Yep, this is the case. What I am planning at this point is following.

Plotters doesn't directly response any event, however, Plotters helps to dispatch events. But handling a event should be out of Plotters' scope.

Let's say, if there's an point element in the drawing area, once a click event is acknowledged by whatever UI infrastructure (e.g HTML canvas or GTK, etc), we should expose a function that accepts a event (type, pixel coordinate, etc... e.g. Hover(100,100)), and returns the dispatched event like Hover on a particular element.

It's pretty much like something happens here https://github.com/38/plotters/blob/98c78d84579edade6f55335748141d82d8177745/examples/wasm-demo/www/index.js#L47 (P.S. This is exactly my prototype of interactivity back to the very early days of Plotters)

So I think if you need a bubble tooltip, probably we can use two layers of canvas and one for the actual plot and another for the tool tips and the code might be like.

function onMouseHover(event) {
      var dispatched_event = chart.dispatch_event(event));
      if(dispatched_event != null && dispatched_event.element_type = "point") {
            draw_tooltip(....);
      }
}

And ideally, the interactivity shouldn't be related to the backend - Since it's application's responsibility to decide whatever they need to do, Plotters is only responsible for identify the event and dispatch it.

That's what I mean by saying add a model layer - A data structure that tracking interactive elements has been drawn to the chart. And once a event is feed into Plotters, it query the data structure and figure out which interactive element should response to this.

And we can provide some standard helper javascript, so that people can do zoom, tooltips, etc very easily. I believe this is the second step.

This idea is actually in my mind for almost one year, but it still only a rough plan. Please let me know if you feel anything isn't right.

Thanks so much!

[feature request] Interactivity #13

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