feat(slint): favorites albums group-by (Off / A-Z / Artist)

Add a group QbzSelect to the Albums toolbar. derive_albums buckets the
filtered set by artist name or by the title's first letter (# for
non-alphabetic), sections ordered alphabetically, rendered through the
shared AlbumCollectionView grouped path. albums-shown carries the
post-filter count so the count line + no-match state stay correct in
grouped mode.

cc

crates/qbz-slint/src/favorites.rs

@@ -8,6 +8,7 @@
 //! relevant branch into typed qbz-models items and maps them to the
 //! Slint row/card structs.
 
+use std::collections::HashMap;
 use std::sync::{Arc, LazyLock, Mutex};
 
 use qbz_app::shell::AppRuntime;
@@ -19,8 +20,8 @@ use slint::{ComponentHandle, Model, ModelRc, VecModel};
 use crate::album_map::{self, map_album, to_item, AlbumCard};
 use crate::artwork::{ArtworkJob, ArtworkTarget};
 use crate::{
-    AlbumCardItem, AppWindow, FavoriteArtistItem, FavoriteLabelItem, FavoritePlaylistItem,
-    FavoritesState, TrackItem,
+    AlbumCardItem, AppWindow, DiscoverSection, FavoriteArtistItem, FavoriteLabelItem,
+    FavoritePlaylistItem, FavoritesState, TrackItem,
 };
 
 /// Page size — matches Tauri's FAVORITES_PAGE_SIZE. We fetch one
@@ -363,11 +364,14 @@ pub fn apply_favorites(window: &AppWindow, data: FavData) {
             // (what the grid/list renders) shares it until a search/sort
             // forks it, so artwork stays live.
             let model = ModelRc::new(VecModel::from(cards));
+            let n = model.row_count() as i32;
             state.set_albums(model.clone());
             state.set_albums_visible(model);
             state.set_albums_total(total as i32);
+            state.set_albums_shown(n);
             state.set_albums_search("".into());
             state.set_albums_sort_by("default".into());
+            state.set_albums_group_mode("off".into());
         }
         FavData::Artists { items, total } => {
             let cards: Vec<FavoriteArtistItem> = items
@@ -472,11 +476,19 @@ pub fn derive_albums(window: &AppWindow) {
     let query_owned = state.get_albums_search().to_lowercase();
     let query = query_owned.trim();
     let sort = state.get_albums_sort_by().to_string();
+    let group = state.get_albums_group_mode().to_string();
     let all = state.get_albums();
-    if query.is_empty() && sort == "default" {
+    let empty_sections = || ModelRc::new(VecModel::from(Vec::<DiscoverSection>::new()));
+
+    // Fast path: no filter, default order, no grouping -> share full model.
+    if query.is_empty() && sort == "default" && group == "off" {
+        let n = all.row_count() as i32;
         state.set_albums_visible(all);
+        state.set_albums_grouped(empty_sections());
+        state.set_albums_shown(n);
         return;
     }
+
     let mut filtered: Vec<AlbumCardItem> = (0..all.row_count())
         .filter_map(|i| all.row_data(i))
         .filter(|a| {
@@ -486,7 +498,59 @@ pub fn derive_albums(window: &AppWindow) {
         })
         .collect();
     album_map::sort_album_items(&mut filtered, &sort);
-    state.set_albums_visible(ModelRc::new(VecModel::from(filtered)));
+    state.set_albums_shown(filtered.len() as i32);
+
+    if group == "off" {
+        state.set_albums_visible(ModelRc::new(VecModel::from(filtered)));
+        state.set_albums_grouped(empty_sections());
+        return;
+    }
+
+    // Grouped: bucket by artist name, or by the title's first letter
+    // (# bucket for non-alphabetic), sections ordered alphabetically.
+    let mut map: Vec<(String, Vec<AlbumCardItem>)> = Vec::new();
+    let mut index: HashMap<String, usize> = HashMap::new();
+    for item in filtered {
+        let key = if group == "artist" {
+            let a = item.artist.to_string();
+            if a.is_empty() {
+                "Unknown".to_string()
+            } else {
+                a
+            }
+        } else {
+            album_alpha_key(item.title.as_str())
+        };
+        let idx = *index.entry(key.clone()).or_insert_with(|| {
+            map.push((key.clone(), Vec::new()));
+            map.len() - 1
+        });
+        map[idx].1.push(item);
+    }
+    map.sort_by(|(a, _), (b, _)| match (a == "#", b == "#") {
+        (true, false) => std::cmp::Ordering::Less,
+        (false, true) => std::cmp::Ordering::Greater,
+        _ => a.to_lowercase().cmp(&b.to_lowercase()),
+    });
+    let sections: Vec<DiscoverSection> = map
+        .into_iter()
+        .map(|(key, items)| DiscoverSection {
+            title: key.into(),
+            endpoint: "".into(),
+            albums: ModelRc::new(VecModel::from(items)),
+        })
+        .collect();
+    state.set_albums_grouped(ModelRc::new(VecModel::from(sections)));
+    state.set_albums_visible(ModelRc::new(VecModel::from(Vec::<AlbumCardItem>::new())));
+}
+
+/// First-letter bucket key for alpha grouping (# for non-alphabetic).
+fn album_alpha_key(title: &str) -> String {
+    match title.trim().chars().next() {
+        Some(c) if c.is_ascii_alphabetic() => c.to_ascii_uppercase().to_string(),
+        Some(c) if c.is_alphabetic() => c.to_uppercase().to_string(),
+        _ => "#".to_string(),
+    }
 }
 
 /// A random album id from the currently-visible set (Shuffle / random).

crates/qbz-slint/src/main.rs

@@ -4300,6 +4300,18 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
                 }
             });
     }
+    {
+        // Group the favorite albums (off / alpha / artist).
+        let weak = window.as_weak();
+        window
+            .global::<FavoritesActions>()
+            .on_albums_set_group(move |g| {
+                if let Some(w) = weak.upgrade() {
+                    w.global::<FavoritesState>().set_albums_group_mode(g);
+                    favorites::derive_albums(&w);
+                }
+            });
+    }
     {
         // Play a random album from the visible favorites set.
         let weak = window.as_weak();

crates/qbz-slint/ui/favorites/FavoritesView.slint

@@ -486,7 +486,7 @@ export component FavoritesView inherits Rectangle {
                         alignment: center;
                         horizontal-stretch: 1;
                         Text {
-                            text: FavoritesState.albums-visible.length
+                            text: FavoritesState.albums-shown
                                 + (FavoritesState.albums-search != ""
                                     ? " / " + FavoritesState.albums.length
                                     : "")
@@ -505,6 +505,24 @@ export component FavoritesView inherits Rectangle {
                             }
                         }
                     }
+                    VerticalLayout {
+                        alignment: center;
+                        QbzSelect {
+                            menu-width: 150px;
+                            options: [
+                                @tr("Group: Off"),
+                                @tr("Group: A-Z"),
+                                @tr("Group: Artist"),
+                            ];
+                            current-index: FavoritesState.albums-group-mode == "off" ? 0
+                                : FavoritesState.albums-group-mode == "alpha" ? 1
+                                : 2;
+                            selected(i) => {
+                                FavoritesActions.albums-set-group(
+                                    i == 0 ? "off" : i == 1 ? "alpha" : "artist");
+                            }
+                        }
+                    }
                     VerticalLayout {
                         alignment: center;
                         QbzSelect {
@@ -563,7 +581,7 @@ export component FavoritesView inherits Rectangle {
                     font-size: Typography.body;
                 }
                 if FavoritesState.albums.length > 0
-                    && FavoritesState.albums-visible.length == 0: Text {
+                    && FavoritesState.albums-shown == 0: Text {
                     text: @tr("No albums match your search.");
                     color: Theme.text-muted;
                     font-size: Typography.body;
@@ -571,8 +589,9 @@ export component FavoritesView inherits Rectangle {
 
                 AlbumCollectionView {
                     albums: FavoritesState.albums-visible;
+                    grouped: FavoritesState.albums-grouped;
                     view-mode: FavoritesState.albums-view-mode;
-                    is-grouped: false;
+                    is-grouped: FavoritesState.albums-group-mode != "off";
                     show-source: false;
                     open-album(id) => {
                         root.open-album(id);

crates/qbz-slint/ui/state.slint

@@ -1461,10 +1461,13 @@ export global FavoritesState {
     in-out property <bool> tracks-multi-select: false;
     in property <int> tracks-selected-count: 0;
     in property <[AlbumCardItem]> albums: [];
-    in property <[AlbumCardItem]> albums-visible: []; // after search + sort (what the grid/list renders)
+    in property <[AlbumCardItem]> albums-visible: []; // after search + sort (flat render)
+    in property <[DiscoverSection]> albums-grouped: []; // group-by sections
     in-out property <string> albums-view-mode: "grid"; // "grid" | "list"
     in-out property <string> albums-search: "";
     in-out property <string> albums-sort-by: "default"; // default|title-asc|title-desc|artist-asc
+    in-out property <string> albums-group-mode: "off"; // off|alpha|artist
+    in property <int> albums-shown: 0; // count after filter (grouped or flat)
     in property <[FavoriteArtistItem]> artists: [];
     in property <[FavoritePlaylistItem]> playlists: [];
     in property <[FavoriteLabelItem]> labels: [];
@@ -1494,6 +1497,7 @@ export global FavoritesActions {
     callback album-action(string /* album id */, string /* action */);
     callback albums-search(string /* query */);
     callback albums-set-sort(string /* sort key */);
+    callback albums-set-group(string /* off | alpha | artist */);
     callback albums-shuffle();
     callback unfavorite-track(string /* track id */);
     callback unfavorite-album(string /* album id */);