Bug Description:

In Theia IDE, tree views like the Explorer cannot be scrolled: there is an overlay covering 100% coming in when hovering over the the vertical scroll bar.

Steps to Reproduce:

1. Open the navigator on a Theia repo, expand node_modules
2. Observe: you get a scroll bar with a thumb of some length
3. Try to grab the scroll-thumb and move it
4. Observe: you can't.

Additional Information

• Operating System: Windows 11
• Theia Version: 1.56.1 Theia IDE

Since we can't fix this for adopters who build their own Theia-based products, I've sent the following message to the dev mailing list for a work around:

we've noticed a problem when creating the new IDE release 1.56.1: #14586. We are, of course, preparing a new release. The problem was caused by picking up a new point version of the "perfect-scrollbar" dependency. The 1.5.6 version is not working with Theia and we're pinning the version to 1.5.5 in Theia IDE. Unfortunately, we cannot force clients of the @Theia packages to use the 1.5.5 version due to limitations in yarn.

So if you build your own Theia-based product you should pin the version as well by adding the following to the package.json at the root of your monorepo:

"resolutions": {
"**/perfect-scrollbar": "1.5.5"
},

You can also check which version of perfect-scrollbar you're using in your product by doing "yarn why perfect-scrollbar". If the versions showing up are < 1.5.6, you're fine.

Being unable to update this dependency is not desirable in the long run and we'll investigate what the root cause of the problem is and take appropriate action.

hope that helps

/Thomas