Icons not visible with the jupyterlab-night theme

[jtpio]

Opening the issue in this repo since they used to be visible before if I recall correctly.

Trying the latest 7.0.0a9 pre-release on Binder with the jupyterlab-night theme (https://github.com/martinRenou/jupyterlab-night), the icons in the menu are not clearly visible:

It might be related to a change in the latest JupyterLab 4.0 pre-releases.

[jtpio]

This is an upstream issue: jupyterlab/jupyterlab#13461

Leaving open until we update to a new release that fixes.

[HaudinFlorence]

In PR #13279, new css variables have been introduced in variable.css file both in light and dark themes and used in the relevant files. The goal is to define colors that are independant of other css variables like for instance --jp-warn-colori for jupyter or notebook icons or --jp-brand-colori for the console icon .

/* File or activity icons and switch semantic variables */
  --jp-jupyter-icon-color: var(--md-orange-900);
  --jp-notebook-icon-color: var(--md-orange-700);
  --jp-json-icon-color: var(--md-orange-700);
  --jp-console-icon-background-color: var(--md-blue-700);
  --jp-console-icon-color: white;
  --jp-terminal-icon-background-color: var(--md-grey-800);
  --jp-terminal-icon-color: var(--md-grey-200);
  --jp-text-editor-icon-color: var(--md-grey-700);
  --jp-inspector-icon-color: var(--md-grey-700);
  --jp-switch-color: var(--md-grey-400);
  --jp-switch-true-position-color: var(--md-orange-700);
  --jp-switch-cursor-color: rgba(255, 255, 255, 1);

I guess that for future custom themes these variables should also be present in the variable.css file to properly render the icons.