Solo an instance from its timeline row, shift-click for more than one

A nested mark is now named by the flat path its row has, [a b mark] rather
than [a [b mark]], so a soloed row is a prefix of what it shows.

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

frontend/src/arthur/domain/clip.cljs

@@ -135,12 +135,14 @@
    :symbols {:main {:id :main :frames blank-frames :nodes {}}}})
 
 (defn- transform-op
-  "Put a symbol's already resolved mark into its instance's parent space."
+  "Put a symbol's already resolved mark into its instance's parent space. Its
+  name becomes its path of instances down to it, the path its timeline row has."
   [op m path]
   (let [at (fn [x y] [(+ (* (aget m 0) x) (* (aget m 2) y) (aget m 4))
                        (+ (* (aget m 1) x) (* (aget m 3) y) (aget m 5))])
         scale (node/mean-scale m)
-        op (assoc op :node (conj path (:node op)))]
+        n (:node op)
+        op (assoc op :node (if (vector? n) (into path n) (conj path n)))]
     (case (:kind op)
       :poly (let [out (js/Float64Array. (.-length (:pts op)))]
               (dotimes [i (:n op)]

frontend/src/arthur/events/ui.cljs

@@ -25,6 +25,18 @@
  (fn [db [_ path]]
    (update-in db [:ui :expanded] #(if (contains? % path) (disj % path) (conj % path)))))
 
+(rf/reg-event-db
+ ::solo
+ (fn [db [_ path more?]]
+   ;; Per open symbol, because a row path only means something from the symbol
+   ;; it was walked from. A click solos that row alone, or un-solos it if it
+   ;; already was; a shift-click adds it to or takes it out of the ones soloed.
+   (update-in db [:ui :solo (get-in db [:ui :open])]
+              (fn [on]
+                (cond more?             (if (contains? on path) (disj on path) (conj (set on) path))
+                      (= on #{path})    #{}
+                      :else             #{path})))))
+
 (defn- where-new-goes
   "The row path, from the open symbol down, of the symbol a new thing goes into:
   INSIDE the selected instance, or BESIDE any other selected node, or at the top

frontend/src/arthur/subs/render.cljs

@@ -19,6 +19,7 @@
 
 (rf/reg-sub ::open (fn [db _] (get-in db [:ui :open])))
 (rf/reg-sub ::sliding (fn [db _] (get-in db [:ui :sliding])))
+(rf/reg-sub ::solo (fn [db _] (get-in db [:ui :solo (get-in db [:ui :open])])))
 
 (rf/reg-sub
  ::clip
@@ -91,6 +92,12 @@
    ;; new blocks, the resolver cannot find them, and the frame throws.
    (:store (footage/entry id))))
 
+(defn- placed?
+  "Does row `path` from symbol `sid` still name an instance, all the way down?"
+  [clip sid path]
+  (reduce (fn [sid id] (or (get-in clip [:symbols sid :nodes id :of]) (reduced nil)))
+          sid path))
+
 (rf/reg-sub
  ::resolver
  :<- [::clip]
@@ -101,3 +108,26 @@
  (fn [[document sid store palette picture-fps] _]
    (when (and document (clip/symbol document sid))
      (clip/resolver document store palette sid {:picture-fps picture-fps}))))
+
+(rf/reg-sub
+ ::shown
+ :<- [::resolver]
+ :<- [::clip]
+ :<- [::open]
+ :<- [::solo]
+ (fn [[resolve document sid solo] _]
+   ;; What the stage draws: `::resolver`, less whatever is not under a soloed
+   ;; row. Its own layer, so soloing does not rebuild the resolver.
+   ;;
+   ;; A soloed row that has since been deleted or moved would otherwise leave
+   ;; the stage blank, with no row left to un-solo it from.
+   (let [solo (filter #(placed? document sid %) solo)]
+     (if (or (nil? resolve) (empty? solo))
+       resolve
+       ;; An op inside an instance is named by the path its row has; one at the
+       ;; top by its bare id.
+       (fn [f]
+         (filterv (fn [{n :node}]
+                    (let [p (if (vector? n) n [n])]
+                      (some #(= % (take (count %) p)) solo)))
+                  (resolve f)))))))

frontend/src/arthur/ui/player.cljs

@@ -100,7 +100,7 @@
   (reset! tracker
           (ratom/run!
            (let [was (:resolver @snapshot)
-                 now @(rf/subscribe [::render/resolver])]
+                 now @(rf/subscribe [::render/shown])]
              (reset! snapshot
                      {:resolver now
                       :palette  @(rf/subscribe [::render/palette])

frontend/src/arthur/ui/timeline.cljs

@@ -204,7 +204,7 @@
     (cond (< y 0.3) :front (> y 0.7) :back :else :into)))
 
 (defn- label-cell [{:keys [path depth label kind node-kind select expandable? expanded? of]}
-                   selection over]
+                   selection over solo]
   (let [node? (= :node kind)
         [over-path where] @over]
     [:div (cond-> {:class (str "tl-label" (when (and select (= select selection)) " on")
@@ -260,6 +260,13 @@
       (when expandable? (if expanded? "▾" "▸"))]
      [:span.name label]
      (when node? [:span.kind (str "·" (name node-kind))])
+     (when (= :instance node-kind)
+       [:button {:class    (str "tl-solo" (when (contains? solo path) " on"))
+                 :title    "show only this on the stage (⇧ for more than one)"
+                 :on-click (fn [^js e]
+                             (.stopPropagation e)
+                             (rf/dispatch [::ui/solo path (.-shiftKey e)]))}
+        "S"])
      (when (and node? (= select selection))
        [:button.tl-delete {:title    "delete, with everything in it (⌫)"
                            :on-click (fn [^js e]
@@ -329,6 +336,7 @@
           selection @(rf/subscribe [::sub/selection])
           expanded  @(rf/subscribe [::sub/expanded])
           drop      @(rf/subscribe [::sub/drop])
+          solo      (set @(rf/subscribe [::render/solo]))
           ;; Where a drag out of the pool would land, as a row of its own at the
           ;; top: its own length, starting on the frame it would start on. The
           ;; stage's drop shows it too, at the playhead.
@@ -357,7 +365,7 @@
                          (rf/dispatch [::ui/move-node from []]))))}
          [:div.tl-corner]
          (doall (for [row visible]
-                  ^{:key (str (:path row))} [label-cell row selection over]))]
+                  ^{:key (str (:path row))} [label-cell row selection over solo]))]
         [:div.tl-tracks
          {:on-drag-enter (fn [^js e] (when (drag/accepts?) (.preventDefault e)))
           :on-drag-over (fn [^js e]

frontend/test/arthur/domain/nest_test.cljs

@@ -63,7 +63,7 @@
               (turn :main u [40 20] (/ js/Math.PI 2) 2)
               (turn :mid v [5 -3] 0.3 1.5)
               (paint/new-shape :box :shape 4 [0 0 10 0 5 10] :brow))
-        draw  #(take 6 (array-seq (:pts (first (filter (fn [op] (= [u [v :shape]] (:node op)))
+        draw  #(take 6 (array-seq (:pts (first (filter (fn [op] (= [u v :shape] (:node op)))
                                                         ((clip/resolver % nil pal/index-of :main) 16))))))
         {:keys [frame matrix time]} (nest/inside c nil :main [u v :shape] 16)
         out   (js/Float64Array. 2)

frontend/test/arthur/flow/multi_face_test.cljs

@@ -134,7 +134,7 @@
       (let [before (snapshot (:clip entry) (:store entry) f)
             after (snapshot (:clip back) (:store back) f)]
         (is (seq before))
-        (is (some #(= [:face-2 :mouth] (second (:node %))) before)))
+        (is (some #(= [:face-2 :mouth] (rest (:node %))) before)))
       (is (= (snapshot (:clip entry) (:store entry) f)
              (snapshot (:clip back) (:store back) f))))))