release stuck keys (#53)

Keys are now released when
- A client disconnects and still has pressed keys
- A client disconnects through CTLR+ALT+SHIFT+WIN
- Lan Mouse terminates with keys still being pressed through a remote client

This is also fixes an issue caused by KDE's implementation of the remote desktop portal backend:
Keys are not correctly released when a remote desktop session is closed while keys are still pressed,
causing them to be permanently stuck until kwin is restarted.

This workaround remembers all pressed keys and releases them when lan-mouse exits or a device disconnects.

closes #15

src/client.rs

@@ -2,7 +2,6 @@ use std::{
     collections::HashSet,
     fmt::Display,
     net::{IpAddr, SocketAddr},
-    time::Instant,
 };
 
 use serde::{Deserialize, Serialize};
@@ -57,10 +56,6 @@ pub struct Client {
     /// This way any event consumer / producer backend does not
     /// need to know anything about a client other than its handle.
     pub handle: ClientHandle,
-    /// `active` address of the client, used to send data to.
-    /// This should generally be the socket address where data
-    /// was last received from.
-    pub active_addr: Option<SocketAddr>,
     /// all socket addresses associated with a particular client
     /// e.g. Laptops usually have at least an ethernet and a wifi port
     /// which have different ip addresses
@@ -71,7 +66,7 @@ pub struct Client {
     pub pos: Position,
 }
 
-#[derive(Debug)]
+#[derive(Clone, Copy, Debug)]
 pub enum ClientEvent {
     Create(ClientHandle, Position),
     Destroy(ClientHandle),
@@ -81,11 +76,18 @@ pub type ClientHandle = u32;
 
 #[derive(Debug, Clone)]
 pub struct ClientState {
+    /// information about the client
     pub client: Client,
+    /// events should be sent to and received from the client
     pub active: bool,
-    pub last_ping: Option<Instant>,
-    pub last_seen: Option<Instant>,
-    pub last_replied: Option<Instant>,
+    /// `active` address of the client, used to send data to.
+    /// This should generally be the socket address where data
+    /// was last received from.
+    pub active_addr: Option<SocketAddr>,
+    /// tracks whether or not the client is responding to pings
+    pub alive: bool,
+    /// keys currently pressed by this client
+    pub pressed_keys: HashSet<u32>,
 }
 
 pub struct ClientManager {
@@ -114,9 +116,6 @@ impl ClientManager {
         // get a new client_handle
         let handle = self.free_id();
 
-        // we dont know, which IP is initially active
-        let active_addr = None;
-
         // store fix ip addresses
         let fix_ips = ips.iter().cloned().collect();
 
@@ -128,7 +127,6 @@ impl ClientManager {
             hostname,
             fix_ips,
             handle,
-            active_addr,
             addrs,
             port,
             pos,
@@ -137,10 +135,10 @@ impl ClientManager {
         // client was never seen, nor pinged
         let client_state = ClientState {
             client,
-            last_ping: None,
-            last_seen: None,
-            last_replied: None,
             active: false,
+            active_addr: None,
+            alive: false,
+            pressed_keys: HashSet::new(),
         };
 
         if handle as usize >= self.clients.len() {