/* BEGIN USAGE */
/**
 * <image-slot> — user-fillable image placeholder.
 *
 * Drop this into a deck, mockup, or page wherever a design needs an image.
 * You control the slot's shape; it sizes to its container by default. When the search_stock_photos tool
 * is available, prefill the slot by default — write the photo's URL into
 * src (with credit/credit-href); the user can still fill or replace it
 * by dragging an image file onto it (or clicking to browse). The dropped
 * image persists across reloads via a .image-slots.state.json sidecar —
 * same read-via-fetch / write-via-window.omelette pattern as
 * design_canvas.jsx, so the filled slot shows on share links, downloaded
 * zips, and PPTX export. Outside the omelette runtime the slot is read-only.
 *
 * The sidecar is a SIBLING of the HTML file that uses this component: the
 * read is a document-relative fetch, and the host resolves the bridge's
 * sidecar writes into the previewed file's directory to match (same
 * contract as design_canvas.jsx). Pages in the same directory share one
 * sidecar; keep slot ids distinct across them.
 *
 * Attributes:
 *   id           Persistence key. REQUIRED for the drop to survive reload —
 *                every slot on the page needs a distinct id.
 *   shape        'rect' | 'rounded' | 'circle' | 'pill'   (default 'rounded')
 *                'circle' applies 50% border-radius; on a non-square slot
 *                that's an ellipse — set equal width and height for a true
 *                circle.
 *   radius       Corner radius in px for 'rounded'.       (default 12)
 *   mask         Any CSS clip-path value. Overrides `shape` — use this for
 *                hexagons, blobs, arbitrary polygons.
 *   fit          Initial framing baseline: cover | contain.   (default 'cover')
 *                cover starts the image filling the frame (overflow cropped);
 *                contain starts it fully visible (letterboxed). Either way the
 *                user can always pan/scale from there — double-click, or the
 *                Edit control, enters reframe mode (drag to move, scroll or
 *                corner-handles to scale; Escape / click-out commits). The
 *                crop persists alongside the image in the sidecar.
 *   placeholder  Empty-state caption.                      (default 'Drop an image')
 *   src          Optional initial/fallback image URL. Prefill it with a real
 *                photo via search_stock_photos when that tool is available
 *                (set credit/credit-href from the result). A user drop
 *                overrides it; clearing the drop reveals src again.
 *   credit       Attribution text shown as a small overlay at the
 *                bottom-left of the filled slot. REQUIRED whenever src
 *                points at any Unsplash host (images.unsplash.com,
 *                plus.unsplash.com, …): an Unsplash src with no credit
 *                renders an error tile INSTEAD of the photo (Unsplash
 *                terms forbid showing their photos unattributed). Use the
 *                exact form 'Photo by {photographer name} on Unsplash' —
 *                the overlay then links the name to credit-href and
 *                'Unsplash' to the Unsplash homepage, and links back to
 *                unsplash.com automatically get the required utm referral
 *                params appended at render time. The credit belongs to
 *                the src image, so it only shows while src is what's
 *                displayed — a user-dropped image hides it.
 *   credit-href  Link for the photographer's name in the credit overlay
 *                (their Unsplash profile URL from the stock-photo search
 *                results). http(s) URLs only — anything else renders the
 *                name as plain text.
 *
 * Sizing: the slot fills its container by default (width/height 100%).
 * Put it in a sized wrapper — absolutely positioned, a grid cell, a fixed
 * frame — and it takes exactly that box. When the parent's height is
 * indefinite (ordinary flow), it falls back to full width at a 3:2 aspect
 * ratio instead of collapsing. In a shrink-to-fit parent (a float,
 * width:max-content, an unsized absolute wrapper), percentages have
 * nothing to resolve against — size the slot or its wrapper explicitly
 * there. For a fixed-size slot, set
 * width/height on the element itself (inline style), which overrides the
 * default. When
 * layering content above a slot (full-bleed layouts), make the overlay
 * click-through — pointer-events: none on scrims/text plates, re-enabled
 * on interactive children — so the slot's hover controls stay reachable.
 * Keep the slot's bottom-left corner visually clear as well: the credit
 * overlay renders there, and a dark fade or text plate covering it hides
 * the attribution Unsplash's terms require — end the fade above that
 * corner, or keep it nearly transparent where the credit sits.
 *
 * Usage:
 *   <div style="position:relative;width:100%;height:100%">      <!-- full-bleed: -->
 *     <image-slot id="bg" shape="rect"></image-slot>            <!-- fills the wrapper -->
 *   </div>
 *   <image-slot id="hero"   style="width:800px;height:450px" shape="rounded" radius="20"
 *               placeholder="Drop a hero image"></image-slot>
 *   <image-slot id="avatar" style="width:120px;height:120px" shape="circle"></image-slot>
 *   <image-slot id="kite"   style="width:300px;height:300px"
 *               mask="polygon(50% 0, 100% 50%, 50% 100%, 0 50%)"></image-slot>
 */
/* END USAGE */

(() => {
  const STATE_FILE = '.image-slots.state.json';

  // Unsplash terms require visible attribution wherever their photos
  // display, and every link back to unsplash.com must carry utm referral
  // params. Two render-time rules enforce that here:
  //  - an Unsplash-src slot with NO credit attribute renders an error
  //    tile INSTEAD of the photo (an uncredited Unsplash photo on screen
  //    is itself the terms violation, so it never renders bare);
  //  - rendered credit links pointing at unsplash.com get the referral
  //    params appended when absent (credit-href values live in page
  //    content that can't be edited after the fact).
  // Keep the utm_source value in sync with UTM_SOURCE in
  // platform/web-agent/unsplash.ts — this file is a project-local
  // artifact and cannot import it (equality is pinned by tests).
  const UNSPLASH_HOMEPAGE_HREF =
    'https://unsplash.com/?utm_source=claude_design&utm_medium=referral';
  // Host rule mirrors the hotlink validator that admits Unsplash srcs into
  // pages in the first place (cdn$ in unsplash.ts: apex or any subdomain)
  // — Unsplash+ results serve from plus.unsplash.com, not just images.*,
  // and an admitted-but-uncredited photo must error whatever unsplash
  // host it rides on.
  // Trailing-dot FQDNs (images.unsplash.com.) are the same host to the
  // browser but would miss the regex — strip one dot so the check fails
  // CLOSED (unrecognized-but-real Unsplash srcs must error, not render).
  const isUnsplashHost = (u) => {
    try {
      return /(^|\.)unsplash\.com$/.test(
        new URL(u, document.baseURI).hostname.replace(/\.$/, '')
      );
    } catch {
      return false;
    }
  };
  // Render-time referral normalization for links back to Unsplash:
  // appends utm_source/utm_medium when absent, preserves every existing
  // query param, never overwrites an existing utm_source, and passes
  // non-Unsplash URLs through untouched. Input is an ABSOLUTE validated
  // http(s) URL (the credit render funnel resolves + validates first).
  const withReferral = (href) => {
    try {
      const u = new URL(href);
      if (!/(^|\.)unsplash\.com$/.test(u.hostname.replace(/\.$/, ''))) {
        return href;
      }
      if (!u.searchParams.has('utm_source')) {
        u.searchParams.set('utm_source', 'claude_design');
      }
      if (!u.searchParams.has('utm_medium')) {
        u.searchParams.set('utm_medium', 'referral');
      }
      return u.toString();
    } catch (e) {
      return href;
    }
  };
  // 2× a ~600px slot in a 1920-wide deck — retina-sharp without making the
  // sidecar enormous. A 1200px WebP at q=0.85 is ~150-300KB.
  const MAX_DIM = 1200;
  // Raster formats only. SVG is excluded (can carry script; createImageBitmap
  // on SVG blobs is inconsistent). GIF is excluded because the canvas
  // re-encode keeps only the first frame, so an animated GIF would silently
  // go still — better to reject than surprise.
  const ACCEPT = ['image/png', 'image/jpeg', 'image/webp', 'image/avif'];

  // ── Shared sidecar store ────────────────────────────────────────────────
  // One fetch + immediate write-on-change for every <image-slot> on the
  // page. Reads via fetch() so viewing works anywhere the HTML and sidecar
  // are served together; writes go through window.omelette.writeFile, which
  // the host allowlists to *.state.json basenames only.
  const subs = new Set();
  let slots = {};
  // ids explicitly cleared before the sidecar fetch resolved — otherwise
  // the merge below can't tell "never set" from "just deleted" and would
  // resurrect the sidecar's stale value.
  const tombstones = new Set();
  let loaded = false;
  let loadP = null;

  function load() {
    if (loadP) return loadP;
    loadP = fetch(STATE_FILE)
      .then((r) => (r.ok ? r.json() : null))
      .then((j) => {
        // Merge: sidecar loses to any in-memory change that raced ahead of
        // the fetch (drop or clear) so neither is clobbered by hydration.
        if (j && typeof j === 'object') {
          const merged = Object.assign({}, j, slots);
          // A framing-only write that raced ahead of hydration must not
          // drop a user image that's only on disk — inherit u from the
          // sidecar for any in-memory entry that lacks one.
          for (const k in slots) {
            if (merged[k] && !merged[k].u && j[k]) {
              merged[k].u = typeof j[k] === 'string' ? j[k] : j[k].u;
            }
          }
          for (const id of tombstones) delete merged[id];
          slots = merged;
        }
        tombstones.clear();
      })
      .catch(() => {})
      .then(() => { loaded = true; subs.forEach((fn) => fn()); });
    return loadP;
  }

  // Serialize writes so two near-simultaneous drops on different slots
  // can't reorder at the backend and leave the sidecar with only the
  // first. A save requested mid-flight just marks dirty and re-fires on
  // completion with the then-current slots.
  let saving = false;
  let saveDirty = false;
  // Unload-time flush: save()'s serialization defers a mid-RTT re-fire to a
  // .then that never runs in an unloading document, silently dropping a
  // pagehide commit. Post the current slots immediately instead — content
  // is a superset snapshot of any in-flight save's, the write is a
  // whole-file last-writer-wins replace, and postMessage FIFO delivers it
  // to the host after the in-flight one, so a backend-side reorder at
  // worst reproduces the dropped-commit outcome this flush improves on.
  // Guarded on the initial sidecar read: pre-hydration slots can miss
  // other slots' persisted entries, and flushing it would clobber them —
  // that narrow case stays best-effort (the in-memory merge in load()
  // cannot happen in an unloading document anyway).
  function flushNow() {
    if (!loaded) return;
    const w = window.omelette && window.omelette.writeFile;
    if (!w) return;
    try { Promise.resolve(w(STATE_FILE, JSON.stringify(slots))).catch(() => {}); } catch (e) {}
  }
  function save() {
    if (saving) { saveDirty = true; return; }
    const w = window.omelette && window.omelette.writeFile;
    if (!w) return;
    saving = true;
    Promise.resolve(w(STATE_FILE, JSON.stringify(slots)))
      .catch(() => {})
      .then(() => { saving = false; if (saveDirty) { saveDirty = false; save(); } });
  }

  const S_MAX = 5;
  const clampS = (s) => Math.max(1, Math.min(S_MAX, s));

  // Normalize a stored slot value. Pre-reframe sidecars stored a bare
  // data-URL string; newer ones store {u, s, x, y}. Either shape is valid.
  function getSlot(id) {
    const v = slots[id];
    if (!v) return null;
    return typeof v === 'string' ? { u: v, s: 1, x: 0, y: 0 } : v;
  }

  function setSlot(id, val) {
    if (!id) return;
    if (val) { slots[id] = val; tombstones.delete(id); }
    else { delete slots[id]; if (!loaded) tombstones.add(id); }
    subs.forEach((fn) => fn());
    // A drop is rare + high-value — write immediately so nav-away can't lose
    // it. Gate on the initial read so we don't overwrite a sidecar we haven't
    // merged yet; the merge in load() keeps this change once the read lands.
    if (loaded) save(); else load().then(save);
  }

  // ── Image downscale ─────────────────────────────────────────────────────
  // Encode through a canvas so the sidecar carries resized bytes, not the
  // raw upload. Longest side is capped at 2× the slot's rendered width
  // (retina) and at MAX_DIM. WebP keeps alpha and is ~10× smaller than PNG
  // for photos, so there's no need for per-image format picking.
  async function toDataUrl(file, targetW) {
    const bitmap = await createImageBitmap(file);
    try {
      const cap = Math.min(MAX_DIM, Math.max(1, Math.round(targetW * 2)) || MAX_DIM);
      const scale = Math.min(1, cap / Math.max(bitmap.width, bitmap.height));
      const w = Math.max(1, Math.round(bitmap.width * scale));
      const h = Math.max(1, Math.round(bitmap.height * scale));
      const canvas = document.createElement('canvas');
      canvas.width = w; canvas.height = h;
      canvas.getContext('2d').drawImage(bitmap, 0, 0, w, h);
      return canvas.toDataURL('image/webp', 0.85);
    } finally {
      bitmap.close && bitmap.close();
    }
  }

  // ── Custom element ──────────────────────────────────────────────────────
  const stylesheet =
    // Fill the container by default: slots are usually placed inside a
    // sized wrapper (a hero frame, a grid cell, an inset:0 layer) and are
    // expected to take that box — a fixed intrinsic size would render as
    // a small tile in the corner of a full-bleed wrapper instead.
    // aspect-ratio is the companion fallback that keeps a bare slot
    // visible when the parent's height is indefinite: height:100%
    // resolves to auto there, and the ratio then derives height from
    // width instead of letting the slot collapse to zero height.
    // Explicit width/height on the element override all of this.
    // color:inherit (not a fixed near-black): the placeholder chrome —
    // empty-state icon/caption (currentColor) and the dashed ring — must
    // read on dark decks too, and the slide's own text color is the one
    // color guaranteed to contrast with the slide background. The soft
    // look comes from opacity on those parts, not from a baked-in alpha.
    ':host{display:block;position:relative;' +
    '  font:13px/1.3 system-ui,-apple-system,sans-serif;' +
    '  width:100%;height:100%;aspect-ratio:3/2}' +
    '.empty .cap,.empty .sub{opacity:.75}' +
    '.frame{position:absolute;inset:0;overflow:hidden;background:rgba(127,127,127,.08)}' +
    // .frame img (clipped) and .spill (unclipped ghost + handles) share the
    // same left/top/width/height in frame-%, computed by _applyView(), so the
    // inside-mask crop and the outside-mask spill stay pixel-aligned.
    '.frame img{position:absolute;max-width:none;transform:translate(-50%,-50%);' +
    '  -webkit-user-drag:none;user-select:none;touch-action:none}' +
    // Reframe mode (double-click): the full image spills past the mask. The
    // spill layer is sized to the IMAGE bounds so its corners are where the
    // resize handles belong. The ghost <img> inside is translucent; the real
    // clipped <img> underneath shows the opaque in-mask crop.
    // popover=manual promotes the spill to the top layer on reframe, so it is
    // not clipped by any overflow:hidden / clip-path / scroll-container
    // ancestor (a plain z-index can't escape overflow clipping). UA popover
    // defaults (inset:0;margin:auto) are reset; _applyView sets viewport px.
    '.spill{position:fixed;margin:0;inset:auto;border:0;padding:0;background:transparent;' +
    '  overflow:visible;transform:translate(-50%,-50%);z-index:1;cursor:grab;touch-action:none}' +
    ':host([data-panning]) .spill{cursor:grabbing}' +
    '.spill .ghost{position:absolute;inset:0;width:100%;height:100%;opacity:.35;' +
    '  pointer-events:none;-webkit-user-drag:none;user-select:none;' +
    '  box-shadow:0 0 0 1px rgba(0,0,0,.2),0 12px 32px rgba(0,0,0,.2)}' +
    '.spill .handle{position:absolute;width:12px;height:12px;border-radius:50%;' +
    '  background:#fff;box-shadow:0 0 0 1.5px #c96442,0 1px 3px rgba(0,0,0,.3);' +
    '  transform:translate(-50%,-50%)}' +
    '.spill .handle[data-c=nw]{left:0;top:0;cursor:nwse-resize}' +
    '.spill .handle[data-c=ne]{left:100%;top:0;cursor:nesw-resize}' +
    '.spill .handle[data-c=sw]{left:0;top:100%;cursor:nesw-resize}' +
    '.spill .handle[data-c=se]{left:100%;top:100%;cursor:nwse-resize}' +
    ':host([data-reframe]){z-index:10}' +
    ':host([data-reframe]) .frame{box-shadow:0 0 0 2px #c96442}' +
    '.empty{position:absolute;inset:0;display:flex;flex-direction:column;align-items:center;' +
    '  justify-content:center;gap:6px;text-align:center;padding:12px;box-sizing:border-box;' +
    '  cursor:pointer;user-select:none}' +
    '.empty svg{opacity:.45}' +
    '.empty .cap{max-width:90%;font-weight:500;letter-spacing:.01em}' +
    '.empty .sub{font-size:11px}' +
    '.empty .sub u{text-underline-offset:2px}' +
    '.empty:hover .sub{opacity:1}' +
    ':host([data-over]) .frame{outline:2px solid #c96442;outline-offset:-2px;' +
    '  background:rgba(201,100,66,.10)}' +
    '.ring{position:absolute;inset:0;pointer-events:none;border:1.5px dashed currentColor;' +
    '  opacity:.35;transition:border-color .12s,opacity .12s}' +
    ':host([data-over]) .ring{border-color:#c96442;opacity:1}' +
    ':host([data-filled]) .ring{display:none}' +
    // Controls overlay INSIDE the frame, pinned to the top-right corner, so
    // a full-bleed slot in an overflow:hidden container still shows them
    // (the old below-mask placement got clipped). Credit sits bottom-left,
    // so top-right avoids collision. The blurred pill background keeps them
    // legible over the image.
    // The UA [popover] base rule styles the element in EVERY state (only
    // display:none is gated on :not(:popover-open), and the display:flex
    // below overrides that) — so the UA resets live HERE, like .spill's,
    // or the ordinary hover-state strip renders as a bordered Canvas box
    // centered by margin:auto. inset:auto precedes top/right (shorthand).
    '.ctl{position:absolute;inset:auto;top:8px;right:8px;margin:0;border:0;padding:0;' +
    '  background:transparent;overflow:visible;' +
    '  display:flex;gap:6px;opacity:0;pointer-events:none;transition:opacity .12s;z-index:2;' +
    '  white-space:nowrap}' +
    // While reframing, the spill owns the top layer and would swallow every
    // click on the in-frame controls. Promoting .ctl into the top layer
    // ABOVE the spill (shown after it — later popovers stack higher) keeps
    // Edit-as-toggle and Replace clickable mid-reframe. _applyView pins it
    // to the frame's top-right in viewport px (translateX(-100%)
    // right-aligns against the computed left edge); inset:auto clears the
    // base rule's top/right so the inline left/top position it alone.
    '.ctl:popover-open{position:fixed;inset:auto;transform:translateX(-100%)}' +
    ':host([data-filled][data-editable]:hover) .ctl,:host([data-reframe]) .ctl' +
    '  {opacity:1;pointer-events:auto}' +
    '.ctl button{appearance:none;border:0;border-radius:6px;padding:5px 10px;cursor:pointer;' +
    '  background:rgba(0,0,0,.65);color:#fff;font:11px/1 system-ui,-apple-system,sans-serif;' +
    '  backdrop-filter:blur(6px)}' +
    '.ctl button:hover{background:rgba(0,0,0,.8)}' +
    '.err{position:absolute;left:8px;bottom:8px;right:8px;color:#b3261e;font-size:11px;' +
    '  background:rgba(255,255,255,.85);padding:4px 6px;border-radius:5px;pointer-events:none}' +
    // Replacement in flight: after a src swap the browser keeps painting
    // the PREVIOUS image until the new one decodes, so a Replace would
    // flash the old photo and then pop. Hide the stale frame (visibility,
    // not display — _applyView geometry still applies) and spin until the
    // new image reports in (load/error clears data-swapping).
    ':host([data-swapping]) .frame img{visibility:hidden}' +
    '.loading{position:absolute;inset:0;display:none;align-items:center;' +
    '  justify-content:center;pointer-events:none}' +
    ':host([data-swapping]) .loading{display:flex}' +
    '.loading::after{content:"";width:22px;height:22px;border-radius:50%;' +
    '  border:2px solid rgba(127,127,127,.25);border-top-color:currentColor;' +
    '  animation:om-slot-spin .7s linear infinite}' +
    '@keyframes om-slot-spin{to{transform:rotate(360deg)}}' +
    // Reduced motion: the static two-tone ring still reads as "working".
    '@media (prefers-reduced-motion:reduce){.loading::after{animation:none}}' +
    '.credit{position:absolute;left:6px;bottom:6px;max-width:calc(100% - 12px);display:none;' +
    '  padding:3px 7px;border-radius:5px;background:rgba(0,0,0,.55);color:#fff;' +
    '  font:10px/1.2 system-ui,-apple-system,sans-serif;text-decoration:none;' +
    '  white-space:nowrap;overflow:hidden;text-overflow:ellipsis;backdrop-filter:blur(6px)}' +
    // The credit is a SPAN holding one or two <a>s (Unsplash's prescribed
    // form links the photographer AND Unsplash) — anchors style inline so
    // the overlay reads as one line of text.
    '.credit a{color:inherit;text-decoration:none}' +
    '.credit a:hover,.credit a:focus-visible{text-decoration:underline}' +
    ':host([data-filled][data-credit]) .credit{display:block}' +
    // Exports must ship JUST the image — no hover controls, no credit chip
    // (the host marks <html data-om-exporting> for the capture window; the
    // page-level hide script can't reach shadow DOM, this rule can).
    ':host-context([data-om-exporting]) .ctl,' +
    ':host-context([data-om-exporting]) .credit{display:none !important}' +
    // Print must ship just the image too: the hover-gated controls can be
    // mid-hover when print() fires, and the credit chip is screen chrome —
    // the same rule the capture window gets, keyed on print media instead
    // of the host's data-om-exporting mark (the print path sets no mark).
    '@media print{.ctl,.credit{display:none !important}}' +
    // No export-window mask rules here on purpose: the export capture
    // releases the replacement mask by REMOVING data-swapping (the
    // shadow-root pass in pages/export/shared.ts HIDE_EXPORT_CHROME_SCRIPT)
    // — attribute removal works in every engine (:host-context is
    // Chromium-only), is scoped by construction to slots actually
    // mid-swap, and hides the spinner through the same gate. A masked img
    // would otherwise be silently dropped from PPTX decks (the capture
    // walk skips visibility:hidden imgs).
    // Attribution error tile: REPLACES the photo when an Unsplash src has
    // no credit attribute — rendering the photo uncredited is the terms
    // violation, so the photo must not appear at all.
    // Calm and neutral on purpose (review feedback): the tile informs the
    // user; the fix instructions are machine-facing (usage docblock, tool
    // description, and the turn-end scan's bounce copy name the attributes
    // for the agent).
    '.attr-error{position:absolute;inset:0;display:none;flex-direction:column;align-items:center;' +
    '  justify-content:center;gap:6px;text-align:center;padding:12px;box-sizing:border-box;' +
    '  background:#f2f1ef;color:#6e6c66;user-select:none;' +
    '  font:13px/1.45 system-ui,-apple-system,sans-serif}' +
    '.attr-error svg{opacity:.55}' +
    '.attr-error .cap{max-width:92%;font-weight:500;letter-spacing:.01em}' +
    ':host([data-attribution-error]) .attr-error{display:flex}' +
    ':host([data-attribution-error]) .ring{display:none}';

  const icon =
    '<svg width="28" height="28" viewBox="0 0 24 24" fill="none" stroke="currentColor" ' +
    'stroke-width="1.6" stroke-linecap="round" stroke-linejoin="round">' +
    '<rect x="3" y="3" width="18" height="18" rx="2"/><circle cx="8.5" cy="8.5" r="1.5"/>' +
    '<path d="m21 15-5-5L5 21"/></svg>';

  const warnIcon =
    '<svg width="28" height="28" viewBox="0 0 24 24" fill="none" stroke="currentColor" ' +
    'stroke-width="1.6" stroke-linecap="round" stroke-linejoin="round">' +
    '<path d="m21.73 18-8-14a2 2 0 0 0-3.46 0l-8 14A2 2 0 0 0 4 21h16a2 2 0 0 0 1.73-3"/>' +
    '<path d="M12 9v4"/><path d="M12 17h.01"/></svg>';

  class ImageSlot extends HTMLElement {
    static get observedAttributes() {
      return ['shape', 'radius', 'mask', 'fit', 'placeholder', 'src', 'id', 'credit', 'credit-href'];
    }

    /** Duplicate-slide hook (called by deck-stage, see its
     *  _remintDuplicateIds): copy this id's stored image, if any, under a
     *  freshly minted key and return that key — so a duplicated slide's
     *  slot keeps its dropped photo instead of reverting to the
     *  placeholder. 'isFree' is the caller's uniqueness check (document
     *  ids); candidates must ALSO be unused in the sidecar, which can
     *  hold keys from other pages sharing the project root. (An EMPTY
     *  slot on another page leaves no sidecar entry, so its id is not
     *  detectable here — a minted key can collide with it and that slot
     *  would show this photo. Same blast radius as two pages reusing an
     *  id by hand, which the shared sidecar already permits.) Returns null
     *  when no id could be minted (caller strips the id, today's
     *  behavior). */
    static cloneSlot(fromId, isFree) {
      if (typeof fromId !== 'string' || !fromId) return null;
      // Pre-hydration the store can't veto candidates or source the copy
      // — degrade to the strip (today's behavior) rather than mint
      // against keys we can't see yet. Any rendered (= droppable) slot
      // means load() has already settled.
      if (!loaded) return null;
      const stem = fromId.replace(/-\d+$/, '') || fromId;
      for (let n = 2; n < 100; n++) {
        const toId = stem + '-' + n;
        if (toId === fromId) continue;
        if (slots[toId] !== undefined) {
          // Reuse a key holding this exact value (bytes AND crop) if no
          // live element here owns it — a duplicate op the host refused
          // after minting leaves such a key behind, and reusing keeps
          // refused retries from accumulating one orphaned copy per
          // attempt. Full equality (not just bytes) so a byte-identical
          // key another PAGE owns with its own crop is stepped past, not
          // adopted or rewritten. (Entries without .u never match.)
          const prev = getSlot(toId);
          const cur = getSlot(fromId);
          if (!(prev && cur && prev.u && prev.u === cur.u &&
                prev.s === cur.s && prev.x === cur.x && prev.y === cur.y &&
                (typeof isFree !== 'function' || isFree(toId)))) continue;
          return toId;
        }
        if (typeof isFree === 'function' && !isFree(toId)) continue;
        const v = getSlot(fromId);
        if (v) setSlot(toId, Object.assign({}, v));
        return toId;
      }
      return null;
    }

    constructor() {
      super();
      // clonable: rail thumbnails deep-clone slides and carry this shadow
      // along; reuse an already-cloned root so upgrade-after-clone works.
      // (Deliberately NOT serializable — a getHTML consumer would embed
      // multi-MB sidecar data-URLs into serialized page HTML.)
      const root = this.shadowRoot ||
        this.attachShadow({ mode: 'open', clonable: true });
      // .spill and .ctl sit OUTSIDE .frame so overflow:hidden + border-radius
      // on the frame (circle, pill, rounded) can't clip them.
      root.innerHTML =
        '<style>' + stylesheet + '</style>' +
        '<div class="frame" part="frame">' +
        '  <img part="image" alt="" draggable="false" style="display:none">' +
        '  <div class="empty" part="empty">' + icon +
        '    <div class="cap"></div>' +
        '    <div class="sub">or <u>browse files</u></div></div>' +
        '  <div class="attr-error" part="attribution-error">' + warnIcon +
        '    <div class="cap">This photo needs attribution</div></div>' +
        '  <div class="loading" part="loading"></div>' +
        '  <div class="ring" part="ring"></div>' +
        '</div>' +
        // Outside .frame, like .spill/.ctl — the frame's overflow:hidden +
        // border-radius/clip-path would cut the credit off on circle/pill/mask.
        // A SPAN, not an <a>: the prescribed Unsplash credit holds two links
        // (photographer + Unsplash), built per-render in _render().
        '<span class="credit" part="credit"></span>' +
        '<div class="spill" popover="manual" data-dc-edit-transparent>' +
        '  <img class="ghost" alt="" draggable="false">' +
        '  <div class="handle" data-c="nw"></div><div class="handle" data-c="ne"></div>' +
        '  <div class="handle" data-c="sw"></div><div class="handle" data-c="se"></div>' +
        '</div>' +
        // data-dc-edit-transparent: the DC editor's edit-mode picker lets
        // clicks through for chrome marked with it (EDIT_TRANSPARENT_SEL)
        // — without it, Replace/Edit clicks in Edit mode are swallowed by
        // element selection and the controls look dead.
        '<div class="ctl" popover="manual" data-dc-edit-transparent><button data-act="replace" title="Replace image">Replace</button>' +
        '  <button data-act="edit" title="Reframe image">Edit</button></div>' +
        '<input type="file" accept="' + ACCEPT.join(',') + '" hidden>';
      this._frame = root.querySelector('.frame');
      this._ring = root.querySelector('.ring');
      this._img = root.querySelector('.frame img');
      this._empty = root.querySelector('.empty');
      this._cap = root.querySelector('.cap');
      this._sub = root.querySelector('.sub');
      this._spill = root.querySelector('.spill');
      this._ctl = root.querySelector('.ctl');
      this._credit = root.querySelector('.credit');
      this._attrError = root.querySelector('.attr-error');
      // Credit clicks open the link, not browse/reframe.
      this._credit.addEventListener('click', (e) => e.stopPropagation());
      this._credit.addEventListener('dblclick', (e) => e.stopPropagation());
      this._ghost = root.querySelector('.ghost');
      this._err = null;
      this._input = root.querySelector('input');
      this._depth = 0;
      this._gen = 0;
      // Encode-in-flight marker (the owning _ingest generation): while set,
      // the same-src "nothing in flight" clear in _render must not fire —
      // the stored value still points at the OLD image until the encode
      // lands, so that clear would unmask the stale image mid-replace.
      this._swapGen = 0;
      // Render-owned swap in flight: set when _render assigns a new src,
      // cleared only by the img's own load/error (or the empty branch).
      // img.complete CANNOT stand in for this — setting src only QUEUES
      // the current-request swap (a microtask), so synchronously after an
      // assignment, complete still reports the OLD settled request. The
      // pick path does exactly that: the host sets src, credit, and
      // credit-href back-to-back in one task, and renders #2/#3 would
      // read the stale complete === true and drop the mask one render
      // after it was set.
      this._loadPending = false;
      // See _render's empty branch: a transient attribution-error wipe of a
      // showing image must make the follow-up render a replacement (spinner),
      // not a first fill (blank frame).
      this._hidShowing = false;
      this._view = { s: 1, x: 0, y: 0 };
      this._subFn = () => this._render();
      // Shadow-DOM listeners live with the shadow DOM — bound once here so
      // disconnect/reconnect (e.g. React remount) doesn't stack handlers.
      this._empty.addEventListener('click', () => this._input.click());
      root.addEventListener('click', (e) => {
        const act = e.target && e.target.getAttribute && e.target.getAttribute('data-act');
        if (!act) return;
        // The hidden controls are opacity-0 but still tabbable — without
        // this gate a keyboard user could drive them on a read-only share
        // link (mirrors the dblclick handler's editable gate).
        if (!this.hasAttribute('data-editable')) return;
        if (act === 'replace') {
          this._exitReframe(true);
          // Host-owned picker (Unsplash modal; it also offers local import).
          this.dispatchEvent(new CustomEvent('image-slot:pick', {
            bubbles: true, composed: true, detail: { id: this.id || null }
          }));
        }
        if (act === 'edit') {
          if (!this._reframes()) return;
          if (this.hasAttribute('data-reframe')) this._exitReframe(true);
          else this._enterReframe();
        }
      });
      this._input.addEventListener('change', () => {
        const f = this._input.files && this._input.files[0];
        if (f) this._ingest(f);
        this._input.value = '';
      });
      // naturalWidth/Height aren't known until load — re-apply so the cover
      // baseline is computed from real dimensions, not the 100%×100% fallback.
      // load/error also release the replacement-in-flight mask (via the
      // single discipline in _releaseMask): the swap is only revealed once
      // the new image can actually paint (on error the frame shows its
      // background, same as a fresh slot with a broken src).
      this._img.addEventListener('load', () => {
        this._loadPending = false;
        this._releaseMask(true);
        this._applyView();
      });
      this._img.addEventListener('error', () => {
        this._loadPending = false;
        this._releaseMask(true);
      });
      // Gated only on editable — any filled slot can be repositioned/scaled,
      // regardless of fit. Share links (no writeFile) stay static.
      this.addEventListener('dblclick', (e) => {
        if (!this.hasAttribute('data-editable') || !this._reframes()) return;
        e.preventDefault();
        if (this.hasAttribute('data-reframe')) this._exitReframe(true);
        else this._enterReframe();
      });
      // Pan + resize both originate on the spill layer. A handle pointerdown
      // drives an aspect-locked resize anchored at the opposite corner; any
      // other pointerdown on the spill pans. Offsets are frame-% so a
      // reframed slot survives responsive resize / PPTX export.
      this._spill.addEventListener('pointerdown', (e) => {
        if (e.button !== 0 || !this.hasAttribute('data-reframe')) return;
        e.preventDefault();
        e.stopPropagation();
        this._spill.setPointerCapture(e.pointerId);
        const rect = this.getBoundingClientRect();
        const fw = rect.width || 1, fh = rect.height || 1;
        const corner = e.target.getAttribute && e.target.getAttribute('data-c');
        let move;
        if (corner) {
          // Resize about the OPPOSITE corner. Viewport-px throughout (rect
          // fw/fh, not clientWidth) so the math survives a transform:scale()
          // ancestor — deck_stage renders slides scaled-to-fit.
          const iw = this._img.naturalWidth || 1, ih = this._img.naturalHeight || 1;
          const contain = (this.getAttribute('fit') || 'cover').toLowerCase() === 'contain';
          const base = contain ? Math.min(fw / iw, fh / ih) : Math.max(fw / iw, fh / ih);
          const sx = corner.includes('e') ? 1 : -1;
          const sy = corner.includes('s') ? 1 : -1;
          const s0 = this._view.s;
          const w0 = iw * base * s0, h0 = ih * base * s0;
          const cx0 = (50 + this._view.x) / 100 * fw;
          const cy0 = (50 + this._view.y) / 100 * fh;
          const ox = cx0 - sx * w0 / 2, oy = cy0 - sy * h0 / 2;
          const diag0 = Math.hypot(w0, h0);
          const ux = sx * w0 / diag0, uy = sy * h0 / diag0;
          move = (ev) => {
            const proj = (ev.clientX - rect.left - ox) * ux +
                         (ev.clientY - rect.top - oy) * uy;
            const s = clampS(s0 * proj / diag0);
            const d = diag0 * s / s0;
            this._view.s = s;
            this._view.x = (ox + ux * d / 2) / fw * 100 - 50;
            this._view.y = (oy + uy * d / 2) / fh * 100 - 50;
            this._clampView();
            this._applyView();
          };
        } else {
          this.setAttribute('data-panning', '');
          const start = { px: e.clientX, py: e.clientY, x: this._view.x, y: this._view.y };
          move = (ev) => {
            this._view.x = start.x + (ev.clientX - start.px) / fw * 100;
            this._view.y = start.y + (ev.clientY - start.py) / fh * 100;
            this._clampView();
            this._applyView();
          };
        }
        const up = () => {
          try { this._spill.releasePointerCapture(e.pointerId); } catch {}
          this._spill.removeEventListener('pointermove', move);
          this._spill.removeEventListener('pointerup', up);
          this._spill.removeEventListener('pointercancel', up);
          this.removeAttribute('data-panning');
          this._dragUp = null;
        };
        // Stashed so _exitReframe (Escape / outside-click mid-drag) can
        // tear the capture + listeners down synchronously.
        this._dragUp = up;
        this._spill.addEventListener('pointermove', move);
        this._spill.addEventListener('pointerup', up);
        this._spill.addEventListener('pointercancel', up);
      });
      // Wheel zoom stays available inside reframe mode as a trackpad nicety —
      // zooms toward the cursor (offset' = cursor·(1-k) + offset·k).
      this.addEventListener('wheel', (e) => {
        if (!this.hasAttribute('data-reframe')) return;
        e.preventDefault();
        const r = this.getBoundingClientRect();
        const cx = (e.clientX - r.left) / r.width * 100 - 50;
        const cy = (e.clientY - r.top) / r.height * 100 - 50;
        const prev = this._view.s;
        const next = clampS(prev * Math.pow(1.0015, -e.deltaY));
        if (next === prev) return;
        const k = next / prev;
        this._view.s = next;
        this._view.x = cx * (1 - k) + this._view.x * k;
        this._view.y = cy * (1 - k) + this._view.y * k;
        this._clampView();
        this._applyView();
      }, { passive: false });
    }

    connectedCallback() {
      // Warn once per page — an id-less slot works for the session but
      // cannot persist, and two id-less slots would share nothing.
      if (!this.id && !ImageSlot._warned) {
        ImageSlot._warned = true;
        console.warn('<image-slot> without an id will not persist its dropped image.');
      }
      this.addEventListener('dragenter', this);
      this.addEventListener('dragover', this);
      this.addEventListener('dragleave', this);
      this.addEventListener('drop', this);
      subs.add(this._subFn);
      // The host may inject window.omelette.writeFile AFTER the first render;
      // re-render on hover so the editable-gated controls reliably appear.
      this.addEventListener('pointerenter', this._subFn);
      // width%/height% in _applyView encode the frame aspect at call time —
      // a host resize (responsive grid, pane divider) would stretch the
      // image until the next _render. Re-render on size change: _render()
      // re-seeds _view from stored before clamp/apply, so a shrink→grow
      // cycle round-trips instead of ratcheting x/y toward the narrower
      // frame's clamp range.
      this._ro = new ResizeObserver(() => this._render());
      this._ro.observe(this);
      load();
      this._render();
    }

    disconnectedCallback() {
      subs.delete(this._subFn);
      this.removeEventListener('pointerenter', this._subFn);
      this.removeEventListener('dragenter', this);
      this.removeEventListener('dragover', this);
      this.removeEventListener('dragleave', this);
      this.removeEventListener('drop', this);
      if (this._ro) { this._ro.disconnect(); this._ro = null; }
      // commit=false: a disconnect is not a user intent — committing here
      // would persist whatever half-finished drag a React remount or DOM
      // splice happened to interrupt. Deliberate exits commit on their own
      // paths (Escape/click-out/toggle), and unloads commit via pagehide.
      this._exitReframe(false);
    }

    _enterReframe() {
      if (this.hasAttribute('data-reframe')) return;
      this.setAttribute('data-reframe', '');
      this._signalReframe(true);
      // Best-effort commit when the document unloads mid-reframe (a host
      // navigation racing the enter signal, a manual reload, tab close):
      // the sidecar write rides the host bridge, which outlives this
      // document, so the crop survives even though the mode dies with the
      // DOM. Held on the instance so _exitReframe detaches exactly what
      // was attached.
      this._pagehide = () => { this._exitReframe(true); flushNow(); };
      window.addEventListener('pagehide', this._pagehide);
      // Promote spill to the top layer, then keep it pinned over the frame:
      // scroll/resize cover the common cases, and a per-frame rect check
      // catches layout shifts that fire neither (an image above finishing
      // load, streamed DOM pushing the slot down, an ancestor transform
      // change) so the overlay can't detach from the frame.
      try { this._spill.showPopover(); } catch {}
      // After the spill, so the controls stack above it in the top layer.
      try { this._ctl.showPopover(); } catch {}
      this._reposition = () => { if (this.hasAttribute('data-reframe')) this._applyView(); };
      window.addEventListener('scroll', this._reposition, true);
      window.addEventListener('resize', this._reposition);
      this._lastRect = '';
      this._watch = () => {
        if (!this.hasAttribute('data-reframe')) return;
        const r = this.getBoundingClientRect();
        const key = r.left + ',' + r.top + ',' + r.width + ',' + r.height;
        if (key !== this._lastRect) { this._lastRect = key; this._applyView(); }
        this._watchId = requestAnimationFrame(this._watch);
      };
      this._watchId = requestAnimationFrame(this._watch);
      this._applyView();
      // Close on click outside (the spill handler stopPropagation()s so
      // in-image drags don't reach this) and on Escape. Listeners are held
      // on the instance so _exitReframe / disconnectedCallback can detach
      // exactly what was attached.
      this._outside = (e) => {
        if (e.composedPath && e.composedPath().includes(this)) return;
        this._exitReframe(true);
      };
      this._esc = (e) => { if (e.key === 'Escape') this._exitReframe(true); };
      document.addEventListener('pointerdown', this._outside, true);
      document.addEventListener('keydown', this._esc, true);
    }

    _exitReframe(commit) {
      if (!this.hasAttribute('data-reframe')) return;
      if (this._dragUp) this._dragUp();
      this.removeAttribute('data-reframe');
      this.removeAttribute('data-panning');
      if (this._outside) document.removeEventListener('pointerdown', this._outside, true);
      if (this._esc) document.removeEventListener('keydown', this._esc, true);
      this._outside = this._esc = null;
      if (this._reposition) {
        window.removeEventListener('scroll', this._reposition, true);
        window.removeEventListener('resize', this._reposition);
        this._reposition = null;
      }
      if (this._watchId) { cancelAnimationFrame(this._watchId); this._watchId = 0; }
      if (this._pagehide) {
        window.removeEventListener('pagehide', this._pagehide);
        this._pagehide = null;
      }
      try { this._spill.hidePopover(); } catch {}
      try { this._ctl.hidePopover(); } catch {}
      this._ctl.style.left = ''; this._ctl.style.top = '';
      if (commit) this._commitView();
      this._signalReframe(false);
    }

    // Reframe state lives only in this DOM until commit, invisible to the
    // host's dirty signals — announce enter/exit so the host can hold
    // auto-reloads for exactly the gesture (the guest bundle forwards
    // image-slot:reframe to the host as imageSlotReframe). Dispatched on
    // the element (composed, so it escapes shadow roots) while connected;
    // a disconnected exit (disconnectedCallback) falls back to document so
    // the host still hears it.
    _signalReframe(active) {
      const target = this.isConnected ? this : document;
      target.dispatchEvent(new CustomEvent('image-slot:reframe', {
        bubbles: true, composed: true,
        detail: { active: active, id: this.id || null }
      }));
    }

    // Public: host's "Import from computer" calls this to run local browse.
    openFilePicker() { this._exitReframe(true); this._input.click(); }

    // A src write is a newer intent for this slot's content — the host
    // pick path (setImageSlotImage) or an agent edit — so it must win
    // over any encode still in flight from an earlier drop: left live,
    // that encode lands later, passes _ingest's gen guard, and its
    // setSlot silently overwrites the pick (the stored value shadows
    // src in _render). Bumping _gen kills the encode before its own
    // _swapGen clear runs, so clear the dead claim here too — otherwise
    // _releaseMask (gated on !_swapGen) never fires and the pick's
    // spinner is stranded. src ONLY: the pick sets credit/credit-href
    // in the same task, and clearing _swapGen on those would let the
    // same-src branch unmask the old image mid-encode.
    attributeChangedCallback(name, oldVal, newVal) {
      if (name === 'src' && oldVal !== newVal) {
        this._gen++;
        this._swapGen = 0;
      }
      if (this.shadowRoot) this._render();
    }

    // handleEvent — one listener object for all four drag events keeps the
    // add/remove symmetric and the depth counter correct.
    handleEvent(e) {
      if (e.type === 'dragenter' || e.type === 'dragover') {
        // Without preventDefault the browser never fires 'drop'.
        e.preventDefault();
        e.stopPropagation();
        if (e.dataTransfer) e.dataTransfer.dropEffect = 'copy';
        if (e.type === 'dragenter') this._depth++;
        this.setAttribute('data-over', '');
      } else if (e.type === 'dragleave') {
        // dragenter/leave fire for every descendant crossing — count depth
        // so hovering the icon inside the empty state doesn't flicker.
        if (--this._depth <= 0) { this._depth = 0; this.removeAttribute('data-over'); }
      } else if (e.type === 'drop') {
        e.preventDefault();
        e.stopPropagation();
        this._depth = 0;
        this.removeAttribute('data-over');
        const f = e.dataTransfer && e.dataTransfer.files && e.dataTransfer.files[0];
        if (f) this._ingest(f);
      }
    }

    async _ingest(file) {
      this._setError(null);
      if (!file || ACCEPT.indexOf(file.type) < 0) {
        this._setError('Drop a PNG, JPEG, WebP, or AVIF image.');
        return;
      }
      // toDataUrl can take hundreds of ms on a large photo. A Clear or a
      // newer drop during that window would be clobbered when this await
      // resumes — bump + capture a generation so stale encodes bail.
      const gen = ++this._gen;
      // Replacing a shown image: surface the swap through the encode too,
      // not just the decode — otherwise the old photo sits there with no
      // feedback while the canvas re-encode runs. An empty slot keeps its
      // placeholder (no spinner) until the encode lands, as before.
      // _swapGen guards the mask against re-renders DURING the encode
      // (pointerenter, ResizeObserver, another slot's store write): the
      // stored value still resolves to the old image there, so _render's
      // same-src clear would otherwise unmask it mid-replace.
      if (this.hasAttribute('data-filled')) {
        this.setAttribute('data-swapping', '');
        this._swapGen = gen;
      }
      try {
        const w = this.clientWidth || this.offsetWidth || MAX_DIM;
        const url = await toDataUrl(file, w);
        if (gen !== this._gen) return;
        // Only exit reframe once the new image is in hand — a rejected type
        // or decode failure leaves the in-progress crop untouched.
        this._exitReframe(false);
        // Clear BEFORE setSlot: its synchronous re-render must see no
        // pending encode, so a byte-identical re-upload (same data URL, no
        // load event coming) still clears the mask via the complete branch.
        this._swapGen = 0;
        const val = { u: url, s: 1, x: 0, y: 0 };
        setSlot(this.id || '', val);
        // Keep a session-local copy for id-less slots so the drop still
        // shows, even though it cannot persist.
        if (!this.id) { this._local = val; this._render(); }
      } catch (err) {
        if (gen !== this._gen) return;
        this._swapGen = 0;
        // Reveal the kept old image — unless another replacement (a
        // remote pick's src swap) is still in flight, in which case the
        // mask stays until THAT image settles (its load/error releases).
        this._releaseMask();
        this._setError('Could not read that image.');
        console.warn('<image-slot> ingest failed:', err);
      }
    }

    _setError(msg) {
      if (this._err) { this._err.remove(); this._err = null; }
      if (!msg) return;
      const d = document.createElement('div');
      d.className = 'err'; d.textContent = msg;
      this.shadowRoot.appendChild(d);
      this._err = d;
      setTimeout(() => { if (this._err === d) { d.remove(); this._err = null; } }, 3000);
    }

    // Reframing (pan/resize) is available on any filled slot — the user can
    // always reposition/scale. `fit` only sets the initial baseline (see
    // _geom): contain starts fully-visible, cover starts frame-filling.
    _reframes() {
      return this.hasAttribute('data-filled');
    }

    // The single release discipline for the replacement-in-flight mask
    // (data-swapping). The mask comes off only when BOTH hold:
    //  - no encode is pending (_swapGen) — mid-encode the stored value
    //    still resolves to the old image, so any reveal paints it;
    //  - the frame img has settled on its current src — an unsettled src
    //    means some replacement is still in flight (e.g. a remote pick),
    //    whoever started it, and revealing would paint the previous
    //    frame. The load/error listeners pass settled=true (the event IS
    //    the settlement signal, per spec complete is true by then);
    //    other callers rely on the complete flag (covers loaded AND
    //    failed).
    // Every release path funnels through here EXCEPT _render's empty
    // branch (the img is being cleared — nothing will ever settle).
    _releaseMask(settled) {
      if (
        !this._swapGen &&
        !this._loadPending &&
        (settled || this._img.complete)
      ) {
        this.removeAttribute('data-swapping');
      }
    }

    // Baseline geometry, shared by clamp/apply/resize. `base` is the scale at
    // view-scale s=1: cover = fill the frame (overflow on the looser axis),
    // contain = fit fully inside (letterboxed). Zooming a contain image past
    // s where it overflows naturally becomes a crop. Null until the img has
    // loaded (naturalWidth is 0 before that) or when the slot has no layout
    // box — ResizeObserver fires with a 0×0 rect under display:none, and
    // clamping against a degenerate 1×1 frame would silently pull the stored
    // pan toward zero.
    _geom() {
      const iw = this._img.naturalWidth, ih = this._img.naturalHeight;
      const fw = this.clientWidth, fh = this.clientHeight;
      if (!iw || !ih || !fw || !fh) return null;
      const contain = (this.getAttribute('fit') || 'cover').toLowerCase() === 'contain';
      const base = contain
        ? Math.min(fw / iw, fh / ih)
        : Math.max(fw / iw, fh / ih);
      return { iw, ih, fw, fh, base };
    }

    _clampView() {
      // Pan range on each axis is half the overflow past the frame edge.
      const g = this._geom();
      if (!g) return;
      const mx = Math.max(0, (g.iw * g.base * this._view.s / g.fw - 1) * 50);
      const my = Math.max(0, (g.ih * g.base * this._view.s / g.fh - 1) * 50);
      this._view.x = Math.max(-mx, Math.min(mx, this._view.x));
      this._view.y = Math.max(-my, Math.min(my, this._view.y));
    }

    _applyView() {
      const g = this._geom();
      // Top-layer controls: pin to the frame's top-right in viewport px
      // (the same 8px inset as the in-frame layout; unscaled — top-layer UI
      // reads as chrome, not page content). BEFORE the geometry branch:
      // placement needs only the frame rect, and a not-yet-loaded or broken
      // src must not leave the promoted strip floating unpositioned. Gated
      // on the popover actually being open: without the Popover API,
      // showPopover() threw (swallowed in _enterReframe), .ctl stays in
      // its in-frame absolute layout, and viewport-px coordinates would
      // shove it off-frame — and matches(':popover-open') itself throws
      // there (unknown pseudo-class), hence the try/catch.
      if (this.hasAttribute('data-reframe')) {
        let onTop = false;
        try { onTop = this._ctl.matches(':popover-open'); } catch {}
        if (onTop) {
          const r = this.getBoundingClientRect();
          this._ctl.style.left = (r.right - 8) + 'px';
          this._ctl.style.top = (r.top + 8) + 'px';
        }
      }
      if (!g) {
        // Dimensions not known yet (before img load) — centered fit so there
        // is no flash of an unpositioned image before the geometry lands.
        const contain = (this.getAttribute('fit') || 'cover').toLowerCase() === 'contain';
        this._img.style.width = '100%';
        this._img.style.height = '100%';
        this._img.style.left = '50%';
        this._img.style.top = '50%';
        this._img.style.objectFit = contain ? 'contain' : 'cover';
        return;
      }
      // Baseline (cover-fill or contain-fit) × view scale. Width/height and
      // left/top are all frame-% — depends only on the frame aspect ratio, so
      // a responsive resize keeps the same crop. The spill layer mirrors the
      // same box so its corners = image corners.
      const k = g.base * this._view.s;
      const w = (g.iw * k / g.fw * 100) + '%';
      const h = (g.ih * k / g.fh * 100) + '%';
      const l = (50 + this._view.x) + '%';
      const t = (50 + this._view.y) + '%';
      this._img.style.width = w; this._img.style.height = h;
      this._img.style.left = l; this._img.style.top = t;
      this._img.style.objectFit = '';
      if (this.hasAttribute('data-reframe')) {
        // Top-layer spill: position in viewport px over the frame. The top
        // layer escapes ancestor transforms entirely, so EVERY term must be
        // in viewport units: getBoundingClientRect gives the frame's scaled
        // origin AND size, and the rect/layout ratio rescales the ghost —
        // sizing from layout px alone renders it 1/scale too large under a
        // scaled deck slide. Inner ghost + handles stay box-relative.
        const r = this.getBoundingClientRect();
        const sx = g.fw ? r.width / g.fw : 1;
        const sy = g.fh ? r.height / g.fh : 1;
        this._spill.style.width = (g.iw * k * sx) + 'px';
        this._spill.style.height = (g.ih * k * sy) + 'px';
        this._spill.style.left = (r.left + (50 + this._view.x) / 100 * r.width) + 'px';
        this._spill.style.top = (r.top + (50 + this._view.y) / 100 * r.height) + 'px';
      }
    }

    _commitView() {
      const v = { s: this._view.s, x: this._view.x, y: this._view.y };
      if (this._userUrl) v.u = this._userUrl;
      // Framing-only (no u) persists too so an author-src slot remembers its
      // crop; clearing the sidecar still falls through to src=.
      if (this.id) setSlot(this.id, v);
      else { this._local = v; }
    }

    _render() {
      // Shape / mask. Presets use border-radius so the dashed ring can
      // follow the rounded outline; clip-path is only applied for an
      // explicit `mask` (the ring is hidden there since a rectangle
      // dashed border chopped by an arbitrary polygon looks broken).
      const mask = this.getAttribute('mask');
      const shape = (this.getAttribute('shape') || 'rounded').toLowerCase();
      let radius = '';
      if (shape === 'circle') radius = '50%';
      else if (shape === 'pill') radius = '9999px';
      else if (shape === 'rounded') {
        const n = parseFloat(this.getAttribute('radius'));
        radius = (Number.isFinite(n) ? n : 12) + 'px';
      }
      this._frame.style.borderRadius = mask ? '' : radius;
      this._frame.style.clipPath = mask || '';
      this._ring.style.borderRadius = mask ? '' : radius;
      this._ring.style.display = mask ? 'none' : '';

      // Controls and reframe entry gate on this so share links stay read-only.
      const editable = !!(window.omelette && window.omelette.writeFile);
      this.toggleAttribute('data-editable', editable);
      this._sub.style.display = editable ? '' : 'none';

      // Content. The sidecar is also writable by the agent's write_file
      // tool, so its value isn't guaranteed canvas-originated — only accept
      // data:image/ URLs from it. The `src` attribute is author-controlled
      // (Claude wrote it into the HTML) so it passes through unchanged.
      let stored = this.id ? getSlot(this.id) : this._local;
      if (stored && stored.u && !/^data:image\//i.test(stored.u)) stored = null;
      const srcAttr = this.getAttribute('src') || '';
      this._userUrl = (stored && stored.u) || null;
      const url = this._userUrl || srcAttr;
      // Don't clobber an in-flight reframe with a store-triggered re-render.
      if (!this.hasAttribute('data-reframe')) {
        this._view = {
          s: stored && Number.isFinite(stored.s) ? clampS(stored.s) : 1,
          x: stored && Number.isFinite(stored.x) ? stored.x : 0,
          y: stored && Number.isFinite(stored.y) ? stored.y : 0,
        };
      }
      this._cap.textContent = this.getAttribute('placeholder') || 'Drop an image';
      // Toggle via style.display — the [hidden] attribute alone loses to
      // the display:flex / display:block rules in the stylesheet above.
      // An Unsplash src with no credit attribute must NOT render — showing
      // the photo uncredited is the Unsplash-terms violation itself. The
      // error tile replaces the photo until the credit is written. A
      // user-dropped image is the user's own content and always renders.
      // Trimmed: credit is agent/user-editable content, and a whitespace-
      // only value must count as missing — otherwise it would suppress the
      // error tile AND render an empty credit box (no text, no links),
      // exactly the unattributed state this gate exists to prevent.
      const credit = (this.getAttribute('credit') || '').trim();
      const attrError = !!(
        !credit && !this._userUrl && srcAttr && isUnsplashHost(srcAttr)
      );
      this.toggleAttribute('data-attribution-error', attrError);
      if (url && !attrError) {
        const prev = this._img.getAttribute('src');
        if (prev !== url) {
          // Replacing an already-shown image: mark the swap BEFORE setting
          // src so the stale frame is never revealed (see the data-swapping
          // stylesheet rules). First fill (prev empty) keeps the existing
          // placeholder-until-load behavior — no spinner. _hidShowing
          // covers the pick path's transient attribution-error wipe: prev
          // is gone, but an image WAS showing, so this is a replacement.
          if (prev || this._hidShowing) this.setAttribute('data-swapping', '');
          // Mark the swap BEFORE assigning src: complete keeps reporting
          // the old settled request until the browser's
          // update-the-image-data microtask runs, so same-task re-renders
          // (the pick path's credit/credit-href setAttributes) need this
          // flag, not complete, to know a load is in flight.
          this._loadPending = true;
          this._img.src = url;
          this._ghost.src = url;
        } else {
          // Same-src re-render — release if settled, so an ingest-set
          // spinner can't stick after a byte-identical re-upload (same
          // data URL, no further load event ever fires).
          this._releaseMask();
        }
        this._hidShowing = false;
        this._img.style.display = 'block';
        this._empty.style.display = 'none';
        this.setAttribute('data-filled', '');
        this._clampView();
        this._applyView();
      } else {
        this.removeAttribute('data-swapping');
        // The src is being removed — no load/error will ever fire for it.
        this._loadPending = false;
        // A transient attribution-error wipe of a showing image happens on
        // the pick path: the host sets src one setAttribute before credit,
        // so render N hides the old image (attrError) and render N+1
        // restores a URL. Remember the wipe so that restore renders as a
        // replacement (spinner), not a first fill (blank frame).
        this._hidShowing = attrError && !!this._img.getAttribute('src');
        this._img.style.display = 'none';
        this._img.removeAttribute('src');
        this._ghost.removeAttribute('src');
        // The error tile owns the blocked-photo state; .empty stays for
        // the genuinely-empty slot.
        this._empty.style.display = attrError ? 'none' : 'flex';
        this.removeAttribute('data-filled');
      }

      // Credit belongs to the author src, so a user drop hides it.
      // textContent + the http(s)-only funnel keep external strings inert.
      const showCredit = !!(url && credit && !this._userUrl && !attrError);
      this._credit.textContent = '';
      if (showCredit) {
        // Validate once (resolved against the document, http(s) only),
        // then append the terms-required utm referral params to links
        // that point back at unsplash.com.
        let href = '';
        const rawHref = this.getAttribute('credit-href') || '';
        if (rawHref) {
          try {
            const u = new URL(rawHref, document.baseURI);
            if (u.protocol === 'http:' || u.protocol === 'https:') {
              href = withReferral(u.href);
            }
          } catch {}
        }
        const mkLink = (text, linkHref) => {
          const a = document.createElement('a');
          a.setAttribute('target', '_blank');
          a.setAttribute('rel', 'noopener noreferrer');
          a.setAttribute('href', linkHref);
          a.textContent = text;
          return a;
        };
        // Unsplash's prescribed credit is TWO links — the photographer's
        // name to their profile (credit-href) and 'Unsplash' to the
        // homepage. Render that split whenever the text has the canonical
        // shape; other text keeps the legacy single-link rendering.
        const m = /^Photo by (.+) on Unsplash$/.exec(credit);
        if (m) {
          this._credit.appendChild(document.createTextNode('Photo by '));
          this._credit.appendChild(
            href ? mkLink(m[1], href) : document.createTextNode(m[1])
          );
          this._credit.appendChild(document.createTextNode(' on '));
          this._credit.appendChild(mkLink('Unsplash', UNSPLASH_HOMEPAGE_HREF));
        } else if (href) {
          this._credit.appendChild(mkLink(credit, href));
        } else {
          this._credit.textContent = credit;
        }
      }
      this.toggleAttribute('data-credit', showCredit);
    }
  }

  if (!customElements.get('image-slot')) {
    customElements.define('image-slot', ImageSlot);
  }
})();
