feat(app,player): choose audio and subtitle languages in desktop Settings

The phones have had this, and the desktop could only set languages from
the player, after a file had already opened in the wrong one. Settings
now has an audio language and a subtitle choice: off, the file's
default, or a language. The names come from the list pstr-player already
names tracks with, now exported as LANGUAGES.

crates/pstr-app/src/app.rs

@@ -223,6 +223,13 @@ pub enum Action {
     PlayAdjacent(Adjacent),
     /// Start or stop the next episode playing on its own at the end of one.
     SetAutoplay(bool),
+    /// The audio and subtitle languages a file is opened with, for titles
+    /// without a choice of their own. `subtitles` false is "off".
+    SetLanguages {
+        audio: Option<String>,
+        subtitles: bool,
+        subtitle: Option<String>,
+    },
     /// Play faster or slower, and keep doing so for the next file.
     SetSpeed(f64),
     /// Seek past openings and credits without being asked.
@@ -1877,6 +1884,17 @@ impl App {
                 prefs.autoplay_next = autoplay;
                 self.engine.set_playback_prefs(prefs, true);
             }
+            Action::SetLanguages {
+                audio,
+                subtitles,
+                subtitle,
+            } => {
+                let mut prefs = self.engine.playback_prefs();
+                prefs.audio_language = audio;
+                prefs.subtitles = subtitles;
+                prefs.subtitle_language = subtitle;
+                self.engine.set_playback_prefs(prefs, true);
+            }
             Action::SetAppearance(appearance) => {
                 self.engine.set_appearance(appearance);
                 theme::apply(ctx, appearance);
@@ -2218,6 +2236,7 @@ impl eframe::App for App {
             let prefs = ui::settings::Prefs {
                 autoplay: playback_prefs.autoplay_next,
                 auto_skip: playback_prefs.auto_skip,
+                playback: &playback_prefs,
                 appearance: self.engine.appearance(),
                 desktop: self.engine.desktop_prefs(),
                 cache_used: (self.page == Page::Settings)

crates/pstr-app/src/ui/settings.rs

@@ -7,6 +7,8 @@
 
 use pstr_core::appearance::{Accent, Appearance, Flavor, Tiles};
 use pstr_core::metadata::{MetadataConfig, ProviderId, TitleNames};
+use pstr_core::prefs::PlaybackPrefs;
+use pstr_player::LANGUAGES;
 
 use crate::app::Action;
 use crate::desktop_prefs::{CACHE_CHOICES, DesktopPrefs};
@@ -19,9 +21,11 @@ use crate::ui;
 /// they are read-only, and passing them one by one is what pushed this
 /// function past the argument count anybody can read.
 #[derive(Debug, Clone, Copy)]
-pub struct Prefs {
+pub struct Prefs<'a> {
     pub autoplay: bool,
     pub auto_skip: bool,
+    /// The languages, read from here.
+    pub playback: &'a PlaybackPrefs,
     pub appearance: Appearance,
     pub desktop: DesktopPrefs,
     /// What the streaming cache holds, once the shares are open.
@@ -35,7 +39,7 @@ const COLUMN: f32 = 760.0;
 pub fn show(
     ui: &mut egui::Ui,
     settings: &mut MetadataConfig,
-    prefs: Prefs,
+    prefs: Prefs<'_>,
     api_key: &mut String,
     actions: &mut Vec<Action>,
 ) {
@@ -271,16 +275,18 @@ fn swatch(ui: &mut egui::Ui, appearance: Appearance, accent: Accent) -> egui::Re
 
 /// The playback settings that are not per-file.
 ///
-/// Volume, audio language, subtitle language and speed are all set from the
-/// player itself, where a viewer can hear the result.
-fn playback_form(ui: &mut egui::Ui, prefs: Prefs, actions: &mut Vec<Action>) {
+/// Volume and speed are set from the player itself, where a viewer can hear
+/// the result. The languages are here as well as there: what a first episode
+/// opens with is decided before there is a player to choose from.
+fn playback_form(ui: &mut egui::Ui, prefs: Prefs<'_>, actions: &mut Vec<Action>) {
     ui::widgets::settings_group(
         ui,
         "Playback",
         Some(
-            "Volume, audio, subtitles and speed are set from the player, and remembered from there.",
+            "Volume and speed are set from the player. A language chosen in the player for one show is kept for that show.",
         ),
         |ui| {
+            languages(ui, prefs.playback, actions);
             let mut autoplay = prefs.autoplay;
             ui::widgets::settings_row(
                 ui,
@@ -322,8 +328,80 @@ fn playback_form(ui: &mut egui::Ui, prefs: Prefs, actions: &mut Vec<Action>) {
     );
 }
 
+/// The audio and subtitle languages every file opens with, until a show has a
+/// choice of its own.
+fn languages(ui: &mut egui::Ui, playback: &PlaybackPrefs, actions: &mut Vec<Action>) {
+    let name = |tag: &Option<String>| match tag {
+        Some(tag) => pstr_player::language_name(tag),
+        None => "The file's default".to_owned(),
+    };
+    let audio = playback.audio_language.clone();
+    ui::widgets::settings_row(
+        ui,
+        "Audio language",
+        Some("Played when a file has it."),
+        |ui| {
+            egui::ComboBox::from_id_salt("audio-language")
+                .selected_text(name(&audio))
+                .show_ui(ui, |ui| {
+                    for choice in
+                        std::iter::once(None).chain(LANGUAGES.map(|tag| Some(tag.to_owned())))
+                    {
+                        if ui
+                            .selectable_label(audio == choice, name(&choice))
+                            .clicked()
+                            && audio != choice
+                        {
+                            actions.push(Action::SetLanguages {
+                                audio: choice,
+                                subtitles: playback.subtitles,
+                                subtitle: playback.subtitle_language.clone(),
+                            });
+                        }
+                    }
+                });
+        },
+    );
+    // Off, the file's default, or a language: "off" is a decision of its
+    // own, which no language expresses.
+    let subtitle = playback
+        .subtitles
+        .then(|| playback.subtitle_language.clone());
+    let subtitle_name = |choice: &Option<Option<String>>| match choice {
+        None => "Off".to_owned(),
+        Some(tag) => name(tag),
+    };
+    ui::widgets::settings_row(
+        ui,
+        "Subtitles",
+        Some("Shown when a file has them in this language."),
+        |ui| {
+            egui::ComboBox::from_id_salt("subtitle-language")
+                .selected_text(subtitle_name(&subtitle))
+                .show_ui(ui, |ui| {
+                    let choices = [None, Some(None)]
+                        .into_iter()
+                        .chain(LANGUAGES.map(|tag| Some(Some(tag.to_owned()))));
+                    for choice in choices {
+                        if ui
+                            .selectable_label(subtitle == choice, subtitle_name(&choice))
+                            .clicked()
+                            && subtitle != choice
+                        {
+                            actions.push(Action::SetLanguages {
+                                audio: playback.audio_language.clone(),
+                                subtitles: choice.is_some(),
+                                subtitle: choice.flatten(),
+                            });
+                        }
+                    }
+                });
+        },
+    );
+}
+
 /// The streaming cache: how big it may get, and a way to empty it.
-fn storage_form(ui: &mut egui::Ui, prefs: Prefs, actions: &mut Vec<Action>) {
+fn storage_form(ui: &mut egui::Ui, prefs: Prefs<'_>, actions: &mut Vec<Action>) {
     ui::widgets::settings_group(
         ui,
         "Storage",

crates/pstr-player/src/lib.rs

@@ -52,4 +52,4 @@ pub use player::{
 };
 pub use registry::{PROTOCOL, StreamHandle, StreamRegistry};
 pub use render::VideoRenderer;
-pub use tracks::{Track, TrackKind, language_name, pick_track};
+pub use tracks::{LANGUAGES, Track, TrackKind, language_name, pick_track};

crates/pstr-player/src/tracks.rs

@@ -190,6 +190,16 @@ fn flag(mpv: &Mpv, index: i64, field: &str) -> bool {
         .unwrap_or(false)
 }
 
+/// The languages offered by name where a preference is chosen ahead of any
+/// file, as the three-letter tag a Matroska file carries. The same list
+/// [`language_name`] knows, and the phones' `LANGUAGES`; mpv treats the two-
+/// and three-letter forms as one.
+pub const LANGUAGES: [&str; 29] = [
+    "jpn", "eng", "ger", "fre", "spa", "ita", "por", "dut", "rus", "pol", "swe", "dan", "nor",
+    "fin", "cze", "hun", "tur", "ara", "heb", "hin", "kor", "chi", "tha", "vie", "ukr", "rum",
+    "gre", "ind", "may",
+];
+
 /// A readable name for a language tag, falling back to the tag itself.
 ///
 /// Deliberately a short list rather than a full ISO 639 table: it covers what