Fix (finally) bug with tooltips when multiple charts on one page.

[ralphwetzel]

Hi!
I as well encountered #88, yet #89 hasn't solved the issue for me.
Therefore I created this minor mod to fix #88 finally.

Best Regards, Ralph

[drewnoakes]

Looks good. Can you explain why you renamed the callback properties?

[ralphwetzel]

With the current implementation I've seen something best described as a scoping issue.

1. mousemove is used to name a property as well as a function.
2. this.canvas.addEventListener('mousemove', this.mousemove); was intended to provide the property as callback for the event. It yet provided the (raw) function.
3. As a result, when the event called the callback function for the first time, var el = this.getTooltipEl(); found no associated this.tooltipEl and created an additional one.
4. All the manipulations in SmoothieChart.prototype.mousemove were then affecting this wrongly created, additional tooltip item.

The easiest way - for me - to compensate for that misbehavior was to get rid of the potential ambiguity due to the scope by defining an explicit name for the callback properties.

[drewnoakes]

mousemove is a property, the value of which is a function. I don't believe there's any reason to rename it as such, though I might be missing something. Any issue around scoping likely applies to the value of this, which is why it we use .bind(this) when re-assigning it to itself.

The SmoothieChart.tooltipEl to this.tooltipEl change is definitely a bug fix though. I've merged that as 59521ce.

If you believe there's still a bug, please provide a repro for it.

[ralphwetzel]

I am patching SmoothieChart ... and this definitely creates an issue with the scope of this.
Yet, as I found a way to solve this within my patch, there's no more need to alter your code.