logan
3479ae8d39
Scrolling the albums grid pops art in: the cards already draw the smallest adequate tier and are already lazy, so what was left is *when* the request happens. The grids are virtualized, so the `<img>` — and therefore the fetch — does not exist until the virtualizer renders its card, which is about 1000px past the viewport, or two screens on the reference device. The issue asks for a larger overscan and that is not available: `_overhang` is a hard-coded `protected` field on `BaseLayout` with no configuration surface. So the request is issued ahead of the element instead. `utils/image-prefetch.ts` warms a bounded window either side of the rendered range, from `rangeChanged` rather than `visibilityChanged` — the two report different ranges, and a window measured from what is *visible* is spent on cards that already exist. Cover and artist URLs are served under `Cache-Control: immutable` (content-hashed filenames), so a prefetched image is a cache hit by the time its card is drawn. The bytes are the browser's; what this holds is the set of URLs asked for, capped and reported to `__yjCacheStats()`. Measured on the bulk seed (4 988 albums), ten 2 400px jumps, covers in the viewport with `naturalWidth === 0`: 254 of 258 blank one frame after the jump and 214 two frames after, against 117 and 77 with the prefetch. Closes #65