为什么jsxgraph抛物线不能很好地渲染虚线？

Question

比较抛物线渲染和directrix的渲染-它已经正确地渲染了破折号。我只看过抛物线的这个问题。使用dash时，所有其他对象似乎都工作得很好。

https://jsfiddle.net/8df1n2me/

var point1 = board.create('point', [0,3])
var point2 = board.create('point', [-3,1])
var point3 = board.create('point', [3,1])

var directrix = board.create('line', [point2, point3], {fixed:false,dash:2, strokeWidth:1})

var parabola2Params = {
    dash: 2,
    strokeWidth: 1,
  fixed: false
}
var parabola2 = board.create('parabola', [point1, directrix],parabola2Params)

Answer 1

这是1.2.2之前的所有版本中的错误。该错误现在已在https://github.com/jsxgraph/jsxgraph的1.2.3分支中修复。一种快速的解决方法是将绘图限制为间隔0，2π，即将代码更改为：

var point1 = board.create('point', [0,3])
var point2 = board.create('point', [-3,1])
var point3 = board.create('point', [3,1])

var directrix = board.create('line', [point2, point3], {fixed:false,dash:2, strokeWidth:1})

var parabola2Params = {
    dash: 2,
    strokeWidth: 1,
  fixed: false
}
var parabola2 = board.create('parabola', [point1, directrix, 0, 2*Math.PI], parabola2Params);