QPen画笔

QPen用户绘图时对线条进行设置，包括线宽、颜色、线型等。

void setColor(const QColor &color)	设置画笔颜色，即线条颜色
void setWidth(int width)	设置线条宽度
void setStyle(Qt::PenStyle)	设置线条样式
void setCapStyle(Qt::PenCapStyle pcs)	设置线条端点样式
void setJoinStyle(Qt::PenJoinStyle pcs)	设置连接样式

1. 线条样式：Qt::PenStyle

Qt::NoPen	0	no line at all. For example, QPainter::drawRect() fills but does not draw any boundary line.
Qt::SolidLine	1	A plain line.
Qt::DashLine	2	Dashes separated by a few pixels.
Qt::DotLine	3	Dots separated by a few pixels.
Qt::DashDotLine	4	Alternate dots and dashes.
Qt::DashDotDotLine	5	One dash, two dots, one dash, two dots.
Qt::CustomDashLine	6	A custom pattern defined using QPainterPathStroker::setDashPattern().

除上述几种基本线条样式外，可以自定义线条样式，自定义线条样式时需要用到setDashOffset()和setDashPattern()函数。

2. 线条端点样式：Qt::PenCapStyle

Qt::FlatCap	0x00	不包含最后一个点
Qt::SquareCap	0x10	是一种包含了最后一个点的方形端点，使用半个线宽覆盖
Qt::RoundCap	0x20	是包含最后一个点的圆形端点

 

3. 线条连接样式：Qt::PenJoinStyle

Qt::MiterJoin	0x00	The outer edges of the lines are extended to meet at an angle, and this area is filled.
Qt::BevelJoin	0x40	The triangular notch between the two lines is filled.
Qt::RoundJoin	0x80	A circular arc between the two lines is filled.