Set z-index of hovers to 1000

[sgraband]

What it does

Value taken from #15154.

Part of #15118.

How to test

1. Build this branch
2. Open Theia
3. Set the window.tabbar.enhancedPreview to visual or enhanced
4. Check that this does not happen:
   

Follow-ups

Breaking changes

• This PR introduces breaking changes and requires careful review. If yes, the breaking changes section in the changelog has been updated.

Attribution

Review checklist

• As an author, I have thoroughly tested my changes and carefully followed the review guidelines

Reminder for reviewers

• As a reviewer, I agree to behave in accordance with the review guidelines

[JonasHelming]

@cdamus Do you want to review this?

[cdamus]

@cdamus Do you want to review this?

Happy to.

[cdamus]

LGTM, thanks! The problems I had did not recur. I assume that this is unrelated as it appears to be a transparency glitch. I mean, who would put the icons of toolbar buttons at a higher z-index than 1000, amirite?

[sgraband]

Is the behavior from the screenshot on this branch? If yes, which view is this?

[cdamus]

Is the behavior from the screenshot on this branch? If yes, which view is this?

Yes, I captured it in testing this PR. The toolbar icons are from the File Explorer.

[sgraband]

Thanks. I can reproduce this. I will take a look and fix this with this PR as well, while i am at it.

[sgraband]

It's a bit more complicated than originally thought and the question would be where to stop, as we have z-index issues all over the place. Therefore i will go ahead and merge this. I have created #15214 to hopefully fix the z-index issues and make the values a bit more maintainable.

[sgraband]

@JonasHelming can you approve?