Spike position in unified hover mode

[emmanuelle]

https://codepen.io/emmanuelle-plotly/pen/eYNxQba?editable=true (hover on the scatter point at x=0, the spike line stays at the middle of the bar)

[archmoj]

Is this really a bug?

[alexcjohnson]

If there's a hover label, the spikeline should get its position from something within that label. In this case the bar is setting the spikeline position, but only the scatter point is in the hover label.

[nicolaskruchten]

Definitely a bug, because it doesn't happen if the cursor or point is above the bar rather than within it.

[nicolaskruchten]

Compare hovering over the scatter points within the two bars' ranges here: https://codepen.io/nicolaskruchten/pen/abZrYJO?editors=0010

[nicolaskruchten]

Note that the behaviour in hovermode: "x" with xaxis.showspikes: true is also pretty bad: https://codepen.io/nicolaskruchten/pen/yLVQXYy?editors=0010

[nicolaskruchten]

Can I see a pen with just this PR please so I can approve this one's behaviour separately from the other one? (it was nice to see them together as well, but now I'd like to see just this one broken out please :)

[archmoj]

Can I see a pen with just this PR please so I can approve this one's behaviour separately from the other one? (it was nice to see them together as well, but now I'd like to see just this one broken out please :)

Here is a before vs after codepen.

[nicolaskruchten]

✨ for the behaviour! just need a dancer from @alexcjohnson and then we can tackle #5292 on its own

[archmoj]

#5542 is merged.
@nicolaskruchten you may close this.