Expose onResize hook in gemini-scrollbar

[richvdh]

This exposes the onResize hook added by noeldelgado/gemini-scrollbar#26.

[noeldelgado]

Thanks for the pull request @richvdh. I am not sure if this approach will work for React components, since we will be creating nodes in componentDidMount (the new element) which goes against React rules. We may need to explicitly put the new element in the render method and make sure gemini doesn't try to create this element again.

Will do some tests and see how it goes. For now I updated this package to use gemini v1.3.x so the window.resize event is still attached.

[richvdh]

In my testing, I found that trying to create the object element in render gave some very strange results, as I alluded to here.

Creating the new element in componentDidMount should be fine - once react has created the GeminiScrollbar, it doesn't need to look at the children of the DOM element. I wasn't able to find a reference to this being against the rules.

[richvdh]

@noeldelgado: any feedback on this?

[noeldelgado]

@richvdh: sorry, I haven't had time, I will try to check it this week.

[noeldelgado]

Hi @richvdh, I just check it and found out a problem when the render method depends on state (setState...), the result is that React will re-render the whole thing losing the scroll position (scrolling up), I'm thinking about adding an extra option to tell gemini-scrollbar to do not dynamically add the resizer object (something like _addResizeObject: <Boolean[true]>) so React does not render the whole tree on every update, this option is suppose to be used by us specifically (kinda a private option) and not by other users. I will be working on this in the following days, if you want to see a working example of what I am referring to, let me know, I will try to publish it. Thank you so much for your contribution.

[richvdh]

@noeldelgado: I'm not sure I follow you.

It's certainly true that setState will make React re-render (that's kinda the point). But that shouldn't make the browser lose the scroll position, because the DOM shouldn't change (much). Our application does a setState on parent components of the gemini-scrollbar all the time, without problems. Do you have a demonstration of the problem?

[noeldelgado]

Hi, @richvdh,

Sorry for the late response. I just tried this change once again and it works as expected, so I'll proceed to merge it.

Thanks.