Run song length calculations asynchronously

Cargo.lock

@@ -790,6 +790,7 @@ dependencies = [
 name = "delyrium"
 version = "0.1.0"
 dependencies = [
+ "blocking",
  "exoquant",
  "iced",
  "iced_futures",

Cargo.toml

@@ -19,6 +19,10 @@ iced_native = "0.4.0"
 # Native file dialogs
 rfd = "0.6.3"
 
+# Run long-running blocking tasks in another thread
+# Also used by iced, so we share a threadpool
+blocking = "1.1.0"
+
 [dependencies.symphonia]
 # Music decoding and metadata parsing
 features = ["isomp4", "aac", "mp3"]

src/app.rs

@@ -91,7 +91,9 @@ impl Application for DelyriumApp {
 			Message::FileOpened(path) => {
 				println!("File opened! {}", path.display());
 				let song = load_song(&path).unwrap().format;
-				self.lyrics_component = Some(Editor::new(song, self.size));
+				let (editor, cmd) = Editor::new(song, self.size);
+				self.lyrics_component = Some(editor);
+				command = Some(cmd);
 			},
 			Message::PromptForFile => {
 				let task = async {

src/controls.rs

@@ -1,3 +1,5 @@
+use iced::Command;
+use core::time::Duration;
 use iced::Length;
 use iced::Color;
 use symphonia::core::formats::FormatReader;
@@ -14,11 +16,13 @@ use iced::canvas::Program;
 use iced::Canvas;
 use iced::mouse::{self, Button};
 use crate::player::Player;
+use blocking::unblock;
 
 #[derive(Debug, Clone, Copy)]
 pub enum ControlsEvent {
 	SeekPosition(f32),
 	TogglePlay,
+	DurationDiscovered(Duration),
 }
 
 enum ErrorState {
@@ -36,20 +40,26 @@ pub struct Controls {
 }
 
 impl Controls {
-	pub fn new(song: Box<dyn FormatReader>) -> Self {
+	pub fn new(song: Box<dyn FormatReader>) -> (Self, Command<Message>) {
 		match Player::new(song) {
 			Ok(player) => {
-				Controls {
+				let duration_task = unblock(player.compute_duration());
+				let duration_cmd = Command::perform(
+					duration_task,
+					|d| Message::ControlsEvent(ControlsEvent::DurationDiscovered(d)),
+				);
+
+				(Controls {
 					error_state: NoError {
 						has_device: player.has_output_device(),
 						player,
 					}
-				}
+				}, duration_cmd)
 			},
 			Err(e) => {
-				Controls {
+				(Controls {
 					error_state: Error(e)
-				}
+				}, Command::none())
 			}
 		}
 	}
@@ -65,6 +75,11 @@ impl Controls {
 			let result = match event {
 				ControlsEvent::SeekPosition(pos) => player.seek_percentage(pos),
 				ControlsEvent::TogglePlay => player.toggle_play(),
+				ControlsEvent::DurationDiscovered(d) => {
+					player.set_duration(d);
+					println!("Found duration!  {:?}", d);
+					Ok(player.has_output_device())
+				},
 			};
 
 			match result {

src/editor.rs

@@ -1,3 +1,4 @@
+use iced::Command;
 use iced::Image;
 use iced::image::Handle;
 use image::DynamicImage;
@@ -28,7 +29,7 @@ pub struct Editor {
 }
 
 impl Editor {
-	pub fn new(mut song: Box<dyn FormatReader>, size: (u32, u32)) -> Self {
+	pub fn new(mut song: Box<dyn FormatReader>, size: (u32, u32)) -> (Self, Command<Message>) {
 		let cover = extract_cover(song.as_mut());
 
 		let theme = cover.as_ref()
@@ -43,14 +44,14 @@ impl Editor {
 				cover.blur((cover.width() / 50) as f32).into_bgra8()
 		);
 
-		let controls = Controls::new(song);
+		let (controls, cmd) = Controls::new(song);
 
-		Self {
+		(Self {
 			lyrics: Lyrics::new(),
 			dimensions: size,
 			cached_resized_bg: None,
 			controls, theme, bg_img,
-		}
+		}, cmd)
 	}
 
 	// TODO: work on untangling this mess

src/player.rs

@@ -29,13 +29,18 @@ pub struct Player {
 impl Player {
 
 	/// Create a new player from a song
+	///
+	/// IMPORTANT:  Because computing the duration of a song is currently a very expensive
+	/// task, this DOES NOT COMPUTE THE DURATION.  All calculations that require a
+	/// duration assume a duration of 2:30s until a duration is manually calculated with
+	/// [`compute_duration()`] AND passed back into [`set_duration()`].
 	pub fn new(song: Box<dyn FormatReader>) -> Result<Self, PlayerError> {
 
 		let song = Decoder::new_from_format_reader(song)
 			.map_err(PlayerError::DecoderError)?
 			.buffered();
 
-		let duration = get_duration_of_song(song.clone());
+		let duration = Duration::from_secs(150);
 
 		let mut player = Player {
 			sink: None,
@@ -221,20 +226,49 @@ impl Player {
 		// nightly: self.position().div_duration_f32(self.duration)
 		self.position().as_secs_f32() / self.duration.as_secs_f32()
 	}
-}
 
-/// Manually calculate the exact length of a given song
-///
-/// This is really expensive, and involves decoding and inefficiently counting the number
-/// of samples in the song, but produces an exact output.  Use sparingly.
-fn get_duration_of_song(song: Song) -> Duration {
-	let sample_rate = song.sample_rate() as u64;
-	let n_channels = song.channels() as u64;
-	let n_samples = song.count() as u64; // expensive!
-	let n_whole_seconds = n_samples / n_channels / sample_rate;
-	let remaining_samples = n_samples % sample_rate;
-	let n_nanos = remaining_samples * 1_000_000_000 / sample_rate;
-	Duration::new(n_whole_seconds, n_nanos as u32)
+	/// Computes the exact duration of the current song.
+	///
+	/// This is an EXPENSIVE, BLOCKING long-running function that should be run in a
+	/// seperate thread.  Hopefully this will be optimized in the future, but this is what
+	/// we have for now.
+	///
+	/// This does not set the duration of this song, so be sure to call [`set_duration()`]
+	/// with the result of this call after it finishes executing.
+	///
+	/// Note:  This doesn't actually preform the calculation, but instead returns a
+	/// `'static FnOnce` that can be used to do so, in order to simplify running the
+	/// transaction in another thread.
+	///
+	/// Technical Details:  Currently, this involves decoding and inefficiently counting
+	/// the number of samples in the song.  Hopefully, we'll be able to do this more
+	/// efficiently in the future, pending mostly on
+	/// https://github.com/RustAudio/rodio/issues/405
+	pub fn compute_duration(&self) -> impl FnOnce() -> Duration {
+		let sample_rate = self.song.sample_rate() as u64;
+		let n_channels = self.song.channels() as u64;
+		let song_clone = self.song.clone();
+
+		move|| {
+			let n_samples = song_clone.count() as u64; // expensive!
+			let n_whole_seconds = n_samples / n_channels / sample_rate;
+			let remaining_samples = n_samples % sample_rate;
+			let n_nanos = remaining_samples * 1_000_000_000 / sample_rate;
+			Duration::new(n_whole_seconds, n_nanos as u32)
+		}
+	}
+
+	/// Set the duration of the song
+	///
+	/// This struct does not automatically compute its own duration, so until this method
+	/// is called, we just assume the duration is 2:30s for any calculations that require
+	/// it.
+	///
+	/// In order to use an exact duration, use another thread to run
+	/// [`compute_duration()`] and pass the result into this method.
+	pub fn set_duration(&mut self, duration: Duration) {
+		self.duration = duration;
+	}
 }
 
 #[derive(Debug)]