//barchart and simpleplot
bool QObject::connect (
const QObject * sender, const QMetaMethod & signal,
const QObject * receiver, const QMetaMethod & method,
Qt::ConnectionType type = Qt::AutoConnection ) [static]
Creates a connection of the given type from the signal in the sender object to the method in the receiver object.
prompt $s$g //
gdb xxx
break xxx
run
bt
gdb n //step by step
print variable//
c // continuing
q //quit
How does the 'ls' command work in Linux/Unix?
Legend（图例）
使用方法是先 new 一个QwtLegend 类
然后使用setItemMode 来确定Legend的模式。
最后调用Plot中的insertLegend方法，将Legend插入