Fix fullscreen container dimension detection when not directly on body

[CGNonofr]

If the workbench is rendered in another container than the body, everything works fine except the fullscreen mode.

This PR make the layout service not rely on the parent element size in fullscreen mode as it doesn't make sense and rely on the body size instead.

I don't think it can't break anything as in the browser, the parent element is currently already the main window body

[bpasero]

Is there an associated issue that this PR fixes?

[CGNonofr]

Is there an associated issue that this PR fixes?

Not at all, it's more a code improvement than a bugfix since no issue can be reproduced in VSCode but it may impact forks and custom builds

Should I still create an issue?

[bpasero]

But how can we hard-code a reference to document.body when the parent of the workbench might be something else? I am worried about regressions here actually, but I also do not fully understand the issue yet. If there is a repro, that would help.

Note that your change impacts not only web but also VS Code for desktop.

[CGNonofr]

But how can we hard-code a reference to document.body when the parent of the workbench might be something else?

In fullscreen mode, the parent doesn't really matter as it doesn't impact the container size at all, so it doesn't make sense to measure it to layout the container

I am worried about regressions here actually

In both cases (web.main.ts and desktop.main.ts) the given parent is mainWindow.document.body so I don't think it can actually change anything

but I also do not fully understand the issue yet. If there is a repro, that would help.

It's not simple to provide a repro

I'm integrating VSCode oss in a webpage between a header and a footer. Here's the result in fullscreen (an empty area at the bottom whose size is the height of the footer and the header combined):

Note that your change impacts not only web but also VS Code for desktop.

Indeed, I was confused by the browser directory

[bpasero]

I see the issue now, I think having a comment to explain this would be good.