Connect image elements to render resources

crates/obscura-js/js/bootstrap.js

@@ -3880,6 +3880,249 @@ function _parseWebVttCues(src) {
   return cues;
 }
 
+function _imageEncodingError() {
+  return new DOMException("The source image cannot be decoded.", "EncodingError");
+}
+
+// HTMLImageElement is backed by the same retained resource cache used by
+// layout/paint. The render-only native op fetches and sniffs the ordinary
+// `src`; bootstrap owns only the observable request state and event timing.
+// Responsive candidate selection remains explicitly deferred to the renderer.
+class HTMLImageElement extends Element {
+  constructor(nid) {
+    super(nid);
+    this._imageRequest = 0;
+    this._imageQueued = false;
+    this._imageComplete = !this.getAttribute("src");
+    this._imageDecoded = false;
+    this._imageNaturalWidth = 0;
+    this._imageNaturalHeight = 0;
+    this._imageCurrentSrc = "";
+    this._imageDecodeWaiters = [];
+    // Parser images stay lazy until script observes their lifecycle or paint
+    // asks for the same cache entry. Inline handlers are observers too.
+    if (!this._imageComplete
+        && (this.hasAttribute("onload") || this.hasAttribute("onerror"))) {
+      this._queueImageRequest();
+    }
+  }
+
+  get src() {
+    const raw = this.getAttribute("src");
+    if (!raw) return "";
+    try { return new URL(raw, this.baseURI || globalThis.location?.href || "about:blank").href; }
+    catch (_error) { return raw; }
+  }
+  set src(value) { this.setAttribute("src", value); }
+
+  get currentSrc() {
+    this._refreshImageFromCache();
+    this._queueImageRequest();
+    return this._imageCurrentSrc;
+  }
+  get complete() {
+    this._refreshImageFromCache();
+    this._queueImageRequest();
+    return this._imageComplete;
+  }
+  get naturalWidth() {
+    this._refreshImageFromCache();
+    this._queueImageRequest();
+    return this._imageNaturalWidth;
+  }
+  get naturalHeight() {
+    this._refreshImageFromCache();
+    this._queueImageRequest();
+    return this._imageNaturalHeight;
+  }
+  get onload() { return this._imageOnload || null; }
+  set onload(value) {
+    this._imageOnload = typeof value === "function" ? value : null;
+    if (this._imageOnload) {
+      this._refreshImageFromCache();
+      this._queueImageRequest();
+    }
+  }
+  get onerror() { return this._imageOnerror || null; }
+  set onerror(value) {
+    this._imageOnerror = typeof value === "function" ? value : null;
+    if (this._imageOnerror) {
+      this._refreshImageFromCache();
+      this._queueImageRequest();
+    }
+  }
+
+  get width() {
+    const value = Number.parseInt(this.getAttribute("width") || "", 10);
+    return Number.isFinite(value) && value >= 0 ? value : this._imageNaturalWidth;
+  }
+  set width(value) { this.setAttribute("width", Math.max(0, Number(value) || 0)); }
+  get height() {
+    const value = Number.parseInt(this.getAttribute("height") || "", 10);
+    return Number.isFinite(value) && value >= 0 ? value : this._imageNaturalHeight;
+  }
+  set height(value) { this.setAttribute("height", Math.max(0, Number(value) || 0)); }
+
+  get srcset() { return this.getAttribute("srcset") || ""; }
+  set srcset(value) { this.setAttribute("srcset", value); }
+  get sizes() { return this.getAttribute("sizes") || ""; }
+  set sizes(value) { this.setAttribute("sizes", value); }
+  get loading() { return this.getAttribute("loading") || "eager"; }
+  set loading(value) { this.setAttribute("loading", value); }
+  get decoding() { return this.getAttribute("decoding") || "auto"; }
+  set decoding(value) { this.setAttribute("decoding", value); }
+  get fetchPriority() { return this.getAttribute("fetchpriority") || "auto"; }
+  set fetchPriority(value) { this.setAttribute("fetchpriority", value); }
+  get crossOrigin() { return this.getAttribute("crossorigin"); }
+  set crossOrigin(value) {
+    if (value === null) this.removeAttribute("crossorigin");
+    else this.setAttribute("crossorigin", value);
+  }
+
+  setAttribute(name, value) {
+    const normalized = String(name).toLowerCase();
+    super.setAttribute(name, value);
+    if (normalized === "src") this._imageSourceChanged();
+    else if ((normalized === "onload" || normalized === "onerror")
+        && !this._imageComplete) this._queueImageRequest();
+  }
+
+  removeAttribute(name) {
+    const normalized = String(name).toLowerCase();
+    super.removeAttribute(name);
+    if (normalized === "src") this._imageSourceChanged();
+  }
+
+  decode() {
+    this._refreshImageFromCache();
+    if (this._imageComplete) {
+      return this._imageDecoded
+        ? Promise.resolve()
+        : Promise.reject(_imageEncodingError());
+    }
+    this._queueImageRequest();
+    return new Promise((resolve, reject) => {
+      this._imageDecodeWaiters.push({ resolve, reject, request: this._imageRequest });
+    });
+  }
+
+  _imageSourceChanged() {
+    this._rejectImageDecodes();
+    this._imageRequest++;
+    this._imageQueued = false;
+    this._imageNaturalWidth = 0;
+    this._imageNaturalHeight = 0;
+    this._imageDecoded = false;
+    this._imageCurrentSrc = "";
+    this._imageComplete = !this.getAttribute("src");
+    if (!this._imageComplete) this._queueImageRequest();
+  }
+
+  _queueImageRequest() {
+    if (this._imageQueued || this._imageComplete) return;
+    this._imageQueued = true;
+    const request = this._imageRequest;
+    Promise.resolve().then(() => {
+      this._imageQueued = false;
+      if (request === this._imageRequest && !this._imageComplete) {
+        this._runImageRequest(request);
+      }
+    });
+  }
+
+  _runImageRequest(request) {
+    let metadata = null;
+    try {
+      const op = Deno.core.ops.op_image_metadata;
+      if (typeof op === "function") {
+        metadata = JSON.parse(op(this._nid >>> 0, false));
+      } else {
+        // Non-render builds have no authoritative resource cache. Preserve the
+        // old non-blocking compatibility behavior without issuing a duplicate
+        // network fetch: the request succeeds with unknown intrinsic size.
+        metadata = { ok: true, currentSrc: this.src, width: 0, height: 0 };
+      }
+    } catch (_error) {
+      metadata = { ok: false, currentSrc: this.src };
+    }
+    if (request !== this._imageRequest) return;
+    this._applyImageMetadata(metadata, request, true);
+  }
+
+  _refreshImageFromCache() {
+    if (this._imageComplete || !this.getAttribute("src")) return;
+    try {
+      const op = Deno.core.ops.op_image_metadata;
+      if (typeof op !== "function") return;
+      const metadata = JSON.parse(op(this._nid >>> 0, true));
+      if (!metadata || metadata.state === "pending") return;
+      this._applyImageMetadata(metadata, this._imageRequest, false);
+    } catch (_error) {}
+  }
+
+  _applyImageMetadata(metadata, request, dispatchEvent) {
+    if (request !== this._imageRequest) return;
+    this._imageComplete = true;
+    this._imageCurrentSrc = metadata && metadata.currentSrc
+      ? String(metadata.currentSrc)
+      : this.src;
+    const width = Number(metadata && metadata.width);
+    const height = Number(metadata && metadata.height);
+    const loaded = !!(metadata && metadata.ok)
+      && (typeof Deno.core.ops.op_image_metadata !== "function"
+        || (Number.isFinite(width) && width > 0 && Number.isFinite(height) && height > 0));
+    if (loaded) {
+      this._imageDecoded = true;
+      this._imageNaturalWidth = Number.isFinite(width) && width > 0 ? Math.round(width) : 0;
+      this._imageNaturalHeight = Number.isFinite(height) && height > 0 ? Math.round(height) : 0;
+      this._resolveImageDecodes(request);
+      if (dispatchEvent) {
+        try { this.dispatchEvent(new Event("load")); } catch (_error) {}
+      }
+    } else {
+      this._imageDecoded = false;
+      this._imageNaturalWidth = 0;
+      this._imageNaturalHeight = 0;
+      this._rejectImageDecodes(request);
+      if (dispatchEvent) {
+        try { this.dispatchEvent(new Event("error")); } catch (_error) {}
+      }
+    }
+  }
+
+  _resolveImageDecodes(request) {
+    const remaining = [];
+    for (const waiter of this._imageDecodeWaiters) {
+      if (waiter.request === request) waiter.resolve();
+      else remaining.push(waiter);
+    }
+    this._imageDecodeWaiters = remaining;
+  }
+
+  _rejectImageDecodes(request) {
+    const remaining = [];
+    for (const waiter of this._imageDecodeWaiters) {
+      if (request === undefined || waiter.request === request) {
+        waiter.reject(_imageEncodingError());
+      } else {
+        remaining.push(waiter);
+      }
+    }
+    this._imageDecodeWaiters = remaining;
+  }
+
+  addEventListener(type, callback, options) {
+    super.addEventListener(type, callback, options);
+    if ((String(type) === "load" || String(type) === "error") && callback) {
+      this._refreshImageFromCache();
+      this._queueImageRequest();
+    }
+  }
+}
+globalThis.HTMLImageElement = HTMLImageElement;
+_markNative(HTMLImageElement);
+_markNative(HTMLImageElement.prototype.decode);
+
 // Media elements need canPlayType for codec detection fingerprinting.
 // Values match Chrome 145 on Linux x86_64 without proprietary codecs.
 class HTMLMediaElement extends Element {
@@ -3959,6 +4202,7 @@ globalThis.VTTCue = VTTCue;
 function _elementClassFor(nid) {
   const tag = _domParse("tag_name", nid);
   if (tag === "FORM" && globalThis.HTMLFormElement) return globalThis.HTMLFormElement;
+  if (tag === "IMG") return HTMLImageElement;
   if (tag === "AUDIO") return HTMLAudioElement;
   if (tag === "VIDEO") return HTMLVideoElement;
   if (tag === "TRACK") return HTMLTrackElement;
@@ -7287,7 +7531,7 @@ globalThis.HTMLDivElement = Element;
 globalThis.HTMLSpanElement = Element;
 globalThis.HTMLParagraphElement = Element;
 globalThis.HTMLAnchorElement = Element;
-globalThis.HTMLImageElement = Element;
+globalThis.HTMLImageElement = HTMLImageElement;
 globalThis.HTMLInputElement = Element;
 globalThis.HTMLButtonElement = Element;
 globalThis.HTMLFormElement = class HTMLFormElement extends Element {
@@ -9472,39 +9716,10 @@ if (typeof Image === 'undefined') {
   // `new Image().style` was `undefined` and libraries that touch it on a
   // detached image threw (issue #350). Build a real element so `.style`,
   // attribute reflection, and event dispatch all come for free.
-  const _imgSrcDesc = Object.getOwnPropertyDescriptor(globalThis.HTMLImageElement.prototype, 'src');
   globalThis.Image = function Image(width, height) {
     const img = document.createElement('img');
-    img.onload = null; img.onerror = null;
-    img.complete = false; img.naturalWidth = 0; img.naturalHeight = 0;
-    img.width = width !== undefined ? (width >>> 0) : 0;
-    img.height = height !== undefined ? (height >>> 0) : 0;
-    // There is no real image decoder, so emulate a successful decode: assigning
-    // `.src` flips `complete` and fires `load` on a microtask-later tick. Lazy
-    // loaders and preloaders that create `new Image()`, set `.src`, and wait for
-    // `onload` (or addEventListener('load')) would hang forever otherwise.
-    // Anti-bot scripts (Booking.com, issue #394) pre-define a non-configurable
-    // own `src` on <img> elements; redefining it throws "Cannot redefine
-    // property: src" and kills the constructor. Skip the load emulation then:
-    // a page that owns `src` is instrumenting loads itself.
-    const ownSrc = Object.getOwnPropertyDescriptor(img, 'src');
-    if (!ownSrc || ownSrc.configurable) {
-      Object.defineProperty(img, 'src', {
-        configurable: true, enumerable: true,
-        get() { return _imgSrcDesc.get.call(img); },
-        set(v) {
-          _imgSrcDesc.set.call(img, v);
-          if (!img.getAttribute('src')) return;
-          img.complete = false;
-          setTimeout(function () {
-            img.complete = true;
-            img.naturalWidth = img.naturalWidth || img.width || 0;
-            img.naturalHeight = img.naturalHeight || img.height || 0;
-            try { img.dispatchEvent(new Event('load')); } catch (e) {}
-          }, 0);
-        },
-      });
-    }
+    if (width !== undefined) img.width = width >>> 0;
+    if (height !== undefined) img.height = height >>> 0;
     return img;
   };
   globalThis.Image.prototype = globalThis.HTMLImageElement.prototype;

crates/obscura-js/src/ops.rs

@@ -2048,6 +2048,7 @@ pub fn build_extension() -> Extension {
     // probes with typeof before calling, so the op's absence is a clean fallback.
     #[cfg(feature = "render")]
     {
+        ops.push(op_image_metadata());
         ops.push(op_layout_geometry());
         ops.push(op_layout_metrics());
         ops.push(op_scroll_offset());
@@ -2102,6 +2103,70 @@ pub(crate) fn ensure_prepared_render(
     state.prepared_render.as_ref()
 }
 
+/// Probe one ordinary `<img src>` through the renderer's page-scoped resource
+/// cache. This is deliberately a synchronous render-only op: the current
+/// renderer loader is synchronous too, and sharing it is what guarantees that
+/// HTMLImageElement lifecycle state and the subsequent paint see the same
+/// success/failure and retained bytes.
+#[cfg(feature = "render")]
+#[op2]
+#[string]
+fn op_image_metadata(state: &OpState, nid: u32, cached_only: bool) -> String {
+    let shared = state.borrow::<SharedState>().clone();
+    let mut gs = shared.borrow_mut();
+    let node_id = NodeId::new(nid);
+    let src = gs.dom.as_ref().and_then(|dom| {
+        let node = dom.get_node(node_id)?;
+        let element = node.as_element()?;
+        if element.local.as_ref() != "img" {
+            return None;
+        }
+        node.get_attribute("src").map(str::to_string)
+    });
+    let Some(src) = src.filter(|src| !src.trim().is_empty()) else {
+        return serde_json::json!({ "ok": false, "currentSrc": "" }).to_string();
+    };
+    let base_url = document_base_url(&gs);
+    let metadata = if cached_only {
+        match gs
+            .render_resources
+            .cached_image_metadata(&src, base_url.as_deref())
+        {
+            None => {
+                return serde_json::json!({ "state": "pending" }).to_string();
+            }
+            Some(metadata) => metadata,
+        }
+    } else {
+        gs.render_resources
+            .image_metadata(&src, base_url.as_deref())
+    };
+    match metadata {
+        Some((current_src, width, height)) => serde_json::json!({
+            "state": "loaded",
+            "ok": true,
+            "currentSrc": current_src,
+            "width": width,
+            "height": height,
+        })
+        .to_string(),
+        None => {
+            let current_src = base_url
+                .as_deref()
+                .and_then(|base| url::Url::parse(base).ok())
+                .and_then(|base| base.join(&src).ok())
+                .map(|url| url.to_string())
+                .unwrap_or(src);
+            serde_json::json!({
+                "state": "error",
+                "ok": false,
+                "currentSrc": current_src,
+            })
+            .to_string()
+        }
+    }
+}
+
 #[cfg(feature = "render")]
 pub(crate) fn clamp_scroll_offset(state: &mut ObscuraState, requested: (f32, f32)) -> (f32, f32) {
     state.scroll_offset = ensure_prepared_render(state)

crates/obscura-js/src/runtime.rs

@@ -4218,6 +4218,243 @@ mod tests {
         assert_eq!(rt.evaluate("document.links.length").unwrap().as_f64().unwrap() as i64, 1);
     }
 
+    #[cfg(feature = "render")]
+    fn parser_image_runtime(
+        html: &str,
+        loader: impl obscura_render::RenderResourceLoader + 'static,
+    ) -> ObscuraJsRuntime {
+        let mut rt = ObscuraJsRuntime::new();
+        rt.set_dom(parse_html(html));
+        rt.set_url("http://example.com/page/index.html");
+        rt.state.borrow_mut().render_resources =
+            obscura_render::RenderResourceCache::with_loader(loader);
+        rt.run_page_init();
+        rt
+    }
+
+    #[cfg(feature = "render")]
+    fn two_by_three_png() -> Vec<u8> {
+        use base64::Engine as _;
+        base64::engine::general_purpose::STANDARD
+            .decode(
+                "iVBORw0KGgoAAAANSUhEUgAAAAIAAAADCAYAAAC56t6B\
+                 AAAAFklEQVR4nGP8z8Dwn4GBgYGJAQrgDAAxOwIE7x6DkQAAAABJRU5ErkJggg=="
+                    .replace(char::is_whitespace, ""),
+            )
+            .unwrap()
+    }
+
+    #[cfg(feature = "render")]
+    #[tokio::test(flavor = "current_thread")]
+    async fn parser_image_lifecycle_uses_shared_render_resource() {
+        let calls = std::sync::Arc::new(std::sync::atomic::AtomicUsize::new(0));
+        let loader_calls = calls.clone();
+        let png = two_by_three_png();
+        let mut rt = parser_image_runtime(
+            r#"<img id="hero" src="../assets/hero.png">"#,
+            move |_url: &str| {
+                loader_calls.fetch_add(1, std::sync::atomic::Ordering::SeqCst);
+                Some(png.clone())
+            },
+        );
+        rt.execute_script(
+            "observe-parser-image",
+            r#"
+                globalThis.__imageEvents = [];
+                globalThis.__decodeState = "pending";
+                const image = document.getElementById("hero");
+                globalThis.__imageInitial = [
+                    image instanceof HTMLImageElement,
+                    image.complete,
+                    image.naturalWidth,
+                    image.naturalHeight
+                ];
+                image.addEventListener("load", () => __imageEvents.push("load"));
+                image.addEventListener("error", () => __imageEvents.push("error"));
+                image.decode().then(
+                    () => { __decodeState = "resolved"; },
+                    error => { __decodeState = error.name; }
+                );
+            "#,
+        )
+        .unwrap();
+        assert_eq!(
+            rt.evaluate("__imageInitial").unwrap(),
+            serde_json::json!([true, false, 0, 0])
+        );
+
+        rt.run_event_loop_bounded(100).await.unwrap();
+        assert_eq!(
+            rt.evaluate(
+                r#"[
+                    image.complete,
+                    image.naturalWidth,
+                    image.naturalHeight,
+                    image.currentSrc,
+                    __imageEvents,
+                    __decodeState
+                ]"#,
+            )
+            .unwrap(),
+            serde_json::json!([
+                true,
+                2,
+                3,
+                "http://example.com/assets/hero.png",
+                ["load"],
+                "resolved"
+            ])
+        );
+        assert_eq!(calls.load(std::sync::atomic::Ordering::SeqCst), 1);
+
+        // A subsequent request for the same URL is served by the retained
+        // renderer bytes rather than calling the loader again.
+        rt.execute_script("reload-image", r#"image.src = "../assets/hero.png";"#)
+            .unwrap();
+        rt.run_event_loop_bounded(100).await.unwrap();
+        assert_eq!(calls.load(std::sync::atomic::Ordering::SeqCst), 1);
+    }
+
+    #[cfg(feature = "render")]
+    #[tokio::test(flavor = "current_thread")]
+    async fn parser_image_failure_completes_and_rejects_decode() {
+        let calls = std::sync::Arc::new(std::sync::atomic::AtomicUsize::new(0));
+        let loader_calls = calls.clone();
+        let mut rt = parser_image_runtime(
+            r#"<img id="broken" src="missing.png">"#,
+            move |_url: &str| {
+                loader_calls.fetch_add(1, std::sync::atomic::Ordering::SeqCst);
+                None
+            },
+        );
+        rt.execute_script(
+            "observe-broken-image",
+            r#"
+                globalThis.__brokenEvents = [];
+                globalThis.__brokenDecode = "pending";
+                const broken = document.getElementById("broken");
+                broken.onload = () => __brokenEvents.push("load");
+                broken.onerror = () => __brokenEvents.push("error");
+                broken.decode().then(
+                    () => { __brokenDecode = "resolved"; },
+                    error => { __brokenDecode = error.name; }
+                );
+            "#,
+        )
+        .unwrap();
+        rt.run_event_loop_bounded(100).await.unwrap();
+        assert_eq!(
+            rt.evaluate(
+                "[broken.complete, broken.naturalWidth, broken.naturalHeight, \
+                  __brokenEvents, __brokenDecode]"
+            )
+            .unwrap(),
+            serde_json::json!([true, 0, 0, ["error"], "EncodingError"])
+        );
+        assert_eq!(calls.load(std::sync::atomic::Ordering::SeqCst), 1);
+    }
+
+    #[cfg(feature = "render")]
+    #[test]
+    fn parser_image_first_getter_observes_prepare_seeded_cache_synchronously() {
+        let calls = std::sync::Arc::new(std::sync::atomic::AtomicUsize::new(0));
+        let loader_calls = calls.clone();
+        let png = two_by_three_png();
+        let mut rt = parser_image_runtime(
+            r#"<img id="cached" src="cached.png">"#,
+            move |_url: &str| {
+                loader_calls.fetch_add(1, std::sync::atomic::Ordering::SeqCst);
+                Some(png.clone())
+            },
+        );
+        {
+            let mut state = rt.state.borrow_mut();
+            assert!(ensure_prepared_render(&mut state).is_some());
+        }
+        assert_eq!(calls.load(std::sync::atomic::Ordering::SeqCst), 1);
+
+        // Constructing the JS wrapper happens here, after prepare_dom loaded
+        // the resource. The first complete getter must see that cache hit
+        // immediately; it must not briefly regress to pending/zero.
+        assert_eq!(
+            rt.evaluate(
+                r#"(() => {
+                    const cached = document.getElementById("cached");
+                    return [
+                        cached.complete,
+                        cached.naturalWidth,
+                        cached.naturalHeight,
+                        cached.currentSrc
+                    ];
+                })()"#,
+            )
+            .unwrap(),
+            serde_json::json!([
+                true,
+                2,
+                3,
+                "http://example.com/page/cached.png"
+            ])
+        );
+        assert_eq!(calls.load(std::sync::atomic::Ordering::SeqCst), 1);
+    }
+
+    #[cfg(feature = "render")]
+    #[tokio::test(flavor = "current_thread")]
+    async fn parser_image_source_replacement_cancels_queued_completion() {
+        let requests = std::sync::Arc::new(std::sync::Mutex::new(Vec::new()));
+        let seen = requests.clone();
+        let first = two_by_three_png();
+        use base64::Engine as _;
+        let second = base64::engine::general_purpose::STANDARD
+            .decode(
+                "iVBORw0KGgoAAAANSUhEUgAAAAQAAAAFCAYAAABirU3b\
+                 AAAAFUlEQVR4nGNk+M/wnwEJMDGgATIEAKVaAgg/Jbt7AAAAAElFTkSuQmCC"
+                    .replace(char::is_whitespace, ""),
+            )
+            .unwrap();
+        let mut rt = parser_image_runtime(
+            r#"<img id="swap" src="old.png">"#,
+            move |url: &str| {
+                seen.lock().unwrap().push(url.to_string());
+                if url.ends_with("/new.png") {
+                    Some(second.clone())
+                } else {
+                    Some(first.clone())
+                }
+            },
+        );
+        rt.execute_script(
+            "replace-image-source",
+            r#"
+                globalThis.__swapEvents = [];
+                const swap = document.getElementById("swap");
+                swap.addEventListener("load", () => __swapEvents.push(swap.currentSrc));
+                swap.src = "new.png";
+            "#,
+        )
+        .unwrap();
+        rt.run_event_loop_bounded(100).await.unwrap();
+        assert_eq!(
+            rt.evaluate(
+                "[swap.complete, swap.naturalWidth, swap.naturalHeight, \
+                  swap.currentSrc, __swapEvents]"
+            )
+            .unwrap(),
+            serde_json::json!([
+                true,
+                4,
+                5,
+                "http://example.com/page/new.png",
+                ["http://example.com/page/new.png"]
+            ])
+        );
+        assert_eq!(
+            *requests.lock().unwrap(),
+            vec!["http://example.com/page/new.png".to_string()]
+        );
+    }
+
     /// Regression for #105: `HTMLFormElement` must expose `.elements` so
     /// frameworks that probe form field collections work.
     #[test]

crates/obscura-render/src/paint.rs

@@ -22,6 +22,7 @@ use crate::dom::layout_dom_with_web_fonts;
 
 const DEFAULT_RESOURCE_CACHE_ENTRIES: usize = 512;
 const DEFAULT_RESOURCE_CACHE_BYTES: usize = 64 * 1024 * 1024;
+const MISSING_RESOURCE_RETRY_AFTER: std::time::Duration = std::time::Duration::from_secs(2);
 
 /// Synchronous byte loader used by [`RenderResourceCache`]. The default
 /// implementation uses Obscura's pooled image agent; tests and embedding
@@ -106,12 +107,70 @@ impl RenderResourceCache {
         self.retained_bytes
     }
 
+    /// Resolve, fetch, and inspect one image through the exact byte cache used
+    /// by layout and paint. The JS image-element lifecycle calls this narrow
+    /// bridge so `complete`/`naturalWidth` and the eventual screenshot are
+    /// driven by one resource outcome instead of issuing an independent fetch.
+    ///
+    /// This intentionally accepts a plain `src`, not a DOM node: responsive
+    /// `picture`/`srcset` selection remains owned by `prepare_dom`.
+    pub fn image_metadata(
+        &mut self,
+        src: &str,
+        base_url: Option<&str>,
+    ) -> Option<(String, f32, f32)> {
+        let resolved_url = resolve_resource_url(src, base_url)?;
+        let bytes = fetch_bytes(&resolved_url, None, self)?;
+        let (width, height) = image_metadata_from_bytes(&bytes)?;
+        Some((resolved_url, width, height))
+    }
+
+    /// Inspect an image only when its renderer-cache outcome is already known.
+    /// `None` means no live cache entry (the caller may queue a load);
+    /// `Some(None)` means a retained load/decode failure; `Some(Some(...))`
+    /// means success. `data:` sources have no network entry and are cheap to
+    /// inspect directly.
+    pub fn cached_image_metadata(
+        &self,
+        src: &str,
+        base_url: Option<&str>,
+    ) -> Option<Option<(String, f32, f32)>> {
+        let resolved_url = resolve_resource_url(src, base_url)?;
+        if resolved_url.starts_with("data:") {
+            let mut scratch = RenderResourceCache::with_loader_and_limits(
+                |_url: &str| None,
+                0,
+                0,
+            );
+            return Some(
+                fetch_bytes(&resolved_url, None, &mut scratch)
+                    .and_then(|bytes| image_metadata_from_bytes(&bytes))
+                    .map(|(width, height)| (resolved_url, width, height)),
+            );
+        }
+        match self.entries.get(&resolved_url) {
+            Some(CachedResource::Bytes(bytes)) => Some(
+                image_metadata_from_bytes(bytes)
+                    .map(|(width, height)| (resolved_url, width, height)),
+            ),
+            Some(CachedResource::Missing(at))
+                if at.elapsed() < MISSING_RESOURCE_RETRY_AFTER =>
+            {
+                Some(None)
+            }
+            _ => None,
+        }
+    }
+
     fn get_or_load(&mut self, url: &str) -> Option<Arc<[u8]>> {
-        const MISSING_RETRY_AFTER: std::time::Duration = std::time::Duration::from_secs(2);
         if let Some(entry) = self.entries.get(url) {
             match entry {
                 CachedResource::Bytes(bytes) => return Some(Arc::clone(bytes)),
-                CachedResource::Missing(at) if at.elapsed() < MISSING_RETRY_AFTER => return None,
+                CachedResource::Missing(at)
+                    if at.elapsed() < MISSING_RESOURCE_RETRY_AFTER =>
+                {
+                    return None;
+                }
                 CachedResource::Missing(_) => {}
             }
         }
@@ -2513,6 +2572,16 @@ fn image_dimensions(bytes: &[u8]) -> Option<(u32, u32)> {
         .ok()
 }
 
+fn image_metadata_from_bytes(bytes: &[u8]) -> Option<(f32, f32)> {
+    let (width, height) = image_dimensions(bytes)
+        .map(|(width, height)| (width as f32, height as f32))
+        .or_else(|| svg_intrinsic(bytes))?;
+    if !width.is_finite() || !height.is_finite() || width <= 0.0 || height <= 0.0 {
+        return None;
+    }
+    Some((width, height))
+}
+
 fn background_image_rect(
     src: &str,
     base_url: Option<&str>,