Show and set colour labels in the grid and develop, and filter by them

Colour labels could be read from a Lightroom sidecar and queried by the
selector, but nothing drew one or set one, so the only labels a library
held were ones another program had written.

Every mark carries its label's initial on its colour — R, Y, G, B, P —
so a label is read without telling red from green, which is what
NFR-A11Y-3 asks of colour labels by name. A grid cell shows the mark
before its filename. In the grid, 6, 7, 8 and 9 set red, yellow, green and
blue as Lightroom's keys do, on the photograph under the pointer or on
the selection by the rule the star keys follow; the same key again takes
the label off, and over a mixed selection it sets it on all. The
selection bar gains Label, which opens the six choices — each a mark and
a name — and purple, which has no key, is there. In develop the top bar
says "Label: Green" beside the mark, opens the same choices, and 6-9
label the open photograph.

Each gesture is one catalog transaction, then the grid, the counts and
both sidecars are written as a rating's are. The filter bar gains a chip
per label, its mark and its name with a count, one at a time; the filter
is one SQL term, travels in the place record, and "All" clears it.

ui/dr-ui/src/library/filters.rs

@@ -153,6 +153,10 @@ pub struct RatingFilter {
     /// a star count does, and nothing here rejects or rates a frame — the
     /// line §3.9.1 draws.
     pub eyes_open: bool,
+    /// TRACES: FR-CAT-6
+    /// Only photographs carrying this colour label. One at a time, as the
+    /// flag is: the chips are a choice of one pile, not a set of them.
+    pub label: Option<dr_types::ColourLabel>,
 }
 
 /// How several people combine when the grid is narrowed by identity.
@@ -188,6 +192,7 @@ impl RatingFilter {
             && self.captured_to.is_none()
             && self.people.is_empty()
             && !self.eyes_open
+            && self.label.is_none()
     }
 
     /// Whether a date range is narrowing the grid.
@@ -349,6 +354,19 @@ impl RatingFilter {
             ));
         }
 
+        // TRACES: FR-CAT-6
+        // A code this module owns, formatted in like the flag above. No
+        // coalesce: an unlabelled image's NULL never equals a code, which is
+        // the answer.
+        if let Some(label) = self.label {
+            terms.push(format!(
+                "(SELECT dv.label FROM versions dv
+                   WHERE dv.image_id = i.id AND dv.is_default = 1
+                   LIMIT 1) = {}",
+                dr_catalog::rating::label_code(label)
+            ));
+        }
+
         if self.local_only {
             // `tier_actual`, not `tier_desired`: the question is what is
             // *here*, not what a pin has promised will be. An image queued for
@@ -419,6 +437,31 @@ mod tests {
         assert_eq!(local_original_count(&catalog).unwrap(), 3);
     }
 
+    #[test]
+    fn a_label_chip_shows_that_label_and_nothing_else() {
+        // TRACES: FR-CAT-6
+        let catalog = with_images(4);
+        let ids = image_ids(&catalog);
+        let c = catalog.connection();
+        dr_catalog::rating::set_label(c, ids[0], Some(dr_types::ColourLabel::Red)).unwrap();
+        dr_catalog::rating::set_label(c, ids[1], Some(dr_types::ColourLabel::Red)).unwrap();
+        dr_catalog::rating::set_label(c, ids[2], Some(dr_types::ColourLabel::Green)).unwrap();
+
+        let red = RatingFilter {
+            label: Some(dr_types::ColourLabel::Red),
+            ..Default::default()
+        };
+        assert!(!red.is_unfiltered());
+        assert_eq!(read_cells_all(&catalog, &red, 0, 120).unwrap().len(), 2);
+        assert_eq!(total_images_filtered(&catalog, &red).unwrap(), 2);
+
+        let purple = RatingFilter {
+            label: Some(dr_types::ColourLabel::Purple),
+            ..Default::default()
+        };
+        assert_eq!(total_images_filtered(&catalog, &purple).unwrap(), 0);
+    }
+
     #[test]
     fn a_cached_preview_is_not_a_local_original() {
         // The filter answers "can I open this in develop right now", and a

ui/dr-ui/src/library/scan.rs

@@ -914,15 +914,24 @@ mod tests {
     fn a_label_from_another_device_reaches_the_catalog_and_none_clears_nothing() {
         // TRACES: FR-CAT-5
         let cat = library(&["2026/a.CR2"]);
-        assert_eq!(apply_judgement(cat.connection(), 1, "2026/a.drsc", 0, 0, 4).unwrap(), 1);
+        assert_eq!(
+            apply_judgement(cat.connection(), 1, "2026/a.drsc", 0, 0, 4).unwrap(),
+            1
+        );
         let label = |cat: &Catalog| -> Option<i64> {
             cat.connection()
-                .query_row("SELECT label FROM versions WHERE is_default = 1", [], |r| r.get(0))
+                .query_row("SELECT label FROM versions WHERE is_default = 1", [], |r| {
+                    r.get(0)
+                })
                 .unwrap()
         };
         assert_eq!(label(&cat), Some(4));
         apply_judgement(cat.connection(), 1, "2026/a.drsc", 3, 0, 0).unwrap();
-        assert_eq!(label(&cat), Some(4), "a sidecar with no label left it alone");
+        assert_eq!(
+            label(&cat),
+            Some(4),
+            "a sidecar with no label left it alone"
+        );
     }
 
     /// The regression, in one line: a rating in a sidecar reaches the grid.