perf(ui): #1136 dialogs count once per library change, not every frame

Create Smart Album ran a full query for its count and Rename Keyword
scanned every photo on each frame the dialog was open; Merge Keywords
recomputed suggestions. They use Caches::dialog_count (keyed by catalog
revision and what is counted, and the minute for relative-date rules) and
the cached suggestions.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

crates/ui-egui/src/lib.rs

@@ -1477,6 +1477,9 @@ pub struct Caches {
     /// What the open smart-album rule dialog shows besides the rules ([`Caches::rules_view`]).
     rules_view: Option<(u64, std::sync::Arc<RulesView>)>,
     pub rules_view_scans: usize,
+    /// A count an open dialog shows ([`Caches::dialog_count`]), by what it counts.
+    dialog_count: Option<(u64, usize)>,
+    pub dialog_count_scans: usize,
     /// The problems of every saved smart album that has some ([`Caches::smart_album_problems`]).
     smart_problems: Option<(u64, std::sync::Arc<std::collections::HashMap<lightcraft_catalog::AlbumId, Vec<lightcraft_catalog::rules::Problem>>>)>,
     pub smart_problem_scans: usize,
@@ -1749,6 +1752,21 @@ impl Caches {
         v
     }
 
+    /// A count an open dialog shows (photos a filter matches, photos with a keyword…): `count` runs
+    /// again only when the catalog or `what` (what is counted) changes, not every frame.
+    pub(crate) fn dialog_count(&mut self, cat: &lightcraft_catalog::Catalog, what: impl std::hash::Hash, count: impl FnOnce() -> usize) -> usize {
+        let k = key_of((cat.revision, what));
+        if let Some((key, n)) = self.dialog_count
+            && key == k
+        {
+            return n;
+        }
+        let n = count();
+        self.dialog_count_scans += 1;
+        self.dialog_count = Some((k, n));
+        n
+    }
+
     /// The problems of every saved smart album that has some (`Catalog::smart_album_problems`),
     /// for the sidebar's ⚠ marks: worked out again only when the catalog changes.
     pub fn smart_album_problems(

crates/ui-egui/src/panels/dialogs.rs

@@ -430,7 +430,13 @@ pub fn show(app: &mut LightcraftApp, ctx: &egui::Context) {
                         confirm = true;
                     }
                     let rules = app.session.view_rules();
-                    let n = app.session.catalog.query(&rules, &Default::default()).len();
+                    // counted when the library or the rules change (or, for "in the last…" rules, the minute), not every frame
+                    let now = (app.session.clock)();
+                    let minute = if rules.depends_on_now() { now.get(..16).unwrap_or(&now) } else { "" };
+                    let n = app.caches.dialog_count(&app.session.catalog, ("smartAlbum", format!("{rules:?}"), minute), || {
+                        lightcraft_catalog::rules::set_now(Some(now.clone()));
+                        app.session.catalog.query(&rules, &Default::default()).len()
+                    });
                     ui.label(egui::RichText::new(crate::i18n::tr_format!("Matches: {}", crate::i18n::filter_label(&rules, &app.session.catalog))).color(t.text_label));
                     ui.label(
                         egui::RichText::new(crate::i18n::tr_format!("{n} photo{} now · updates automatically as photos change", if n == 1 { "" } else { "s" }, n = n))
@@ -573,7 +579,9 @@ pub fn show(app: &mut LightcraftApp, ctx: &egui::Context) {
                     }
                 }
                 Dialog::RenameKeyword { from, to } => {
-                    let n = app.session.catalog.photos().filter(|p| p.meta.keywords.iter().any(|k| lightcraft_catalog::keywords::is_under(k, from))).count();
+                    let n = app.caches.dialog_count(&app.session.catalog, ("renameKeyword", from.as_str()), || {
+                        app.session.catalog.photos().filter(|p| p.meta.keywords.iter().any(|k| lightcraft_catalog::keywords::is_under(k, from))).count()
+                    });
                     if dialog_field(ui, "field:keywordName", to, "New name") {
                         confirm = true;
                     }
@@ -589,11 +597,11 @@ pub fn show(app: &mut LightcraftApp, ctx: &egui::Context) {
                         confirm = true;
                     }
                     let options: Vec<String> = app
-                        .session
-                        .catalog
-                        .keyword_suggestions(from, into, 12)
-                        .into_iter()
+                        .caches
+                        .suggestions(&app.session.catalog, from, into, 12)
+                        .iter()
                         .filter(|k| !from.iter().any(|f| lightcraft_catalog::keywords::is_under(k, f)))
+                        .cloned()
                         .collect();
                     ui.horizontal_wrapped(|ui| {
                         for k in options {

crates/ui-egui/src/tests_keywording.rs

@@ -227,3 +227,24 @@ fn containing_keywords_view_lists_parents_too() {
     }
     assert!(!has(&h, "keywordChip:beach"), "the chips give way");
 }
+
+/// Rename Keyword's "used by n photos" and Create Smart Album's live count scan the library once
+/// per change to it, not every frame the dialog is open.
+#[test]
+fn open_dialogs_count_once_per_library_change() {
+    let (mut h, ids) = two_selected();
+    h.app.ui.dialog = Some(crate::state::Dialog::RenameKeyword { from: "beach".into(), to: "beach".into() });
+    let before = h.app.caches.dialog_count_scans;
+    for _ in 0..10 {
+        h.step();
+    }
+    assert_eq!(h.app.caches.dialog_count_scans, before + 1, "unchanged frames reuse the count");
+    ask(&mut h, "engine.execute", json!({"command": "photo.setMeta", "params": {"ids": [ids[1]], "keywords": ["sea"]}}));
+    h.step();
+    assert_eq!(h.app.caches.dialog_count_scans, before + 2, "a library change counts again");
+    h.app.ui.dialog = Some(crate::state::Dialog::NewSmartAlbum { name: "Beach".into(), parent: None });
+    for _ in 0..10 {
+        h.step();
+    }
+    assert_eq!(h.app.caches.dialog_count_scans, before + 3, "another dialog counts its own photos, once");
+}