🐛 Fix unmoved layout child stretched during wasm gap drag (#12831)

Follow-up to 419513011c: only pure moves pass down to children in wasm.
Remove unused set-wasm-rotation-modifiers.

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

@@ -727,15 +727,16 @@
         computed))))
 
 (defn- without-inherited-transforms
-  "Drops the entries that repeat their parent's transform. Only for WASM, which applies it to
-  the subtree; the UI looks transforms up per shape. WASM does not expand into bool operands
-  nor masks, so those are kept."
+  "Drops the pure-move entries that repeat their parent's transform. Only for WASM, which
+  applies a parent's move to the subtree; the UI looks transforms up per shape. WASM does not
+  expand into bool operands nor masks, so those are kept."
   [objects modifiers]
   (let [transforms (into {} modifiers)]
     (into []
           (remove (fn [[id transform]]
                     (let [parent (get objects (dm/get-in objects [id :parent-id]))]
                       (and (= transform (get transforms (:id parent)))
+                           (gmt/move? transform)
                            (not (cfh/bool-shape? parent))
                            (not (and (cfh/mask-shape? parent)
                                      (= id (first (:shapes parent)))))))))
@@ -971,34 +972,6 @@
    (filter #(:rotation (get editable-attrs (:type %))))
    (map :id)))
 
-;; Rotation use different algorithm to calculate children
-;; modifiers (and do not use child constraints).
-(defn set-wasm-rotation-modifiers
-  ([angle shapes]
-   (set-wasm-rotation-modifiers angle shapes (-> shapes gsh/shapes->rect grc/rect->center)))
-
-  ([angle shapes center]
-   (ptk/reify ::set-wasm-rotation-modifiers
-     ptk/EffectEvent
-     (effect [_ state _]
-       (ensure-interactive-transform-start!)
-       (let [objects (dsh/lookup-page-objects state)
-             ids     (sequence xf-rotation-shape shapes)
-
-             get-modifier
-             (fn [shape]
-               (ctm/rotation-modifiers shape center angle))
-
-             modif-tree
-             (build-modif-tree ids objects get-modifier)
-
-             modifiers
-             (mapv (fn [[id {:keys [modifiers]}]]
-                     (d/vec2 id (ctm/modifiers->transform modifiers)))
-                   modif-tree)]
-
-         (wasm.api/set-modifiers modifiers))))))
-
 (defn set-rotation-modifiers
   ([angle shapes]
    (set-rotation-modifiers angle shapes (-> shapes gsh/shapes->rect grc/rect->center)))

render-wasm/src/state/shapes_pool.rs

@@ -308,10 +308,11 @@ impl ShapesPoolImpl {
             }
         }
 
-        // Expand every root modifier to its full descendant subtree.
+        // Expand every pure-move root modifier to the descendants without one.
         // When CLJS sends only root shapes (translation on drag), descendants
-        // need the same matrix.
-        // For resize/rotate, propagate-modifiers already includes all descendants.
+        // need the same matrix. Other matrices come from propagate-modifiers,
+        // where a missing child means the child stays put (e.g. an auto-size
+        // layout parent or a layout child that does not move).
         // Descendants are NOT pushed into `ids` / `modifier_uuids`: rebuild_modifier_tiles
         // runs for roots, and drops the non-clipping ancestors' extrects separately.
         let root_pairs: Vec<(usize, skia::Matrix)> = ids
@@ -319,7 +320,7 @@ impl ShapesPoolImpl {
             .filter_map(|uuid| {
                 let idx = self.uuid_to_idx.get(uuid).copied()?;
                 let matrix = modifiers_with_idx.get(&idx).copied()?;
-                Some((idx, matrix))
+                math::is_move_only_matrix(&matrix).then_some((idx, matrix))
             })
             .collect();
 
@@ -599,4 +600,33 @@ mod tests {
         pool.get_mut(&id).expect("shape").set_opacity(0.5);
         assert_eq!(pool.get(&id).expect("shape").opacity, 0.5);
     }
+
+    fn pool_with_parent_and_child() -> (ShapesPool, Uuid, Uuid) {
+        let mut pool = ShapesPool::new();
+        pool.initialize(2);
+        let parent = Uuid::new_v4();
+        let child = Uuid::new_v4();
+        pool.add_shape(parent).add_child(child);
+        pool.add_shape(child).set_parent(parent);
+        (pool, parent, child)
+    }
+
+    #[test]
+    fn set_modifiers_passes_a_move_down_to_children() {
+        let (mut pool, parent, child) = pool_with_parent_and_child();
+        let translate = skia::Matrix::translate((10.0, 0.0));
+
+        pool.set_modifiers(HashMap::from([(parent, translate)]));
+
+        assert_eq!(pool.get_modifier(&child), Some(&translate));
+    }
+
+    #[test]
+    fn set_modifiers_keeps_a_resize_on_the_parent() {
+        let (mut pool, parent, child) = pool_with_parent_and_child();
+
+        pool.set_modifiers(HashMap::from([(parent, skia::Matrix::scale((1.0, 2.4)))]));
+
+        assert_eq!(pool.get_modifier(&child), None);
+    }
 }