Hold or tween any keyed channel's gaps, as a drawing's

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

frontend/src/arthur/domain/node.cljs

@@ -94,6 +94,16 @@
                                                 (:segments c) (update :segments dissoc f))
                 :else                         (ch/framed v)))))
 
+(defn set-segment-interp
+  "Choose how channel `path`'s key at `left` leads to the next one: `:hold` cuts
+  there, `:linear` tweens. The same for a drawing's points as for a transform —
+  only a gap that exists, between a key and a later one, can be chosen."
+  [n path left interp]
+  (let [ks (:keys (get (channels n) path))]
+    (if (and (contains? ks left) (some #(< left %) (keys ks)) (#{:hold :linear} interp))
+      (assoc-in n [:channels path :segments left] interp)
+      n)))
+
 ;; ---------------------------------------------------------------------------
 ;; time maps
 ;;

frontend/src/arthur/domain/paint.cljs

@@ -46,13 +46,3 @@
     (if (and points (< (inc i) (count points)))
       (assoc-in clip path (-> points (assoc i x) (assoc (inc i) y)))
       clip)))
-
-(defn set-segment-interp [clip sid id key-frame interp]
-  (let [node (get-in clip [:symbols sid :nodes id])
-        keys (get-in node [:channels geometry :keys])]
-    (if (and (:paint? node) (contains? keys key-frame)
-             (some #(< key-frame %) (clojure.core/keys keys))
-             (#{:hold :linear} interp))
-      (assoc-in clip [:symbols sid :nodes id :channels geometry
-                      :segments key-frame] interp)
-      clip)))

frontend/src/arthur/events/paint.cljs

@@ -23,8 +23,3 @@
  ::set-vertex
  (fn [db [_ sid id key-frame vertex point]]
    (edit/edit db #(paint/set-vertex % sid id key-frame vertex point))))
-
-(rf/reg-event-db
- ::set-segment-interp
- (fn [db [_ sid id key-frame interp]]
-   (edit/edit db #(paint/set-segment-interp % sid id key-frame interp))))

frontend/src/arthur/events/project.cljs

@@ -624,6 +624,11 @@
  (fn [db [_ sid id path frame]]
    (edit/edit db #(update-in % [:symbols sid :nodes id] node/toggle-key path frame))))
 
+(rf/reg-event-db
+ ::set-segment-interp
+ (fn [db [_ sid id path left interp]]
+   (edit/edit db #(update-in % [:symbols sid :nodes id] node/set-segment-interp path left interp))))
+
 (rf/reg-event-fx
  ::list
  (fn [{:keys [db]} _]

frontend/src/arthur/ui/params.cljs

@@ -123,6 +123,16 @@
     :else         (let [v (:value ch)]
                     (str "framed · " (if (channel/nothing? v) "absent" (pr-str v))))))
 
+(defn- segment-select
+  "Hold or tween, for the gap after the key at `left` — the same choice on a
+  drawing as on a transform."
+  [sid id path ch left]
+  [:select.interp {:value (name (or (channel/segment-interp ch left) :hold))
+                   :on-change #(rf/dispatch [::project/set-segment-interp
+                                             sid id path left (keyword (.. % -target -value))])}
+   [:option {:value "hold"} "hold"]
+   [:option {:value "linear"} "tween"]])
+
 (defn- drawing-keys
   "The polygon controls: jump to a drawing key, add one here, and choose what the
   gap after the current one does. Lifted out of the old stage toolbar unchanged —
@@ -158,23 +168,23 @@
      (when next-k
        [:div.row {:style {:margin-top "5px"}}
         [:label.dim (str "key " active " → " next-k " ")
-         [:select {:value (name (or (channel/segment-interp geom active) :hold))
-                   :on-change #(rf/dispatch [::paint-events/set-segment-interp
-                                             sid id active (keyword (.. % -target -value))])}
-          [:option {:value "hold"} "hold"]
-          [:option {:value "linear"} "tween"]]]])]))
+         [segment-select sid id paint/geometry geom active]]])]))
 
 ;; The transform and visibility, which every node has, as one row each: ◆ keys
 ;; the channel here or takes the key here off, and an edit writes a key on a
 ;; keyed channel or the one value on one that is not. `frame` is the node's own,
 ;; nil when it is not on screen, where a keyed channel has no here to write to.
-;; Rotation is shown in degrees.
+;; Rotation is shown in degrees. Between two keys, the gap after the one here
+;; holds or tweens, as a drawing's does.
 
 (defn- channel-control [sid id path ch frame]
   (let [keyed? (some? (:keys ch))
         v      (channel/value-at ch (or frame 0))
         off?   (and keyed? (nil? frame))
         deg?   (= path [:xform :rot])
+        ;; A boolean has nothing between true and false to tween through.
+        left   (when (and keyed? frame (not (boolean? v))) (paint/active-frame ch frame))
+        gap?   (and left (some #(< left %) (keys (:keys ch))))
         put    #(rf/dispatch [::project/set-channel sid id path frame %])
         field  (fn [i x on-number]
                  ^{:key i}
@@ -193,7 +203,8 @@
                              :on-change #(put (.. % -target -checked))}]
        (number? v)  (field 0 v put)
        :else        (doall (map-indexed (fn [i x] (field i x #(put (assoc (vec v) i %))))
-                                        v)))]))
+                                        v)))
+     (when gap? [segment-select sid id path ch left])]))
 
 (defn- node-section [[sid id n]]
   (let [[start end] (:span n)]

frontend/test/arthur/domain/node_test.cljs

@@ -200,4 +200,13 @@
     (let [d (node/toggle-key b [:xform :rot] 3)]
       (is (not (:animated? (get-in d [:channels [:xform :rot]]))) "the last key off is one value again")
       (is (= 1.0 (rot d 0))))
-    (is (= :hold (get-in (node/toggle-key n [:vis] 0) [:channels [:vis] :interp])) "a boolean holds")))
+    (is (= :hold (get-in (node/toggle-key n [:vis] 0) [:channels [:vis] :interp])) "a boolean holds")
+    (let [h (node/set-segment-interp c [:xform :pos] 0 :hold)]
+      (is (= [5 5] (pos h 5)) "a gap set to hold cuts at the next key")
+      (is (= [10 0] (pos h 10)))
+      (is (= [7.5 2.5] (pos (node/set-segment-interp h [:xform :pos] 0 :linear) 5)) "and back to a tween")
+      (is (= h (node/set-segment-interp h [:xform :pos] 10 :hold)) "the last key has no gap after it")
+      (is (empty? (ch/problems (get-in h [:channels [:xform :pos]])))))
+    (let [d (node/toggle-key (node/set-segment-interp c [:xform :pos] 0 :hold) [:xform :pos] 0)]
+      (is (not (contains? (get-in d [:channels [:xform :pos] :segments]) 0))
+          "taking a key off takes its gap's choice with it"))))

frontend/test/arthur/domain/paint_test.cljs

@@ -3,6 +3,7 @@
             [arthur.demo :as demo]
             [arthur.domain.channel :as channel]
             [arthur.domain.leaf :as leaf]
+            [arthur.domain.node :as node]
             [arthur.domain.paint :as paint]
             [arthur.domain.symbol :as symbol]))
 
@@ -17,7 +18,8 @@
         c3 (paint/add-key c2 :main :paint-test 15)
         c4 (paint/set-vertex c3 :main :paint-test 15 0 [34 10])
         held (geometry c4)
-        mixed-clip (paint/set-segment-interp c4 :main :paint-test 9 :linear)
+        mixed-clip (update-in c4 [:symbols :main :nodes :paint-test]
+                               node/set-segment-interp paint/geometry 9 :linear)
         mixed (geometry mixed-clip)]
     (is (= [3 229] (get-in c2 [:symbols :main :nodes :paint-test :span])))
     (is (= a (channel/value-at held 8)))