fix(segmentation): Allow for debounced pub/sub events to be reliably cancelled when unsubscribed to. (#5092)

extensions/cornerstone/src/index.tsx

@@ -132,6 +132,10 @@ const cornerstoneExtension: Types.Extensions.Extension = {
   },
   getPanelModule,
   onModeExit: ({ servicesManager }: withAppTypes): void => {
+    unsubscriptions.forEach(unsubscribe => unsubscribe());
+    // Clear the unsubscriptions
+    unsubscriptions.length = 0;
+
     const { cineService, segmentationService } = servicesManager.services;
     // Empty out the image load and retrieval pools to prevent memory leaks
     // on the mode exits
@@ -150,10 +154,6 @@ const cornerstoneExtension: Types.Extensions.Extension = {
     useToggleOneUpViewportGridStore.getState().clearToggleOneUpViewportGridStore();
     useSegmentationPresentationStore.getState().clearSegmentationPresentationStore();
     segmentationService.removeAllSegmentations();
-
-    unsubscriptions.forEach(unsubscribe => unsubscribe());
-    // Clear the unsubscriptions
-    unsubscriptions.length = 0;
   },
 
   /**

extensions/cornerstone/src/services/SegmentationService/SegmentationService.ts

@@ -255,7 +255,7 @@ class SegmentationService extends PubSubService {
       this._onSegmentationAddedFromSource
     );
 
-    this.listeners = {};
+    this.reset();
   };
 
   public async addSegmentationRepresentation(

extensions/cornerstone/src/utils/segmentationHandlers.ts

@@ -9,7 +9,11 @@ export function setupSegmentationDataModifiedHandler({
   customizationService,
   commandsManager,
 }) {
-  const { unsubscribe } = segmentationService.subscribeDebounced(
+  // A flag to indicate if the event is unsubscribed to. This is important because
+  // the debounced callback does an await and in that period of time the event may have
+  // been unsubscribed.
+  let isUnsubscribed = false;
+  const { unsubscribe: debouncedUnsubscribe } = segmentationService.subscribeDebounced(
     segmentationService.EVENTS.SEGMENTATION_DATA_MODIFIED,
     async ({ segmentationId }) => {
       const segmentation = segmentationService.getSegmentation(segmentationId);
@@ -42,7 +46,7 @@ export function setupSegmentationDataModifiedHandler({
         readableText,
       });
 
-      if (updatedSegmentation) {
+      if (!isUnsubscribed && updatedSegmentation) {
         segmentationService.addOrUpdateSegmentation({
           segmentationId,
           segments: updatedSegmentation.segments,
@@ -52,6 +56,10 @@ export function setupSegmentationDataModifiedHandler({
     1000
   );
 
+  const unsubscribe = () => {
+    isUnsubscribed = true;
+    debouncedUnsubscribe();
+  };
   return { unsubscribe };
 }