backend: Add simple custom logger

backend/Cargo.toml

@@ -9,7 +9,7 @@ gio = "0.9.1"
 glib = "0.10.3"
 gstreamer = "0.16.4"
 gstreamer-player = "0.16.3"
-log = "0.4.14"
+log = { version = "0.4.14", features = ["std"] }
 musicus_client = { version = "0.1.0", path = "../client" }
 musicus_database = { version = "0.1.0", path = "../database" }
 musicus_import = { version = "0.1.0", path = "../import" }

backend/src/lib.rs

@@ -20,6 +20,8 @@ pub use error::*;
 pub mod library;
 pub use library::*;
 
+mod logger;
+
 pub mod player;
 pub use player::*;
 
@@ -70,8 +72,11 @@ pub struct Backend {
 
 impl Backend {
     /// Create a new backend initerface. The user interface should subscribe to the state stream
-    /// and call init() afterwards.
+    /// and call init() afterwards. There may be only one backend for a process and this method
+    /// may only be called exactly once. Otherwise it will panic.
     pub fn new() -> Self {
+        logger::register();
+
         let (state_sender, _) = broadcast::channel(1024);
         let (library_updated_sender, _) = broadcast::channel(1024);
 

backend/src/logger.rs

@@ -0,0 +1,63 @@
+use log::{Level, LevelFilter, Log, Metadata, Record};
+use std::{fmt::Display, sync::Mutex};
+
+/// Register the custom logger. This will panic if called more than once.
+pub fn register() {
+    log::set_boxed_logger(Box::new(Logger::default()))
+        .map(|()| log::set_max_level(LevelFilter::Info))
+        .unwrap();
+}
+
+/// A simple logging handler that prints out all messages and caches them for
+/// later access by the user interface.
+struct Logger {
+    /// All messages since the start of the program.
+    messages: Mutex<Vec<LogMessage>>,
+}
+
+impl Default for Logger {
+    fn default() -> Self {
+        Self {
+            messages: Mutex::new(Vec::new()),
+        }
+    }
+}
+
+impl Log for Logger {
+    fn enabled(&self, metadata: &Metadata) -> bool {
+        metadata.level() <= Level::Info
+    }
+
+    fn log(&self, record: &Record) {
+        if record.level() <= Level::Info {
+            let message = record.into();
+            println!("{}", message);
+            self.messages.lock().unwrap().push(message);
+        }
+    }
+
+    fn flush(&self) {}
+}
+
+/// A simplified representation of a [`Record`].
+struct LogMessage {
+    pub level: String,
+    pub module: String,
+    pub message: String,
+}
+
+impl<'a> From<&Record<'a>> for LogMessage {
+    fn from(record: &Record<'a>) -> Self {
+        Self {
+            level: record.level().to_string(),
+            module: String::from(record.module_path().unwrap_or_else(|| record.target())),
+            message: format!("{}", record.args()),
+        }
+    }
+}
+
+impl Display for LogMessage {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "{} ({}): {}", self.module, self.level, self.message)
+    }
+}

musicus/Cargo.toml

@@ -6,7 +6,6 @@ edition = "2018"
 [dependencies]
 anyhow = "1.0.33"
 async-trait = "0.1.42"
-env_logger = "0.8.3"
 futures-channel = "0.3.5"
 gettext-rs = { version = "0.5.0", features = ["gettext-system"] }
 gstreamer = "0.16.4"

musicus/src/main.rs

@@ -25,8 +25,6 @@ fn main() {
     gettextrs::bindtextdomain("musicus", config::LOCALEDIR);
     gettextrs::textdomain("musicus");
 
-    env_logger::init();
-
     gstreamer::init().expect("Failed to initialize GStreamer!");
     gtk::init().expect("Failed to initialize GTK!");
     libadwaita::init();