The diagram serves its purpose, but it looks a bit dull. Add some shine to it by defining three new color properties in the canvas object–color, topColor, bottomColor–and setting their default values to black, red, and blue, respectively.
Since points and arg should not really be public properties that anyone can change behind our backs, we'll correct it now. Declare a child element of the canvas of QtObject and set its ID to priv. Move declarations of points and arg inside that object. Move the onArgChanged handler there, as well:
QtObject {
id: priv
property var points: []
property real arg: -Math.PI
onArgChanged: {
points.push(func(arg))
points = points.slice(-canvas.width)
canvas.requestPaint()
}
}Then, search through the whole code and prefix all occurrences of arg and points outside the newly declared object with priv, so that each of their invocations lead to the priv object.