Editing frameless window in Qt - c++

Question

I've been created a frameless window in Qt that have widgets and background. but i have a problem in that form, when i resize form all widgets resize good but background not
See this pic for demonstration
When no resize occured:
http://0000.2.img98.net/out.php/i20624_no-resize.jpg
when resize occured:
http://0000.2.img98.net/out.php/i20625_with-resize.jpg
and here is my code for creating Form:
#ifndef MYWIDGET_H
#define MYWIDGET_H
#include <QPushButton>
#include <QLabel>
#include <QComboBox>
#include <QPixmap>
#include <QVBoxLayout>
#include <QPainter>
#include <QMouseEvent>
#include <QtGui>
#include <QSizeGrip>
class MyWidget : public QWidget {
Q_OBJECT
private:
QPushButton* button;
QLabel* label;
QComboBox* combobox;
QPixmap pixmap;
public:
explicit MyWidget(QWidget *parent = 0) : QWidget(parent, Qt::FramelessWindowHint)
{
// Create some controls
button = new QPushButton();
label = new QLabel();
combobox = new QComboBox();
QVBoxLayout* l = new QVBoxLayout();
l->addWidget(button);
l->addWidget(label);
l->addWidget(combobox);
QSizeGrip *grip = new QSizeGrip(parent);
l->addWidget(grip, 0, Qt::AlignBottom | Qt::AlignRight);
setLayout(l);
resize (400, 500);
setAttribute(Qt::WA_TranslucentBackground); // enable translucent background
pixmap = QPixmap("./1.png");
}
protected:
virtual void paintEvent (QPaintEvent* event) {
QPainter painter(this);
painter.setPen(Qt::NoPen);
painter.setBrush(QColor(0, 0, 0, 0));
QRect rec = pixmap.rect();
painter.drawRect(this->rect());
painter.drawPixmap(this->rect(), pixmap, rec);
}
private:
bool pressed;
QPoint mousePressPoint;
protected:
virtual void mousePressEvent ( QMouseEvent * event ) {
QWidget::mousePressEvent(event);
if (!pressed) {
pressed = true;
mousePressPoint = event->pos();
}
}
#endif // MYWIDGET_H

Answer 1

Since your controls are centered in the window but don't look like they are, it might indicate that there is a transparent border around the non-transparent part of the image you are using as background.
You can remove the transparency from the brush in paintEvent to confirm that, with, for example:
painter.setBrush(QColor(0, 0, 0, 255));
To be more clear, the problem is not in your code, but in the image: open the image with an editor, select only the non-transparent part, keep only that part by using the "cropping tool", and finally save the image.