config: expose configuration generation number

src/config/mod.rs

@@ -39,7 +39,7 @@ pub use unix::*;
 lazy_static! {
     static ref HOME_DIR: PathBuf = dirs::home_dir().expect("can't find HOME dir");
     static ref RUNTIME_DIR: PathBuf = compute_runtime_dir().unwrap();
-    static ref CONFIG: ConfigHandle = ConfigHandle::new();
+    static ref CONFIG: Configuration = Configuration::new();
 }
 
 /// Discard the current configuration and replace it with
@@ -49,13 +49,13 @@ pub fn use_default_configuration() {
 }
 
 /// Returns a handle to the current configuration
-pub fn configuration() -> Arc<Config> {
+pub fn configuration() -> ConfigHandle {
     CONFIG.get()
 }
 
 /// If there was an error loading the preferred configuration,
 /// return it, otherwise return the current configuration
-pub fn configuration_result() -> Result<Arc<Config>, Error> {
+pub fn configuration_result() -> Result<ConfigHandle, Error> {
     if let Some(error) = CONFIG.get_error() {
         failure::bail!("{}", error);
     }
@@ -65,6 +65,7 @@ pub fn configuration_result() -> Result<Arc<Config>, Error> {
 struct ConfigInner {
     config: Arc<Config>,
     error: Option<String>,
+    generation: usize,
 }
 
 impl ConfigInner {
@@ -76,10 +77,12 @@ impl ConfigInner {
             Ok(config) => Self {
                 config: Arc::new(config),
                 error: None,
+                generation: 0,
             },
             Err(err) => Self {
                 config: Arc::new(Config::default_config()),
                 error: Some(err.to_string()),
+                generation: 0,
             },
         }
     }
@@ -94,6 +97,7 @@ impl ConfigInner {
             Ok(config) => {
                 self.config = Arc::new(config);
                 self.error.take();
+                self.generation += 1;
             }
             Err(err) => {
                 self.error.replace(err.to_string());
@@ -107,14 +111,15 @@ impl ConfigInner {
     fn use_defaults(&mut self) {
         self.config = Arc::new(Config::default_config());
         self.error.take();
+        self.generation += 1;
     }
 }
 
-pub struct ConfigHandle {
+pub struct Configuration {
     inner: Mutex<ConfigInner>,
 }
 
-impl ConfigHandle {
+impl Configuration {
     pub fn new() -> Self {
         Self {
             inner: Mutex::new(ConfigInner::load()),
@@ -122,8 +127,12 @@ impl ConfigHandle {
     }
 
     /// Returns the effective configuration.
-    pub fn get(&self) -> Arc<Config> {
-        Arc::clone(&self.inner.lock().unwrap().config)
+    pub fn get(&self) -> ConfigHandle {
+        let inner = self.inner.lock().unwrap();
+        ConfigHandle {
+            config: Arc::clone(&inner.config),
+            generation: inner.generation,
+        }
     }
 
     /// Reset the configuration to defaults
@@ -153,6 +162,29 @@ impl ConfigHandle {
     }
 }
 
+#[derive(Clone, Debug)]
+pub struct ConfigHandle {
+    config: Arc<Config>,
+    generation: usize,
+}
+
+impl ConfigHandle {
+    /// Returns the generation number for the configuration,
+    /// allowing consuming code to know whether the config
+    /// has been reloading since they last derived some
+    /// information from the configuration
+    pub fn generation(&self) -> usize {
+        self.generation
+    }
+}
+
+impl std::ops::Deref for ConfigHandle {
+    type Target = Config;
+    fn deref(&self) -> &Config {
+        &*self.config
+    }
+}
+
 #[derive(Debug, Deserialize, Clone)]
 pub struct Config {
     /// The font size, measured in points

src/font/mod.rs

@@ -8,7 +8,6 @@ use self::hbwrap as harfbuzz;
 use std::cell::RefCell;
 use std::collections::HashMap;
 use std::rc::Rc;
-use std::sync::Arc;
 
 pub mod system;
 pub use self::system::*;
@@ -28,7 +27,7 @@ pub mod fontloader;
 #[cfg(any(target_os = "macos", windows))]
 pub mod fontloader_and_freetype;
 
-use super::config::{configuration, Config, TextStyle};
+use super::config::{configuration, ConfigHandle, TextStyle};
 use term::CellAttributes;
 
 type FontPtr = Rc<RefCell<Box<dyn NamedFont>>>;
@@ -194,7 +193,7 @@ impl FontConfiguration {
     /// cell attributes.
     pub fn match_style<'a>(
         &self,
-        config: &'a Arc<Config>,
+        config: &'a ConfigHandle,
         attrs: &CellAttributes,
     ) -> &'a TextStyle {
         // a little macro to avoid boilerplate for matching the rules.

src/frontend/gui/termwindow.rs

@@ -2,7 +2,7 @@ use super::quad::*;
 use super::renderstate::*;
 use super::utilsprites::RenderMetrics;
 use crate::clipboard::SystemClipboard;
-use crate::config::{configuration, Config};
+use crate::config::{configuration, ConfigHandle};
 use crate::font::{FontConfiguration, FontSystemSelection};
 use crate::frontend::gui::tabbar::{TabBarItem, TabBarState};
 use crate::frontend::{executor, front_end};
@@ -356,7 +356,7 @@ impl WindowCallbacks for TermWindow {
 
 impl TermWindow {
     pub fn new_window(
-        config: &Arc<Config>,
+        config: &ConfigHandle,
         fontconfig: &Rc<FontConfiguration>,
         tab: &Rc<dyn Tab>,
         mux_window_id: MuxWindowId,

src/main.rs

@@ -342,7 +342,7 @@ impl SshParameters {
     }
 }
 
-fn run_ssh(config: Arc<config::Config>, opts: &SshCommand) -> Fallible<()> {
+fn run_ssh(config: config::ConfigHandle, opts: &SshCommand) -> Fallible<()> {
     let front_end_selection = opts.front_end.unwrap_or(config.front_end);
     let gui = front_end_selection.try_new()?;
 
@@ -410,7 +410,7 @@ fn run_ssh(config: Arc<config::Config>, opts: &SshCommand) -> Fallible<()> {
     gui.run_forever()
 }
 
-fn run_serial(config: Arc<config::Config>, opts: &SerialCommand) -> Fallible<()> {
+fn run_serial(config: config::ConfigHandle, opts: &SerialCommand) -> Fallible<()> {
     let font_system = opts.font_system.unwrap_or(config.font_system);
     font_system.set_default();
 
@@ -437,7 +437,7 @@ fn run_serial(config: Arc<config::Config>, opts: &SerialCommand) -> Fallible<()>
     gui.run_forever()
 }
 
-fn client_domains(config: &Arc<config::Config>) -> Vec<ClientDomainConfig> {
+fn client_domains(config: &config::ConfigHandle) -> Vec<ClientDomainConfig> {
     let mut domains = vec![];
     for unix_dom in &config.unix_domains {
         domains.push(ClientDomainConfig::Unix(unix_dom.clone()));
@@ -453,7 +453,7 @@ fn client_domains(config: &Arc<config::Config>) -> Vec<ClientDomainConfig> {
     domains
 }
 
-fn run_mux_client(config: Arc<config::Config>, opts: &ConnectCommand) -> Fallible<()> {
+fn run_mux_client(config: config::ConfigHandle, opts: &ConnectCommand) -> Fallible<()> {
     let client_config = client_domains(&config)
         .into_iter()
         .find(|c| c.name() == opts.domain_name)
@@ -500,7 +500,7 @@ fn run_mux_client(config: Arc<config::Config>, opts: &ConnectCommand) -> Fallibl
     gui.run_forever()
 }
 
-fn run_terminal_gui(config: Arc<config::Config>, opts: &StartCommand) -> Fallible<()> {
+fn run_terminal_gui(config: config::ConfigHandle, opts: &StartCommand) -> Fallible<()> {
     #[cfg(unix)]
     {
         if opts.daemonize {