)
        {
            button[i] = new QPushButton(QIcon("qt4.png"),NULL,this);
            button[i] -> setIconSize(button[i]->rect().size());
            Gh -> addWidget(button[i],a[i],b[i],1,3);
            button[i]  -> setGeometry(a[i],b[i],100,100);
            button[i]  -> setMaximumSize(100,100);
            connect(button[i],SIGNAL(clicked()),this,SLOT(fun()));
        }
}

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the fun is used to delete the layouts and buttons so that the calendar can be launched.
so nss2.jpeg is window after this fun is called.

but here i observe some strange thing .
even after deleting buttons i can see some buttons in the background.
in the attached jpeg this can be seen clearly..

i need help in understanding , from where those buttons are coming.

//void MainWindow ::fun(int i)
void MainWindow ::fun()
{
 
    for(int i=0;i<9;i++)
        if(button[i])
            delete button[i],button[i]=NULL;
    if (Gh)
        delete Gh,Gh=NULL;
 
    Gh = new QGridLayout;
    display->setLayout(Gh);
    createPreviewGroupBox();
    Gh->addWidget(previewGroupBox, 0, 0);
 
    button[0] = new QPushButton(QIcon("qt4.png"),NULL,this);
    Gh -> addWidget(button[0],3,2,1,3);
     button[0]  -> setGeometry(3,2,100,100);
     button[0]  -> setMaximumSize(50,50);
     connect(button[0],SIGNAL(clicked()),this,SLOT(LoadApplication()));
 
}

//void MainWindow ::fun(int i)
void MainWindow ::fun()
{

    for(int i=0;i<9;i++)
        if(button[i])
            delete button[i],button[i]=NULL;
    if (Gh)
        delete Gh,Gh=NULL;

    Gh = new QGridLayout;
    display->setLayout(Gh);
    createPreviewGroupBox();
    Gh->addWidget(previewGroupBox, 0, 0);

    button[0] = new QPushButton(QIcon("qt4.png"),NULL,this);
    Gh -> addWidget(button[0],3,2,1,3);
     button[0]  -> setGeometry(3,2,100,100);
     button[0]  -> setMaximumSize(50,50);
     connect(button[0],SIGNAL(clicked()),this,SLOT(LoadApplication()));

}

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this is for standard calendar widget

void MainWindow::createPreviewGroupBox()
{
    previewGroupBox = new QGroupBox(tr("Preview"));
 
    calendar = new QCalendarWidget;
    calendar->setMinimumDate(QDate(1900, 1, 1));
    calendar->setMaximumDate(QDate(3000, 1, 1));
    calendar->setGridVisible(true);
 
    connect(calendar, SIGNAL(currentPageChanged(int,int)),
            this, SLOT(reformatCalendarPage()));
 
    previewLayout = new QGridLayout;
    previewLayout->addWidget(calendar, 0, 0, 0);//Qt::AlignCenter);
    previewGroupBox->setLayout(previewLayout);
}

void MainWindow::createPreviewGroupBox()
{
    previewGroupBox = new QGroupBox(tr("Preview"));

    calendar = new QCalendarWidget;
    calendar->setMinimumDate(QDate(1900, 1, 1));
    calendar->setMaximumDate(QDate(3000, 1, 1));
    calendar->setGridVisible(true);

    connect(calendar, SIGNAL(currentPageChanged(int,int)),
            this, SLOT(reformatCalendarPage()));

    previewLayout = new QGridLayout;
    previewLayout->addWidget(calendar, 0, 0, 0);//Qt::AlignCenter);
    previewGroupBox->setLayout(previewLayout);
}

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