Basic screen idle timer daemon

- Use x11 ScreenSaver extension to track idle time
- Placeholder lock function and hardcoded timer

glock-d/Cargo.toml

@@ -6,3 +6,4 @@ description = "Screen idle time tracker daemon for glock screenlock"
 
 [dependencies]
 glock-conf = { version = "0.1.0", path = "../glock-conf" }
+x11rb = { version = "0.13.2", features = ["screensaver"] }

glock-d/src/main.rs

@@ -1,3 +1,54 @@
-fn main() {
-    println!("Hello, world!");
+// Screen idle timeout daemon that triggers the screen locker.
+//
+// This daemon runs continuously, queries the X server for global
+// user idle time, and triggers the screen locker once the idle
+// timeout is exceeded.
+
+use std::thread;
+use std::time::Duration;
+
+use x11rb::connection::Connection;
+use x11rb::protocol::screensaver;
+
+fn main() -> Result<(), Box<dyn std::error::Error>> {
+    // Daemon entry point.
+    // For now, this only prints when the screen should be locked.
+    println!("glock-d: starting idle tracker daemon");
+
+    // Hard-coded idle timeout in milliseconds.
+    // This will later be loaded from the config crate.
+    let idle_timeout_ms: u64 = 60_000;
+
+    // Interval between idle checks.
+    // Short enough to feel responsive, long enough to stay efficient.
+    let poll_interval = Duration::from_millis(500);
+
+    // Connect to the X server using the default display.
+    // The screen number is required to access the root window.
+    let (conn, screen_num) = x11rb::connect(None)?;
+
+    // The root window represents the entire screen.
+    // XScreenSaver reports idle time relative to this window.
+    let root = conn.setup().roots[screen_num].root;
+
+    // Main daemon loop.
+    // This loop runs forever unless the process is terminated.
+    loop {
+        // Sleep before querying to avoid busy-looping and CPU waste.
+        thread::sleep(poll_interval);
+
+        // Query the XScreenSaver extension for idle information.
+        // The value returned is milliseconds since last keyboard or mouse input.
+        let reply = screensaver::query_info(&conn, root)?.reply()?;
+        let idle_ms = u64::from(reply.ms_since_user_input);
+
+        // If the user has been idle longer than the timeout,
+        // trigger the screen lock.
+        if idle_ms >= idle_timeout_ms {
+            // Placeholder for the real locker invocation.
+            // In the final version, this will spawn the glock locker
+            // and wait for it to exit before continuing.
+            println!("screen lock");
+        }
+    }
 }