一、控件阴影效果
为子部件添加阴影比较简单，使用如下方式：
QGraphicsDropShadowEffect *shadow_effect = new QGraphicsDropShadowEffect(this); shadow_effect->setOffset(-5, 5); shadow_effect->setColor(Qt::gray); shadow_effect->setBlurRadius(8); network_group_box->setGraphicsEffect(shadow_effect);
效果如下：
二、 窗口阴影效果（代码实现）
void DropShadowWidget::paintEvent(QPaintEvent *event)
{
QPainterPath path;
path.setFillRule(Qt::WindingFill);
path.addRect(10, 10, this->width()-20, this->height()-20);
QPainter painter(this);
painter.setRenderHint(QPainter::Antialiasing, true);
painter.fillPath(path, QBrush(Qt::white));
QColor color(0, 0, 0, 50);
for(int i=0; i<10; i++)
{
QPainterPath path;
path.setFillRule(Qt::WindingFill);
path.addRect(10-i, 10-i, this->width()-(10-i)*2, this->height()-(10-i)*2);
color.setAlpha(150 - qSqrt(i)*50);
painter.setPen(color);
painter.drawPath(path);
}
}
三、窗口阴影效果（图片绘制）
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！
效果如下：
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));
}