diff --git a/common/src/app/common/flags.cljc b/common/src/app/common/flags.cljc
index 0584d0f0f7..79f94d2639 100644
--- a/common/src/app/common/flags.cljc
+++ b/common/src/app/common/flags.cljc
@@ -169,6 +169,7 @@
 
     :mcp
     :background-blur
+    :available-viewer-wasm
     :stroke-path})
 
 (def all-flags
diff --git a/frontend/src/app/main/data/viewer.cljs b/frontend/src/app/main/data/viewer.cljs
index 3b2ca792b8..d05df4bd13 100644
--- a/frontend/src/app/main/data/viewer.cljs
+++ b/frontend/src/app/main/data/viewer.cljs
@@ -17,6 +17,7 @@
    [app.common.types.shape-tree :as ctt]
    [app.common.types.shape.interactions :as ctsi]
    [app.common.uuid :as uuid]
+   [app.config :as cf]
    [app.main.data.comments :as dcmt]
    [app.main.data.common :as dcm]
    [app.main.data.event :as ev]
@@ -219,7 +220,8 @@
   (ptk/reify ::update-page-position-data
     ptk/WatchEvent
     (watch [_ state _]
-      (if (features/active-feature? state "render-wasm/v1")
+      (if (and (features/active-feature? state "render-wasm/v1")
+               (contains? cf/flags :available-viewer-wasm))
         (let [objects (dsh/lookup-page-objects state file-id page-id)
 
               shapes
diff --git a/frontend/src/app/main/render.cljs b/frontend/src/app/main/render.cljs
index 7c6ee76e1e..5bd1a63f6d 100644
--- a/frontend/src/app/main/render.cljs
+++ b/frontend/src/app/main/render.cljs
@@ -30,6 +30,7 @@
    [app.common.types.shape.layout :as ctl]
    [app.config :as cfg]
    [app.main.fonts :as fonts]
+   [app.main.render-viewer-wasm :as rwv]
    [app.main.ui.context :as muc]
    [app.main.ui.shapes.bool :as bool]
    [app.main.ui.shapes.circle :as circle]
@@ -524,32 +525,6 @@
        (for [shape shapes]
          [:& shape-wrapper {:key (dm/str (:id shape)) :shape shape}])]]]))
 
-(defn render-to-canvas
-  [objects canvas bounds scale object-id on-render]
-  (let [width (.-width canvas)
-        height (.-height canvas)
-        os-canvas (js/OffscreenCanvas. width height)]
-    (try
-      (when (wasm.api/init-canvas-context os-canvas)
-        (wasm.api/initialize-viewport
-         objects scale bounds
-         :background-opacity 0
-         :on-render
-         (fn []
-           (wasm.api/render-sync-shape object-id)
-           (ts/raf
-            (fn []
-              (let [bitmap (.transferToImageBitmap os-canvas)
-                    ctx2d (.getContext canvas "2d")]
-                (.clearRect ctx2d 0 0 width height)
-                (.drawImage ctx2d bitmap 0 0)
-                (dom/set-attribute! canvas "id" (dm/str "screenshot-" object-id))
-                (wasm.api/clear-canvas)
-                (on-render)))))))
-      (catch :default e
-        (js/console.error "Error initializing canvas context:" e)
-        false))))
-
 (mf/defc object-wasm
   {::mf/wrap [mf/memo]}
   [{:keys [objects object-id skip-children scale on-render] :as props}]
@@ -574,7 +549,7 @@
               (p/fmap
                (fn [ready?]
                  (when ready?
-                   (render-to-canvas objects canvas bounds scale object-id on-render))))))))
+                   (rwv/render-to-canvas objects canvas bounds scale object-id on-render))))))))
 
     [:canvas {:ref canvas-ref
               :width (* scale width)
diff --git a/frontend/src/app/main/render_viewer_wasm.cljs b/frontend/src/app/main/render_viewer_wasm.cljs
new file mode 100644
index 0000000000..7de082b675
--- /dev/null
+++ b/frontend/src/app/main/render_viewer_wasm.cljs
@@ -0,0 +1,241 @@
+;; This Source Code Form is subject to the terms of the Mozilla Public
+;; License, v. 2.0. If a copy of the MPL was not distributed with this
+;; file, You can obtain one at http://mozilla.org/MPL/2.0/.
+;;
+;; Copyright (c) KALEIDOS INC Sucursal en España SL
+
+(ns app.main.render-viewer-wasm
+  "WASM offscreen rendering for the shared viewer (snapshot + fixed-scroll)."
+  (:require
+   [app.common.data.macros :as dm]
+   [app.render-wasm.api :as wasm.api]
+   [app.render-wasm.wasm :as wasm]
+   [app.util.dom :as dom]
+   [app.util.timers :as ts]
+   [goog.events :as events]
+   [promesa.core :as p]
+   [rumext.v2 :as mf]))
+
+;; The WASM module is a single global instance; serialize offscreen work.
+(defonce ^:private wasm-render-queue (atom (p/resolved nil)))
+
+(defn- enqueue-wasm-render!
+  [task]
+  (let [next-p (-> @wasm-render-queue
+                   (p/handle (fn [_ _] (task))))]
+    (reset! wasm-render-queue (p/handle next-p (fn [_ _] nil)))
+    next-p))
+
+(defonce ^:private viewer-snapshot
+  (atom {:os-canvas nil
+         :page-key  nil
+         :canvas-w  0
+         :canvas-h  0}))
+
+(defn- reset-viewer-snapshot! []
+  (reset! viewer-snapshot
+          {:os-canvas nil
+           :page-key nil
+           :canvas-w 0
+           :canvas-h 0}))
+
+(defn- draw-bitmap!
+  [canvas os-canvas object-id vis-w vis-h finish]
+  (ts/raf
+   (fn []
+     (let [ctx2d (.getContext canvas "2d")]
+       (.clearRect ctx2d 0 0 vis-w vis-h)
+       ;; Draw directly from OffscreenCanvas so it can be reused across passes.
+       (.drawImage ctx2d os-canvas 0 0 vis-w vis-h)
+       (dom/set-attribute! canvas "id" (str "screenshot-" object-id))
+       (finish)))))
+
+(defn- viewer-disable-wasm-ui-overlay!
+  "Workspace WASM UI (rulers + rounded viewport frame) is composited in
+  `present_frame`; the viewer must not show that chrome."
+  []
+  (wasm.api/set-rulers-frame-visible! false)
+  (wasm.api/set-rulers-visible! false))
+
+(defn- viewer-apply-layer-mask!
+  [include-ids clear-fills-ids]
+  (wasm.api/clear-render-include-filter!)
+  (when (seq include-ids)
+    (wasm.api/set-render-include-filter! include-ids))
+  (doseq [id clear-fills-ids]
+    (wasm.api/use-shape id)
+    (wasm.api/clear-shape-fills!)))
+
+(defn- viewer-restore-layer-mask!
+  [page-objects clear-fills-ids]
+  (wasm.api/clear-render-include-filter!)
+  (doseq [id clear-fills-ids]
+    (wasm.api/use-shape id)
+    (wasm.api/set-shape-fills id (get-in page-objects [id :fills] []) false)))
+
+(defn- viewer-do-render!
+  [page-objects canvas os-canvas object-id vis-w vis-h scale size
+   include-ids clear-fills-ids finish]
+  (viewer-disable-wasm-ui-overlay!)
+  (viewer-apply-layer-mask! include-ids clear-fills-ids)
+  (wasm.api/set-viewer-viewport! scale size)
+  (wasm.api/render-sync-shape object-id)
+  (viewer-restore-layer-mask! page-objects clear-fills-ids)
+  (draw-bitmap! canvas os-canvas object-id vis-w vis-h finish))
+
+(defn- render-to-canvas*
+  [objects canvas bounds scale object-id on-render]
+  (p/create
+   (fn [resolve _reject]
+     (let [width        (.-width canvas)
+           height       (.-height canvas)
+           prev-disable @wasm/disable-request-render?
+           finish       (fn []
+                          (reset! wasm/disable-request-render? prev-disable)
+                          (when (fn? on-render) (on-render))
+                          (resolve nil))]
+       (try
+         (reset! wasm/disable-request-render? true)
+         (let [os-canvas (js/OffscreenCanvas. width height)]
+           (if (wasm.api/init-canvas-context os-canvas)
+             (wasm.api/initialize-viewport
+              objects scale bounds
+              :background-opacity 0
+              :force-sync true
+              :on-render
+              (fn []
+                (viewer-disable-wasm-ui-overlay!)
+                (wasm.api/render-sync-shape object-id)
+                (draw-bitmap! canvas os-canvas object-id width height
+                              (fn []
+                                (wasm.api/clear-canvas {:lose-browser-context? false})
+                                (reset-viewer-snapshot!)
+                                (finish)))))
+             (finish)))
+         (catch :default e
+           (js/console.error "Error initializing canvas context:" e)
+           (finish)))))))
+
+(defn render-to-canvas
+  "One-shot WASM render into `canvas` (exports, thumbnails). Serialized globally."
+  [objects canvas bounds scale object-id on-render]
+  (enqueue-wasm-render!
+   (fn []
+     (render-to-canvas* objects canvas bounds scale object-id on-render))))
+
+(defn- render-viewer-frame*
+  [page-key page-objects canvas size scale object-id on-render
+   {:keys [include-ids clear-fills-ids] :or {clear-fills-ids #{}}}]
+  (p/create
+   (fn [resolve _reject]
+     (let [prev-disable @wasm/disable-request-render?
+           finish       (fn []
+                          (reset! wasm/disable-request-render? prev-disable)
+                          (when (fn? on-render) (on-render))
+                          (resolve nil))
+           vis-w        (.-width canvas)
+           vis-h        (.-height canvas)
+           snap         @viewer-snapshot
+           same-page?   (and (some? page-key) (identical? page-key (:page-key snap)))
+           same-size?   (and (= vis-w (:canvas-w snap)) (= vis-h (:canvas-h snap)))
+           os           (:os-canvas snap)
+           do-render!   (fn [os-canvas]
+                          (viewer-do-render! page-objects canvas os-canvas object-id
+                                             vis-w vis-h scale size include-ids
+                                             clear-fills-ids finish))]
+
+       (reset! wasm/disable-request-render? true)
+
+       (try
+         (if (and same-page? (wasm.api/initialized?) os)
+           (do
+             (when-not same-size?
+               (wasm.api/resize-offscreen-canvas! os vis-w vis-h)
+               (swap! viewer-snapshot assoc :canvas-w vis-w :canvas-h vis-h))
+             (do-render! os))
+           (let [os-canvas (js/OffscreenCanvas. vis-w vis-h)]
+             (when (wasm.api/initialized?)
+               (wasm.api/clear-canvas {:lose-browser-context? false}))
+             (if (wasm.api/init-canvas-context os-canvas)
+               (do
+                 (reset! viewer-snapshot
+                         {:os-canvas os-canvas
+                          :page-key  page-key
+                          :canvas-w  vis-w
+                          :canvas-h  vis-h})
+                 (wasm.api/initialize-viewport
+                  page-objects scale size
+                  :background-opacity 0
+                  :force-sync true
+                  :on-render #(do-render! os-canvas)))
+               (finish))))
+         (catch :default e
+           (js/console.error "viewer-snapshot: render error" e)
+           (finish)))))))
+
+(defn- use-fixed-scroll-sync!
+  [enabled? layer-ref]
+  (mf/use-layout-effect
+   (mf/deps enabled?)
+   (fn []
+     (when enabled?
+       (let [section (dom/get-element "viewer-section")
+             sync!
+             (fn []
+               (when-let [layer (mf/ref-val layer-ref)]
+                 (dom/set-style! layer "transform"
+                                 (dm/str "translate("
+                                         (or (dom/get-h-scroll-pos section) 0) "px, "
+                                         (or (dom/get-scroll-pos section) 0) "px)"))))]
+         (when section
+           (sync!)
+           (let [key (events/listen section "scroll" (fn [_] (sync!)))]
+             #(events/unlistenByKey key))))))))
+
+(defn- use-viewer-wasm-layers!
+  [page-id page-objects size scale frame-id not-fixed-ref fixed-ref
+   not-fixed-include-ids fixed-include-ids fixed-clear-fills-ids]
+  (mf/use-layout-effect
+   (mf/deps page-id page-objects size scale frame-id
+            not-fixed-include-ids fixed-include-ids fixed-clear-fills-ids)
+   (fn []
+     (when (get page-objects frame-id)
+       (->> @wasm.api/module
+            (p/fmap
+             (fn [ready?]
+               (when ready?
+                 (let [not-fixed-canvas (mf/ref-val not-fixed-ref)
+                       fixed-canvas     (mf/ref-val fixed-ref)
+                       passes
+                       (cond-> []
+                         not-fixed-canvas
+                         (conj {:canvas not-fixed-canvas
+                                :opts   (cond-> {}
+                                          (seq not-fixed-include-ids)
+                                          (assoc :include-ids not-fixed-include-ids))})
+
+                         (and fixed-canvas (seq fixed-include-ids))
+                         (conj {:canvas fixed-canvas
+                                :opts   (cond-> {:include-ids fixed-include-ids}
+                                          (seq fixed-clear-fills-ids)
+                                          (assoc :clear-fills-ids fixed-clear-fills-ids))}))]
+                   (when (seq passes)
+                     (enqueue-wasm-render!
+                      (fn []
+                        (reduce (fn [chain {:keys [canvas opts]}]
+                                  (p/then chain
+                                          #(render-viewer-frame* page-id page-objects
+                                                                 canvas size scale frame-id
+                                                                 nil opts)))
+                                (p/resolved nil)
+                                passes)))))))))))))
+
+(defn use-viewer-wasm-viewport!
+  "WASM render passes and fixed-scroll DOM sync for the viewer viewport."
+  [page-id page-objects size scale frame-id
+   not-fixed-ref fixed-ref fixed-scroll-layer-ref
+   not-fixed-include-ids fixed-include-ids fixed-clear-fills-ids]
+  (use-fixed-scroll-sync! (some? fixed-scroll-layer-ref) fixed-scroll-layer-ref)
+  (use-viewer-wasm-layers! page-id page-objects size scale frame-id
+                           not-fixed-ref fixed-ref
+                           not-fixed-include-ids fixed-include-ids fixed-clear-fills-ids))
diff --git a/frontend/src/app/main/ui/inspect/render.cljs b/frontend/src/app/main/ui/inspect/render.cljs
index 87cdb901f7..25e223f9e5 100644
--- a/frontend/src/app/main/ui/inspect/render.cljs
+++ b/frontend/src/app/main/ui/inspect/render.cljs
@@ -23,7 +23,7 @@
    [app.main.ui.shapes.shape :refer [shape-container]]
    [app.main.ui.shapes.svg-raw :as svg-raw]
    [app.main.ui.shapes.text :as text]
-   [app.main.ui.viewer.interactions :refer [prepare-objects]]
+   [app.main.ui.viewer.viewport-common :refer [prepare-objects]]
    [app.util.dom :as dom]
    [app.util.object :as obj]
    [rumext.v2 :as mf]))
diff --git a/frontend/src/app/main/ui/viewer/interactions.cljs b/frontend/src/app/main/ui/viewer/interactions.cljs
index 35138ef829..0b1589b36b 100644
--- a/frontend/src/app/main/ui/viewer/interactions.cljs
+++ b/frontend/src/app/main/ui/viewer/interactions.cljs
@@ -9,53 +9,26 @@
   (:require
    [app.common.data :as d]
    [app.common.data.macros :as dm]
-   [app.common.files.helpers :as cfh]
    [app.common.geom.point :as gpt]
-   [app.common.geom.shapes :as gsh]
-   [app.common.types.modifiers :as ctm]
    [app.common.types.page :as ctp]
    [app.common.uuid :as uuid]
+   [app.config :as cf]
    [app.main.data.comments :as dcm]
    [app.main.data.viewer :as dv]
+   [app.main.features :as features]
    [app.main.store :as st]
    [app.main.ui.components.dropdown :refer [dropdown]]
    [app.main.ui.hooks :as h]
    [app.main.ui.icons :as deprecated-icon]
    [app.main.ui.viewer.shapes :as shapes]
+   [app.main.ui.viewer.viewport-common :as vpc]
+   [app.main.ui.viewer.viewport-wasm :as viewport.wasm]
    [app.util.dom :as dom]
    [app.util.i18n :as i18n :refer [tr]]
    [app.util.keyboard :as kbd]
    [goog.events :as events]
    [rumext.v2 :as mf]))
 
-(defn prepare-objects
-  [frame size delta objects]
-  (let [frame-id  (:id frame)
-        vector  (-> (gpt/point (:x size) (:y size))
-                    (gpt/add delta)
-                    (gpt/negate))
-        update-fn #(d/update-when %1 %2 gsh/transform-shape (ctm/move-modifiers vector))]
-    (->> (cfh/get-children-ids objects frame-id)
-         (into [frame-id])
-         (reduce update-fn objects))))
-
-(defn get-fixed-ids
-  [objects]
-  (let [fixed-ids (filter cfh/fixed-scroll? (vals objects))
-
-        ;; we have to consider the children if the fixed element is a group
-        fixed-children-ids
-        (into #{} (mapcat #(cfh/get-children-ids objects (:id %)) fixed-ids))
-
-        parent-children-ids
-        (->> fixed-ids
-             (mapcat #(cons (:id %) (cfh/get-parent-ids objects (:id %))))
-             (remove #(= % uuid/zero)))
-
-        fixed-ids
-        (concat fixed-children-ids parent-children-ids)]
-    fixed-ids))
-
 (mf/defc viewport-svg
   {::mf/wrap [mf/memo]
    ::mf/wrap-props false}
@@ -74,7 +47,7 @@
         objects   (:objects page)
         objects   (cond-> objects fixed? (assoc-in [(:id frame) :fixed-scroll] true))
 
-        fixed-ids (get-fixed-ids objects)
+        fixed-ids (vpc/get-fixed-ids objects)
 
         not-fixed-ids
         (->> (remove (set fixed-ids) (keys objects))
@@ -86,7 +59,7 @@
                (map (d/getf objects))
                (concat [frame])
                (d/index-by :id)
-               (prepare-objects frame size delta)))
+               (vpc/prepare-objects frame size delta)))
 
         objects-fixed
         (mf/with-memo [fixed-ids page frame size delta]
@@ -175,7 +148,10 @@
         page   (unchecked-get props "page")
         frame  (unchecked-get props "frame")
         base   (unchecked-get props "base-frame")
-        fixed? (unchecked-get props "fixed?")]
+        fixed? (unchecked-get props "fixed?")
+
+        render-wasm? (and (features/use-feature "render-wasm/v1")
+                          (contains? cf/flags :available-viewer-wasm))]
 
     (mf/with-effect [mode]
       (let [on-click
@@ -210,13 +186,21 @@
           (events/unlistenByKey key2)
           (events/unlistenByKey key3))))
 
-    [:& viewport-svg {:page page
-                      :frame frame
-                      :base base
-                      :offset offset
-                      :size size
-                      :delta delta
-                      :fixed? fixed?}]))
+    (if ^boolean render-wasm?
+      [:& viewport.wasm/viewport-wasm {:page page
+                                       :frame frame
+                                       :base base
+                                       :offset offset
+                                       :size size
+                                       :delta delta
+                                       :fixed? fixed?}]
+      [:& viewport-svg {:page page
+                        :frame frame
+                        :base base
+                        :offset offset
+                        :size size
+                        :delta delta
+                        :fixed? fixed?}])))
 
 (mf/defc flows-menu*
   {::mf/wrap [mf/memo]}
diff --git a/frontend/src/app/main/ui/viewer/shapes.cljs b/frontend/src/app/main/ui/viewer/shapes.cljs
index 880c515c49..9f407b6714 100644
--- a/frontend/src/app/main/ui/viewer/shapes.cljs
+++ b/frontend/src/app/main/ui/viewer/shapes.cljs
@@ -294,6 +294,80 @@
               :pointer-events "none"
               :transform (gsh/transform-str shape)}])))
 
+;; --- WASM viewer hotspots ---
+;; In WASM viewer mode the frame pixels come from a WASM snapshot, so we don't
+;; render the SVG visuals at all. We only render the actionable areas (hotspots)
+;; on top of the image: a transparent hit/highlight rect per interactive shape,
+;; wired to the same interaction handlers as the regular SVG tree.
+
+(mf/defc hotspot*
+  {::mf/wrap-props false}
+  [props]
+  (let [shape        (unchecked-get props "shape")
+        all-objects  (unchecked-get props "all-objects")
+        base-frame   (mf/use-ctx base-frame-ctx)
+        frame-offset (mf/use-ctx frame-offset-ctx)
+        show-interactions (mf/deref ref:viewer-show-interactions)
+        overlays     (mf/deref refs/viewer-overlays)
+        interactions (:interactions shape)
+        {:keys [x y width height]} (:selrect shape)
+
+        on-pd (mf/use-fn (mf/deps shape base-frame frame-offset all-objects overlays)
+                         #(on-pointer-down % shape base-frame frame-offset all-objects overlays))
+        on-pu (mf/use-fn (mf/deps shape base-frame frame-offset all-objects overlays)
+                         #(on-pointer-up % shape base-frame frame-offset all-objects overlays))
+        on-pe (mf/use-fn (mf/deps shape base-frame frame-offset all-objects overlays)
+                         #(on-pointer-enter % shape base-frame frame-offset all-objects overlays))
+        on-pl (mf/use-fn (mf/deps shape base-frame frame-offset all-objects overlays)
+                         #(on-pointer-leave % shape base-frame frame-offset all-objects overlays))]
+
+    (mf/with-effect []
+      (let [sems (on-load shape base-frame frame-offset all-objects overlays)]
+        (partial run! tm/dispose! sems)))
+
+    [:g {:style {:cursor (when (ctsi/actionable? interactions) "pointer")}
+         :on-pointer-down on-pd
+         :on-pointer-up on-pu
+         :on-pointer-enter on-pe
+         :on-pointer-leave on-pl}
+     [:rect {:x (- x 1)
+             :y (- y 1)
+             :width (+ width 2)
+             :height (+ height 2)
+             :fill "var(--color-accent-tertiary)"
+             :stroke "var(--color-accent-tertiary)"
+             :stroke-width (if show-interactions 1 0)
+             :fill-opacity (if show-interactions 0.2 0)
+             ;; This rect is the only hit target, so it must always capture
+             ;; pointer events even when fully transparent.
+             :pointer-events "all"
+             :transform (gsh/transform-str shape)}]]))
+
+(mf/defc frame-hotspots*
+  "Renders interaction hotspots for a frame subtree (WASM viewer mode).
+  `objects` must be the prepared (vbox-space) objects and `frame` the prepared
+  frame; only shapes with interactions produce a hotspot.
+
+  Optional `shape-filter` is a predicate that receives the shape id and returns
+  true when it should be included (used to split fixed-scroll vs normal layers)."
+  {::mf/wrap-props false}
+  [props]
+  (let [objects     (unchecked-get props "objects")
+        all-objects (or (unchecked-get props "all-objects") objects)
+        shape-filter (unchecked-get props "shape-filter")
+        frame       (unchecked-get props "frame")
+        frame-id    (:id frame)
+        ids         (cond->> (cons frame-id (cfh/get-children-ids objects frame-id))
+                      shape-filter (filter shape-filter))
+        hotspots    (->> ids
+                         (keep #(get objects %))
+                         (filter (fn [s] (and (not (:hidden s))
+                                              (seq (:interactions s))))))]
+    [:* (for [shape hotspots]
+          [:& hotspot* {:key (str (:id shape))
+                        :shape shape
+                        :all-objects all-objects}])]))
+
 
 ;; TODO: use-memo use-fn
 
diff --git a/frontend/src/app/main/ui/viewer/viewport_common.cljs b/frontend/src/app/main/ui/viewer/viewport_common.cljs
new file mode 100644
index 0000000000..e2ebb1b881
--- /dev/null
+++ b/frontend/src/app/main/ui/viewer/viewport_common.cljs
@@ -0,0 +1,67 @@
+;; This Source Code Form is subject to the terms of the Mozilla Public
+;; License, v. 2.0. If a copy of the MPL was not distributed with this
+;; file, You can obtain one at http://mozilla.org/MPL/2.0/.
+;;
+;; Copyright (c) KALEIDOS INC Sucursal en España SL
+
+(ns app.main.ui.viewer.viewport-common
+  "Shared object preparation for viewer viewports (SVG and WASM)."
+  (:require
+   [app.common.data :as d]
+   [app.common.files.helpers :as cfh]
+   [app.common.geom.point :as gpt]
+   [app.common.geom.shapes :as gsh]
+   [app.common.types.modifiers :as ctm]
+   [app.common.uuid :as uuid]))
+
+(defn prepare-objects
+  [frame size delta objects]
+  (let [frame-id  (:id frame)
+        vector  (-> (gpt/point (:x size) (:y size))
+                    (gpt/add delta)
+                    (gpt/negate))
+        update-fn #(d/update-when %1 %2 gsh/transform-shape (ctm/move-modifiers vector))]
+    (->> (cfh/get-children-ids objects frame-id)
+         (into [frame-id])
+         (reduce update-fn objects))))
+
+(defn get-fixed-ids
+  [objects]
+  (let [fixed-ids (filter cfh/fixed-scroll? (vals objects))
+
+        fixed-children-ids
+        (into #{} (mapcat #(cfh/get-children-ids objects (:id %)) fixed-ids))
+
+        parent-children-ids
+        (->> fixed-ids
+             (mapcat #(cons (:id %) (cfh/get-parent-ids objects (:id %))))
+             (remove #(= % uuid/zero)))
+
+        fixed-ids
+        (concat fixed-children-ids parent-children-ids)]
+    fixed-ids))
+
+(defn frame-fixed-mask-ids
+  "Fixed-layer shape ids inside `frame-id` (same rules as `get-fixed-ids`)."
+  [objects frame-id]
+  (when frame-id
+    (let [subtree (into #{} (cfh/get-children-ids-with-self objects frame-id))]
+      (into #{}
+            (filter #(contains? subtree %)
+                    (get-fixed-ids objects))))))
+
+(defn prepare-page-objects
+  "Transform all page objects into vbox-space (for overlay positioning)."
+  [objects size delta]
+  (let [vector (-> (gpt/point (:x size) (:y size))
+                   (gpt/add delta)
+                   (gpt/negate))
+        update-fn #(d/update-when %1 %2 gsh/transform-shape (ctm/move-modifiers vector))
+        ids (->> (keys objects) (remove #(= % uuid/zero)))]
+    (reduce update-fn objects ids)))
+
+(defn viewer-scale
+  [size]
+  (if (and (:base-width size) (pos? (:base-width size)))
+    (/ (:width size) (:base-width size))
+    1))
diff --git a/frontend/src/app/main/ui/viewer/viewport_wasm.cljs b/frontend/src/app/main/ui/viewer/viewport_wasm.cljs
new file mode 100644
index 0000000000..2c9b5a31e4
--- /dev/null
+++ b/frontend/src/app/main/ui/viewer/viewport_wasm.cljs
@@ -0,0 +1,160 @@
+;; This Source Code Form is subject to the terms of the Mozilla Public
+;; License, v. 2.0. If a copy of the MPL was not distributed with this
+;; file, You can obtain one at http://mozilla.org/MPL/2.0/.
+;;
+;; Copyright (c) KALEIDOS INC Sucursal en España SL
+
+(ns app.main.ui.viewer.viewport-wasm
+  (:require-macros [app.main.style :as stl])
+  (:require
+   [app.common.files.helpers :as cfh]
+   [app.common.geom.point :as gpt]
+   [app.main.render-viewer-wasm :as rwv]
+   [app.main.ui.viewer.shapes :as shapes]
+   [app.main.ui.viewer.viewport-common :as vpc]
+   [app.util.object :as obj]
+   [rumext.v2 :as mf]))
+
+(defn- canvas-dimensions
+  [scale size]
+  {:width (js/Math.round (* scale (:base-width size)))
+   :height (js/Math.round (* scale (:base-height size)))})
+
+(defn- frame-hotspots-props
+  "frame-hotspots* uses ::mf/wrap-props false and expects string keys."
+  [prepared prepared-all prepared-frame shape-filter]
+  (let [props #js {"objects" prepared
+                   "all-objects" prepared-all
+                   "frame" prepared-frame}]
+    (when shape-filter
+      (obj/set! props "shape-filter" shape-filter))
+    props))
+
+(mf/defc wasm-hotspots-svg
+  [{:keys [vbox size class prepared prepared-all prepared-frame shape-filter]}]
+  [:svg {:view-box vbox
+         :width (:width size)
+         :height (:height size)
+         :version "1.1"
+         :xmlnsXlink "http://www.w3.org/1999/xlink"
+         :xmlns "http://www.w3.org/2000/svg"
+         :fill "none"
+         :style {:position "absolute"
+                 :top 0
+                 :left 0}
+         :class class}
+   [:& shapes/frame-hotspots*
+    (frame-hotspots-props prepared prepared-all prepared-frame shape-filter)]])
+
+(mf/defc wasm-layer
+  [{:keys [canvas-ref scale size vbox svg-props]}]
+  (let [{:keys [width height]} (canvas-dimensions scale size)]
+    [:div {:style {:position "absolute"
+                   :top 0
+                   :left 0}}
+     [:canvas {:ref canvas-ref :width width :height height :style {:width "100%"
+                                                                   :height "100%"
+                                                                   :background "transparent"
+                                                                   :pointer-events "none"}}]
+     [:& wasm-hotspots-svg (assoc svg-props :vbox vbox :size size)]]))
+
+(defn- fixed-scroll-layer-ids
+  [objects frame-id has-fixed?]
+  (let [frame-subtree-ids (into #{} (cfh/get-children-ids-with-self objects frame-id))
+        fixed-mask-ids (when has-fixed? (vpc/frame-fixed-mask-ids objects frame-id))
+        fixed-mask-set (or fixed-mask-ids #{})
+        not-fixed-include-ids
+        (when has-fixed?
+          (into []
+                (distinct
+                 (conj (->> frame-subtree-ids
+                            (remove #(contains? fixed-mask-set %)))
+                       frame-id))))
+        fixed-include-ids
+        (when has-fixed?
+          (vec (conj (or fixed-mask-ids #{}) frame-id)))
+        fixed-clear-fills-ids (when has-fixed? #{frame-id})]
+    {:fixed-mask-set fixed-mask-set
+     :not-fixed-include-ids not-fixed-include-ids
+     :fixed-include-ids fixed-include-ids
+     :fixed-clear-fills-ids fixed-clear-fills-ids}))
+
+(mf/defc viewport-wasm
+  {::mf/wrap [mf/memo]
+   ::mf/wrap-props false}
+  [props]
+  (let [page    (unchecked-get props "page")
+        frame   (unchecked-get props "frame")
+        base    (unchecked-get props "base")
+        offset  (unchecked-get props "offset")
+        size    (unchecked-get props "size")
+        delta   (or (unchecked-get props "delta") (gpt/point 0 0))
+        vbox    (:vbox size)
+        fixed?  (true? (unchecked-get props "fixed?"))
+
+        fixed-layer-ref      (mf/use-ref nil)
+        not-fixed-wasm-ref   (mf/use-ref nil)
+        fixed-wasm-ref       (mf/use-ref nil)
+
+        objects  (:objects page)
+        frame-id (:id frame)
+        scale    (vpc/viewer-scale size)
+        page-id  (:id page)
+
+        frame   (cond-> frame fixed? (assoc :fixed-scroll true))
+        objects (cond-> objects fixed? (assoc-in [frame-id :fixed-scroll] true))
+
+        has-fixed?
+        (and (not fixed?)
+             (some #(cfh/fixed-scroll? (get objects %))
+                   (cfh/get-children-ids objects frame-id)))
+
+        prepared
+        (mf/with-memo [objects frame size delta]
+          (vpc/prepare-objects frame size delta objects))
+
+        prepared-all
+        (mf/with-memo [objects size delta]
+          (vpc/prepare-page-objects objects size delta))
+
+        {:keys [fixed-mask-set not-fixed-include-ids fixed-include-ids fixed-clear-fills-ids]}
+        (mf/with-memo [objects frame-id has-fixed?]
+          (fixed-scroll-layer-ids objects frame-id has-fixed?))
+
+        prepared-frame (get prepared frame-id)
+
+        svg-base {:prepared prepared
+                  :prepared-all prepared-all
+                  :prepared-frame prepared-frame}]
+
+    (rwv/use-viewer-wasm-viewport!
+     page-id objects size scale frame-id
+     not-fixed-wasm-ref fixed-wasm-ref
+     (when has-fixed? fixed-layer-ref)
+     not-fixed-include-ids fixed-include-ids fixed-clear-fills-ids)
+
+    [:& (mf/provider shapes/base-frame-ctx) {:value (get prepared-all (:id base))}
+     [:& (mf/provider shapes/frame-offset-ctx) {:value offset}
+      [:*
+       [:& wasm-layer
+        {:canvas-ref not-fixed-wasm-ref
+         :scale scale
+         :size size
+         :vbox vbox
+         :svg-props (assoc svg-base
+                           :class (if has-fixed?
+                                    (stl/css :not-fixed)
+                                    (when fixed? (stl/css :fixed)))
+                           :shape-filter (when has-fixed?
+                                           #(not (contains? fixed-mask-set %))))}]
+
+       (when has-fixed?
+         [:div {:ref fixed-layer-ref}
+          [:& wasm-layer
+           {:canvas-ref fixed-wasm-ref
+            :scale scale
+            :size size
+            :vbox vbox
+            :svg-props (assoc svg-base
+                              :class (stl/css :not-fixed)
+                              :shape-filter #(contains? fixed-mask-set %))}]])]]]))
diff --git a/frontend/src/app/render_wasm/api.cljs b/frontend/src/app/render_wasm/api.cljs
index c4ae182fc0..71402806b4 100644
--- a/frontend/src/app/render_wasm/api.cljs
+++ b/frontend/src/app/render_wasm/api.cljs
@@ -931,6 +931,13 @@
   [hidden]
   (h/call wasm/internal-module "_set_shape_hidden" hidden))
 
+(defn clear-shape-fills!
+  "Clear the fills of the currently-selected shape (call `use-shape` first).
+  Equivalent to `set-shape-fills` with an empty collection."
+  []
+  (when (initialized?)
+    (h/call wasm/internal-module "_clear_shape_fills")))
+
 (defn set-shape-bool-type
   [bool-type]
   (h/call wasm/internal-module "_set_shape_bool_type" (sr/translate-bool-type bool-type)))
@@ -1666,6 +1673,27 @@
       (h/call wasm/internal-module "_set_focus_mode")
       (request-render "set-focus-mode"))))
 
+(defn clear-render-include-filter!
+  "Clear the viewer include filter (render all shapes in the subtree again)."
+  []
+  (when (initialized?)
+    (h/call wasm/internal-module "_clear_render_include_filter")))
+
+(defn set-render-include-filter!
+  "Restrict the next render to `shape-ids` and descendants of whitelisted nodes.
+  Used for viewer fixed-scroll layers; does not change shape hidden flags."
+  [shape-ids]
+  (when (and (initialized?) (seq shape-ids))
+    (let [ids    (vec shape-ids)
+          size   (mem/get-alloc-size ids UUID-U8-SIZE)
+          heap   (mem/get-heap-u32)
+          offset (mem/alloc->offset-32 size)]
+      (reduce (fn [offset id]
+                (mem.h32/write-uuid offset heap id))
+              offset
+              ids)
+      (h/call wasm/internal-module "_set_render_include_filter"))))
+
 (defn set-structure-modifiers
   [entries]
   (when-not ^boolean (empty? entries)
@@ -1865,6 +1893,24 @@
   [width height]
   (h/call wasm/internal-module "_resize_viewbox" width height))
 
+(defn set-viewer-viewport!
+  "Update viewer zoom/pan and rebuild the tile index (frame hops in the viewer).
+  `vbox` must have at least `:x` and `:y` keys (design-space top-left corner)."
+  [zoom vbox]
+  (h/call wasm/internal-module "_set_view" zoom (- (:x vbox)) (- (:y vbox)))
+  (when (initialized?)
+    (h/call wasm/internal-module "_set_view_end")
+    (reset! view-interaction-active? false)))
+
+(defn resize-offscreen-canvas!
+  "Resize a persistent OffscreenCanvas to new physical-pixel dimensions and
+  update the WASM render surfaces accordingly (via `_resize_viewbox`). The
+  design state (shape pool) is preserved so `set-objects` is not needed again."
+  [canvas new-physical-w new-physical-h]
+  (set! (.-width canvas) new-physical-w)
+  (set! (.-height canvas) new-physical-h)
+  (resize-viewbox (/ new-physical-w dpr) (/ new-physical-h dpr)))
+
 (defn- debug-flags
   []
   (cond-> 0
diff --git a/render-wasm/src/main.rs b/render-wasm/src/main.rs
index a0939cdd95..83b3ad23f8 100644
--- a/render-wasm/src/main.rs
+++ b/render-wasm/src/main.rs
@@ -151,6 +151,31 @@ pub extern "C" fn render_blurred_snapshot(blur_radius: f32) -> Result<()> {
     Ok(())
 }
 
+#[no_mangle]
+#[wasm_error]
+pub extern "C" fn clear_render_include_filter() -> Result<()> {
+    with_state!(state, {
+        state.clear_include_filter();
+    });
+    Ok(())
+}
+
+#[no_mangle]
+#[wasm_error]
+pub extern "C" fn set_render_include_filter() -> Result<()> {
+    let bytes = mem::bytes();
+
+    let entries: Vec<Uuid> = bytes
+        .chunks(size_of::<<Uuid as SerializableResult>::BytesType>())
+        .map(|data| Uuid::try_from(data).map_err(|e| Error::RecoverableError(e.to_string())))
+        .collect::<Result<Vec<Uuid>>>()?;
+
+    with_state!(state, {
+        state.set_include_filter(entries);
+    });
+    Ok(())
+}
+
 #[no_mangle]
 #[wasm_error]
 pub extern "C" fn render_sync() -> Result<()> {
diff --git a/render-wasm/src/render.rs b/render-wasm/src/render.rs
index 1f7d9842b2..f5712be7e6 100644
--- a/render-wasm/src/render.rs
+++ b/render-wasm/src/render.rs
@@ -372,6 +372,10 @@ pub(crate) struct RenderState {
     pub show_grid: Option<Uuid>,
     pub rulers: RulerState,
     pub focus_mode: FocusMode,
+    /// Viewer-only whitelist for fixed-scroll layer passes.
+    pub include_filter: Option<HashSet<Uuid>>,
+    /// Frame id passed as `base_object` for viewer renders; always traversed.
+    pub viewer_render_root: Option<Uuid>,
     pub touched_ids: HashSet<Uuid>,
     /// Temporary flag used for off-screen passes (drop-shadow masks, filter surfaces, etc.)
     /// where we must render shapes without inheriting ancestor layer blurs. Toggle it through
@@ -568,6 +572,8 @@ impl RenderState {
             show_grid: None,
             rulers: RulerState::default(),
             focus_mode: FocusMode::new(),
+            include_filter: None,
+            viewer_render_root: None,
             touched_ids: HashSet::default(),
             ignore_nested_blurs: false,
             preview_mode: false,
@@ -850,7 +856,14 @@ impl RenderState {
     /// on top of Target, then present. Backbuffer is left clean so it can be reused
     /// as-is across interactive-transform frames without stale overlay pixels.
     pub fn present_frame(&mut self, tree: ShapesPoolRef) {
-        self.surfaces.copy_backbuffer_to_target();
+        // Viewer masked passes render a partial scene onto a transparent backbuffer.
+        // SrcOver would keep pass-1 pixels wherever the backbuffer stays transparent.
+        if self.viewer_masked_pass() {
+            self.surfaces.clear_target(skia::Color::TRANSPARENT);
+            self.surfaces.copy_backbuffer_to_target_replace();
+        } else {
+            self.surfaces.copy_backbuffer_to_target();
+        }
         if self.options.is_debug_visible() {
             debug::render(self);
         }
@@ -942,6 +955,20 @@ impl RenderState {
             return Ok(());
         }
 
+        // Viewer masked passes render a partial scene. Reusing the tile texture cache would
+        // SrcOver-blend onto textures from the previous pass and leak pixels into the blob.
+        if self.viewer_masked_pass() {
+            // Use viewbox-aligned bounds (not grid-snapped) to match interactive-transform
+            // compositing and avoid a visible offset vs the DOM canvas.
+            let tile_rect = self.get_current_tile_bounds()?;
+            self.surfaces.draw_current_tile_into_backbuffer(
+                &tile_rect,
+                self.background_color,
+                surfaces::DrawOnCache::No,
+            );
+            return Ok(());
+        }
+
         let fast_mode = self.options.is_fast_mode();
         // Decide *now* (at the first real cache blit) whether we need to clear Cache.
         // This avoids clearing Cache on renders that don't actually paint tiles (e.g. hover/UI),
@@ -1043,6 +1070,55 @@ impl RenderState {
         self.focus_mode.set_shapes(shapes);
     }
 
+    pub fn clear_include_filter(&mut self) {
+        self.include_filter = None;
+    }
+
+    pub fn set_include_filter(&mut self, shapes: Vec<Uuid>) {
+        self.include_filter = Some(shapes.into_iter().collect());
+    }
+
+    fn viewer_masked_pass(&self) -> bool {
+        self.include_filter.is_some()
+    }
+
+    fn reset_viewer_masked_surfaces(&mut self) {
+        self.surfaces.clear_backbuffer(self.background_color);
+        self.surfaces.clear_tile_atlas();
+    }
+
+    /// True when the shape or any descendant is whitelisted.
+    pub fn shape_visible_in_include_filter(&self, shape_id: &Uuid, tree: ShapesPoolRef) -> bool {
+        let Some(ref include) = self.include_filter else {
+            return true;
+        };
+        if include.contains(shape_id) {
+            return true;
+        }
+        let Some(shape) = tree.get(shape_id) else {
+            return false;
+        };
+        shape
+            .children_ids_iter(false)
+            .any(|child_id| self.shape_visible_in_include_filter(child_id, tree))
+    }
+
+    /// When an include whitelist is active, only those ids are painted.
+    fn shape_should_paint_for_viewer_layer(&self, shape_id: &Uuid) -> bool {
+        match &self.include_filter {
+            Some(include) => include.contains(shape_id),
+            None => true,
+        }
+    }
+
+    /// Viewer layer mask: traverse whitelisted subtrees; paint only listed ids.
+    pub fn shape_visible_for_viewer_layer(&self, shape_id: &Uuid, tree: ShapesPoolRef) -> bool {
+        if self.viewer_render_root.as_ref() == Some(shape_id) {
+            return true;
+        }
+        self.shape_visible_in_include_filter(shape_id, tree)
+    }
+
     fn get_inherited_drop_shadows(&self) -> Option<Vec<skia_safe::Paint>> {
         let drop_shadows: Vec<&Shadow> = self
             .nested_shadows
@@ -2113,6 +2189,13 @@ impl RenderState {
             self.interactive_target_seeded = false;
         }
 
+        // Viewer fixed-scroll passes reuse the same WASM context; `reset` does not
+        // clear Backbuffer, so pass 2 would otherwise keep pass-1 pixels in regions
+        // that render no shapes for the current mask. Target is cleared in present_frame.
+        if self.viewer_masked_pass() {
+            self.reset_viewer_masked_surfaces();
+        }
+
         let surface_ids = SurfaceId::Strokes as u32
             | SurfaceId::Fills as u32
             | SurfaceId::InnerShadows as u32
@@ -3146,6 +3229,33 @@ impl RenderState {
                     continue;
                 }
 
+                if !self.shape_visible_for_viewer_layer(&node_id, tree) {
+                    continue;
+                }
+
+                // Ancestors needed to reach whitelisted descendants: traverse only.
+                if self.include_filter.is_some()
+                    && self.shape_visible_for_viewer_layer(&node_id, tree)
+                    && !self.shape_should_paint_for_viewer_layer(&node_id)
+                {
+                    if element.is_recursive() {
+                        let children_ids: Vec<_> =
+                            element.children_ids_iter(false).copied().collect();
+                        let children_ids = sort_z_index(tree, element, children_ids);
+                        for child_id in children_ids.iter() {
+                            self.pending_nodes.push(NodeRenderState {
+                                id: *child_id,
+                                visited_children: false,
+                                clip_bounds: clip_bounds.clone(),
+                                visited_mask: false,
+                                mask: false,
+                                flattened: false,
+                            });
+                        }
+                    }
+                    continue;
+                }
+
                 // For frames and groups, we must use extrect because they can have nested content
                 // that extends beyond their selrect. Using selrect for early exit would incorrectly
                 // skip frames/groups that have nested content in the current tile.
@@ -3428,6 +3538,7 @@ impl RenderState {
         allow_stop: bool,
     ) -> Result<FrameType> {
         let mut should_stop = false;
+        self.viewer_render_root = base_object.copied();
         let root_ids = {
             if let Some(shape_id) = base_object {
                 vec![*shape_id]
@@ -3443,7 +3554,10 @@ impl RenderState {
             if let Some(current_tile) = self.current_tile {
                 // NOTE: For now we don't need to cover the case where the tile
                 // is not cached because everything will be handled from draw_atlas.
-                if !self.surfaces.has_cached_tile_surface(current_tile) {
+                // Viewer masked passes (include_filter) must not reuse cached tiles from
+                // a previous pass; otherwise pass-1 pixels can leak into pass 2.
+                if self.viewer_masked_pass() || !self.surfaces.has_cached_tile_surface(current_tile)
+                {
                     performance::begin_measure!("render_shape_tree::uncached");
                     let (is_empty, early_return) = self
                         .render_shape_tree_partial_uncached(tree, timestamp, allow_stop, false)?;
@@ -3454,6 +3568,7 @@ impl RenderState {
                     }
 
                     if early_return {
+                        self.viewer_render_root = None;
                         return Ok(FrameType::Partial);
                     }
                     performance::end_measure!("render_shape_tree::uncached");
@@ -3504,12 +3619,15 @@ impl RenderState {
                 // empty tile.
                 self.current_tile_had_shapes = false;
 
+                let viewer_masked_pass = self.viewer_masked_pass();
+
                 let Some(ids) = self.tiles.get_shapes_at(next_tile) else {
                     // If the tile is empty we do not need to render it.
                     continue;
                 };
 
-                if self.surfaces.has_cached_tile_surface(next_tile) {
+                // Never skip based on cached surfaces during viewer masked passes.
+                if !viewer_masked_pass && self.surfaces.has_cached_tile_surface(next_tile) {
                     // If the tile is cached, then we do not need to
                     // render it.
                     continue;
@@ -3563,6 +3681,8 @@ impl RenderState {
             }
         }
 
+        self.viewer_render_root = None;
+
         // Mark cache as valid for render_from_cache.
         // Only update for full-quality renders (non-fast mode).
         // An async render can complete while fast mode is active
diff --git a/render-wasm/src/render/surfaces.rs b/render-wasm/src/render/surfaces.rs
index 04d6948371..867b657c7b 100644
--- a/render-wasm/src/render/surfaces.rs
+++ b/render-wasm/src/render/surfaces.rs
@@ -864,6 +864,30 @@ impl Surfaces {
         );
     }
 
+    /// Replace `Target` pixels with `Backbuffer` (Src blend).
+    ///
+    /// Used for viewer masked passes: transparent backbuffer regions must not
+    /// preserve prior `Target` content from an earlier pass.
+    pub fn copy_backbuffer_to_target_replace(&mut self) {
+        let sampling_options = self.sampling_options;
+        let mut paint = skia::Paint::default();
+        paint.set_blend_mode(skia::BlendMode::Src);
+        self.backbuffer.draw(
+            self.target.canvas(),
+            (0.0, 0.0),
+            sampling_options,
+            Some(&paint),
+        );
+    }
+
+    pub fn clear_target(&mut self, color: skia::Color) {
+        self.target.canvas().clear(color);
+    }
+
+    pub fn clear_tile_atlas(&mut self) {
+        self.tile_atlas.canvas().clear(skia::Color::TRANSPARENT);
+    }
+
     /// Seed `Backbuffer` from `Target` (last presented frame).
     pub fn seed_backbuffer_from_target(&mut self) {
         let sampling_options = self.sampling_options;
@@ -1026,6 +1050,17 @@ impl Surfaces {
         }
     }
 
+    /// Full backbuffer clear (viewer layer passes must not reuse prior pass pixels).
+    pub fn clear_backbuffer(&mut self, color: skia::Color) {
+        self.backbuffer.canvas().clear(color);
+    }
+
+    pub fn clear_backbuffer_rect(&mut self, rect: skia::Rect, color: skia::Color) {
+        let mut paint = Paint::default();
+        paint.set_color(color);
+        self.backbuffer.canvas().draw_rect(rect, &paint);
+    }
+
     pub fn reset(&mut self, color: skia::Color) {
         self.canvas(SurfaceId::Fills).restore_to_count(1);
         self.canvas(SurfaceId::InnerShadows).restore_to_count(1);
diff --git a/render-wasm/src/state.rs b/render-wasm/src/state.rs
index 970c9cef1a..3b6835fd30 100644
--- a/render-wasm/src/state.rs
+++ b/render-wasm/src/state.rs
@@ -118,6 +118,14 @@ impl State {
         get_render_state().set_focus_mode(shapes);
     }
 
+    pub fn clear_include_filter(&mut self) {
+        get_render_state().clear_include_filter();
+    }
+
+    pub fn set_include_filter(&mut self, shapes: Vec<Uuid>) {
+        get_render_state().set_include_filter(shapes);
+    }
+
     pub fn init_shapes_pool(&mut self, capacity: usize) {
         self.shapes.initialize(capacity);
     }