docs: Wayland

One popup per session, so the frontend is picked at startup: a compositor
with zwp_input_method_v2 gets that frontend and neither XIM nor the X11
popup is started.  The answer for a user is one sentence -- on Wayland set
none of the module variables -- and the two exceptions the plan asked to
check turned out this way: GTK 4 binds text-input-v3 by itself, with
GTK_IM_MODULE unset (4.22 under sway 1.12, typed and composed), and
Chromium is beyond help either way, since it asks for text-input-v1 and
wlroots implements only v3.

The plan is deleted, as it said to be once the README described what
landed.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

README.md

@@ -1,8 +1,10 @@
 # strans
 
 strans is a small, single-user input method for Korean, Japanese, English,
-emoji, and symbols. It provides one engine for IBus (which GTK 4 and
-Qt use), XIM, and GTK 3. Vietnamese Telex is also available as a
+emoji, and symbols. It provides one engine for Wayland compositors that
+speak `zwp_input_method_v2` — the wlroots and smithay families, so sway,
+river, labwc, Wayfire, dwl, niri and COSMIC — and for IBus (which GTK 4
+and Qt use), XIM, and GTK 3. Vietnamese Telex is also available as a
 compatibility mode.
 
 ## Input modes
@@ -72,6 +74,7 @@ clicking elsewhere commits what is pending.
 
 | Frontend | Preedit | Candidates |
 | --- | --- | --- |
+| Wayland input method | inline in the client | strans popup |
 | GTK 3 and IBus | inline in the client | strans popup |
 | XIM PreeditCallbacks | inline through XIM callbacks | strans popup |
 | XIM PreeditPosition | strans popup | strans popup |
@@ -90,11 +93,13 @@ style, and above the line when there is no room below; otherwise the popup
 sits under the focus window, or under the client window when no focus
 window is set.
 
-The popup is an X11 window sized by `GDK_SCALE` on HiDPI displays, XIM is
-X11-only, and GTK popup placement converts the GTK caret to X11 root
-coordinates. There is no native Wayland popup surface or Wayland caret
-positioning. GTK and IBus clients can still use inline preedit where their
-display environment supports it.
+On a compositor with `zwp_input_method_v2` the popup is a Wayland surface
+that the compositor itself puts at the text cursor, flipping it above the
+line when there is no room below; a client that reports no cursor location
+gets it under its window instead. Everywhere else the popup is an X11 window,
+placed from the XIM spot or from the GTK caret converted to root
+coordinates, and XIM is X11-only. Either way `GDK_SCALE` sizes it for
+HiDPI displays.
 
 ## Build and test
 
@@ -109,7 +114,7 @@ make docker-build
 Build output:
 
 ```text
-strans              daemon with IBus and XIM frontends
+strans              daemon with Wayland, IBus, and XIM frontends
 gtk/im-strans.so    GTK 3 frontend module
 ```
 
@@ -133,6 +138,8 @@ development files for:
 - Plan 9 port (`9c`, `9l`, `libthread`, and `libbio`);
 - D-Bus development files;
 - XCB, XCB RandR, XCB XKB, xcb-util, xcb-imdkit, xkbcommon, and xkbcommon-x11;
+- the Wayland client library and `wayland-scanner`, which writes the
+  input-method and virtual-keyboard bindings from the XML in `proto/`;
 - Pango, PangoCairo, Cairo, and Fontconfig;
 - GTK 3, plus libibus and Xlib for the live clients;
 - Xvfb for the X11 live tests;
@@ -158,8 +165,9 @@ build-tree daemon in the background, and returns to the shell. It requires
 `pkill` from procps. Startup and frontend failures remain visible on the
 caller's standard error. A service supervisor should instead run
 `./strans map` directly in the foreground, with the session's
-`XDG_RUNTIME_DIR` and `DISPLAY`: the GTK module finds the daemon at
-`$XDG_RUNTIME_DIR/strans.sock` (else `/tmp/strans.UID`), and IBus clients
+`XDG_RUNTIME_DIR` and its `WAYLAND_DISPLAY` or `DISPLAY`: the GTK module
+finds the daemon at `$XDG_RUNTIME_DIR/strans.sock` (else
+`/tmp/strans.UID`), and IBus clients
 through the address file libibus expects under `~/.config/ibus/bus/`,
 which strans writes as `ibus-daemon` would, named after `WAYLAND_DISPLAY`
 when there is one and `DISPLAY` otherwise.
@@ -169,6 +177,20 @@ opens `hira.map`, `kata.map`, `telex.map`, `kanji.dict`, `emoji.dict`, and
 `hanja.dict` from `DIR` at runtime; `run.sh` passes the tracked `map/`
 directory. Only the GTK subdirectory has install and uninstall targets.
 
+strans shows one popup per session, so it picks its frontend at startup: a
+session whose compositor offers `zwp_input_method_v2` gets that frontend,
+and neither XIM nor the X11 popup is started; every other session gets XIM
+as before. The IBus endpoint and the GTK 3 module are served in both.
+
+On Wayland, then, set none of the variables below. GTK, Qt and Firefox
+speak text-input-v3 themselves and need nothing — GTK 4 binds it without
+`GTK_IM_MODULE`, checked with 4.22 under sway 1.12 — and `GTK_IM_MODULE`
+is what pushes them off the path that works. A client that reaches strans
+over IBus or the GTK 3 module while the Wayland frontend runs still
+composes inline, but shows no candidate list, because the popup belongs to
+that frontend. Chromium is helped by neither: it still asks for
+`text-input-v1`, which wlroots does not implement at all.
+
 Configure clients as needed:
 
 ```sh
@@ -201,8 +223,9 @@ doas make -C gtk uninstall
 strans provides its own IBus endpoint; `ibus-daemon` and fcitx are not
 required. IBus clients that process keys synchronously — GTK 4, or GTK 3
 with `IBUS_ENABLE_SYNC_MODE=1` — get their commits and preedits through
-`PostProcessKeyEvent`, in order with the key. Without `DISPLAY`, the daemon and IBus frontend still work, but XIM
-is not started and the popup is disabled.
+`PostProcessKeyEvent`, in order with the key. With neither
+`WAYLAND_DISPLAY` nor `DISPLAY`, the daemon, its IBus endpoint and its
+socket still work, but no frontend draws a popup.
 
 ## Dictionary data