Drop deprecated "p-*" Phosphor-based selectors

[nmichaud]

I've noticed that dragging tabs in the TabBar widget feels much laggier than before. I narrowed the culprit down to the merge that migrated the CSS selectors to new 'lm-*' based prefixes (#20) while keeping the original ones. Chrome seems to have some issues when an element has two different selectors with identical stylesheets. Is there a timeline to remove the deprecated selectors from the codebase? I assume JupyterLab has fully migrated over by now.

[jasongrout]

An update: JLab 3 still has the phosphor compatibility shim, and the hope is to remove it in JLab 4 (planned release at the end of this year) to fully migrate to Lumino with no backwards compatibility for Phosphor.

Chrome seems to have some issues when an element has two different selectors with identical stylesheets.

Interesting. I haven't noticed a lag. Do you have a reference link or Chrome bug report for problem?

[nmichaud]

Chrome seems to have some issues when an element has two different selectors with identical stylesheets.

Interesting. I haven't noticed a lag. Do you have a reference link or Chrome bug report for problem?

Sorry that was a red herring. Turns out it was this issue - #128. Removing all the phosphor based selectors ended up fixing the problem but hid what the underlying problem was.

[jasongrout]

Thanks for following up.