Add the ability to switch to a different monitor input when usb disco…

…nnected

Closes #7

README.md

@@ -26,13 +26,18 @@ Configuration file settings:
 
 ```ini
   usb_device = "1050:0407"
-  monitor_input = "Hdmi1"
+  on_usb_connect = "Hdmi1"
+  on_usb_disconnect = "Hdmi2"
 ```
 
-`usb_device` is which USB device to watch (vendor id / device id in hex), and `monitor_input` is which monitor input
-to switch to, when this device is connected. Supported values are `Hdmi1`, `Hdmi2`, `DisplayPort1`, `DisplayPort2`
+`usb_device` is which USB device to watch (vendor id / device id in hex), and `on_usb_connect` is which monitor input
+to switch to, when this device is connected. Supported values are `Hdmi1`, `Hdmi2`, `DisplayPort1`, `DisplayPort2`.
 If your monitor has an USB-C port, it's usually reported as `DisplayPort2`. Input can also be specified as a "raw"
-decimal or hexadecimal value: `monitor_input = 0x10`
+decimal or hexadecimal value: `on_usb_connect = 0x10`
+
+The optional `on_usb_disconnect` settings allows to switch in the other direction when the USB device is disconnected.
+Note that the preferred way is to have this app installed on both computers. Switching "away" is problematic: if the
+other computer has put the monitors to sleep, they will switch immediately back to the original input.
 
 ### USB Device IDs
 To locate the ID of your USB device ID on Windows:

src/app.rs

@@ -18,16 +18,24 @@ impl usb::UsbCallback for App {
     fn device_added(&self, device_id: &str) {
         debug!("Detected device change. Added device: {:?}", device_id);
         if device_id == self.config.usb_device {
-            info!("Detected device we're looking for {:?}", &self.config.usb_device);
+            info!("Monitored device ({:?}) is connected", &self.config.usb_device);
             std::thread::spawn(|| {
                 wake_displays().map_err(|err| error!("{:?}", err));
             });
-            display_control::switch_to(self.config.monitor_input);
+            if let Some(input) = self.config.on_usb_connect {
+                display_control::switch_to(input);
+            }
         }
     }
 
     fn device_removed(&self, device_id: &str) {
         debug!("Detected device change. Removed device: {:?}", device_id);
+        if device_id == self.config.usb_device {
+            info!("Monitored device is ({:?}) is disconnected", &self.config.usb_device);
+            if let Some(input) = self.config.on_usb_disconnect {
+                display_control::switch_to(input);
+            }
+        }
     }
 }
 

src/configuration.rs

@@ -11,7 +11,9 @@ use serde::{Deserialize, Deserializer};
 pub struct Configuration {
     #[serde(deserialize_with = "Configuration::deserialize_usb_device")]
     pub usb_device: String,
-    pub monitor_input: InputSource,
+    #[serde(alias = "monitor_input")]
+    pub on_usb_connect: Option<InputSource>,
+    pub on_usb_disconnect: Option<InputSource>,
 }
 
 impl Configuration {
@@ -99,11 +101,13 @@ mod tests {
         let config = load_test_config(
             r#"
             usb_device = "dead:BEEF"
-            monitor_input = "DisplayPort2"
+            on_usb_connect = "DisplayPort2"
+            on_usb_disconnect = DisplayPort1
         "#,
         )
         .unwrap();
-        assert_eq!(config.monitor_input.value(), 0x10);
+        assert_eq!(config.on_usb_connect.unwrap().value(), 0x10);
+        assert_eq!(config.on_usb_disconnect.unwrap().value(), 0x0f);
     }
 
     #[test]
@@ -112,21 +116,25 @@ mod tests {
             r#"
             usb_device = "dead:BEEF"
             monitor_input = 22
+            on_usb_disconnect = 33
         "#,
         )
         .unwrap();
-        assert_eq!(config.monitor_input.value(), 22);
+        assert_eq!(config.on_usb_connect.unwrap().value(), 22);
+        assert_eq!(config.on_usb_disconnect.unwrap().value(), 33);
     }
 
     #[test]
     fn test_hexadecimal_input_deserialization() {
         let config = load_test_config(
             r#"
             usb_device = "dead:BEEF"
-            monitor_input = "0x10"
+            on_usb_connect = "0x10"
+            on_usb_disconnect = "0x20"
         "#,
         )
         .unwrap();
-        assert_eq!(config.monitor_input.value(), 16);
+        assert_eq!(config.on_usb_connect.unwrap().value(), 0x10);
+        assert_eq!(config.on_usb_disconnect.unwrap().value(), 0x20);
     }
 }

src/input_source.rs

@@ -3,11 +3,11 @@
 // This code is licensed under MIT license (see LICENSE.txt for details)
 //
 
+use paste::paste;
 use serde::de::Error;
 use serde::{Deserialize, Deserializer};
 use std::convert::TryFrom;
 use std::fmt;
-use paste::paste;
 
 macro_rules! symbolic_input_source {
     (