ui: xbiff(1) support

ui/src/components/notifications.rs

@@ -152,6 +152,22 @@ impl Component for NotificationFilter {
                     debug!("{:?}", v);
                 }
             }
+
+            match kind {
+                Some(NotificationType::NewMail) => {
+                    if let Some(ref path) = context.runtime_settings.notifications.xbiff_file_path {
+                        let mut file = std::fs::OpenOptions::new().append(true) /* writes will append to a file instead of overwriting previous contents */
+                         .create(true) /* a new file will be created if the file does not yet already exist.*/
+                         .open(path).unwrap();
+                        if file.metadata().unwrap().len() > 128 {
+                            file.set_len(0).unwrap();
+                        } else {
+                            std::io::Write::write_all(&mut file, b"z").unwrap();
+                        }
+                    }
+                }
+                _ => {}
+            }
         }
         false
     }

ui/src/conf/notifications.rs

@@ -33,6 +33,11 @@ pub struct NotificationsSettings {
     /// Default: None
     #[serde(default = "none")]
     pub script: Option<String>,
+    /// A file location which has its size changed when new mail arrives (max 128 bytes). Can be
+    /// used to trigger new mail notifications eg with `xbiff(1)`
+    /// Default: None
+    #[serde(default = "none")]
+    pub xbiff_file_path: Option<String>,
     #[serde(deserialize_with = "toggleflag_de", default = "internal_value_false")]
     pub play_sound: super::ToggleFlag,
     #[serde(default = "none")]