keyboard_layout: Add xkbswitch support (#1985)

src/blocks/keyboard_layout.rs

@@ -2,6 +2,7 @@
 //!
 //! Four drivers are available:
 //! - `setxkbmap` which polls setxkbmap to get the current layout
+//! - `xkbswitch` which utilizes [XkbSwitch](https://github.com/grwlf/xkb-switch) to monitor and retrieve the current layout and variant
 //! - `localebus` which can read asynchronous updates from the systemd `org.freedesktop.locale1` D-Bus path
 //! - `kbddbus` which uses [kbdd](https://github.com/qnikst/kbdd) to monitor per-window layout changes via DBus
 //! - `sway` which can read asynchronous updates from the sway IPC
@@ -12,7 +13,7 @@
 //!
 //! Key | Values | Default
 //! ----|--------|--------
-//! `driver` | One of `"setxkbmap"`, `"localebus"`, `"kbddbus"` or `"sway"`, depending on your system. | `"setxkbmap"`
+//! `driver` | One of `"setxkbmap"`, `"xkbswitch"`, "localebus"`, `"kbddbus"` or `"sway"`, depending on your system. | `"setxkbmap"`
 //! `interval` | Update interval, in seconds. Only used by the `"setxkbmap"` driver. | `60`
 //! `format` | A string to customise the output of this block. See below for available placeholders. | `" $layout "`
 //! `sway_kb_identifier` | Identifier of the device you want to monitor, as found in the output of `swaymsg -t get_inputs`. | Defaults to first input found
@@ -34,6 +35,15 @@
 //! interval = 15
 //! ```
 //!
+//! Check `xkbswitch` every 15 seconds
+//!
+//! ```toml
+//! [[block]]
+//! block = "keyboard_layout"
+//! driver = "xkbswitch"
+//! interval = 15
+//! ```
+//!
 //! Listen to D-Bus for changes:
 //!
 //! ```toml
@@ -82,6 +92,9 @@
 mod set_xkb_map;
 use set_xkb_map::SetXkbMap;
 
+mod xkb_switch;
+use xkb_switch::XkbSwitch;
+
 mod locale_bus;
 use locale_bus::LocaleBus;
 
@@ -109,6 +122,7 @@ pub struct Config {
 pub enum KeyboardLayoutDriver {
     #[default]
     SetXkbMap,
+    XkbSwitch,
     LocaleBus,
     KbddBus,
     Sway,
@@ -119,6 +133,7 @@ pub async fn run(config: &Config, api: &CommonApi) -> Result<()> {
 
     let mut backend: Box<dyn Backend> = match config.driver {
         KeyboardLayoutDriver::SetXkbMap => Box::new(SetXkbMap::new(config.interval)),
+        KeyboardLayoutDriver::XkbSwitch => Box::new(XkbSwitch::new(config.interval)),
         KeyboardLayoutDriver::LocaleBus => Box::new(LocaleBus::new().await?),
         KeyboardLayoutDriver::KbddBus => Box::new(KbddBus::new().await?),
         KeyboardLayoutDriver::Sway => Box::new(Sway::new(config.sway_kb_identifier.clone()).await?),

src/blocks/keyboard_layout/xkb_switch.rs

@@ -0,0 +1,44 @@
+use super::*;
+use tokio::process::Command;
+
+pub(super) struct XkbSwitch(Seconds);
+
+impl XkbSwitch {
+    pub(super) fn new(update_interval: Seconds) -> Self {
+        Self(update_interval)
+    }
+}
+
+#[async_trait]
+impl Backend for XkbSwitch {
+    async fn get_info(&mut self) -> Result<Info> {
+        // This command output is in the format of "layout(variant)" or "layout"
+        let output = Command::new("xkb-switch")
+            .arg("-p")
+            .output()
+            .await
+            .error("Failed to execute 'xkb-switch -p'")?;
+
+        let output =
+            String::from_utf8(output.stdout).error("xkb-switch produces a non-UTF8 output")?;
+
+        let mut components = output.trim_end().split('(');
+
+        let layout = components
+            .next()
+            .error("Could not find layout entry in xkb-switch")?
+            .to_string();
+
+        let variant = components
+            .last()
+            // Remove the trailing parenthesis ")"
+            .map(|variant_str| variant_str.split_at(variant_str.len() - 1).0.to_string());
+
+        Ok(Info { layout, variant })
+    }
+
+    async fn wait_for_change(&mut self) -> Result<()> {
+        sleep(self.0 .0).await;
+        Ok(())
+    }
+}