Be more robust in restoring canonical mode

src/main.rs

@@ -22,6 +22,28 @@ lazy_static! {
     pub static ref ORIGINAL_TERMIOS: Arc<Mutex<Termios>> = Arc::new(Mutex::new(get_termios(STDOUT_FILENO)));
 }
 
+struct OnExit<T: FnOnce() -> ()> {
+    destructor: Option<T>,
+}
+
+impl<T> OnExit<T> where T: FnOnce() -> () {
+    fn new(destructor: T) -> OnExit<T> {
+        OnExit {
+            destructor: Some(destructor),
+        }
+    }
+}
+
+impl<T> Drop for OnExit<T> where T: FnOnce() -> () {
+    fn drop(&mut self) {
+        if self.destructor.is_some() {
+            let option = self.destructor.take();
+            let destructor = option.unwrap();
+            destructor();
+        }
+    }
+}
+
 fn main() -> Result<(), Error> {
     // Save existing Termios settings
     lazy_static::initialize(&ORIGINAL_TERMIOS);
@@ -29,6 +51,9 @@ fn main() -> Result<(), Error> {
     // Disable canonical/"cooked" terminal mode
     enable_raw_mode();
 
+    // Revert raw mode on exit
+    let _destructor = OnExit::new(disable_raw_mode);
+
     // Initialize the editor
     let mut editor = Editor::new();
 
@@ -51,8 +76,5 @@ fn main() -> Result<(), Error> {
         }
     }
 
-    // Restore previous terminal flags before exit
-    disable_raw_mode();
-
     Ok(())
 }