element.getComputedStyle returns null in Firefox iFrame with display:none

[drewjenkins]

Do you want to request a feature or report a bug?
Bug

What is the current behavior?
When DraftJS calls getLineHeightPx in expandRangeToStartOfLine.js, it uses getComputedStyle, which in Firefox potentially returns null, due to a documented Firefox issue found here https://bugzilla.mozilla.org/show_bug.cgi?id=548397

What is the expected behavior?
Don't assume getComputedStyle will return an object.

Which versions of Draft.js, and which browser / OS are affected by this issue? Did this work in previous versions of Draft.js?
All Firefox

This is a pretty severe bug in our app, since DraftJS is the main place the enduser does their input. We can work around it now by doing what was suggested here https://bugzilla.mozilla.org/show_bug.cgi?id=548397#c8 but it is a pretty hacky workaround

[flarnie]

Thanks for the great info! Sounds like there could be an easy fix? Would you like to submit a PR?

Also for your awareness - If you are using Draft.js inside of an iframe I think there are other potential problems that you will encounter. It's worth taking a look at #765 and also facebook/react#12037

So while we're working towards full support of rendering inside iframes, there are some known issues with that use case.

[johnmryan]

Any update on this issue? I am running into a similar problem because of this Firefox API behavior:

https://github.com/facebook/draft-js/blob/main/src/component/selection/setDraftEditorSelection.js#L136

selection is null in Firefox here when the iframe is display:none, so we get a type error here. Would you be willing to review a PR to default to an empty object if the browser returns null for the Selection?