Browser, Electron restore widgets differently on show

[colin-grant-work]

Bug Description:

A propos #8077, the behavior of the Preferences Widget, and perhaps React widgets more generally, is different in when Theia is run in the browser and when it is run in Electron. Here is an example of the scrollTop of the preferences-editor-widget during switch from that widget to another editor widget and back.

Here's the browser during a show-hide sequence:

And here's Electron with the same code:

Steps to Reproduce:

1. Running in the browser,
2. Open the preferences widget
3. In the main pane, scroll down to an arbitrary point
4. Open another editor widget and switch focus to that widget (at this point, do not enter Zen mode by double-clicking on a widget tab. If you do that, your scroll will be lost on both platforms)
5. Switch focus back to the preferences widget.
6. Observe that your scroll position was preserved
7. Repeat in Electron, observe that your scroll position was lost.

Additional Information

• Operating System: RHEL 7
• Theia Version: 1.2.0

[vince-fugnitto]

@colin-grant-work I opened the following issue but I'll keep yours opened since it has additional information: #8077 :)

[colin-grant-work]

@vince-fugnitto, yes, sorry it took me a while to open the issue!

[vince-fugnitto]

@colin-grant-work I believe the issue has been fixed, I cannot reproduce it any longer.

[colin-grant-work]

I can't reproduce it either. 👍