feat(core,fuse,gui,cli): filter the photos timeline to photos in no album

A new pill next to the favorites filter narrows the timeline to the photos
no album of ours holds yet, so what is left to file is easy to find. A
RAW+JPEG pair counts as filed when any of its files is in an album.

PhotosTimeline gains an optional not_in_album flag; older front-ends omit it
and get the whole timeline. Album contents are fetched lazily, so the first
filtered page fetches the contents of any album not yet listed. Photos added
to an album while the filter is on leave the timeline at once.

crates/pdfs-gui/src/app/main.rs

@@ -561,6 +561,8 @@ fn build_window(app: &adw::Application) {
             range: Cell::new(None),
             favorites_btn: gallery_widgets.favorites_btn.clone(),
             favorites: Cell::new(false),
+            not_in_album_btn: gallery_widgets.not_in_album_btn.clone(),
+            not_in_album: Cell::new(false),
             date_suppress: Cell::new(false),
             loading: Cell::new(false),
             has_more: Cell::new(false),

crates/pdfs-gui/src/app/pages/albums.rs

@@ -468,6 +468,16 @@ fn add_to_album(ui: &Rc<Ui>, album: String, photos: Vec<String>) {
                         ),
                     );
                 }
+                // Filed photos no longer belong in a timeline of unfiled ones.
+                // The daemon's filter drops them too, so the paging offset stays
+                // in step with what is left.
+                if ui.gallery.not_in_album.get() && ui.gallery.album.borrow().is_none() {
+                    ui.gallery
+                        .selected
+                        .borrow_mut()
+                        .retain(|uid| !changed.contains(uid));
+                    remove_photos(&ui, &changed);
+                }
                 reload_album_grid(&ui);
             }
             Ok(Ok(Response::Error { message, kind })) => {

crates/pdfs-gui/src/app/pages/photo_viewer.rs

@@ -813,7 +813,10 @@ fn gallery_total(ui: &Rc<Ui>) -> Option<usize> {
     if let Some(album) = ui.gallery.album.borrow().as_ref() {
         return Some(album.photo_count);
     }
-    if ui.gallery.range.get().is_some() || ui.gallery.favorites.get() {
+    if ui.gallery.range.get().is_some()
+        || ui.gallery.favorites.get()
+        || ui.gallery.not_in_album.get()
+    {
         return None;
     }
     let (photos, videos, raw) = ui.gallery.counts.get()?;

crates/pdfs-gui/src/app/pages/photos.rs

@@ -108,6 +108,10 @@ pub(crate) struct GalleryState {
     /// restricted to photos carrying Proton's `Favorite` tag.
     pub(crate) favorites_btn: gtk4::ToggleButton,
     pub(crate) favorites: Cell<bool>,
+    /// The album filter toggle, and whether it is on. When on, the timeline is
+    /// restricted to photos no album of ours holds yet.
+    pub(crate) not_in_album_btn: gtk4::ToggleButton,
+    pub(crate) not_in_album: Cell<bool>,
     /// Set while the date dropdown is being repopulated, so resetting its model
     /// doesn't fire the selection handler and kick off a spurious reload.
     pub(crate) date_suppress: Cell<bool>,
@@ -355,6 +359,7 @@ pub(crate) struct GalleryWidgets {
     /// to [`kind_for_tab`]).
     pub(crate) tabs: [gtk4::ToggleButton; 4],
     pub(crate) favorites_btn: gtk4::ToggleButton,
+    pub(crate) not_in_album_btn: gtk4::ToggleButton,
     /// The date-jump dropdown, populated with the timeline's months.
     pub(crate) dates: gtk4::DropDown,
 }
@@ -564,6 +569,13 @@ pub(crate) fn build_gallery_page() -> (gtk4::Widget, GalleryWidgets) {
         .build();
     favorites_btn.add_css_class("pill");
 
+    // Not in an album: a filter like favorites, for filing what is left.
+    let not_in_album_btn = gtk4::ToggleButton::builder()
+        .icon_name("view-grid-symbolic")
+        .tooltip_text(gettext("Show only photos not in an album"))
+        .build();
+    not_in_album_btn.add_css_class("pill");
+
     // Date jump: "All dates" plus a row per month, filled in once the timeline's
     // months are known (see [`refresh_photo_months`]). Pushed to the far end of
     // the filter row, opposite the kind toggles.
@@ -577,6 +589,7 @@ pub(crate) fn build_gallery_page() -> (gtk4::Widget, GalleryWidgets) {
     filters.set_hexpand(true);
     filters.append(&tab_group);
     filters.append(&favorites_btn);
+    filters.append(&not_in_album_btn);
     let spacer = gtk4::Box::new(gtk4::Orientation::Horizontal, 0);
     spacer.set_hexpand(true);
     filters.append(&spacer);
@@ -709,6 +722,7 @@ pub(crate) fn build_gallery_page() -> (gtk4::Widget, GalleryWidgets) {
             select_done,
             tabs,
             favorites_btn,
+            not_in_album_btn,
             dates,
             albums,
             albums_stack,
@@ -1059,6 +1073,17 @@ pub(crate) fn wire_gallery(
         load_gallery(&ui_fav, false);
     });
 
+    // Not in an album: the same kind of filter, and just as independent.
+    let ui_unfiled = ui.clone();
+    ui.gallery.not_in_album_btn.connect_toggled(move |btn| {
+        let on = btn.is_active();
+        if ui_unfiled.gallery.not_in_album.get() == on {
+            return;
+        }
+        ui_unfiled.gallery.not_in_album.set(on);
+        load_gallery(&ui_unfiled, false);
+    });
+
     // Date jump: selecting a month loads that window; "All dates" (row 0) clears
     // it. Skipped while the model is being repopulated (see `gallery_date_suppress`).
     let ui_dates = ui.clone();
@@ -2150,9 +2175,13 @@ pub(crate) fn update_gallery_subtitle(ui: &Rc<Ui>) {
     let kind = ui.gallery.kind.get();
     // The whole library for this filter, not the page count — the subtitle sits
     // next to tabs carrying the same totals, and the two disagreeing reads as a
-    // bug. A date jump is the exception: there the window is the subject.
-    let total = match (ui.gallery.range.get(), ui.gallery.counts.get()) {
-        (None, Some((photos, videos, raw))) => match kind {
+    // bug. A date jump or a filter is the exception: the counts are the
+    // library's, not the filter's, so there the loaded count is the honest one.
+    let narrowed = ui.gallery.range.get().is_some()
+        || ui.gallery.favorites.get()
+        || ui.gallery.not_in_album.get();
+    let total = match (narrowed, ui.gallery.counts.get()) {
+        (false, Some((photos, videos, raw))) => match kind {
             Some(PhotoKind::Photo) => photos,
             Some(PhotoKind::Video) => videos,
             Some(PhotoKind::Raw) => raw,
@@ -2261,16 +2290,23 @@ pub(crate) fn short_capture_time(secs: i64) -> String {
 
 /// Fetch a timeline page from the daemon. When `append` is false the model is
 /// cleared first (fresh load); otherwise the next page is tacked on.
-/// The empty state for a timeline filtered to `kind`, favorites and/or a
-/// `month`: what is missing, in the filter's own words.
+/// The empty state for a timeline filtered to `kind`, favorites, the photos
+/// in no album and/or a `month`: what is missing, in the filter's own words.
 pub(crate) fn empty_timeline_text(
     kind: Option<PhotoKind>,
     favorites: bool,
+    not_in_album: bool,
     month: Option<&str>,
 ) -> (String, String) {
     let args = [("month", month.unwrap_or_default())];
     let video = kind == Some(PhotoKind::Video);
     let raw = kind == Some(PhotoKind::Raw);
+    if not_in_album && !favorites && kind.is_none() && month.is_none() {
+        return (
+            gettext("Every photo is in an album"),
+            gettext("Turn off the album filter to see everything."),
+        );
+    }
     match (favorites, kind, month) {
         (false, None, None) => (
             gettext("No photos yet"),
@@ -2333,11 +2369,12 @@ fn fill_scrubber(ui: &Rc<Ui>, months: &[PhotoMonth]) {
 }
 
 /// Show the scrubber only where a month jump makes sense: the whole timeline,
-/// not an album, a date window or the favorites.
+/// not an album, a date window, the favorites or the unfiled photos.
 pub(crate) fn sync_scrubber(ui: &Rc<Ui>) {
     let whole = ui.gallery.album.borrow().is_none()
         && ui.gallery.range.get().is_none()
-        && !ui.gallery.favorites.get();
+        && !ui.gallery.favorites.get()
+        && !ui.gallery.not_in_album.get();
     ui.gallery
         .scrubber
         .set_visible(whole && ui.gallery.months.borrow().len() > 1);
@@ -2644,6 +2681,7 @@ pub(crate) fn load_gallery(ui: &Rc<Ui>, append: bool) {
             kind: ui.gallery.kind.get(),
             range: ui.gallery.range.get(),
             favorites: ui.gallery.favorites.get(),
+            not_in_album: ui.gallery.not_in_album.get(),
         },
     };
     let rx = spawn_request(ui.dirs.control_socket(), request);
@@ -2697,6 +2735,7 @@ pub(crate) fn load_gallery(ui: &Rc<Ui>, append: bool) {
                 if ui.gallery.model.n_items() == 0 {
                     let filtered = ui.gallery.kind.get().is_some()
                         || ui.gallery.favorites.get()
+                        || ui.gallery.not_in_album.get()
                         || ui.gallery.range.get().is_some();
                     let (title, description) = if ui.gallery.album.borrow().is_some() {
                         (
@@ -2714,6 +2753,7 @@ pub(crate) fn load_gallery(ui: &Rc<Ui>, append: bool) {
                         empty_timeline_text(
                             ui.gallery.kind.get(),
                             ui.gallery.favorites.get(),
+                            ui.gallery.not_in_album.get(),
                             month.as_deref(),
                         )
                     };
@@ -2843,15 +2883,25 @@ mod tests {
 
     #[test]
     fn an_empty_filter_names_what_it_filtered() {
-        assert_eq!(empty_timeline_text(None, false, None).0, "No photos yet");
-        assert_eq!(empty_timeline_text(None, true, None).0, "No favorites yet");
         assert_eq!(
-            empty_timeline_text(Some(PhotoKind::Video), false, Some("June 2024")).0,
+            empty_timeline_text(None, false, false, None).0,
+            "No photos yet"
+        );
+        assert_eq!(
+            empty_timeline_text(None, true, false, None).0,
+            "No favorites yet"
+        );
+        assert_eq!(
+            empty_timeline_text(Some(PhotoKind::Video), false, false, Some("June 2024")).0,
             "No videos in June 2024"
         );
         assert_eq!(
-            empty_timeline_text(Some(PhotoKind::Raw), true, None).0,
+            empty_timeline_text(Some(PhotoKind::Raw), true, false, None).0,
             "No favorite raw files"
         );
+        assert_eq!(
+            empty_timeline_text(None, false, true, None).0,
+            "Every photo is in an album"
+        );
     }
 }