Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=55047
Shrinking the clipping rect to make sure we do not ignore the grab causes some issues. Instead, pass the set_cursor flags to the WM_WINE_CLIPCURSOR message, and introduce a new fullscreen window clipping flag.
As described in the WineHQ bug, an alternative fix would be to keep the shrink but disable fullscreen grabs entirely when the option is disabled [*]. This would break the tests when the option is on but it is not the default. I think that this approach with a flag is better as it doesn't modify the clipping rect.
[*] I don't think they are doing anything but I'm maybe missing something. Maybe grabbing the cursor over the entire virtual screen is preventing the cursor from going over host dock bars or something like that?