add squeekboard toggle button

README.md

@@ -7,7 +7,7 @@ A bottom desktop-environment panel for wlroots-based compositors, built on
 | ------- | ----------------------------------------------------------------- |
 | Left    | Application menu built from `.desktop` entries, with search        |
 | Middle  | Open windows (task list), click to focus, middle-click to close    |
-| Right   | Wifi, bluetooth, and a session menu: log out, suspend, restart, shut down |
+| Right   | On-screen keyboard, wifi, bluetooth, and a session menu: log out, suspend, restart, shut down |
 
 No clock, no tray, no status readouts — it is designed to sit alongside a
 separate status bar.
@@ -25,6 +25,8 @@ separate status bar.
 - NetworkManager for the wifi section, likewise optional. A NetworkManager
   configured with `wifi.backend=iwd` is fine — and is what this was built
   against — since the connection still goes through iwd underneath
+- squeekboard, as a systemd user unit, for the keyboard button — also optional;
+  where the unit is not installed the button is absent
 
 The window list uses the foreign-toplevel protocol rather than any single
 compositor's IPC, so it works the same everywhere — except under river 0.4,
@@ -84,6 +86,13 @@ The `launcher`, `wifi`, `bluetooth` and `power` IPC targets each accept
 focused window. Only one menu is open at a time, so `close` closes whichever it
 is.
 
+The `osk` target takes the same three and shows or hides the keyboard instead,
+which is what to bind to a hardware key or a tablet-mode switch:
+
+```sh
+att_menu ipc call osk toggle
+```
+
 ## Behaviour
 
 **Placement.** The panel is a layer-shell surface anchored to the left, right and
@@ -113,6 +122,17 @@ The launcher is a full-screen overlay layer surface rather than an
 `xdg-popup`, which is what makes click-away dismissal and keyboard focus work on
 any wlroots compositor without compositor-specific focus grabs.
 
+**On-screen keyboard.** One button shows squeekboard, another click hides it,
+and the button is accented while the keyboard is up. squeekboard runs as a
+systemd user unit (`oskUnit`, `squeekboard.service` by default): showing starts
+it if it is not already running, hiding leaves it running, since stopping it
+would only make the next keypress wait for a fresh start. Whatever manages the
+unit — a tablet-mode hook, say — stays in charge of when it exists at all.
+
+The keyboard also raises and lowers itself when a text field takes or loses
+focus, so the button follows squeekboard's own `Visible` property rather than
+remembering what it last asked for, and stays right either way.
+
 **Wifi.** The button shows signal strength in the arcs and the SSID in use next
 to them, struck through when the radio is off. The menu lists the networks in
 range — connected first, then saved, then by strength — with the switch in the
@@ -176,6 +196,8 @@ running with `qs --path .`).
     small output still gets a usable menu.
   - `terminal` — argv prefix for entries with `Terminal=true`. Honours
     `$TERMINAL`; otherwise change the `["foot"]` fallback to your terminal.
+  - `showOsk` — set `false` to drop the on-screen keyboard button entirely.
+  - `oskUnit` — the systemd user unit squeekboard runs as.
   - `showWifi` — set `false` to drop the wifi button entirely.
   - `wifiLabelMaxWidth` — cap on the SSID shown on the panel.
   - `wifiMenuWidth` / `wifiMenuHeight` — also clamped to the screen.
@@ -196,12 +218,14 @@ config/Config.qml      Behaviour, power actions, compositor detection
 services/Session.qml   Which menu is open, and on which screen
 services/AppLauncher.qml  Desktop-entry launching
 services/Attwm.qml     attwm's IPC socket, when there is one
+services/Osk.qml       squeekboard: its unit, and its DBus state
 modules/Bar.qml        The panel window and its three sections
 modules/AppMenu.qml    Left: launcher button
 modules/Launcher.qml   The application menu overlay
 modules/AppEntry.qml   One row in the menu
 modules/WindowList.qml Middle: task list
 modules/WindowButton.qml  One task button
+modules/OskMenu.qml    Right: on-screen keyboard button
 modules/WifiMenu.qml   Right: wifi button
 modules/WifiPanel.qml  The network list overlay
 modules/WifiNetworkEntry.qml One network row
@@ -215,6 +239,7 @@ components/AppIcon.qml    Icon resolution with fallbacks
 components/PanelButton.qml Shared hover/press surface
 components/BluetoothGlyph.qml The bluetooth rune, drawn
 components/WifiGlyph.qml      The wifi fan, drawn
+components/KeyboardGlyph.qml  The keyboard, drawn
 components/ToggleSwitch.qml   On/off switch
 ```
 
@@ -251,6 +276,21 @@ components/ToggleSwitch.qml   On/off switch
   the compositor it shares the session's group, where wrapping buys nothing. A
   scope rather than a service, so the app inherits the environment it needs —
   `WAYLAND_DISPLAY` above all.
+- **Why the keyboard button shells out.** Quickshell has no generic DBus
+  binding, and squeekboard is driven entirely over DBus, so `services/Osk.qml`
+  uses `busctl`: a call per request, and one long-lived `busctl --json=short
+  monitor` as the state feed, parsed a line at a time. A monitor connection
+  sees signals it is not the destination of, which is what lets the button
+  follow a keyboard raised by something else. The two match rules deliberately
+  do not name a `sender`: dbus-broker does not deliver the bus driver's own
+  signals to a monitor that asks for them that way, and `NameOwnerChanged` —
+  how the panel notices squeekboard going away, since it does not announce that
+  itself — would never arrive. Showing retries the call for a few seconds
+  because the unit goes active a moment before squeekboard claims its name.
+- `qs ipc call` cannot reach a handler function named `show`: the name collides
+  with the `ipc show` subcommand and the call silently turns into a listing. The
+  `osk` target uses `open` and `close` instead, which matches the menu targets
+  anyway.
 - Icons are resolved through the Qt icon theme, falling back to the last segment
   of a reverse-DNS app id (`org.qutebrowser.qutebrowser` → `qutebrowser`), then
   to a lettered tile. The packaged build adds Adwaita and hicolor to