feat: pack annotation lanes into shared rows

The annotation lane above the tracks now collapses non-overlapping
annotations onto a single row. Each annotation is assigned a lane by
greedy first-fit in definition order (:created): it takes the topmost
lane it doesn't time-overlap, so overlapping annotations stack with the
earlier-defined one on top and the newer beneath.

- annotations carry :created (new ones stamp Date.now; seed has explicit
  values; old saved data defaults to 0 = oldest)
- pane order: by start, then longest-first so a section leads a tie
- seed data reworked to overlap (Act I / rally / baseline / glance / net,
  plus an overlapping nested child) so the packing is visible; one-time
  localStorage reset bumped so it lands

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

tl/src/tl/core.cljs

@@ -22,9 +22,9 @@
 ;; one-time dev reset: wipe saved marks once so the nested-timeline seed data
 ;; shows, then flag it so persistence resumes normally. Safe to delete later.
 (defn- reset-marks-once! []
-  (when-not (.getItem js/localStorage "tl/seed-reset-1")
+  (when-not (.getItem js/localStorage "tl/seed-reset-2")
     (.removeItem js/localStorage "tl/marks")
-    (.setItem js/localStorage "tl/seed-reset-1" "1")))
+    (.setItem js/localStorage "tl/seed-reset-2" "1")))
 
 (defn init []
   (reset-marks-once!)

tl/src/tl/db.cljs

@@ -21,25 +21,48 @@
    ;;
    ;; The annotations below are seed data (shown on a fresh localStorage) so the
    ;; expand/nest flow is testable: "Opening rally" has two children.
+   ;; The seed is laid out to exercise lane packing. Root level (by frame):
+   ;;   Act I        0–414   (section)     created 1  -> lane 0 (earliest, top)
+   ;;   Opening rally 129–385               created 2  -> lane 1 (overlaps Act I)
+   ;;   Baseline      64–128                created 3  -> lane 1 (fits before rally)
+   ;;   Tashi glance  150–175               created 4  -> lane 2 (overlaps both)
+   ;;   Net-cam beat  542–609               created 5  -> lane 0 (collapses after Act I)
    :marks
    {:timeline-stack [:root]
     :groups {:root {:type :timeline :name "Sequence"}
 
+             :ann-act1
+             {:type :annotation :parent :root :name "Act I — the warmup" :color "#8a8f3a"
+              :created 1 :content "The whole opening movement."
+              :marks [[0 414]]}
              :ann-rally
              {:type :annotation :parent :root :name "Opening rally" :color "#4e8fc2"
+              :created 2
               :content "The first volley — CU coverage across the three principals."
               :marks [:t2-c0 :t3-c0 :t4-c0]}
+             :ann-baseline
+             {:type :annotation :parent :root :name "Baseline establishing" :color "#c28f4e"
+              :created 3 :marks [:t1-c0]}
+             :ann-glance
+             {:type :annotation :parent :root :name "Tashi glance" :color "#c24e9a"
+              :created 4 :marks [[150 175]]}
+             :ann-net
+             {:type :annotation :parent :root :name "Net-cam beat" :color "#9a7ac2"
+              :created 5 :marks [:t6-c0]}
+
+             ;; children of "Opening rally" (visible only when expanded into it):
+             ;;   Tashi's read 129–190 / Art reacts 192–266  -> share lane 0
+             ;;   the spin     140–205                         -> lane 1 (overlaps both)
              :ann-tashi-read
              {:type :annotation :parent :ann-rally :name "Tashi's read" :color "#c2624e"
-              :content "She clocks the spin early."
+              :created 6 :content "She clocks the spin early."
               :marks [[[:at :t2-c0 0] [:at :t2-c0 -1]]]}
              :ann-art-react
              {:type :annotation :parent :ann-rally :name "Art reacts" :color "#5ab07a"
-              :marks [:t3-c0]}
+              :created 7 :marks [:t3-c0]}
-
+             :ann-spin
-             :ann-net
+             {:type :annotation :parent :ann-rally :name "the spin" :color "#4ec2b0"
-             {:type :annotation :parent :root :name "Net-cam beat" :color "#9a7ac2"
+              :created 8 :marks [[140 205]]}}}
-              :marks [:t6-c0]}}}
 
    ;; transient view state (mutates while scrubbing/zooming)
    :view {:zoom          50           ; X zoom: pixels per SECOND (px/frame = zoom/fps)

tl/src/tl/events.cljs

@@ -115,7 +115,8 @@
    ;; new annotations are children of whatever context we're currently in
    (let [id    (keyword (str "ann-" (random-uuid)))
          parent (last (get-in db [:marks :timeline-stack]))
-         group (cond-> {:type :annotation :parent parent :name name :color color :marks marks}
+         group (cond-> {:type :annotation :parent parent :name name :color color
+                        :marks marks :created (.now js/Date)}   ; defines stacking order
                  (seq content) (assoc :content content))
          db'   (assoc-in db [:marks :groups id] group)]
      {:db db' :tl/save (:marks db')})))

tl/src/tl/subs.cljs

@@ -59,9 +59,12 @@
                    (let [spans (marks/resolve-group idx groups gid)]
                      {:id gid :name (:name g) :content (:content g) :color (:color g)
                       :marks (:marks g) :children (get child-count gid 0)
+                      :created (:created g 0)                       ; definition order
                       :spans spans :anchor (marks/anchor spans)
+                      :end (when (seq spans) (reduce max (map :end spans)))
                       :instant? (every? :instant? spans)})))
-            (sort-by :anchor)
+            ;; pane order: by start, then longest first (sections lead a tie)
+            (sort-by (juxt #(or (:anchor %) 0) #(- (or (:end %) 0))))
             vec)))))
 
 ;; Breadcrumb trail for the stack: root + each expanded annotation's name.

tl/src/tl/views.cljs

@@ -260,18 +260,46 @@
 
 ;; --- timeline -------------------------------------------------------------
 
+(defn- ann-extent
+  "[earliest-start, latest-end] across an annotation's spans (its footprint)."
+  [spans] [(reduce min (map :start spans)) (reduce max (map :end spans))])
+
+(defn- assign-lanes
+  "Pack annotations into as few rows as possible. Processed in definition order
+  (earliest :created first), each takes the topmost lane it doesn't time-overlap
+  — so non-overlapping annotations collapse onto one row, and when they do
+  overlap the earlier-defined one sits above. Returns each with a :lane index."
+  [anns]
+  (let [ordered (sort-by (juxt #(:created % 0) #(first (ann-extent (:spans %)))) anns)]
+    (loop [[a & more] ordered, lanes [], out []]
+      (if (nil? a)
+        out
+        (let [[s e] (ann-extent (:spans a))
+              fits? (fn [ivs] (every? (fn [[s2 e2]] (or (<= e s2) (>= s e2))) ivs))
+              li    (or (first (keep-indexed (fn [i ivs] (when (fits? ivs) i)) lanes))
+                        (count lanes))
+              lanes (update (if (< li (count lanes)) lanes (conj lanes [])) li conj [s e])]
+          (recur more lanes (conj out (assoc a :lane li))))))))
+
+(defn- lane-count [placed]
+  (if (seq placed) (inc (reduce max (map :lane placed))) 0))
+
 (defn annotation-lane
-  "One labeled row per annotation, above the tracks. Bars are positioned in
+  "The annotation rows above the tracks. Annotations are packed into shared rows
-  display frames (same coordinate as clips), so they align with the timeline.
+  (see assign-lanes); each row holds every annotation assigned to that lane.
-  `off` is the crop offset (frames): positions are drawn relative to it."
+  Bars are positioned in display frames relative to the crop offset `off`."
-  [fps zoom off annotations active]
+  [fps zoom off placed active]
   [:div
    (doall
-    (for [{:keys [id name spans preview?] c :color} annotations]
+    (for [[li items] (->> placed (group-by :lane) (into (sorted-map)))]
+      ^{:key li}
+      [:div.ann-lane-row
+       (doall
+        (for [{:keys [id name spans preview?] c :color} items]
           (let [color (or c "#4e8fc2")
                 on?   (= id active)]
             ^{:key id}
-        [:div.ann-lane-row
+            [:<>
              (doall
               (for [[j s] (map-indexed vector spans)]
                 (let [left (* (secs (- (:start s) off) fps) zoom)
@@ -283,7 +311,7 @@
                             :background (cond preview? (str color "44") on? color :else (str color "80"))
                             :border (str (if preview? "1px dashed " "1px solid ") color)}}])))
              (when-let [a (some-> spans first :start)]
-           [:div.ann-bar-label {:style {:left (+ 4 (* (secs (- a off) fps) zoom))}} name])])))])
+               [:div.ann-bar-label {:style {:left (+ 4 (* (secs (- a off) fps) zoom))}} name])])))]))])
 
 (defn clip-block [fps zoom off row-h authoring? {:keys [id name media-in duration] :as _clip}]
   (let [left  (* (secs (- media-in off) fps) zoom)
@@ -361,12 +389,16 @@
                                       (try (marks/resolve-marks cidx groups #{} marks)
                                            (catch :default _ nil)))]
                          (when (seq spans)
-                           {:id ::draft :preview? true :color (:color d)
+                           ;; newest :created so the in-progress draft sinks below
+                           ;; existing annotations when they overlap
+                           {:id ::draft :preview? true :color (:color d) :created js/Infinity
                             :name (or (not-empty (str/trim (str (:name d)))) "(new)")
                             :spans spans})))
             lane-anns (let [base (if (:id d) (remove #(= (:id %) (:id d)) anns) anns)]
-                        (cond-> (vec base) preview (conj preview)))
+                        (->> (cond-> (vec base) preview (conj preview))
-            lane-h   (* 18 (count lane-anns))
+                             (filterv (comp seq :spans))))   ; need a footprint to pack
+            placed   (assign-lanes lane-anns)
+            lane-h   (* 18 (lane-count placed))
             end      (+ off vframes)
             width    (* (secs vframes fps) zoom)]
         (when (and playing? @following?)
@@ -391,7 +423,7 @@
            (let [x (* (secs (- playhead off) fps) zoom)]
              [:div.playhead {:style {:left x}}
               [:div.playhead-handle]])
-           [annotation-lane fps zoom off lane-anns active]
+           [annotation-lane fps zoom off placed active]
            (for [t vtracks]
              ^{:key (:id t)} [track-row fps zoom off row-h (some? d) t])]]]))))