Media: look a clip up on the slide it belongs to (#994)

The PPTX import numbers shapes per slide, so two slides can hold different
videos under one shape id. find_clip searched the whole deck and took the
first match, so the show's media cues, the keep-across-slides filter and
the media.* requests all got the first slide's clip: from slide 3 on, video 2
played. find_clip now takes the slide the request comes from and searches it
first, then the rest of the deck.

Co-Authored-By: Claude <noreply@anthropic.com>

crates/ui-egui/src/lib.rs

@@ -1347,8 +1347,9 @@ impl SlideApp {
                 }
                 UiRequest::Media { action, shape, ms } => {
                     let owner = if self.show.is_some() { media::Owner::Show } else { media::Owner::Editor };
-                    if let Some((uid, doc)) = self.session.active().map(|d| (d.uid, d.doc.clone())) {
-                        self.media.request(uid, &doc, &action, shape, ms, owner);
+                    let shown = self.show.as_ref().map(|s| s.state.slide);
+                    if let Some((uid, doc, slide)) = self.session.active().map(|d| (d.uid, d.doc.clone(), shown.unwrap_or(d.selection.slide))) {
+                        self.media.request(uid, &doc, slide, &action, shape, ms, owner);
                     }
                 }
             }

crates/ui-egui/src/media.rs

@@ -318,9 +318,10 @@ impl MediaHost {
     }
 
     /// Carry out a `media.*` request from the engine for presentation `doc_uid`.
-    pub fn request(&mut self, doc_uid: u64, doc: &Presentation, action: &str, id: ShapeId, ms: Option<u64>, owner: Owner) {
+    /// `slide` is the slide the request comes from: shape ids are only unique per slide.
+    pub fn request(&mut self, doc_uid: u64, doc: &Presentation, slide: usize, action: &str, id: ShapeId, ms: Option<u64>, owner: Owner) {
         self.ensure_doc(doc_uid);
-        let Some(clip) = find_clip(doc, id) else { return };
+        let Some(clip) = find_clip(doc, id, Some(slide)) else { return };
         let t = ms.map(|v| v as f64 / 1000.0);
         match action {
             "play" => self.play(doc_uid, doc, id, &clip, t, owner),
@@ -333,8 +334,9 @@ impl MediaHost {
     }
 }
 
-/// The clip of media shape `id` anywhere in the deck.
-pub fn find_clip(doc: &Presentation, id: ShapeId) -> Option<MediaClip> {
+/// The clip of media shape `id`. Ids are only unique per slide (the PPTX import numbers each slide
+/// afresh), so the `near` slide is searched first, then the rest of the deck.
+pub fn find_clip(doc: &Presentation, id: ShapeId, near: Option<usize>) -> Option<MediaClip> {
     fn walk(shapes: &[deckcraft_model::Shape], id: ShapeId) -> Option<MediaClip> {
         shapes.iter().find_map(|s| match &s.kind {
             ShapeKind::Media(m) if s.id == id => Some(m.clone()),
@@ -342,7 +344,7 @@ pub fn find_clip(doc: &Presentation, id: ShapeId) -> Option<MediaClip> {
             _ => None,
         })
     }
-    doc.slides.iter().find_map(|s| walk(&s.shapes, id))
+    near.and_then(|i| doc.slides.get(i)).and_then(|s| walk(&s.shapes, id)).or_else(|| doc.slides.iter().find_map(|s| walk(&s.shapes, id)))
 }
 
 /// Media shapes directly on slide `index`: (id, box in slide points, clip).
@@ -617,4 +619,18 @@ mod tests {
         host.set_document(None);
         assert!(host.gifs.is_empty());
     }
+
+    #[test]
+    fn a_clip_is_looked_up_on_the_slide_it_was_asked_from() {
+        // The PPTX import numbers shapes per slide, so two slides can hold different clips under one id.
+        let (mut doc, id, first) = deck(4000, wav_level(0.05, 0.5));
+        let other = doc.add_media("two.wav", "audio/wav", wav_level(0.05, 0.25)).expect("media");
+        let mut second = (*doc.slides[0]).clone();
+        second.shapes.last_mut().expect("shape").kind = ShapeKind::Media(MediaClip { media: other, volume: 1.0, ..Default::default() });
+        doc.slides.push(Arc::new(second));
+        assert_eq!(find_clip(&doc, id, Some(0)).map(|c| c.media), Some(first.media));
+        assert_eq!(find_clip(&doc, id, Some(1)).map(|c| c.media), Some(other), "the second slide's own clip");
+        assert_eq!(find_clip(&doc, id, None).map(|c| c.media), Some(first.media), "without a hint: first match");
+        assert_eq!(find_clip(&doc, id, Some(9)).map(|c| c.media), Some(first.media), "a slide that doesn't exist");
+    }
 }

crates/ui-egui/src/show.rs

@@ -1070,7 +1070,7 @@ fn show_media(app: &mut SlideApp, show: &mut Show, doc_uid: u64, doc: &Presentat
     if show.media_slide == cur {
         return;
     }
-    show.media_slide = cur;
+    let previous = std::mem::replace(&mut show.media_slide, cur);
     let trans = cur.and_then(|i| doc.slides.get(i)).and_then(|s| s.transition.as_ref());
     let sound = trans.and_then(|t| t.sound);
     let sound_loop = trans.is_some_and(|t| t.sound_loop);
@@ -1081,7 +1081,7 @@ fn show_media(app: &mut SlideApp, show: &mut Show, doc_uid: u64, doc: &Presentat
             .media
             .ids()
             .into_iter()
-            .filter(|id| crate::media::find_clip(doc, *id).is_some_and(|c| c.play_across_slides))
+            .filter(|id| crate::media::find_clip(doc, *id, previous).is_some_and(|c| c.play_across_slides))
             // A transition sound plays to its end, as in PowerPoint, unless the new slide has its own.
             .chain((sound.is_none() && !stop_previous).then_some(TRANSITION_SOUND).filter(|id| app.media.is_playing(*id)))
             .collect(),
@@ -1110,7 +1110,7 @@ fn show_media(app: &mut SlideApp, show: &mut Show, doc_uid: u64, doc: &Presentat
 /// the clip is already playing, Pause toggles, Stop stops.
 fn run_media_cues(app: &mut SlideApp, show: &mut Show, doc_uid: u64, doc: &Presentation) {
     for (id, effect) in std::mem::take(&mut show.media_cues) {
-        let Some(clip) = crate::media::find_clip(doc, id) else { continue };
+        let Some(clip) = crate::media::find_clip(doc, id, Some(show.state.slide)) else { continue };
         match effect.as_str() {
             "pause" => app.media.toggle(doc_uid, doc, id, &clip, crate::media::Owner::Show),
             "stop" => app.media.stop(id),