fix(core,player,app): styled subtitles keep their size and place unless restyled

mpv's default sub-ass-override, `scale`, hands an ASS track sub-scale,
and sub-pos reaches it under every mode but `no`. So with "Restyle
styled subtitles" off, the subtitle size and position settings still
resized and moved typeset dialogue and signs.

The override is now `yes` when restyling is off, which keeps sub-scale
off ASS. A styled track also ignores the style's position, and moves
only to stay clear of the player's controls. A frame from an ASS track
rendered with every other option changed now matches the untouched one
pixel for pixel. Plain (SRT) tracks still take the whole style.

crates/pstr-app/src/playback.rs

@@ -302,6 +302,11 @@ impl Playback {
         } else {
             100.0
         };
+        self.place_subtitles();
+    }
+
+    /// Move subtitles to [`Self::subtitle_position`], when that has changed.
+    fn place_subtitles(&mut self) {
         let position = self.subtitle_position();
         if position != self.subtitle_position {
             self.subtitle_position = position;
@@ -311,8 +316,21 @@ impl Playback {
 
     /// Where subtitles go: where the style puts them, unless the controls
     /// would cover that, in which case just above the controls.
+    ///
+    /// A styled track ignores the style's position unless it is restyled:
+    /// mpv applies `sub-pos` to it either way, and its signs were placed by
+    /// hand. The lift still applies, because a line under the seek bar cannot
+    /// be read however carefully it was placed.
     fn subtitle_position(&self) -> f64 {
-        self.subtitle_style.position.min(self.lifted_position)
+        let styled = self
+            .selected_track(TrackKind::Subtitle)
+            .is_some_and(|track| is_styled(track.codec.as_deref()));
+        let position = if styled && !self.subtitle_style.restyle_styled {
+            100.0
+        } else {
+            self.subtitle_style.position
+        };
+        position.min(self.lifted_position)
     }
 
     /// Restyle the subtitles of this file, now.
@@ -409,7 +427,11 @@ impl Playback {
             PlayerEvent::FileLoaded => self.loaded = true,
             PlayerEvent::Volume(volume) => self.volume = *volume,
             PlayerEvent::Muted(muted) => self.muted = *muted,
-            PlayerEvent::Tracks(tracks) => self.tracks = tracks.clone(),
+            PlayerEvent::Tracks(tracks) => {
+                self.tracks = tracks.clone();
+                // A switch between a plain and a styled track moves the line.
+                self.place_subtitles();
+            }
             PlayerEvent::Chapters(chapters) => {
                 self.chapters = chapters.clone();
                 self.reclassify();
@@ -516,6 +538,11 @@ fn build_player(
     Ok((Arc::new(player), None))
 }
 
+/// Whether a subtitle codec carries its own styling, as mpv names them.
+fn is_styled(codec: Option<&str>) -> bool {
+    matches!(codec, Some("ass" | "ssa"))
+}
+
 /// The player defaults with the viewer's preferences folded in.
 fn from_prefs(
     prefs: &PlaybackPrefs,
@@ -863,3 +890,17 @@ fn save(
         watch_state(position, duration, watched),
     );
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn only_ass_and_ssa_tracks_count_as_styled() {
+        assert!(is_styled(Some("ass")));
+        assert!(is_styled(Some("ssa")));
+        assert!(!is_styled(Some("subrip")));
+        assert!(!is_styled(Some("hdmv_pgs_subtitle")));
+        assert!(!is_styled(None));
+    }
+}

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

@@ -432,14 +432,14 @@ fn languages(ui: &mut egui::Ui, playback: &PlaybackPrefs, actions: &mut Vec<Acti
 /// How subtitles look, with a sample line to judge it by.
 ///
 /// Every change reaches a playing file as it is made, so the film itself is
-/// the other preview. A styled track takes only the size and the position
-/// unless it is asked to take the rest; see [`SubtitleStyle`].
+/// the other preview. A styled track takes none of it unless it is asked to;
+/// see [`SubtitleStyle`].
 fn subtitle_form(ui: &mut egui::Ui, style: &SubtitleStyle, actions: &mut Vec<Action>) {
     ui::widgets::settings_group(
         ui,
         "Subtitles",
         Some(
-            "Changes show on the playing video straight away. Plain subtitles (SRT) take all of this; styled ones (ASS) only the size and the position, unless you restyle them below.",
+            "Changes show on the playing video straight away. Plain subtitles (SRT) take all of this; styled ones (ASS) keep their own look unless you restyle them below.",
         ),
         |ui| {
             let mut chosen = style.clone();
@@ -532,7 +532,7 @@ fn subtitle_form(ui: &mut egui::Ui, style: &SubtitleStyle, actions: &mut Vec<Act
                 ui,
                 "Restyle styled subtitles",
                 Some(
-                    "Repaint styled (ASS) dialogue in this style too. Signs, songs and karaoke can come out wrong.",
+                    "Draw styled (ASS) dialogue in this style too, size and position included. Signs, songs and karaoke can come out wrong.",
                 ),
                 |ui| {
                     ui::widgets::toggle(ui, &mut chosen.restyle_styled, "");

crates/pstr-core/src/prefs.rs

@@ -70,8 +70,9 @@ pub struct PlaybackPrefs {
 /// Every default is mpv's own, so a viewer who never opens the section sees
 /// what any mpv shows. Plain (SRT) tracks take all of it. A styled (ASS) track
 /// was typeset by somebody, its signs placed and coloured by hand, and painting
-/// over that undoes the work — so by default it takes only the size and the
-/// position, and the rest reaches it only with [`Self::restyle_styled`].
+/// over that undoes the work — so by default it takes none of this, and moves
+/// only to stay clear of the player's controls. All of it reaches a styled
+/// track only with [`Self::restyle_styled`].
 #[derive(Debug, Clone, PartialEq, serde::Serialize, serde::Deserialize)]
 #[serde(default)]
 pub struct SubtitleStyle {
@@ -100,8 +101,9 @@ pub struct SubtitleStyle {
     /// Where the line sits, as a percentage of the picture's height from the
     /// top: 100 is the bottom edge, mpv's usual place.
     pub position: f64,
-    /// Whether styled (ASS) tracks are repainted in this style too. Off by
-    /// default: it turns signs and karaoke into dialogue-looking text.
+    /// Whether styled (ASS) tracks are drawn in this style too, size and
+    /// position included. Off by default: it turns signs and karaoke into
+    /// dialogue-looking text.
     pub restyle_styled: bool,
 }
 

crates/pstr-player/src/player.rs

@@ -619,21 +619,19 @@ const BORDER_STYLE: &str = "sub-border-style";
 /// The mpv options that draw `style`, every one of them every time, so that
 /// changing a value back to its default while playing lands too.
 ///
-/// `sub-ass-override` is `scale` unless the viewer asked otherwise: a styled
-/// track then takes the size and keeps its own fonts, colours and placement.
-/// `force` repaints it whole. See [`SubtitleStyle`] for why that is opt-in.
+/// `sub-ass-override` is `yes` unless the viewer asked otherwise, so a styled
+/// track keeps its own size, fonts and colours. Not mpv's default, `scale`,
+/// which hands it `sub-scale` as well. `force` repaints it whole. See
+/// [`SubtitleStyle`] for why that is opt-in. `sub-pos` reaches a styled track
+/// under `yes` too, so where a styled track sits is the caller's to decide:
+/// see `pstr-app`'s `Playback::lift_subtitles`.
 /// The border options come last, led by [`BORDER_STYLE`].
 pub fn subtitle_options(style: &SubtitleStyle) -> Vec<(&'static str, String)> {
     let flag = |on: bool| if on { "yes" } else { "no" }.to_owned();
     let mut options = vec![
         (
             "sub-ass-override",
-            if style.restyle_styled {
-                "force"
-            } else {
-                "scale"
-            }
-            .to_owned(),
+            if style.restyle_styled { "force" } else { "yes" }.to_owned(),
         ),
         ("sub-scale", format!("{:.2}", style.scale)),
         (
@@ -723,9 +721,10 @@ mod tests {
     #[test]
     fn the_default_subtitle_style_is_what_mpv_would_do_anyway() {
         let options = subtitle_options(&SubtitleStyle::default());
-        // mpv 0.41's own defaults, from `mpv --list-options`.
+        // mpv 0.41's own defaults, from `mpv --list-options` — all but
+        // `sub-ass-override`, which mpv has at `scale`.
         for (name, value) in [
-            ("sub-ass-override", "scale"),
+            ("sub-ass-override", "yes"),
             ("sub-scale", "1.00"),
             ("sub-font", "sans-serif"),
             ("sub-bold", "no"),
@@ -756,9 +755,14 @@ mod tests {
     }
 
     #[test]
-    fn styled_subtitles_are_repainted_only_when_asked() {
-        let kept = subtitle_options(&SubtitleStyle::default());
-        assert_eq!(option(&kept, "sub-ass-override"), Some("scale"));
+    fn styled_subtitles_are_repainted_or_resized_only_when_asked() {
+        // `scale` would hand a styled track the size; `yes` hands it nothing
+        // but the `sub-ass-*` options, none of which this sets.
+        let kept = subtitle_options(&SubtitleStyle {
+            scale: 1.5,
+            ..SubtitleStyle::default()
+        });
+        assert_eq!(option(&kept, "sub-ass-override"), Some("yes"));
         let repainted = subtitle_options(&SubtitleStyle {
             restyle_styled: true,
             ..SubtitleStyle::default()

docs/FAQ.md

@@ -25,8 +25,8 @@ with hardware decoding where the device has it.
 
 Yes. In **Settings → Subtitles** you can set the size, position, font, colours, outline, box,
 shadow and blur. A **Box** background is easiest to read on bright scenes. Styled subtitles (ASS)
-keep the look their makers gave them and take only the size and position, unless you turn on
-**Restyle styled subtitles**.
+keep the look, size and place their makers gave them, unless you turn on **Restyle styled
+subtitles**.
 
 ## The subtitles are early or late.
 

docs/USER_GUIDE.md

@@ -86,7 +86,8 @@ The picture plays inside the app's window. Move the mouse to show the controls.
   **Play now**, **Cancel** or **Watch till the end**.
 - **Subtitles and audio** are chosen from the buttons at the bottom right. The app remembers your
   choice for each show. The subtitle menu also has **Size** and **Position**, which are saved like
-  the ones in Settings, and **Delay**, which moves subtitles earlier or later for this file only.
+  the ones in Settings and change styled subtitles only when they are restyled, and **Delay**,
+  which moves subtitles earlier or later for this file only.
 - **Speed** goes from 0.5× to 3×, and stays for the next episode.
 
 ### Keyboard
@@ -202,8 +203,9 @@ a video that is playing changes at once.
   read on bright scenes.
 - **Shadow** and **Blur**.
 - **Restyle styled subtitles** (off). Plain subtitles (SRT) always take the whole style. Styled
-  subtitles (ASS) keep the look their makers gave them and take only the size and position,
-  unless this is on. Turned on, signs and songs can come out wrong.
+  subtitles (ASS) keep the look, size and place their makers gave them unless this is on; they
+  only move up while the player's controls are showing. Turned on, signs and songs can come out
+  wrong.
 - **Reset** goes back to the default look.
 
 **Storage**