Warnings on b-form-select open/close in recent Chrome

[chrismurf]

To recreate:
Go to https://bootstrap-vue.js.org/play/ in Chrome v66 (I believe v51 or newer) and enter the following template:

  <b-form-select>
      <option>Sample</option>
  </b-form-select>

Then open and close the resulting select input several times.

Expected:
Developer console free of warnings and errors.

Actual:
See the following warning in the JavaScript console:

[Violation] Added non-passive event listener to a scroll-blocking 'mousewheel' event. Consider marking event handler as 'passive' to make the page more responsive. See https://www.chromestatus.com/feature/5745543795965952

[chrismurf]

See https://github.com/WICG/EventListenerOptions/blob/gh-pages/explainer.md for a better explanation of the cause.

[itsGabriel]

Any news?

[tmorehouse]

I don't think we add any mousewheel events to b-form-select, but we will investigate

[a21ns1g4ts]

I have error in b-form-select:
[Violation] Added non-passive event listener to a scroll-blocking 'mousewheel' event. Consider marking event handler as 'passive' to make the page more responsive. See https://www.chromestatus.com/feature/5745543795965952

[tmorehouse]

I'm still not sure what would be causing this. b-form-select does not instantiate any 'mousewheel' listeners at all. It has to be something else adding them in.

Do you have any other plugins that may be installing listeners (such as validation)?

[tmorehouse]

I think it might be docs use of v-b-scroll-spy directive... which monitors the page scrolling to highlight the current page section TOC (on the right hand side).

We'll have to update our eventOn handler to detect support of the passive option (not all browsers support it, and if present treat it as wanting to use capture mode).

Will see what we can do over the next week.

[jacobmllr95]

Is this still an issue in Chrome v70? I can't reproduce this.

[tmorehouse]

I think you need to set a flag/option in developer tools to show the warnings.

I know code-mirror editor uses non passive events, which will also show up.

[jacobmllr95]

@tmorehouse I have all log-levels selected.

[tmorehouse]

Ok, maybe it is because v70 (I think) defaults most document listeners to passive by default.

[tmorehouse]

My work laptop still has chrome v60 (can't update it as it is controlled by work IT department), and I see the warning crop up once and a while.