#2371: Not disabling scrollZoom when page (plot) has scroll bar

[marfoldi]

Used to disable scrollzoom when the plot had scrollbars. Ended up with a plot which is not zoomable with mouse scroll on a page which had additional content (had a scrollbar).

[etpinard]

Thanks for the PR!

I'm a little confused with some of the reports in #2371. Would you sharing an example of the situation you're trying to solve?

[marfoldi]

Sure. The scrollToZoom/PinchToZoom is not working (tested on Windows and on Android) when the page is scrollable (the piece of code which I just removed disables it). You can mimic the behavior by opening e.g. the following page: https://codepen.io/plotly/pen/QjKZbg and after the plot is loaded you resize your window. Also when I've opened the issue I've linked an example (http://marfoldi.web.elte.hu/plotly) which contains multiple plots (if you have a kinda regular resolution there should be a scrollbar on page) and none of the plots are zoomable by scrolling (however all of them has the scrollZoom: true property).

[etpinard]

Thanks again for the PR and let me apologize for the delayed response (our 1.42.0 release cycle was a little hectic).

I think I agree that from a pure plotly.js standpoint your patch does indeed fix a bug. As scrollZoom is false by default, we should honor scrollZoom:true no matter what. Now unfortunately, the code you're 🔪 is ancient: there might some apps in the wild that depend on this extra "scroll-or-not-to-scroll" logic.

So, I'll suggest making the scollZoom config option accept another value. I'm thinking scrollZoom: 'always' would always activate scroll and scrollZoom: true would behave the same as currently.

[etpinard]

Hmm. But the comment says if the *plot had scrollbars, not if the page has some.

Maybe we aren't using the correct DOM properties.

[etpinard]

So in https://codepen.io/plotly/pen/QjKZbg,

on full-screen I got:

but after resize to half-screen-width, I get e.g.

---

So perhaps we should compare pc.scrollWidth with fullLayout.width and pc.scrollHeight with fullLayout.height to determine if scroll should be activated.

[etpinard]

Now in #3424 - thanks again @marfoldi !