app: Spawn using double-fork

Cargo.toml

@@ -29,6 +29,7 @@ itertools = "0.11"
 freedesktop-icons = "0.2.4"
 current_locale = "0.1.1"
 url = "2.4"
+nix = "0.26"
 
 [profile.release]
 lto = "thin"

src/app.rs

@@ -239,7 +239,7 @@ impl cosmic::Application for CosmicAppLibrary {
             Message::ActivationToken(token, exec) => {
                 let mut exec = shlex::Shlex::new(&exec);
                 let mut cmd = match exec.next() {
-                    Some(cmd) if !cmd.contains("=") => tokio::process::Command::new(cmd),
+                    Some(cmd) if !cmd.contains("=") => std::process::Command::new(cmd),
                     _ => return Command::none(),
                 };
                 for arg in exec {
@@ -252,7 +252,9 @@ impl cosmic::Application for CosmicAppLibrary {
                     cmd.env("XDG_ACTIVATION_TOKEN", token.clone());
                     cmd.env("DESKTOP_STARTUP_ID", token);
                 }
-                let _ = cmd.spawn();
+                tokio::task::spawn_blocking(|| {
+                    crate::process::spawn(cmd);
+                });
                 return self.update(Message::Hide);
             }
             Message::SelectGroup(i) => {

src/main.rs

@@ -3,6 +3,7 @@ mod config;
 mod app;
 mod app_group;
 mod localize;
+pub mod process;
 mod subscriptions;
 mod widgets;
 

src/process.rs

@@ -0,0 +1,31 @@
+use std::process::{exit, Command, Stdio};
+
+use nix::sys::wait::waitpid;
+use nix::unistd::{fork, ForkResult};
+
+/// Performs a double fork with setsid to spawn and detach a command.
+pub fn spawn(mut command: Command) {
+    command
+        .stdin(Stdio::null())
+        .stdout(Stdio::null())
+        .stderr(Stdio::null());
+
+    unsafe {
+        match fork() {
+            Ok(ForkResult::Parent { child }) => {
+                let _res = waitpid(Some(child), None);
+            }
+
+            Ok(ForkResult::Child) => {
+                let _res = nix::unistd::setsid();
+                let _res = command.spawn();
+
+                exit(0);
+            }
+
+            Err(why) => {
+                println!("failed to fork and spawn command: {}", why.desc());
+            }
+        }
+    }
+}