C++ (Qt)
class MyFrame:public QFrame
{
Q_OBJECT
public:
    Q_PROPERTY(bool headerPressed READ getHeaderPressed WRITE setHeaderPressed NOTIFY headerPressedChanged)
 
    MyFrame(QWidget *parent = 0):QFrame(parent){
        setProperty("headerPressed",false);
        setStyleSheet(
                       "MyFrame{"
                       "background-color: blue;}"
                        "MyFrame[headerPressed=true]{"
                       "background-color: red;}");
    }
 
    bool is_pressed;
    bool getHeaderPressed() const{return is_pressed;}
    void setHeaderPressed(bool pressed){ is_pressed=pressed;}
 
    void mouseReleaseEvent(QMouseEvent *){
        setProperty("headerPressed",false);
        emit headerPressedChanged(false);
    }
    void mousePressEvent(QMouseEvent *)
    {
        setProperty("headerPressed",true);
        emit headerPressedChanged(true);
    }
signals:
    void headerPressedChanged(bool);
};