很簡(jiǎn)單直接上代碼：
#include <dwmapi.h> // DWM APIs
#pragma comment(lib, "dwmapi") //DWM library
class MainWindow : public QMainWindow
{
public:
MainWindow()
{
QPushButton *b = new QPushButton("click me!", this);
MARGINS mar = {40, 40, 100, 100}; //left, right, top, bottom margins.
DwmExtendFrameIntoClientArea ( this->winId(), &mar ); //set the margins
}
void paintEvent ( QPaintEvent * event )
{
QPainter p(this);
p.setCompositionMode(QPainter::CompositionMode_DestinationIn); //it's necessary!
QRect rc = this->rect();
p.fillRect(rc, QColor(0, 0, 0, 0)); //the RGB color is not the point, the alpha value is.
}
};
int main(int argc, char *argv[])
{
QApplication app(argc, argv);
MainWindow mw;
mw.show();
app.exec();
}