Fix theme not being synchronized with external windows on firefox

[CGNonofr]

fix #259835

Firefox doesn't allow to watch style element content using a MutationObserver. A MutationObserver is used to synchronize main windows styles with external windows. As a consequence, the theme is not properly updated on external windows on Firefox.

As a workaround, also add a data-hash attribute on the style elements, and watch it as well in the MutationObserver

[bpasero]

On a glance the direction seems legit, but the implementation is not working for me:

• we need to scope this to only apply for firefox (via isFirefox) and not always
• computing the SHA seems overkill, I would do a pragmatic approach and set some UUID or even easier a counter that just increments, this may produce false positives but I think is fair enough for Firefox

[CGNonofr]

On a glance the direction seems legit, but the implementation is not working for me:

by not working for you you mean that you tried it and it didn't work, or are you just unhappy with the way it's implemented?

• we need to scope this to only apply for firefox (via isFirefox) and not always

I was mainly for the sake of simplicity, and also because I was anticipating it may also impact some other browsers I'm unable to test (like safari?)

• computing the SHA seems overkill, I would do a pragmatic approach and set some UUID or even easier a counter that just increments, this may produce false positives but I think is fair enough for Firefox

I had multiple ideas on how to implement it 🤔 I've started with using a simple counter, an UUID, and at the end I was thinking using a hash was the most elegant way to implement it (Also I'm not sure how to name the attribute if using an UUID 🤔) I'm aware of the additional computation required, but computing a hash is pretty light, and also it's only done when switching the theme so...

Btw it's really not a big deal, I just want that issue fixed and wanted to help do it quickly by suggesting a way to implement it, feel free to refactor it the way you want. I can also do it with clean indications (what attribute name for the UUID? Are you sure to scope it for Firefox only?)

[bpasero]

It works fine for me in all chrome based browsers and safari, so I think its an isolated issue with firefox only. I can do a fix as well but would probably start fresh then.

I am having trouble actually verifying that your fix works running out of sources because somehow NO CSS loads for me in this case. I need to create a build with the fix to verify it.

[CGNonofr]

What about now?

[bpasero]

@CGNonofr better, but I made some changes on top, though I cannot push them back to your branch. I created a new PR at #260037

[CGNonofr]

@CGNonofr better, but I made some changes on top, though I cannot push them back to your branch. I created a new PR at #260037

Sorry, forgot about the UUID tools in VSCode. I've replaced my commit with yours. Feel free to merge either one or the other

[bpasero]

Thank you, this is not a trivial contribution, great work. I confirmed it seems fixed with the change on insiders.vscode.dev

[CGNonofr]

I confirmed it seems fixed with the change on insiders.vscode.dev

I've just tried and it doesn't seem to be deployed 🤔 is there some kind of gradual rollout? I'm still on commit c661d0e

[bpasero]

@CGNonofr try with https://insiders.vscode.dev/?vscode-version=67afbe24e877cd0d0769d32de3014821a9fae306

[CGNonofr]

Oh thanks, nice feature :)