Qt设置背景颜色，QLabel，QWidget……

void setBackground(QWidget* widget, const QBrush& brush)
{
  QPalette palette(widget->palette());
  palette.setBrush(QPalette::Background, brush);
  widget->setAutoFillBackground(true);
  widget->setPalette(palette);
}

void setBackground(QWidget* widget, const QGradient& gradient)
{
  setBackground(widget, QBrush(gradient));
}

void setBackground(QWidget* widget, const QColor& color)
{
  setBackground(widget, QBrush(color));
}

void setBackground(QWidget* widget, Qt::GlobalColor color)
{
  setBackground(widget, QBrush(color));
}