feat(studyPrefetcher): Study Prefetcher (#4206)

extensions/cornerstone/src/init.tsx

@@ -25,6 +25,7 @@ import initCornerstoneTools from './initCornerstoneTools';
 
 import { connectToolsToMeasurementService } from './initMeasurementService';
 import initCineService from './initCineService';
+import initStudyPrefetcherService from './initStudyPrefetcherService';
 import interleaveCenterLoader from './utils/interleaveCenterLoader';
 import nthLoader from './utils/nthLoader';
 import interleaveTopToBottom from './utils/interleaveTopToBottom';
@@ -98,6 +99,7 @@ export default async function init({
     hangingProtocolService,
     viewportGridService,
     stateSyncService,
+    studyPrefetcherService
   } = servicesManager.services;
 
   window.services = servicesManager.services;
@@ -190,6 +192,7 @@ export default async function init({
   this.measurementServiceSource = connectToolsToMeasurementService(servicesManager);
 
   initCineService(servicesManager);
+  initStudyPrefetcherService(servicesManager);
 
   // When a custom image load is performed, update the relevant viewports
   hangingProtocolService.subscribe(

extensions/cornerstone/src/initStudyPrefetcherService.ts

@@ -0,0 +1,33 @@
+import { cache, imageLoadPoolManager, imageLoader, Enums, eventTarget, EVENTS as csEvents } from '@cornerstonejs/core';
+
+function initStudyPrefetcherService(servicesManager: AppTypes.ServicesManager) {
+  const { studyPrefetcherService } = servicesManager.services;
+
+  studyPrefetcherService.requestType = Enums.RequestType.Prefetch;
+  studyPrefetcherService.imageLoadPoolManager = imageLoadPoolManager;
+  studyPrefetcherService.imageLoader = imageLoader;
+
+  studyPrefetcherService.cache = {
+    isImageCached(imageId: string): boolean {
+      return !!cache.getImageLoadObject(imageId);
+    }
+  }
+
+  studyPrefetcherService.imageLoadEventsManager = {
+    addEventListeners(onImageLoaded, onImageLoadFailed) {
+      eventTarget.addEventListener(csEvents.IMAGE_LOADED, onImageLoaded);
+      eventTarget.addEventListener(csEvents.IMAGE_LOAD_FAILED, onImageLoadFailed);
+
+      return [
+        {
+          unsubscribe: () => eventTarget.removeEventListener(csEvents.IMAGE_LOADED, onImageLoaded)
+        },
+        {
+          unsubscribe: () => eventTarget.removeEventListener(csEvents.IMAGE_LOAD_FAILED, onImageLoadFailed)
+        },
+      ]
+    }
+  }
+}
+
+export default initStudyPrefetcherService;