Add DPMS on/off support

We now manage a switch entity in Home Assistant that can be used to turn
the display on or off.  On Linux, this is handled by the X DPMS
extension; presumably there is similar functionality on other platforms
that we can use if we decide to support those as well.

Cargo.toml

@@ -18,4 +18,4 @@ tokio-stream = "0.1.11"
 toml = "0.5.10"
 tracing = "0.1.37"
 tracing-subscriber = { version = "0.3.16", features = ["env-filter", "fmt"] }
-x11 = { version = "2.20.1", features = ["xlib", "xrandr"] }
+x11 = { version = "2.20.1", features = ["dpms", "xlib", "xrandr"] }

src/mqtt.rs

@@ -18,11 +18,13 @@ use crate::hass::{self, HassConfig};
 #[async_trait]
 pub trait MessageHandler {
     async fn navigate(&mut self, publisher: &MqttPublisher, msg: &Message);
+    async fn power(&mut self, publisher: &MqttPublisher, msg: &Message);
 }
 
 #[derive(Debug)]
 pub enum MessageType {
     Navigate,
+    PowerState,
 }
 
 pub struct MqttClient<'a> {
@@ -33,9 +35,7 @@ pub struct MqttClient<'a> {
 }
 
 impl<'a> MqttClient<'a> {
-    pub fn new(
-        config: &'a Configuration,
-    ) -> Result<Self, Error> {
+    pub fn new(config: &'a Configuration) -> Result<Self, Error> {
         let uri = format!(
             "{}://{}:{}",
             if config.mqtt.tls { "ssl" } else { "tcp" },
@@ -68,12 +68,16 @@ impl<'a> MqttClient<'a> {
         Ok(res)
     }
 
-    pub async fn subscribe(&mut self) -> Result<ServerResponse, Error> {
+    pub async fn subscribe(&mut self) -> Result<(), Error> {
+        let client = self.client.lock().await;
         let prefix = &self.config.mqtt.topic_prefix;
         let t_nav = format!("{}/+/navigate", prefix);
-        let res = self.client.lock().await.subscribe(&t_nav, 0).await?;
+        let t_power = format!("{}/power", prefix);
+        client.subscribe(&t_nav, 0).await?;
+        client.subscribe(&t_power, 0).await?;
         self.topics.insert(t_nav, MessageType::Navigate);
-        Ok(res)
+        self.topics.insert(t_power, MessageType::PowerState);
+        Ok(())
     }
 
     pub fn publisher(&mut self) -> MqttPublisher {
@@ -118,6 +122,9 @@ impl<'a> MqttClient<'a> {
                     MessageType::Navigate => {
                         handler.navigate(&publisher, &msg).await;
                     }
+                    MessageType::PowerState => {
+                        handler.power(&publisher, &msg).await;
+                    }
                 }
             }
         }
@@ -198,6 +205,14 @@ impl<'a> MqttPublisher<'a> {
         Ok(())
     }
 
+    pub async fn publish_power_state(&self, state: bool) -> Result<(), Error> {
+        let topic = format!("{}/power_state", self.config.mqtt.topic_prefix);
+        let msg =
+            Message::new_retained(topic, if state { "ON" } else { "OFF" }, 0);
+        self.client.lock().await.publish(msg).await?;
+        Ok(())
+    }
+
     pub async fn publish_config(&self, screen: &str) -> Result<(), Error> {
         debug!("Publishing Home Assistant configuration");
         let prefix = &self.config.mqtt.topic_prefix;
@@ -254,6 +269,27 @@ impl<'a> MqttPublisher<'a> {
         trace!("Publishing message: {:?}", msg);
         self.client.lock().await.publish(msg).await?;
 
+        let unique_id = format!("light.{}", key);
+        let object_id = unique_id.clone();
+        let command_topic = Some(format!("{}/power", prefix));
+        let state_topic = format!("{}/power_state", prefix);
+        let name = "Display Power".into();
+        let config = HassConfig {
+            command_topic,
+            state_topic,
+            name,
+            unique_id,
+            object_id,
+            ..config
+        };
+        let msg = Message::new_retained(
+            format!("homeassistant/light/{}/config", key),
+            serde_json::to_string(&config).unwrap(),
+            0,
+        );
+        trace!("Publishing message: {:?}", msg);
+        self.client.lock().await.publish(msg).await?;
+
         info!("Succesfully published Home Assistant config");
         Ok(())
     }

src/session.rs

@@ -13,7 +13,7 @@ use crate::marionette::{Marionette, MarionetteConnection};
 use crate::monitor::Monitor;
 use crate::mqtt::{Message, MqttClient, MqttPublisher};
 #[cfg(unix)]
-use crate::x11::{xrandr, Display};
+use crate::x11::{dpms, xrandr, Display};
 
 #[derive(Debug)]
 pub enum SessionError {
@@ -230,6 +230,19 @@ impl<'a> crate::mqtt::MessageHandler for MessageHandler<'a> {
             Err(e) => error!("Error getting title: {}", e),
         }
     }
+
+    async fn power(&mut self, publisher: &MqttPublisher, msg: &Message) {
+        match msg.payload_str().as_ref() {
+            "ON" => turn_screen_on(),
+            "OFF" => turn_screen_off(),
+            x => {
+                warn!("Received unexpected power state command: {}", x);
+            }
+        }
+        if let Err(e) = publisher.publish_power_state(is_screen_on()).await {
+            error!("Failed to publish power state: {}", e);
+        }
+    }
 }
 
 #[cfg(unix)]
@@ -246,3 +259,60 @@ fn get_monitors() -> Vec<Monitor> {
         })
         .collect()
 }
+
+fn turn_screen_on() {
+    let display = match Display::open() {
+        Ok(d) => d,
+        Err(_) => {
+            error!("unable to open display \"{}\"", Display::name());
+            return;
+        }
+    };
+    if !dpms::force_level(&display, dpms::DpmsPowerLevel::On) {
+        error!("Failed to turn on display \"{}\"", Display::name());
+    }
+    if !dpms::disable(&display) {
+        error!(
+            "Failed to disable DPMS on display \"{}\"",
+            Display::name()
+        );
+    }
+}
+
+#[cfg(unix)]
+fn turn_screen_off() {
+    let display = match Display::open() {
+        Ok(d) => d,
+        Err(_) => {
+            error!("unable to open display \"{}\"", Display::name());
+            return;
+        }
+    };
+    if !dpms::enable(&display) {
+        error!(
+            "Failed to enable DPMS on display \"{}\"",
+            Display::name()
+        );
+    }
+    if !dpms::force_level(&display, dpms::DpmsPowerLevel::Off) {
+        error!("Failed to turn off display \"{}\"", Display::name());
+    }
+}
+
+#[cfg(unix)]
+fn is_screen_on() -> bool {
+    let display = match Display::open() {
+        Ok(d) => d,
+        Err(_) => {
+            error!("unable to open display \"{}\"", Display::name());
+            return false;
+        }
+    };
+    if dpms::query_extension(&display) && dpms::dpms_capable(&display) {
+        let info = dpms::get_info(&display);
+        if info.state && info.power_level != dpms::DpmsPowerLevel::On {
+            return false;
+        }
+    }
+    true
+}

src/x11/dpms.rs

@@ -0,0 +1,120 @@
+use x11::dpms::{
+    DPMSCapable, DPMSDisable, DPMSEnable, DPMSForceLevel, DPMSGetTimeouts,
+    DPMSInfo, DPMSQueryExtension,
+};
+use x11::dpms::{DPMSModeOff, DPMSModeOn, DPMSModeStandby, DPMSModeSuspend};
+use x11::xmd::{BOOL, CARD16};
+
+use super::Display;
+
+/// DPMS Power Level
+///
+///  There are four power levels specified by the Video Electronics Standards
+///  Association (VESA) Display Power Management Signaling (DPMS) standard.
+///  These are mapped onto the X DPMS Extension
+#[derive(Eq, PartialEq)]
+pub enum DpmsPowerLevel {
+    /// In use
+    On = DPMSModeOn as isize,
+    /// Blanked, low power
+    Standby = DPMSModeStandby as isize,
+    /// Blanked, lower power
+    Suspend = DPMSModeSuspend as isize,
+    /// Shut off, awaiting activity
+    Off = DPMSModeOff as isize,
+    Unknown = -1,
+}
+
+impl From<u16> for DpmsPowerLevel {
+    fn from(v: u16) -> Self {
+        #[allow(non_snake_case)]
+        match v {
+            x if x == DpmsPowerLevel::On as u16 => Self::On,
+            x if x == DpmsPowerLevel::Standby as u16 => Self::Standby,
+            x if x == DpmsPowerLevel::Suspend as u16 => Self::Suspend,
+            x if x == DpmsPowerLevel::Off as u16 => Self::Off,
+            _ => Self::Unknown,
+        }
+    }
+}
+
+/// Result from [`get_info`] function (`DPMSInfo`)
+pub struct DpmsInfo {
+    /// Current power level
+    pub power_level: DpmsPowerLevel,
+    /// DPMS enabled/disabled state
+    pub state: bool,
+}
+
+/// Result from [`get_timeouts`] function (`DPMSGetTimeouts`)
+pub struct DpmsTimeouts {
+    /// Amount of time of inactivity in seconds before standby mode is invoked
+    pub standby: u16,
+    /// Amount of time of inactivity in seconds before the second level of power
+    /// savings is invoked
+    pub suspend: u16,
+    /// Amount of time of inactivity in seconds before the third and final level
+    /// of power savings is invoked
+    pub off: u16,
+}
+
+/// Queries the X server to determine the availability of the DPMS Extension
+pub fn query_extension(display: &Display) -> bool {
+    let mut event_base = 0;
+    let mut error_base = 0;
+    let r = unsafe {
+        DPMSQueryExtension(display.display, &mut event_base, &mut error_base)
+    };
+    r != 0
+}
+
+/// Returns the DPMS capability of the X server, either TRUE (capable of DPMS)
+/// or FALSE (incapable of DPMS)
+pub fn dpms_capable(display: &Display) -> bool {
+    let r = unsafe { DPMSCapable(display.display) };
+    r != 0
+}
+
+/// Returns information about the current DPMS state
+pub fn get_info(display: &Display) -> DpmsInfo {
+    let mut power_level: CARD16 = 0;
+    let mut state: BOOL = 0;
+    unsafe { DPMSInfo(display.display, &mut power_level, &mut state) };
+    DpmsInfo {
+        power_level: power_level.into(),
+        state: state != 0,
+    }
+}
+
+/// Retrieves the timeout values used by the X server for DPMS timings
+pub fn get_timeouts(display: &Display) -> DpmsTimeouts {
+    let mut standby: CARD16 = 0;
+    let mut suspend: CARD16 = 0;
+    let mut off: CARD16 = 0;
+    unsafe {
+        DPMSGetTimeouts(display.display, &mut standby, &mut suspend, &mut off)
+    };
+    DpmsTimeouts {
+        standby,
+        suspend,
+        off,
+    }
+}
+
+/// Forces a DPMS capable display into the specified power level
+pub fn force_level(display: &Display, level: DpmsPowerLevel) -> bool {
+    let r = unsafe { DPMSForceLevel(display.display, level as u16) };
+    r != 0
+}
+
+/// Enables DPMS on the specified display
+pub fn enable(display: &Display) -> bool {
+    let r = unsafe { DPMSEnable(display.display) };
+    r != 0
+}
+
+/// Disables DPMS on the specified display
+pub fn disable(display: &Display) -> bool {
+    let r = unsafe { DPMSDisable(display.display) };
+    r != 0
+}

src/x11/mod.rs

@@ -1,3 +1,5 @@
+#[allow(dead_code)]
+pub mod dpms;
 pub mod xrandr;
 
 use std::ffi::CStr;
@@ -18,6 +20,7 @@ pub struct Display {
     display: *mut _XDisplay,
 }
 
+#[allow(dead_code)]
 impl Display {
     /// Open a connection to the X server
     ///