阴影边框很常见，诸如360以及其他很多软件都有类似效果，了解CSS3的同学们应该都知道box-shadow，它就是来设定阴影效果的，那么Qt呢？看过一些资料，说是QSS是基于CSS2的，既然如此，box-shadow是基于CSS3的！那么Qt定然就用不了！

搜了一些资料，每张图片都做成阴影效果的固然不可能，直接舍弃（即使可以，也不采纳）。如果实时的去画图，效率太低，最后选择了拼图的方式！

左上角、左下角、右上角、右下角、上、下、左、右，这几个方向都绘制对应的图即可！

#include "shadow_widget.h"

ShadowWidget::ShadowWidget(QWidget *parent)
    : QDialog(parent)
{
   setWindowFlags(Qt::FramelessWindowHint | Qt::Dialog);
   setAttribute(Qt::WA_TranslucentBackground);
}

ShadowWidget::~ShadowWidget()
{

}

void ShadowWidget::paintEvent(QPaintEvent *event)
{
    QPainter painter(this);
   this->drawShadow(painter);
   painter.setPen(Qt::NoPen);
   painter.setBrush(Qt::white);
   painter.drawRect(QRect(SHADOW_WIDTH, SHADOW_WIDTH, this->width()-2*SHADOW_WIDTH, this->height()-2*SHADOW_WIDTH));
}

void ShadowWidget::drawShadow(QPainter &painter)
{
   //绘制左上角、左下角、右上角、右下角、上、下、左、右边框
    QList pixmaps;
   pixmaps.append(QPixmap(":/shadow/shadow_left"));
   pixmaps.append(QPixmap(":/shadow/shadow_right"));
   pixmaps.append(QPixmap(":/shadow/shadow_top"));
   pixmaps.append(QPixmap(":/shadow/shadow_bottom"));
   pixmaps.append(QPixmap(":/shadow/shadow_left_top"));
   pixmaps.append(QPixmap(":/shadow/shadow_right_top"));
   pixmaps.append(QPixmap(":/shadow/shadow_left_bottom"));
   pixmaps.append(QPixmap(":/shadow/shadow_right_bottom"));

    painter.drawPixmap(0, 0, SHADOW_WIDTH, SHADOW_WIDTH, pixmaps[4]);
   painter.drawPixmap(this->width()-SHADOW_WIDTH, 0, SHADOW_WIDTH, SHADOW_WIDTH, pixmaps[5]);
   painter.drawPixmap(0,this->height()-SHADOW_WIDTH, SHADOW_WIDTH, SHADOW_WIDTH, pixmaps[6]);
   painter.drawPixmap(this->width()-SHADOW_WIDTH, this->height()-SHADOW_WIDTH, SHADOW_WIDTH, SHADOW_WIDTH, pixmaps[7]);
    painter.drawPixmap(0, SHADOW_WIDTH, SHADOW_WIDTH, this->height()-2*SHADOW_WIDTH, pixmaps[0].scaled(SHADOW_WIDTH, this->height()-2*SHADOW_WIDTH));
   painter.drawPixmap(this->width()-SHADOW_WIDTH, SHADOW_WIDTH, SHADOW_WIDTH, this->height()-2*SHADOW_WIDTH, pixmaps[1].scaled(SHADOW_WIDTH, this->height()- 2*SHADOW_WIDTH));
   painter.drawPixmap(SHADOW_WIDTH, 0, this->width()-2*SHADOW_WIDTH, SHADOW_WIDTH, pixmaps[2].scaled(this->width()-2*SHADOW_WIDTH, SHADOW_WIDTH));
   painter.drawPixmap(SHADOW_WIDTH, this->height()-SHADOW_WIDTH, this->width()-2*SHADOW_WIDTH, SHADOW_WIDTH, pixmaps[3].scaled(this->width()-2*SHADOW_WIDTH, SHADOW_WIDTH));
}

 写一个公共的类，如果窗口要实现阴影效果直接继承就行了！SHADOW_WIDTH为阴影边框的像素，可以根据自己的需求自由调节！

   也可使用QGraphicsDropShadowEffect来实现。。。