open-window-system given no :backend uses the platform's backend,
:win32 on Windows and :wayland elsewhere, since *default-backend* is
gone; no-backend-error's backend is then always a keyword, and its
message for no backend at all is gone too. The pages that described
the choice say so, and Backend Protocol says where a backend becomes a
platform's default.
Backend Protocol's example takes the lock through sys:with-lock, the
local nickname the backends' packages give cl-windowing/sys, which no
longer reads the environment. Events and the API reference say that a
program reads events and backends write them, which is what the
exported setf writers of the event's fields are for.
Follow cl-windowing 031159f: Windows, popups, input methods, cursors, the clipboard
Add pages for popups, input methods, cursors and pointer modes, the
clipboard and the Win32 backend. Bring the others up to date: the Win32
backend beside Wayland, fullscreen and set-window-size, copy-event and the
new event fields and types, the new capabilities and conditions, the
protocols the Wayland backend uses now, and the backend protocol's new
generic functions, reporting functions and lock rules. CI runs the suite
on SBCL only.
