🎉 Remember displacements when duplicating several shapes in a row

CHANGES.md

@@ -9,6 +9,7 @@
 
 - Use space + mouse drag to pan, instead of only space [Taiga #1800](https://tree.taiga.io/project/penpot/us/1800).
 - Allow to zoom with ctrl + middle button [Taiga #1428](https://tree.taiga.io/project/penpot/us/1428).
+- Auto placement of duplicated objects [Taiga #1386](https://tree.taiga.io/project/penpot/us/1386).
 
 ### :bug: Bugs fixed
 ### :arrow_up: Deps updates

frontend/src/app/main/data/workspace/selection.cljs

@@ -383,6 +383,53 @@
 
     (into [fch] sch)))
 
+(defn clear-memorize-duplicated
+  []
+  (ptk/reify ::clear-memorize-duplicated
+    ptk/UpdateEvent
+    (update [_ state]
+      (d/dissoc-in state [:workspace-local :duplicated]))))
+
+(defn memorize-duplicated
+  "When duplicate an object, remember the operation during the following seconds.
+  If the user moves the duplicated object, and then duplicates it again, check
+  the displacement and apply it to the third copy. This is useful for doing
+  grids or cascades of cloned objects."
+  [id-original id-duplicated]
+  (ptk/reify ::memorize-duplicated
+    ptk/UpdateEvent
+    (update [_ state]
+      (assoc-in state [:workspace-local :duplicated] {:id-original id-original
+                                                      :id-duplicated id-duplicated}))
+
+    ptk/WatchEvent
+    (watch [_ _ stream]
+      (let [stoper (rx/filter (ptk/type? ::memorize-duplicated) stream)]
+        (->> (rx/timer 10000) ;; This time may be adjusted after some user testing.
+             (rx/take-until stoper)
+             (rx/map clear-memorize-duplicated))))))
+
+(defn calc-duplicate-delta
+  [obj state objects]
+  (let [{:keys [id-original id-duplicated]}
+        (get-in state [:workspace-local :duplicated])]
+    (if (and (not= id-original (:id obj))
+             (not= id-duplicated (:id obj)))
+
+      ;; The default is leave normal shapes in place, but put
+      ;; new frames to the right of the original.
+      (if (= (:type obj) :frame)
+        (gpt/point (+ (:width obj) 50) 0)
+        (gpt/point 0 0))
+
+      (let [obj-original   (get objects id-original)
+            obj-duplicated (get objects id-duplicated)
+            distance       (gpt/subtract (gpt/point obj-duplicated)
+                                         (gpt/point obj-original))
+            new-pos        (gpt/add (gpt/point obj-duplicated) distance)
+            delta          (gpt/subtract new-pos (gpt/point obj))]
+        delta))))
+
 (def duplicate-selected
   (ptk/reify ::duplicate-selected
     ptk/WatchEvent
@@ -392,9 +439,7 @@
             selected (wsh/lookup-selected state)
             delta    (if (= (count selected) 1)
                        (let [obj (get objects (first selected))]
-                         (if (= (:type obj) :frame)
+                         (calc-duplicate-delta obj state objects))
-                           (gpt/point (+ (:width obj) 50) 0)
-                           (gpt/point 0 0)))
                        (gpt/point 0 0))
 
             unames   (dwc/retrieve-used-names objects)
@@ -405,15 +450,20 @@
             uchanges (mapv #(array-map :type :del-obj :page-id page-id :id (:id %))
                            (reverse rchanges))
 
+            id-original (when (= (count selected) 1) (first selected))
+
             selected (->> rchanges
                           (filter #(selected (:old-id %)))
                           (map #(get-in % [:obj :id]))
-                          (into (d/ordered-set)))]
+                          (into (d/ordered-set)))
+
+            id-duplicated (when (= (count selected) 1) (first selected))]
 
         (rx/of (dch/commit-changes {:redo-changes rchanges
                                     :undo-changes uchanges
                                     :origin it})
-               (select-shapes selected))))))
+               (select-shapes selected)
+               (memorize-duplicated id-original id-duplicated))))))
 
 (defn change-hover-state
   [id value]