Cannot navigate between cells when focused on output in 3.1.0b1

[krassowski]

Description

After clicking on the cell output it is no longer possible to move between the cells using arrows keys.

Reproduce

1. Create a cell with outputs
2. Try to focus the cell below or above using arrow keys
3. See that instead the notebook scrolls

Expected behavior

It should work as in 3.0:

Context

• JupyterLab version: 3.1.0b1

[krassowski]

Removing this.node.tabIndex = 0; introduced in #10282 solves the problem.

jupyterlab/packages/outputarea/src/widget.ts

Lines 1112 to 1122 in 9b0e1d2

	/**
	* A `Panel` that's focused by a `contextmenu` event.
	*/
	export class OutputPanel extends Panel {
	/**
	* Construct a new `OutputPanel` widget.
	*/
	constructor(options?: Panel.IOptions) {
	super(options);
	this.node.tabIndex = 0;
	}

@cameron-toy do you have an example situation for which setting the tabIndex was needed in order to focus the panel?