[orca-list] Firefox sidebar history tree view very slow to navigate with orca

[Peter Vágner <pvdeejay gmail com>]

Hello,

This is with Firefox 59 nightly and orca master on Arch linux running Gnome 3.26.

Steps:

- Open any website in Firefox and make sure orca can read its content

- Press ctrl+h to open up the history in the Firefox sidebar

- The focus is placed to the search history text entry, orca reports it fine. Please notice how the responsiveness feels instantaneous at this point.

- Now press the tab key to navigate to the view menu button. Luckily the responsiveness is still all great.

- Now press the tab key to navigate further.

Results:

When tabbing from the View menu button to the tree view either orca gets stuck for a second or two and it will only report the new focus after that or it will report nothing. Returning back to the View menu button by pressing shift+tab is also slow.

Expected results:

If possible it would be nice to make this part of the Firefox UI more responsive.