Classic block toolbar can't be operated with a keyboard

[afercia]

When using only the keyboard, in the Classic block there's no way to focus the block toolbar to access its formatting controls.

This block is basically a TinyMCE instance and in the WordPress old editor moving focus works by using the shortcut Alt+F10. However, in Gutenberg, Alt+F10 focuses the toolbar for a fraction of a second and then focus is moved to the top toolbar, see screenshot below for clarity:

The block toolbar itself and all its controls have a tabindex="-1" attribute so they're out of the tab sequence and there's really no way to move focus there. Again, this works in the old editor because TinyMCE offers a way to move focus to the toolbar and then focus is managed programmatically with arrows/tab navigation.

I've noticed also other inconsistencies and events conflicts, for example pressing Escape doesn't do what it should. But I won't enter into details since in its current state this block isn't even fully testable with a keyboard.

Considering this block aims to offer the same user experience of the old editor, it should work with the same level of accessibility too. Unfortunately, right now there's a serious accessibility regression here, since it's not usable at all by keyboard users and screen reader users.

[afercia]

Testing note:
removing the Alt+F10 shortcut from editor/components/navigable-toolbar/index.js for testing purposes makes the native TinyMCE Alt+F10 work on the Classic block..
but:
then only Tab navigation works. Arrows don't work because as soon as the right or left arrow keys are pressed, focus is moved to the block content (I guess it's the "Writing Flow").

[afercia]

As far as I see, in most of the cases (except for the post title for example) the keyboard shortcuts events are bound to the document so they're, in a way, "global" shortcuts.

This can be easily checked, for example:

• click on any empty area on the sides of the post content
• press Alt+F10
• focus is moved to the inserter button in the top bar

Not sure this is the behavior users expect. Regardless, the Classic block is basically a TinyMCE instance that uses its own Alt+F10 shortcut implementation. However, when using the shortcut, what actually happens is the same as when no blocks are selected. Also the Gutenberg "global" shortcuts kick in and moves focus to the top bar.