Line chart dataset color should be scriptable for each section of the line

[hrabalp]

Feature Proposal

Line-chart dataset color should be scriptable for each section, currently only fixed color or gradient is applicable

Feature Use Case

Lets asume we have Devicename as axis y, and time as axis x. now we would like to express type of activity of the device with the color, currently this is possible only for point by usage of callbacks, i would like to do the same for line color for better visibility

Possible Implementation

I would sugest spliting line borderColor from Point borderColor and make line borderColor scriptable as well (currently borderColor is used for both)

https://jsfiddle.net/Zmrzlinka/gqfe52Lj/18/ - showcase working for datapoint but not for line

[benmccann]

Line borderColor is scriptable in 3.0: https://www.chartjs.org/samples/next/advanced/line-gradient.html

I'm not sure if you can specify a different borderColor for line and point though

[etimberg]

I think this is asking for the line colour to change between points rather than a single colour for the line

[hrabalp]

there are 2 aspects of this issue. I am currently using 2.9.3 and borderColor is scriptable there already but it behaves confusingly
its called once for interactive tooltip (context.dataIndex undefined), once for line color (context.dataIndex undefined), and than its called for each point (context.dataIndex set to number). This is very fine when you have whole dataset with one color. but once you use scriptable callback it gets confusing in a hurry.
@benmccann I was looking at line gradient but that is not my answer I need sharp chnages of the color (when you turn of device than change of state is immidiate and not gradient)
@etimberg absolutly correct, this is my primary request / concern

[frfancha]

We must add a lineColor property, otherwise for point N you can't give a different color for the border around the point itself and the color for the line segment starting at that point