Add example for monitoring devices

Author: Nemo157

examples/monitor.rs

@@ -0,0 +1,39 @@
+fn log_device(prefix: &str, info: &hidapi::DeviceInfo) {
+    let manufacturer = info.manufacturer_string().unwrap_or_default();
+    let product = info.product_string().unwrap_or_default();
+    let vendor_id = info.vendor_id();
+    let product_id = info.product_id();
+    let path = info.path().to_string_lossy();
+
+    println!("\
+        \n{prefix}\
+        \n    path: {path}\
+        \n    manufacturer: {manufacturer}\
+        \n    product: {product}\
+        \n    id: {vendor_id:4x}:{product_id:4x}\
+    ");
+}
+
+fn main() -> Result<(), hidapi::HidError> {
+    let hidapi1 = hidapi::HidApi::new_without_enumerate()?;
+    let mut hidapi2 = hidapi::HidApi::new_without_enumerate()?;
+
+    // Create the monitor before enumerating existing devices so that we get
+    // duplicates if a device is plugged in during enumeration instead of missing it
+    let monitor = hidapi1.monitor()?;
+
+    hidapi2.add_devices(0, 0)?;
+
+    for device in hidapi2.device_list() {
+        log_device("initial device", device);
+    }
+
+    for event in monitor {
+        match event {
+            hidapi::Event::Add(device) => log_device("new device", &device),
+            event => println!("unknown monitor event: {event:?}"),
+        }
+    }
+
+    Ok(())
+}