fix(web): Create Person face preview not working for video assets

FaceEditor previously required an HTMLImageElement | HTMLVideoElement prop to
compute layout metrics and generate the face crop preview. This was unavailable
for video assets, so the preview thumbnail in the Create Person modal was always
missing, and face positions could be NaN during image load (naturalWidth is 0
before the image decodes).

Replace the DOM element prop with assetSize: Size and containerSize: Size, using
asset metadata dimensions that are always available from the API response.
computeContentMetrics() is extracted as a pure utility alongside
mapContentRectToNatural() for converting face rect coordinates back to original
image space.

For videos, VideoNativeViewer now captures the current frame to canvas when face
edit mode opens and sets assetViewerManager.imgRef, giving FaceEditor the same
image-based preview path as photo assets.

Change-Id: I0e9da549e3af40211abad4ab2c0270706a6a6964

web/src/lib/components/asset-viewer/PhotoViewer.svelte

@@ -284,7 +284,11 @@
     {/snippet}
   </AdaptiveImage>
 
-  {#if assetViewerManager.isFaceEditMode && assetViewerManager.imgRef}
-    <FaceEditor htmlElement={assetViewerManager.imgRef} {containerWidth} {containerHeight} assetId={asset.id} />
+  {#if assetViewerManager.isFaceEditMode && assetViewerManager.imgRef && asset.width && asset.height}
+    <FaceEditor
+      assetSize={{ width: asset.width, height: asset.height }}
+      containerSize={{ width: containerWidth, height: containerHeight }}
+      assetId={asset.id}
+    />
   {/if}
 </div>

web/src/lib/components/asset-viewer/VideoNativeViewer.svelte

@@ -140,9 +140,40 @@
   let containerHeight = $state(0);
 
   $effect(() => {
-    if (assetViewerManager.isFaceEditMode) {
-      videoPlayer?.pause();
+    if (!assetViewerManager.isFaceEditMode || !videoPlayer) {
+      return;
     }
+    videoPlayer.pause();
+
+    const { videoWidth, videoHeight } = videoPlayer;
+    if (videoWidth === 0 || videoHeight === 0) {
+      return;
+    }
+
+    const canvas = document.createElement('canvas');
+    canvas.width = videoWidth;
+    canvas.height = videoHeight;
+    const context = canvas.getContext('2d');
+    if (!context) {
+      return;
+    }
+
+    context.drawImage(videoPlayer, 0, 0);
+    const dataUrl = canvas.toDataURL('image/png');
+    canvas.width = 0;
+
+    const img = new Image();
+    const onLoad = () => {
+      assetViewerManager.imgRef = img;
+    };
+    img.addEventListener('load', onLoad);
+    img.src = dataUrl;
+
+    return () => {
+      img.removeEventListener('load', onLoad);
+      img.src = '';
+      assetViewerManager.imgRef = undefined;
+    };
   });
 </script>
 
@@ -248,7 +279,11 @@
       {/if}
 
       {#if assetViewerManager.isFaceEditMode}
-        <FaceEditor htmlElement={videoPlayer} {containerWidth} {containerHeight} {assetId} />
+        <FaceEditor
+          assetSize={{ width: asset.width ?? 0, height: asset.height ?? 0 }}
+          containerSize={{ width: containerWidth, height: containerHeight }}
+          {assetId}
+        />
       {/if}
     {/if}
   </div>

web/src/lib/components/asset-viewer/face-editor/FaceEditor.svelte

@@ -4,7 +4,7 @@
   import { assetViewerManager } from '$lib/managers/asset-viewer-manager.svelte';
   import FaceCreateTagModal from '$lib/modals/CreateFaceModal.svelte';
   import { getPeopleThumbnailUrl } from '$lib/utils';
-  import { getNaturalSize, scaleToFit } from '$lib/utils/container-utils';
+  import { computeContentMetrics, mapContentRectToNatural, type Size } from '$lib/utils/container-utils';
   import { handleError } from '$lib/utils/handle-error';
   import { createFace, getAllPeople, type PersonResponseDto } from '@immich/sdk';
   import { Button, Input, modalManager, toastManager } from '@immich/ui';
@@ -14,13 +14,12 @@
   import { t } from 'svelte-i18n';
 
   type Props = {
-    htmlElement: HTMLImageElement | HTMLVideoElement;
-    containerWidth: number;
-    containerHeight: number;
+    assetSize: Size;
+    containerSize: Size;
     assetId: string;
   };
 
-  let { htmlElement, containerWidth, containerHeight, assetId }: Props = $props();
+  let { assetSize, containerSize, assetId }: Props = $props();
 
   let canvasEl: HTMLCanvasElement | undefined = $state();
   let canvas: Canvas | undefined = $state();
@@ -54,7 +53,7 @@
   };
 
   const setupCanvas = () => {
-    if (!canvasEl || !htmlElement) {
+    if (!canvasEl) {
       return;
     }
 
@@ -86,24 +85,14 @@
     searchInputEl?.focus();
   });
 
-  const imageContentMetrics = $derived.by(() => {
-    const natural = getNaturalSize(htmlElement);
-    const container = { width: containerWidth, height: containerHeight };
-    const { width: contentWidth, height: contentHeight } = scaleToFit(natural, container);
-    return {
-      contentWidth,
-      contentHeight,
-      offsetX: (containerWidth - contentWidth) / 2,
-      offsetY: (containerHeight - contentHeight) / 2,
-    };
-  });
+  const imageContentMetrics = $derived(computeContentMetrics(assetSize, containerSize));
 
   const setDefaultFaceRectanglePosition = (faceRect: Rect) => {
-    const { offsetX, offsetY } = imageContentMetrics;
+    const { offsetX, offsetY, contentWidth, contentHeight } = imageContentMetrics;
 
     faceRect.set({
-      top: offsetY + 200,
-      left: offsetX + 200,
+      top: offsetY + contentHeight / 2 - 56,
+      left: offsetX + contentWidth / 2 - 56,
     });
 
     faceRect.setCoords();
@@ -116,8 +105,8 @@
     }
 
     canvas.setDimensions({
-      width: containerWidth,
-      height: containerHeight,
+      width: containerSize.width,
+      height: containerSize.height,
     });
 
     if (!faceRect) {
@@ -167,6 +156,9 @@
     const gap = 15;
     const padding = faceRect.padding ?? 0;
     const rawBox = faceRect.getBoundingRect();
+    if (Number.isNaN(rawBox.left) || Number.isNaN(rawBox.width)) {
+      return;
+    }
     const faceBox = {
       left: rawBox.left - padding,
       top: rawBox.top - padding,
@@ -175,11 +167,11 @@
     };
     const selectorWidth = faceSelectorEl.offsetWidth;
     const chromeHeight = faceSelectorEl.offsetHeight - scrollableListEl.offsetHeight;
-    const listHeight = Math.min(MAX_LIST_HEIGHT, containerHeight - gap * 2 - chromeHeight);
+    const listHeight = Math.min(MAX_LIST_HEIGHT, containerSize.height - gap * 2 - chromeHeight);
     const selectorHeight = listHeight + chromeHeight;
 
-    const clampTop = (top: number) => clamp(top, gap, containerHeight - selectorHeight - gap);
-    const clampLeft = (left: number) => clamp(left, gap, containerWidth - selectorWidth - gap);
+    const clampTop = (top: number) => clamp(top, gap, containerSize.height - selectorHeight - gap);
+    const clampLeft = (left: number) => clamp(left, gap, containerSize.width - selectorWidth - gap);
 
     const overlapArea = (position: { top: number; left: number }) => {
       const selectorRight = position.left + selectorWidth;
@@ -238,45 +230,37 @@
   });
 
   const getFaceCroppedCoordinates = () => {
-    if (!faceRect || !htmlElement) {
+    if (!faceRect || imageContentMetrics.contentWidth === 0) {
       return;
     }
 
-    const { left, top, width, height } = faceRect.getBoundingRect();
-    const { offsetX, offsetY, contentWidth, contentHeight } = imageContentMetrics;
-    const natural = getNaturalSize(htmlElement);
-
-    const scaleX = natural.width / contentWidth;
-    const scaleY = natural.height / contentHeight;
-    const imageX = (left - offsetX) * scaleX;
-    const imageY = (top - offsetY) * scaleY;
+    const imageRect = mapContentRectToNatural(faceRect.getBoundingRect(), imageContentMetrics, assetSize);
 
     return {
-      imageWidth: natural.width,
-      imageHeight: natural.height,
-      x: Math.floor(imageX),
-      y: Math.floor(imageY),
-      width: Math.floor(width * scaleX),
-      height: Math.floor(height * scaleY),
+      imageWidth: assetSize.width,
+      imageHeight: assetSize.height,
+      x: Math.floor(imageRect.left),
+      y: Math.floor(imageRect.top),
+      width: Math.floor(imageRect.width),
+      height: Math.floor(imageRect.height),
     };
   };
 
   type FaceCoordinates = NonNullable<ReturnType<typeof getFaceCroppedCoordinates>>;
 
   const getFacePreviewUrl = (data: FaceCoordinates) => {
-    if (!htmlElement) {
+    const imgRef = assetViewerManager.imgRef;
+    if (!imgRef || imageContentMetrics.contentWidth === 0) {
       return;
     }
 
-    const natural = getNaturalSize(htmlElement);
-    if (natural.width <= 0 || natural.height <= 0) {
-      return;
-    }
+    const scaleX = imgRef.naturalWidth / assetSize.width;
+    const scaleY = imgRef.naturalHeight / assetSize.height;
 
-    const x = clamp(data.x, 0, natural.width - 1);
-    const y = clamp(data.y, 0, natural.height - 1);
-    const width = clamp(data.width, 1, natural.width - x);
-    const height = clamp(data.height, 1, natural.height - y);
+    const x = clamp(Math.floor(data.x * scaleX), 0, imgRef.naturalWidth - 1);
+    const y = clamp(Math.floor(data.y * scaleY), 0, imgRef.naturalHeight - 1);
+    const width = clamp(Math.floor(data.width * scaleX), 1, imgRef.naturalWidth - x);
+    const height = clamp(Math.floor(data.height * scaleY), 1, imgRef.naturalHeight - y);
 
     if (width <= 0 || height <= 0) {
       return;
@@ -292,7 +276,7 @@
     }
 
     try {
-      context.drawImage(htmlElement, x, y, width, height, 0, 0, width, height);
+      context.drawImage(imgRef, x, y, width, height, 0, 0, width, height);
       return canvas.toDataURL('image/png');
     } catch {
       return;

web/src/lib/components/assets/thumbnail/Thumbnail.svelte

@@ -33,7 +33,6 @@
     thumbnailSize?: number;
     thumbnailWidth?: number;
     thumbnailHeight?: number;
-    isInViewport?: boolean;
     selected?: boolean;
     selectionCandidate?: boolean;
     disabled?: boolean;
@@ -57,7 +56,6 @@
     thumbnailSize = undefined,
     thumbnailWidth = undefined,
     thumbnailHeight = undefined,
-    isInViewport = true,
     selected = false,
     selectionCandidate = false,
     disabled = false,
@@ -80,7 +78,6 @@
   let mouseOver = $state(false);
   let loaded = $state(false);
   let thumbError = $state(false);
-  let skipFade = $state(false);
 
   let width = $derived(thumbnailSize || thumbnailWidth || 235);
   let height = $derived(thumbnailSize || thumbnailHeight || 235);
@@ -267,11 +264,7 @@
         widthStyle="{width}px"
         heightStyle="{height}px"
         curve={selected}
-        onComplete={(errored) => {
-          skipFade = !isInViewport;
-          loaded = true;
-          thumbError = errored;
-        }}
+        onComplete={(errored) => ((loaded = true), (thumbError = errored))}
       />
       {#if asset.isVideo}
         <div class="pointer-events-none absolute size-full group-focus-visible:rounded-lg">
@@ -316,10 +309,7 @@
         <Thumbhash
           base64ThumbHash={asset.thumbhash}
           data-testid="thumbhash"
-          class={[
-            'absolute top-0 object-cover group-focus-visible:rounded-lg',
-            { 'rounded-xl': selected, hidden: skipFade },
-          ]}
+          class={['absolute top-0 object-cover group-focus-visible:rounded-lg', { 'rounded-xl': selected }]}
           style="width: {width}px; height: {height}px"
           draggable="false"
           fadeOut

web/src/lib/components/shared-components/gallery-viewer/GalleryViewer.svelte

@@ -22,16 +22,11 @@
   import { getJustifiedLayoutFromAssets } from '$lib/utils/layout-utils';
   import { navigate } from '$lib/utils/navigation';
   import { isTimelineAsset, toTimelineAsset } from '$lib/utils/timeline-util';
-  import { TUNABLES } from '$lib/utils/tunables';
   import { AssetVisibility, type AssetResponseDto } from '@immich/sdk';
   import { modalManager } from '@immich/ui';
   import { debounce } from 'lodash-es';
   import { t } from 'svelte-i18n';
 
-  const {
-    TIMELINE: { INTERSECTION_EXPAND_TOP, INTERSECTION_EXPAND_BOTTOM },
-  } = TUNABLES;
-
   type Props = {
     assets: AssetResponseDto[];
     viewerAssets?: AssetResponseDto[];
@@ -39,7 +34,7 @@
     disableAssetSelect?: boolean;
     showArchiveIcon?: boolean;
     viewport: Viewport;
-    onEndReached?: (() => void) | undefined;
+    onIntersected?: (() => void) | undefined;
     showAssetName?: boolean;
     onReload?: (() => void) | undefined;
     pageHeaderOffset?: number;
@@ -55,7 +50,7 @@
     disableAssetSelect = false,
     showArchiveIcon = false,
     viewport,
-    onEndReached = undefined,
+    onIntersected = undefined,
     showAssetName = false,
     onReload = undefined,
     slidingWindowOffset = 0,
@@ -75,31 +70,24 @@
     }),
   );
 
-  const getStyle = (index: number) => {
-    return `top: ${geometry.getTop(index)}px; left: ${geometry.getLeft(index)}px; width: ${geometry.getWidth(index)}px; height: ${geometry.getHeight(index)}px;`;
+  const getStyle = (i: number) => {
+    const geo = geometry;
+    return `top: ${geo.getTop(i)}px; left: ${geo.getLeft(i)}px; width: ${geo.getWidth(i)}px; height: ${geo.getHeight(i)}px;`;
   };
 
-  const isInOrNearViewport = (index: number) => {
+  const isIntersecting = (i: number) => {
+    const geo = geometry;
     const window = slidingWindow;
-    const top = geometry.getTop(index);
-    return top + pageHeaderOffset < window.bottom && top + geometry.getHeight(index) > window.top;
-  };
-
-  const isInViewport = (index: number) => {
-    const top = geometry.getTop(index) + pageHeaderOffset;
-    const bottom = top + geometry.getHeight(index);
-    const viewportTop = (scrollTop || 0) - slidingWindowOffset;
-    const viewportBottom = viewportTop + viewport.height + slidingWindowOffset;
-    return top < viewportBottom && bottom > viewportTop;
+    const top = geo.getTop(i);
+    return top + pageHeaderOffset < window.bottom && top + geo.getHeight(i) > window.top;
   };
 
   let shiftKeyIsDown = $state(false);
   let lastAssetMouseEvent: TimelineAsset | null = $state(null);
   let scrollTop = $state(0);
-
   let slidingWindow = $derived.by(() => {
-    const top = (scrollTop || 0) - slidingWindowOffset - INTERSECTION_EXPAND_TOP;
-    const bottom = top + viewport.height + slidingWindowOffset + INTERSECTION_EXPAND_BOTTOM;
+    const top = (scrollTop || 0) - slidingWindowOffset;
+    const bottom = top + viewport.height + slidingWindowOffset;
     return {
       top,
       bottom,
@@ -113,15 +101,17 @@
 
   const updateSlidingWindow = () => (scrollTop = document.scrollingElement?.scrollTop ?? 0);
 
-  const debouncedOnEndReached = debounce(() => onEndReached?.(), 750, { maxWait: 100, leading: true });
+  const debouncedOnIntersected = debounce(() => onIntersected?.(), 750, { maxWait: 100, leading: true });
 
-  let lastEndReachedHeight = 0;
+  let lastIntersectedHeight = 0;
   $effect(() => {
+    // Intersect if there's only one viewport worth of assets left to scroll.
     if (geometry.containerHeight - slidingWindow.bottom <= viewport.height) {
-      const contentHeight = geometry.containerHeight;
-      if (lastEndReachedHeight !== contentHeight) {
-        debouncedOnEndReached();
-        lastEndReachedHeight = contentHeight;
+      // Notify we got to (near) the end of scroll.
+      const intersectedHeight = geometry.containerHeight;
+      if (lastIntersectedHeight !== intersectedHeight) {
+        debouncedOnIntersected();
+        lastIntersectedHeight = intersectedHeight;
       }
     }
   });
@@ -372,10 +362,10 @@
     style:height={geometry.containerHeight + 'px'}
     style:width={geometry.containerWidth + 'px'}
   >
-    {#each assets as asset, index (asset.id + '-' + index)}
-      {#if isInOrNearViewport(index)}
+    {#each assets as asset, i (asset.id + '-' + i)}
+      {#if isIntersecting(i)}
         {@const currentAsset = toTimelineAsset(asset)}
-        <div class="absolute" style:overflow="clip" style={getStyle(index)}>
+        <div class="absolute" style:overflow="clip" style={getStyle(i)}>
           <Thumbnail
             readonly={disableAssetSelect}
             onClick={() => {
@@ -392,9 +382,8 @@
             asset={currentAsset}
             selected={assetInteraction.hasSelectedAsset(currentAsset.id)}
             selectionCandidate={assetInteraction.hasSelectionCandidate(currentAsset.id)}
-            isInViewport={isInViewport(index)}
-            thumbnailWidth={geometry.getWidth(index)}
-            thumbnailHeight={geometry.getHeight(index)}
+            thumbnailWidth={geometry.getWidth(i)}
+            thumbnailHeight={geometry.getHeight(i)}
           />
           {#if showAssetName && !isTimelineAsset(asset)}
             <div

web/src/lib/components/timeline/AssetLayout.svelte

@@ -21,7 +21,6 @@
         {
           asset: TimelineAsset;
           position: CommonPosition;
-          isInViewport: boolean;
         },
       ]
     >;
@@ -39,7 +38,6 @@
   {#each filterIsInOrNearViewport(viewerAssets) as viewerAsset (viewerAsset.id)}
     {@const position = viewerAsset.position!}
     {@const asset = viewerAsset.asset!}
-    {@const isInViewport = viewerAsset.isInViewport!}
 
     <!-- note: don't remove data-asset-id - its used by web e2e tests -->
     <div
@@ -52,7 +50,7 @@
       out:scale|global={{ start: 0.1, duration: scaleDuration }}
       animate:flip={{ duration: transitionDuration }}
     >
-      {@render thumbnail({ asset, position, isInViewport })}
+      {@render thumbnail({ asset, position })}
       {@render customThumbnailLayout?.(asset)}
     </div>
   {/each}

web/src/lib/components/timeline/Month.svelte

@@ -21,7 +21,6 @@
           position: CommonPosition;
           timelineDay: TimelineDay;
           groupIndex: number;
-          isInViewport: boolean;
         },
       ]
     >;
@@ -106,8 +105,8 @@
       width={timelineDay.width}
       {customThumbnailLayout}
     >
-      {#snippet thumbnail({ asset, position, isInViewport })}
-        {@render thumbnailWithGroup({ asset, position, timelineDay, groupIndex, isInViewport })}
+      {#snippet thumbnail({ asset, position })}
+        {@render thumbnailWithGroup({ asset, position, timelineDay, groupIndex })}
       {/snippet}
     </AssetLayout>
   </section>

web/src/lib/components/timeline/Timeline.svelte

@@ -673,7 +673,7 @@
             manager={timelineManager}
             onTimelineDaySelect={handleGroupSelect}
           >
-            {#snippet thumbnail({ asset, position, timelineDay, groupIndex, isInViewport })}
+            {#snippet thumbnail({ asset, position, timelineDay, groupIndex })}
               {@const isAssetSelectionCandidate = assetInteraction.hasSelectionCandidate(asset.id)}
               {@const isAssetSelected =
                 assetInteraction.hasSelectedAsset(asset.id) || timelineManager.albumAssets.has(asset.id)}
@@ -684,7 +684,6 @@
                 {asset}
                 {albumUsers}
                 {groupIndex}
-                {isInViewport}
                 onClick={(asset) => {
                   if (typeof onThumbnailClick === 'function') {
                     onThumbnailClick(asset, timelineManager, timelineDay, _onClick);

web/src/lib/managers/timeline-manager/viewer-asset.svelte.ts

@@ -3,7 +3,6 @@ import {
   ViewportProximity,
   calculateViewerAssetViewportProximity,
   isInOrNearViewport,
-  isInViewport,
 } from './internal/intersection-support.svelte';
 import type { TimelineDay } from './timeline-day.svelte';
 import type { TimelineAsset } from './types';
@@ -26,10 +25,6 @@ export class ViewerAsset {
     return isInOrNearViewport(this.#viewportProximity);
   }
 
-  get isInViewport() {
-    return isInViewport(this.#viewportProximity);
-  }
-
   position: CommonPosition | undefined = $state.raw();
   asset: TimelineAsset = $state() as TimelineAsset;
   id: string = $derived(this.asset.id);

web/src/lib/utils/container-utils.spec.ts

@@ -1,18 +1,15 @@
 import {
-  getContentMetrics,
+  computeContentMetrics,
   getNaturalSize,
+  mapContentRectToNatural,
   mapNormalizedRectToContent,
   mapNormalizedToContent,
   scaleToCover,
   scaleToFit,
 } from '$lib/utils/container-utils';
 
-const mockImage = (props: {
-  naturalWidth: number;
-  naturalHeight: number;
-  width: number;
-  height: number;
-}): HTMLImageElement => props as unknown as HTMLImageElement;
+const mockImage = (props: { naturalWidth: number; naturalHeight: number }): HTMLImageElement =>
+  props as unknown as HTMLImageElement;
 
 const mockVideo = (props: {
   videoWidth: number;
@@ -49,48 +46,85 @@ describe('scaleToFit', () => {
   });
 });
 
-describe('getContentMetrics', () => {
-  it('should compute zero offsets when aspect ratios match', () => {
-    const img = mockImage({ naturalWidth: 1600, naturalHeight: 900, width: 800, height: 450 });
-    expect(getContentMetrics(img)).toEqual({
+describe('computeContentMetrics', () => {
+  it('should return zero metrics for zero-width content', () => {
+    expect(computeContentMetrics({ width: 0, height: 1080 }, { width: 800, height: 600 })).toEqual({
+      contentWidth: 0,
+      contentHeight: 0,
+      offsetX: 0,
+      offsetY: 0,
+    });
+  });
+
+  it('should return zero metrics for zero-height content', () => {
+    expect(computeContentMetrics({ width: 1920, height: 0 }, { width: 800, height: 600 })).toEqual({
+      contentWidth: 0,
+      contentHeight: 0,
+      offsetX: 0,
+      offsetY: 0,
+    });
+  });
+
+  it('should center wide content vertically', () => {
+    expect(computeContentMetrics({ width: 2000, height: 1000 }, { width: 800, height: 600 })).toEqual({
+      contentWidth: 800,
+      contentHeight: 400,
+      offsetX: 0,
+      offsetY: 100,
+    });
+  });
+
+  it('should center tall content horizontally', () => {
+    expect(computeContentMetrics({ width: 1000, height: 2000 }, { width: 800, height: 600 })).toEqual({
+      contentWidth: 300,
+      contentHeight: 600,
+      offsetX: 250,
+      offsetY: 0,
+    });
+  });
+
+  it('should produce zero offsets when aspect ratios match', () => {
+    expect(computeContentMetrics({ width: 1600, height: 900 }, { width: 800, height: 450 })).toEqual({
       contentWidth: 800,
       contentHeight: 450,
       offsetX: 0,
       offsetY: 0,
     });
   });
+});
 
-  it('should compute horizontal letterbox offsets for tall image', () => {
-    const img = mockImage({ naturalWidth: 1000, naturalHeight: 2000, width: 800, height: 600 });
-    const metrics = getContentMetrics(img);
-    expect(metrics.contentWidth).toBe(300);
-    expect(metrics.contentHeight).toBe(600);
-    expect(metrics.offsetX).toBe(250);
-    expect(metrics.offsetY).toBe(0);
+describe('mapContentRectToNatural', () => {
+  it('should map a full-content rect back to natural size', () => {
+    const metrics = { contentWidth: 800, contentHeight: 400, offsetX: 0, offsetY: 100 };
+    const rect = mapContentRectToNatural({ left: 0, top: 100, width: 800, height: 400 }, metrics, {
+      width: 2000,
+      height: 1000,
+    });
+    expect(rect).toEqual({ left: 0, top: 0, width: 2000, height: 1000 });
   });
 
-  it('should compute vertical letterbox offsets for wide image', () => {
-    const img = mockImage({ naturalWidth: 2000, naturalHeight: 1000, width: 800, height: 600 });
-    const metrics = getContentMetrics(img);
-    expect(metrics.contentWidth).toBe(800);
-    expect(metrics.contentHeight).toBe(400);
-    expect(metrics.offsetX).toBe(0);
-    expect(metrics.offsetY).toBe(100);
+  it('should map a centered sub-rect to natural coordinates', () => {
+    const metrics = { contentWidth: 800, contentHeight: 400, offsetX: 0, offsetY: 100 };
+    const rect = mapContentRectToNatural({ left: 200, top: 200, width: 400, height: 200 }, metrics, {
+      width: 2000,
+      height: 1000,
+    });
+    expect(rect).toEqual({ left: 500, top: 250, width: 1000, height: 500 });
   });
 
-  it('should use clientWidth/clientHeight for video elements', () => {
-    const video = mockVideo({ videoWidth: 1920, videoHeight: 1080, clientWidth: 800, clientHeight: 600 });
-    const metrics = getContentMetrics(video);
-    expect(metrics.contentWidth).toBe(800);
-    expect(metrics.contentHeight).toBe(450);
-    expect(metrics.offsetX).toBe(0);
-    expect(metrics.offsetY).toBe(75);
+  it('should handle letterboxed content with horizontal offset', () => {
+    const metrics = { contentWidth: 300, contentHeight: 600, offsetX: 250, offsetY: 0 };
+    const rect = mapContentRectToNatural({ left: 250, top: 0, width: 300, height: 600 }, metrics, {
+      width: 1000,
+      height: 2000,
+    });
+    expect(rect).toEqual({ left: 0, top: 0, width: 1000, height: 2000 });
   });
 });
 
 describe('getNaturalSize', () => {
   it('should return naturalWidth/naturalHeight for images', () => {
-    const img = mockImage({ naturalWidth: 4000, naturalHeight: 3000, width: 800, height: 600 });
+    const img = mockImage({ naturalWidth: 4000, naturalHeight: 3000 });
     expect(getNaturalSize(img)).toEqual({ width: 4000, height: 3000 });
   });
 

web/src/lib/utils/container-utils.ts

@@ -49,13 +49,6 @@ export const scaleToFit = (dimensions: Size, container: Size): Size => {
   };
 };
 
-const getElementSize = (element: HTMLImageElement | HTMLVideoElement): Size => {
-  if (element instanceof HTMLVideoElement) {
-    return { width: element.clientWidth, height: element.clientHeight };
-  }
-  return { width: element.width, height: element.height };
-};
-
 export const getNaturalSize = (element: HTMLImageElement | HTMLVideoElement): Size => {
   if (element instanceof HTMLVideoElement) {
     return { width: element.videoWidth, height: element.videoHeight };
@@ -63,17 +56,18 @@ export const getNaturalSize = (element: HTMLImageElement | HTMLVideoElement): Si
   return { width: element.naturalWidth, height: element.naturalHeight };
 };
 
-export const getContentMetrics = (element: HTMLImageElement | HTMLVideoElement): ContentMetrics => {
-  const natural = getNaturalSize(element);
-  const client = getElementSize(element);
-  const { width: contentWidth, height: contentHeight } = scaleToFit(natural, client);
+export function computeContentMetrics(content: Size, container: Size): ContentMetrics {
+  if (content.width === 0 || content.height === 0) {
+    return { contentWidth: 0, contentHeight: 0, offsetX: 0, offsetY: 0 };
+  }
+  const { width: contentWidth, height: contentHeight } = scaleToFit(content, container);
   return {
     contentWidth,
     contentHeight,
-    offsetX: (client.width - contentWidth) / 2,
-    offsetY: (client.height - contentHeight) / 2,
+    offsetX: (container.width - contentWidth) / 2,
+    offsetY: (container.height - contentHeight) / 2,
   };
-};
+}
 
 export function mapNormalizedToContent(point: Point, sizeOrMetrics: Size | ContentMetrics): Point {
   if ('contentWidth' in sizeOrMetrics) {
@@ -109,3 +103,25 @@ export function mapNormalizedRectToContent(
     height: br.y - tl.y,
   };
 }
+
+function mapContentToNatural(point: Point, metrics: ContentMetrics, naturalSize: Size): Point {
+  return {
+    x: ((point.x - metrics.offsetX) / metrics.contentWidth) * naturalSize.width,
+    y: ((point.y - metrics.offsetY) / metrics.contentHeight) * naturalSize.height,
+  };
+}
+
+export function mapContentRectToNatural(rect: Rect, metrics: ContentMetrics, naturalSize: Size): Rect {
+  const topLeft = mapContentToNatural({ x: rect.left, y: rect.top }, metrics, naturalSize);
+  const bottomRight = mapContentToNatural(
+    { x: rect.left + rect.width, y: rect.top + rect.height },
+    metrics,
+    naturalSize,
+  );
+  return {
+    top: topLeft.y,
+    left: topLeft.x,
+    width: bottomRight.x - topLeft.x,
+    height: bottomRight.y - topLeft.y,
+  };
+}

web/src/routes/(user)/search/[[photos=photos]]/[[assetId=id]]/+page.svelte

@@ -292,7 +292,7 @@
       <GalleryViewer
         assets={searchResultAssets}
         assetInteraction={assetMultiSelectManager}
-        onEndReached={loadNextPage}
+        onIntersected={loadNextPage}
         showArchiveIcon={true}
         {viewport}
         onReload={onSearchQueryUpdate}