CodeMirror should be configured to use absolute positioning of tooltips

[krassowski]

Description

Tooltips are incorrectly positioned in CodeMirror editor, which affects at least jupyterlab-lsp and jupyterlab-spellchecker extensions.

This is because we use css contain. CodeMirror states in the docs:

By default, tooltips use "fixed" positioning, which has the advantage that tooltips don't get cut off by scrollable parent elements. However, CSS rules like contain: layout can break fixed positioning in child nodes, which can be worked about by using "absolute" here.

All we need to do is add an two liner CodeMirror extension: tooltips({position: 'absolute'}).

The alternative would be for each extension to add it but it would be wasteful - extensions should not need to worry about whether we use contain or not.

Reproduce

Hover over linter in reprex.

See codemirror/dev#1215

Expected behavior

Tooltips are positioned correctly, extensions don't need to do anything.

Context

• JupyterLab version: 4.0.3