This MR tries to implement the SetIMECompositionRect user driver function and partially the WINE_IME_POST_UPDATE message call. It requires support for zwp_text_input_v3 from the compositor. It supports submitting committed text to the win32 side and notifying the compositor about the area of the text cursor rectangle.
This doesn't add support for embedded pre-edit because I couldn't immediately get it to appear. Either I did something incorrect, or it has something to do with Wayland. On X11, the pre-edit appears completely separated to the application window and doesn't move with it, which doesn't seem to be compatible with Wayland.
If Windows has the surrounding text feature, it does not seem possible to support it here with the provided interface.
The IME is always enabled on the focused surface, like on X11. If Windows has a facility that applications can use to say that it does or does not accept text entry at certain parts of the UI, it does not seem possible to support it here with the provided interface.
-- v2: winewayland: Implement SetIMECompositionRect.