cannot resize window properly to 1/4 and resize back to original size

[saman_artorious]

I cannot resize window properly. when the minimize button is clicked,

this->setMaximumSize(400, 400);

this->setMaximumSize(400, 400);

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works, but it overwrites previous window and the other parts of the UI still remain on the screen. The ui does not become smaller. Similarly, when I click minimize again to maximize UI, it again does not become bigger to the original size

ui->widget_display->setGeometry(200, 0, 791, 800);

ui->widget_display->setGeometry(200, 0, 791, 800);

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. I used the update() method, but still does not render the mainwindow from the beginning.

void MainWindow::on_pushButton_clicked()
{
    if(minimized == false)
    {
    this->setMaximumSize(400, 400);
    ui->widget->hide();
    ui->widget_display->setGeometry(10, 10, 400, 400);
    minimized = true;
 
    update();
    }
    else
    {
        this->setMaximumSize(1152, 864);
        ui->widget->show();
        ui->widget_display->setGeometry(200, 0, 791, 800);
        minimized = false;
 
        update();
    }
 
    qDebug() << "Minimizing";
}

void MainWindow::on_pushButton_clicked()
{
    if(minimized == false)
    {
    this->setMaximumSize(400, 400);
    ui->widget->hide();
    ui->widget_display->setGeometry(10, 10, 400, 400);
    minimized = true;

    update();
    }
    else
    {
        this->setMaximumSize(1152, 864);
        ui->widget->show();
        ui->widget_display->setGeometry(200, 0, 791, 800);
        minimized = false;

        update();
    }

    qDebug() << "Minimizing";
}

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[wysota]

What is the purpose of using setMaximumSize() here?