Better isolation of window change event handling code

src/main.rs

@@ -16,7 +16,7 @@ use std::{
 };
 
 use sm_session_notifier::SMSessionNotifier;
-use window_change::{win_event_hook_loop, WIN_CHANGE_CALLBACK};
+use window_change::{await_win_change_events};
 use windows::{
     core::Interface,
     Win32::{
@@ -131,9 +131,7 @@ fn main() {
         .boot_devices()
         .expect("failed to get initial audio devices and sessions");
 
-    *WIN_CHANGE_CALLBACK.lock().unwrap() = Some(Box::new(move |s| {
+    await_win_change_events(Box::new(move |s| {
         muter.lock().unwrap().notify_window_changed(&s)
     }));
-
-    win_event_hook_loop();
 }

src/window_change.rs

@@ -14,7 +14,7 @@ use windows::Win32::{
 
 use crate::pid_to_exe::pid_to_exe_path;
 
-pub static WIN_CHANGE_CALLBACK: Mutex<Option<Box<dyn Fn(&str)+Send>>> = Mutex::new(None);
+static WIN_CHANGE_CALLBACK: Mutex<Option<Box<dyn Fn(&str)+Send>>> = Mutex::new(None);
 
 unsafe extern "system" fn win_event_proc(
     _hook: HWINEVENTHOOK,
@@ -48,7 +48,8 @@ unsafe extern "system" fn win_event_proc(
     }
 }
 
-pub fn win_event_hook_loop() {
+pub fn await_win_change_events(callback: Box<dyn Fn(&str) + Send>) {
+    *WIN_CHANGE_CALLBACK.lock().unwrap() = Some(callback);
     unsafe {
         SetWinEventHook(
             EVENT_SYSTEM_FOREGROUND,