void Plotter::paintEvent(QPaintEvent * /* event */)
{
QStylePainter painter(this);
painter.drawPixmap(0, 0, pixmap);

if (rubberBandIsShown) {
painter.setPen(palette().light().color());
painter.drawRect(rubberBandRect.normalized()
.adjusted(0, 0, -1, -1));
}

if (hasFocus()) {
QStyleOptionFocusRect option;
option.initFrom(this);
option.backgroundColor = palette().dark().color();
painter.drawPrimitive(QStyle::PE_FrameFocusRect, option);
}
}

void Plotter::resizeEvent(QResizeEvent * /* event */)
{
int x = width() - (zoomInButton->width()
+ zoomOutButton->width() + 10);
zoomInButton->move(x, 5);
zoomOutButton->move(x + zoomInButton->width() + 5, 5);
refreshPixmap();
}

int main(){... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ...}