Thanks Chris for your suggestion but I think it’s not the right feature.
I would like to draw a horizontal and vertical line according to the mouse cursor anywhere on the chart, not just at a data point on a trace.
Today, I cheat by having a transparent trace on my graph and by using the hover_data callback from the Graph object but it’s very slow if the graph contains many data points.
Thanks, unfortunately with spike option I need to keep my transparent trace on my graph.
I think it’s impossible to get the spike without having an hidden trace for the moment, isn’t it ?