fix: Having sop instance in a per-frame or shared attribute breaks load

extensions/cornerstone/src/services/ViewportService/CornerstoneViewportService.ts

@@ -1058,11 +1058,12 @@ class CornerstoneViewportService extends PubSubService implements IViewportServi
       // Store the current position presentations for each viewport.
       viewports.forEach(({ id: viewportId }) => {
         const presentation = this._getPositionPresentation(viewportId);
-
         // During a resize, the slice index should remain unchanged. This is a temporary fix for
         // a larger issue regarding the definition of slice index with slab thickness.
         // We need to revisit this to make it more robust and understandable.
-        delete presentation.viewReference.sliceIndex;
+        if (presentation?.viewReference) {
+          delete presentation.viewReference.sliceIndex;
+        }
         this.beforeResizePositionPresentations.set(viewportId, presentation);
       });
 

platform/core/src/utils/combineFrameInstance.ts

@@ -73,27 +73,39 @@ const combineFrameInstance = (frame, instance) => {
         ImagePositionPatientToUse = [position[0], position[1], position[2]];
       }
     }
-    console.debug('🚀 ~ ImagePositionPatientToUse:', ImagePositionPatientToUse);
-
-    const newInstance = Object.assign(instance, { frameNumber: frameNumber });
-
-    // merge the shared first then the per frame to override
-    [...shared, ...perFrame].forEach(item => {
-      Object.entries(item).forEach(([key, value]) => {
-        newInstance[key] = value;
-      });
-    });
-
-    // Todo: we should cache this combined instance somewhere, maybe add it
-    // back to the dicomMetaStore so we don't have to do this again.
-    return {
-      ...newInstance,
-      ImagePositionPatient: ImagePositionPatientToUse ??
-        newInstance.ImagePositionPatient ?? [0, 0, frameNumber],
-    };
+    const sharedInstance = createCombinedValue(instance, shared);
+    const newInstance = createCombinedValue(sharedInstance, perFrame);
+    newInstance.ImagePositionPatient = ImagePositionPatientToUse ??
+      newInstance.ImagePositionPatient ?? [0, 0, frameNumber];
+    newInstance.frameNumber = frameNumber;
+    return newInstance;
   } else {
     return instance;
   }
 };
 
+function createCombinedValue(parent, shared) {
+  if (shared._sharedValue) {
+    return shared._sharedValue;
+  }
+  const newInstance = Object.create(parent);
+
+  // merge the shared first then the per frame to override
+  [...shared].forEach(item => {
+    if (item.SOPInstanceUID) {
+      // This sub-item is a previous value information item, so don't merge it
+      return;
+    }
+    Object.entries(item).forEach(([key, value]) => {
+      newInstance[key] = value;
+    });
+  });
+  Object.defineProperty(shared, '_sharedValue', {
+    value: newInstance,
+    writable: false,
+    enumerable: false,
+  });
+  return newInstance;
+}
+
 export default combineFrameInstance;