Accessibility + Wayland

1. General State

Orca running with the Wayland backend is, for the most part, working. But Orca master is required.
Gtk+ apps running with the Wayland backend with are, for the most part, accessible with Orca.
GNOME Shell should expose the accessibility tree after the changes on bug 735908 and bug 736821

Seems that there are some wayland specific issues: https://bugzilla.gnome.org/show_bug.cgi?id=746627

Note: This was tested in a Wayland GNOME Session by launching "screen keyboard" via the Accessibility menu.

Successes:
- Use OSK to type into X terminator app
- Use OSK to type into X gedit
Failures:
- Use OSK to type into Wayland gnome-shell's Overview search entry
- Use OSK to type into Wayland gedit
Other observations:
- If you are in an X app (e.g. terminator) and then get into the Wayland gnome-shell's Overview, input not only fails to go into the Overview search entry, but winds up in the no-longer-focused X app.
- Launching the OSK causes Caribou to also be launched. You can permanently kill the Caribou process and obtain the same results as described above. We should figure out what the role of the Caribou process is/should/will be. Matthias suggested Caribou itself would no longer be required in Wayland.

Seems to be working as expected and tracking mouse, caret, and focus/selection for non-Wayland apps.
Seems to be tracking mouse and focus/selection for Wayland apps.
Reliably crashes the entire session if typing in a text view of a Wayland app.

Started a 'wayland' branch which is using AT-SPI2 instead of X API calls.
Status on wayland: mousetweaks starts up and waits for AT-SPI2 "mouse:" events (which are currently not emitted as described below).

AT-SPI2 Bug 709999: Mouse events cannot by synthesized via AT-SPI2. Priority: High.
- Orca's mouse routing and clicking functionality of its flat review feature does not work in Wayland.
- MouseTweaks is unable to synthesize mouse button events in Wayland.
AT-SPI2 Bug 710012: Mouse-moved events are not being emitted. This functionality was/is coming from X and we need to implement an equivalent for Wayland. Priority: High.
- Orca's mouse review feature does not work in Wayland.
- Mousetweaks listens for "mouse:abs" and "mouse:button" events.
Caribou Bug 705504: Make on-screen keyboard work under wayland. Priority: High.
A means to get the Z-Order for top-level windows in a libwnckless world (mailing list post). Alternatively, Joanie wonders if toolkits could emit mouse-in/mouse-out signals, or something along those lines (her reply).

Gtk+ Bug 709854: Reliable crash when hovering over items with an associated tooltip. Solution: Fixed.
Mutter Bug 706963: Global keyboard shortcuts do not work when you are in an app using the Wayland backend. This makes launching apps extremely difficult for people who rely upon the keyboard instead of the mouse. Solution: Fixed..
Gtk+ Bug 709852: Reliable crash with typeahead search and when dismissing dialogs. The former makes keyboard navigation in trees tedious (and unstable). The latter makes dialogs the kiss of death for -- including Orca's preferences dialog. Solution: Fixed..
Accerciser Bug 709449: Accerciser reliably crashes upon launch when launched using the Wayland backend. Resolved: Obsolete.
Orca Bug 709447: Orca was frequently crashing upon launch when launched using the Wayland backend. The offending call was commented out so that everyone could continue testing without these crashes. Priority: High