fix: Ensure media info is dispatched after view change (#1587)

src/utils/embla/carousel-controller.ts

@@ -88,6 +88,18 @@ export class CarouselController {
 
   public selectSlide(index: number): void {
     this._carousel.scrollTo(index, this._transitionEffect === 'none');
+
+    // This event exists to allow the caller to know the difference between
+    // programatically force slide selections and user-driven slide selections
+    // (e.g. carousel drags). See the note in auto-media-loaded-info.ts on how
+    // this is used.
+    const newSlide = this.getSlide(index);
+    if (newSlide) {
+      dispatchFrigateCardEvent<CarouselSelected>(this._parent, 'carousel:force-select', {
+        index: index,
+        element: newSlide,
+      });
+    }
   }
 
   protected _refreshCarouselContents = (): void => {
@@ -162,17 +174,6 @@ export class CarouselController {
     };
 
     carousel.on('select', () => selectSlide());
-    carousel.on('settle', () => {
-      const carouselSelected = getCarouselSelectedObject();
-      if (carouselSelected) {
-        dispatchFrigateCardEvent<CarouselSelected>(
-          this._parent,
-          'carousel:settle',
-          carouselSelected,
-        );
-      }
-    });
-
     return carousel;
   }
 }

src/utils/embla/plugins/auto-media-loaded-info/auto-media-loaded-info.ts

@@ -13,6 +13,30 @@ declare module 'embla-carousel/components/Plugins' {
   }
 }
 
+/**
+ * On the relationship between carousel:select and carousel:force-select:
+ *
+ * There is a complex interplay here. `carousel:force-select` is an event
+ * dispatched by the carousel when it is forced to select a particular slide
+ * (i.e. the view has changed). `carousel:select` is dispatched for any
+ * selection -- forced or human (e.g. the user dragging the carousel).
+ *
+ * The media info should only be dispatched _after_ the view object has been
+ * updated (since the view will clear the loaded media info). The setting of the
+ * view (trigged by `carousel:select`) may require async fetches and may take a
+ * while -- and so if the card dispatched media on `carousel:selecte` then the
+ * media info may be dispatched before the view is set (which could result in
+ * the dispatched media immediately being cleared by the view).
+ *
+ * It is fine to have media info dispatched from the `carousel:init` event,
+ * since the carousel will be initialized based on a particular view object. In
+ * practice, the carousel will be initialized before the media is loaded, so
+ * there may not be anything to dispatch at that point.
+ *
+ * When media is loaded, that media loaded info will always be allowed to
+ * propogate upwards as long as it is selected.
+ */
+
 type AutoMediaLoadedInfoType = CreatePluginType<LoosePluginType, LooseOptionsType>;
 
 function AutoMediaLoadedInfo(): AutoMediaLoadedInfoType {
@@ -30,7 +54,9 @@ function AutoMediaLoadedInfo(): AutoMediaLoadedInfoType {
     }
 
     emblaApi.on('init', slideSelectHandler);
-    emblaApi.on('select', slideSelectHandler);
+    emblaApi
+      .containerNode()
+      .addEventListener('frigate-card:carousel:force-select', slideSelectHandler);
   }
 
   function destroy(): void {
@@ -40,7 +66,9 @@ function AutoMediaLoadedInfo(): AutoMediaLoadedInfoType {
     }
 
     emblaApi.off('init', slideSelectHandler);
-    emblaApi.off('select', slideSelectHandler);
+    emblaApi
+      .containerNode()
+      .removeEventListener('frigate-card:carousel:force-select', slideSelectHandler);
   }
 
   function mediaLoadedInfoHandler(ev: CustomEvent<MediaLoadedInfo>): void {

tests/utils/embla/carousel-controller.test.ts

@@ -110,24 +110,35 @@ describe('CarouselController', () => {
   it('should select given slide', () => {
     const children = createTestSlideNodes();
     const parent = createParent({ children: children });
+
+    const forceSelectListener = vi.fn();
+    parent.addEventListener('frigate-card:carousel:force-select', forceSelectListener);
+
     const carousel = new CarouselController(createRoot(), parent);
 
     carousel.selectSlide(4);
 
     expect(getEmblaApi()?.scrollTo).toBeCalledWith(4, false);
+    expect(forceSelectListener).toBeCalledWith(
+      expect.objectContaining({
+        detail: { index: 4, element: children[4] },
+      }),
+    );
   });
 
-  it('should dispatch settle event', () => {
-    const children = createTestSlideNodes();
+  it('should not select non-existent slide', () => {
+    const children = createTestSlideNodes({ n: 10 });
     const parent = createParent({ children: children });
-    new CarouselController(createRoot(), parent);
 
-    const settleHandler = vi.fn();
-    parent.addEventListener('frigate-card:carousel:settle', settleHandler);
+    const forceSelectListener = vi.fn();
+    parent.addEventListener('frigate-card:carousel:force-select', forceSelectListener);
 
-    callEmblaHandler(getEmblaApi(), 'settle');
+    const carousel = new CarouselController(createRoot(), parent);
 
-    expect(settleHandler).toBeCalled();
+    carousel.selectSlide(11);
+
+    expect(getEmblaApi()?.scrollTo).toBeCalledWith(11, false);
+    expect(forceSelectListener).not.toBeCalled();
   });
 
   it('should dispatch select event', () => {

tests/utils/embla/plugins/auto-media-loaded-info/auto-media-loaded-info.test.ts

@@ -6,7 +6,6 @@ import {
 } from '../../../../../src/utils/media-info';
 import { createMediaLoadedInfo, createParent } from '../../../../test-utils';
 import {
-  callEmblaHandler,
   createEmblaApiInstance,
   createTestEmblaOptionHandler,
   createTestSlideNodes,
@@ -30,7 +29,6 @@ describe('AutoMediaLoadedInfo', () => {
     plugin.destroy();
 
     expect(emblaApi.off).toBeCalledWith('init', expect.anything());
-    expect(emblaApi.off).toBeCalledWith('select', expect.anything());
   });
 
   describe('should correctly propogate media load/unload depending on whether media is currently selected', () => {
@@ -82,11 +80,15 @@ describe('AutoMediaLoadedInfo', () => {
     dispatchExistingMediaLoadedInfoAsEvent(children[5], createMediaLoadedInfo());
 
     vi.mocked(emblaApi.selectedScrollSnap).mockReturnValue(4);
-    callEmblaHandler(emblaApi, 'select');
+    emblaApi
+      .containerNode()
+      .dispatchEvent(new Event('frigate-card:carousel:force-select'));
     expect(mediaLoadedHandler).not.toBeCalled();
 
     vi.mocked(emblaApi.selectedScrollSnap).mockReturnValue(5);
-    callEmblaHandler(emblaApi, 'select');
+    emblaApi
+      .containerNode()
+      .dispatchEvent(new Event('frigate-card:carousel:force-select'));
     expect(mediaLoadedHandler).toBeCalled();
   });
 });